Testing and Commissioning Report of Olakha Substation

Testing & Commissioning Report of "66/33KV Olakha Sub-Station"

By: Cheten Tshering Olakha Sub-Station, SMD Semtokha.

Transmission Department Bhutan Power Corporation Limited Thimphu.

BHUTAN POWER CORPORATION LIMITED TRANSMISSION DEPARTMENT SMD, SEMTOKHA 66/33 KV OLAKHA SUB-STATION THIMPHU

Commencing of Construction Testing Test Charge Commissioning of Sub Station Inauguration

: 13th June, 2008. : October 7-November 27, 2009. : November 29, 2009. : December 17, 2009. :

ACKNOWLEDGEMENT I would like to express profound gratitude to the then Officiating General Manager Mr. Nima Dorji for placing me at the up gradation works at 66/33 KV Olakha substation without which, I wouldn’t have been able to come out with this report. This provided me an opportunity to learn regarding the testing and commissioning of various switch gears, no sooner I graduated from the college. The placement was very appropriate and at the right time. I wish to extend sincere gratitude to Mr. Chandan Kamti Chatterjee, Testing Engineer, IPPL for teaching me all the practical aspect of the 'Testing and Commissioning' works and also the theoretical part of the same which are beyond the coverage in the books, which he explained through his 22 years of field experience in 'Testing and Commissioning'. I am indebted for his effort in revisiting my report and for making necessary correction and addition. I would also like to offer sincere appreciation which is due to the staff members of SMD Semtokha and Olakha Substation. Amongst the various persons who have helped me in this endeavor, I would like to mention the following: Mr. Sonam Tobgay (Manager), Mr. Tandin Gyeltshen, Mr. Sonam Norbu and Mr. LB Rai. I gratefully acknowledge the extensive literature referred during the course of writing this report. Last but not the least I would like to thank all those who have assisted me directly or indirectly in coming out with this report.

Cheten Tshering i

ABSTRACT This primary goal of this report is to provide in a simple and more of conventional way of conducting the testing of various switchgears and the system. This report 'Testing and Commissioning Report of 66/33KV Olakha Sub Station' describes about the various testing that are required to be done before commissioning of a substation. It contains in a lucid way, a concise presentation of various technical data and parameters that were obtained while in field testing. This report intends to serve as a history of Olakha substation in terms of its technical data and could be used as future reference while testing however the data may vary with different instruments used and the way it is conducted. This report is also equipped with the practical and pictorial circuit diagram of the exact field testing that was done while in the course of testing. Theories have been provided for every experiment based on the practical hands on experience. The materials presented in this report are intended to serve as a platform from where young and enthusiastic technical people could enhance their learning and explore in the area of testing and commissioning. However it could be used as reference by the one who already have the experience. I would like to solicit the readers' kind suggestions and feedback regarding the report so that I could come up with better one in future.

ii

List of Figures Figure 1 Experimental set up for checking the winding resistance ................................................ 3 Figure 2 Experimental set up for CT Ratio check ........................................................................ 14 Figure 3 Experimental setup for ratio test of PT and CVT........................................................... 23 Figure 4 KPV Testing of Current Transformer ............................................................................ 29 Figure 5 Surge Monitor Testing ................................................................................................... 38 Figure 6 SF6 Circuit Breaker Testing SCOT M3K Timer ............................................................ 41 Figure 7 SF6 Circuit Breaker Testing with Circuit Breaker Operational Analyzer .................... 42 Figure 8 Measurement of Transformer's winding resistance ....................................................... 49 Figure 9 Various testing on Transformer ..................................................................................... 57 Figure 10 Conditioning of Transformer Oil ................................................................................. 67 Figure 11 Winding Resistance Check of 33kv CT & PT............................................................... 79 Figure 12 Ratio Check of 33kv CT ............................................................................................... 80 Figure 13 High POT Test (CABLE HV TEST) ............................................................................. 93 Figure 14 Inverse-Time, Very-Inverse Time and Extremely-Inverse Time characteristics. ....... 100 Figure 15 Testing of IDMT Relays ............................................................................................. 101 Figure 16 System Stability Testing ............................................................................................. 114

iii

Table of Contents ACKNOWLEDGEMENT ............................................................................................................... i ABSTRACT .................................................................................................................................... ii List of Figures ................................................................................................................................ iii Checking the Winding Resistance of CT, PT & CVT ................................................................ 1 CT Ratio Check ......................................................................................................................... 13 Ratio Test of CVT and PT......................................................................................................... 22 Knee Point Voltage Test (KPV Test) of Current Transformer ................................................. 27 Surge Monitor Testing .............................................................................................................. 38 SF6 Circuit Breaker Testing...................................................................................................... 40 Transformer Winding Resistance .............................................................................................. 48 Transformer Testing .................................................................................................................. 54 Transformer Oil Testing ............................................................................................................ 65 Winding Resistance and Ratio Check of 33kv CT & PT .......................................................... 78 High Pot Test (Cable HV Test) ................................................................................................. 92 Relay Testing (Over Current Protection) ................................................................................ 100 Stability Testing Report .......................................................................................................... 113 Reference .................................................................................................................................... 124

iv

Winding Resistance Check of CT, PT & CVT

Checking the Winding Resistance of CT, PT & CVT Bus PT#1 Bus PT#2 CVT#1 CVT#2 CT#1 CT#2 CT#3 CT#4 CT#5 Aim

: PT on Tie Line Side : PT on Jemina Line Side : CVT on Tie Line Side : CVT on Jemina Line Side : CT on Tie Line Side : CT on Transformer I Side : CT on Bus Coupler Side : CT on Jemina Line Side : CT on Transformer II Side

: 1. To check the Secondary Winding Resistance. 2. Insulation Resistance (IR) checks of primary-earth and secondary-secondary winding by using Megger (2.5KV-5KV). 3. Secondary insulation resistance value check of secondary-earth and secondarysecondary terminals.

Objectives : 1. To check the resistance of secondary winding (CT, PT and CVT) and compare with that of name plate rating. 2. To check if there is any short circuit or leakage to ground from primary winding. To check if there is any short circuit between primary and secondary windings. 3. To check if there is any leakage or short circuit between the secondary winding and the earth. To check if there is any short circuit between the secondary windings. Instruments used Sl. no

:

Description

1

Megger

2

Megger

3

Multimeter

4

Connecting wires

Specification Quantity 2.5KV-5KV, 0-10000Mohms, Waco, 1 Type 485/08-09, Sl. no. 933090 1KV, 0-200Mohms, Waco, 1 Sl. no. 91611 Digital Multimeter DM3540A, 1 Motwane --------------------------------------------APR

Remarks

NB: Megger uses Ohm's law V=IR. It gives DC voltage and the current which flows through the winding resistance. The reading shown on the Megger is V/I.

66KV/33KV, Olakha Sub Station, Thimphu. [email protected]

Page 1


Test applied to;

PT

Core 1, Core 2 and Core 3 of PT

Yph

Rph

Bph

Earth Link

Secondary Winding Terminals A (Primary) N

Circuit diagram

1a

1n 2a

2n 3a

3n


Page 2


Experimental Set up :

Multimeter (Ohm meter)

Earth

Pry-Earth Winding Resistance

Secondary Winding Resistance Check IR Value check (Meggering)

Earth/Secondary or Secondary-Earth/ Secondary-secondary Figure 1 Experimental set up for checking the winding resistance


Page 3


Procedure

:

1. Secondary Winding Resistance a. Remove the earth terminal from three phases of PT from the lower side of the box. Make sure there is no connection from the PT to earth. b. Use the Multi meter as ohmmeter and measure the winding resistance of the respective secondary windings and of respective phases. c. Tabulate the reading and compare with the standard/manufacturer value. 2. Insulation resistances check (Meggering). a. Connect the Megger terminal to primary winding and earth terminal. Apply 5KV by Meggering and note down the readings as shown by Megger. NB: Since primary winding is on HV (66KV) side we need to apply high voltage i.e. 5 KV. b. Keeping one of the Megger terminals connected to the primary, connect the other terminal to the various secondary winding one by one. Apply 5KV by Meggering and note down the subsequent readings. 3. Secondary insulation resistances check (Meggering). a. Use lower rating Megger (1KV) for testing. This is because output voltage from the secondary windings is 110V, so we cannot apply very high voltage, otherwise the windings will get burned. b. Connect the Megger to secondary 1- earth terminal, followed by secondary 2earth and secondary 3-earth terminals respectively. Apply 1 KV by Meggering and note down the subsequent readings. Observations : • • •

If there is any short circuit between the windings or earth, then the Megger will show zero value. Else Megger will show some deflections indicating the insulation resistance value. Megger gives DC output


Page 4


Results

:

Bus PT#1, Tie Line PT (Incomer #1) Date:14 /10/09, Wednesday, 3:45pm, Sunny. R-Sl.no. OP 2373/2/7/08, Y-Sl.no. OP 2373/2/3/08, B-Sl.no. OP 2373/2/4/08 Secondary Winding Resistance (DM3540A Multimeter) Terminal R-Phase (Ohm) Y-Phase (Ohm) B-Phase (Ohm) 0.9 0.9 0.9 1a-1n (1&2) 0.9 0.9 0.9 2a-2n (3&4) 0.9 0.8 0.9 3a-3n (5&6) IR Value Check (Meggering), 5KV. Megger 2.5KV-5KV Terminal R-Phase (M-Ohm) Y-Phase (M-Ohm) B-Phase (M-Ohm) 3000 3000 3000 Pry-Earth 5000 3000 5000 Pry-Sec1(1a) 5000 5000 5000 Pry-Sec2(2a) 5000 5000 5000 Pry-Sec3(3a) Secondary IR Value check (Meggering), 1KV. Megger 1KV Terminal R-Phase (M-Ohm) Y-Phase (M-Ohm) B-Phase (M-Ohm) 200 200 200 Sec1-Earth 200 200 200 Sec2-Earth 200 200 200 Sec3-Earth 200 200 200 Sec1-Sec2 (1a-2a) 200 200 200 Sec2-Sec3 (2a-3a) 200 200 200 Sec3-Sec1 (3a-1a) Bus PT#2, Jemina Line Bus PT (Incomer#2) Date:13 /10/09, Tuesday, 5:30pm, Sunset. R-Sl.no. OP 2373/2/5/08, Y-Sl.no. OP 2373/2/6/08, B-Sl.no. OP 2373/2/8/08 Secondary Winding Resistance (DM3540A Multimeter) Terminal R-Phase (Ohm) Y-Phase (Ohm) B-Phase (Ohm) 0.9 0.8 0.8 1a-1n (1&2) 0.9 0.8 0.9 2a-2n (3&4) 0.9 0.8 0.9 3a-3n (5&6) IR Value Check (Meggering), 5KV. Megger 2.5KV-5KV Terminal R-Phase (M-Ohm) Y-Phase (M-Ohm) B-Phase (M-Ohm) 5000 2500 3000 Pry-Earth 4000 5000 5000 Pry-Sec1(1a) 4000 5000 4500 Pry-Sec2(2a) 5000 5000 4500 Pry-Sec3(3a) Secondary IR Value check (Meggering), 1KV. Megger 1KV Terminal R-Phase (M-Ohm) Y-Phase (M-Ohm) B-Phase (M-Ohm) 200 200 200 Sec1-Earth 200 200 200 Sec2-Earth 200 200 200 Sec3-Earth 200 200 200 Sec1-Sec2 (1a-2a) 200 200 200 Sec2-Sec3 (2a-3a) 200 200 200 Sec3-Sec1 (3a-1a)


Page 5


CVT#1, Tie Line (Incomer #1) Date:9/10/09, Friday. R-Sl.no.30309003, Y-Sl.no.30209002, B-Sl.no.30209003 Secondary Winding Resistance (DM3540A Multimeter) Terminal R-Phase (Ohm) Y-Phase (Ohm) B-Phase (Ohm) 1.1 0.7 0.7 1a-1n (1&2) 0.8 0.8 0.7 2a-2n (3&4) 0.8 0.8 0.8 3a-3n (5&6) IR Value Check (Meggering), 5KV. Megger 2.5KV-5KV Terminal R-Phase (M-Ohm) Y-Phase (M-Ohm) B-Phase (M-Ohm) 2000 3000 3000 Pry-Earth 5000 3000 5000 Pry-Sec1(1a) 5000 3000 3000 Pry-Sec2(2a) 5000 3000 5000 Pry-Sec3(3a) Secondary IR Value check (Meggering), 1KV. Megger 1KV Terminal R-Phase (M-Ohm) Y-Phase (M-Ohm) B-Phase (M-Ohm) 200 200 200 Sec1-Earth 200 200 200 Sec2-Earth 200 200 200 Sec3-Earth 200 200 200 Sec1-Sec2 (1a-2a) 200 200 200 Sec2-Sec3 (2a-3a) 200 200 200 Sec3-Sec1 (3a-1a) CVT#2, Jemina Line (Incomer#2) Date:10 /10/09, Saturday. R-Sl.no.30309001, Y-Sl.no.30309002, B-Sl.no.30309004 Secondary Winding Resistance (DM3540A Multimeter) Terminal R-Phase (Ohm) Y-Phase (Ohm) B-Phase (Ohm) 0.8 0.8 0.8 1a-1n (1&2) 0.8 0.8 0.8 2a-2n (3&4) 0.8 0.8 0.7 3a-3n (5&6) IR Value Check (Meggering), 5KV. Megger 2.5KV-5KV Terminal R-Phase (M-Ohm) Y-Phase (M-Ohm) B-Phase (M-Ohm) 4000 4000 4000 Pry-Earth 10000 10000 10000 Pry-Sec1(1a) 10000 10000 10000 Pry-Sec2(2a) 10000 10000 10000 Pry-Sec3(3a) Secondary IR Value check (Meggering), 1KV. Megger 1KV Terminal R-Phase (M-Ohm) Y-Phase (M-Ohm) B-Phase (M-Ohm) 200 200 200 Sec1-Earth 200 200 200 Sec2-Earth 200 200 200 Sec3-Earth 200 200 200 Sec1-Sec2 (1a-2a) 200 200 200 Sec2-Sec3 (2a-3a) 200 200 200 Sec3-Sec1 (3a-1a)


Page 6


CT#1, Tie Line (Incomer #1) Date:9/10/09, Friday. R-Sl.no. OC 2373/1/5/08, Y-Sl.no. OC 2373/1/12/08, B-Sl.no. OC 2373/1/10/08 Secondary Winding Resistance (DM3540A Multimeter) Terminal

R-Phase (Ohm)

Y-Phase (Ohm)

B-Phase (Ohm)

1S1-1S2

3.6

3.6

3.6

1S1-1S3

7.0

6.8

6.8

2S1-2S2

3.1

3.0

3.1

2S1-2S3

5.8

5.6

5.6

3S1-3S2

2.2

2.3

2.1

3S1-3S3

6.1

4.9

6.2

4S1-4S2

2.4

2.2

2.2

4S1-4S3

6.0

5.2

6.2

IR Value Check (Meggering), 5KV. Megger 2.5KV-5KV Terminal

R-Phase (M-Ohm)

Y-Phase (M-Ohm)

B-Phase (M-Ohm)

Pry-Earth

2000

1500

2000

Pry-Sec1 (1a)

2000

3000

5000

Pry-Sec2 (2a)

2000

3000

3000

Pry-Sec3 (3a)

2000

5000

5000

Pry-Sec4 (4a)

2000

5000

5000

Secondary IR Value check (Meggering), 1KV. Megger 1KV Terminal

R-Phase (M-Ohm)

Y-Phase (M-Ohm)

B-Phase (M-Ohm)

Sec1-Earth

50

200

200

Sec2-Earth

50

200

200

Sec3-Earth

50

200

200

Sec4-Earth

50

200

200

Sec1-Sec2 (1a-2a)

50

200

200

Sec2-Sec3 (2a-3a)

50

200

200

Sec3-Sec4 (3a-4a)

50

200

200

Sec4-Sec1 (4a-1a)

50

200

200


Page 7


CT#2, Transformer#1 Side Date:10/10/09, Friday. R-Sl.no. OC 2373/1/15/08, Y-Sl.no. OC 2373/1/9/08, B-Sl.no. OC 2373/1/1/08 Secondary Winding Resistance (DM3540A Multimeter) Terminal

R-Phase (Ohm)

Y-Phase (Ohm)

B-Phase (Ohm)

1S1-1S2

3.6

3.6

3.6

1S1-1S3

7.1

7.1

7.0

2S1-2S2

3.1

3.1

3.1

2S1-2S3

5.8

5.9

5.8

3S1-3S2

2.3

2.2

2.3

3S1-3S3

5.2

5.1

5.1

4S1-4S2

2.3

2.3

2.4

4S1-4S3

5.3

5.2

5.3


R-Phase (M-Ohm)

Y-Phase (M-Ohm)

B-Phase (M-Ohm)

Pry-Earth

4000

4000

4000

Pry-Sec1 (1a)

4000

4000

4000

Pry-Sec2 (2a)

4000

4000

4000

Pry-Sec3 (3a)

4000

4000

4000

Pry-Sec4 (4a)

4000

4000

4000


R-Phase (M-Ohm)

Y-Phase (M-Ohm)

B-Phase (M-Ohm)

Sec1-Earth

200

200

200

Sec2-Earth

200

200

200

Sec3-Earth

200

200

200

Sec4-Earth

200

200

200

Sec1-Sec2 (1a-2a)

200

200

200

Sec2-Sec3 (2a-3a)

200

200

200

Sec3-Sec4 (3a-4a)

200

200

200

Sec4-Sec1 (4a-1a)

200

200

200


Page 8


CT#3, Bus Coupler Side Date:10/10/09, Friday. R-Sl.no. OC 2373/1/7/08, Y-Sl.no. OC 2373/1/8/08, B-Sl.no. OC 2373/1/6/08 Secondary Winding Resistance (DM3540A Multimeter) Terminal

R-Phase (Ohm)

Y-Phase (Ohm)

B-Phase (Ohm)

1S1-1S2

3.6

3.5

3.4

1S1-1S3

6.5

6.3

5.9

2S1-2S2

3.2

3.2

3.2

2S1-2S3

5.9

6.1

6.1

3S1-3S2

2.4

2.4

2.4

3S1-3S3

6.2

6.0

6.0

4S1-4S2

2.3

2.4

2.4

4S1-4S3

6.0

6.1

6.1


R-Phase (M-Ohm)

Y-Phase (M-Ohm)

B-Phase (M-Ohm)

Pry-Earth

4000

3000

3000

Pry-Sec1 (1a)

3000

3000

3000

Pry-Sec2 (2a)

5000

3000

3000

Pry-Sec3 (3a)

5000

3000

3000

Pry-Sec4 (4a)

5000

3000

3000


R-Phase (M-Ohm)

Y-Phase (M-Ohm)

B-Phase (M-Ohm)

Sec1-Earth

200

200

200

Sec2-Earth

200

200

200

Sec3-Earth

200

200

200

Sec4-Earth

200

200

200

Sec1-Sec2 (1a-2a)

200

200

200

Sec2-Sec3 (2a-3a)

200

200

200

Sec3-Sec4 (3a-4a)

200

200

200

Sec4-Sec1 (4a-1a)

200

200

200


Page 9


CT#4, Jemina Line Side Date:10/10/09, Friday. R-Sl.no. OC 2373/1/14/08, Y-Sl.no. OC 2373/1/2/08, B-Sl.no. OC 2373/1/16/08 Secondary Winding Resistance (DM3540A Multimeter) Terminal

R-Phase (Ohm)

Y-Phase (Ohm)

B-Phase (Ohm)

1S1-1S2

2.2

2.4

2.4

1S1-1S3

5.3

5.1

5.3

2S1-2S2

2.3

2.3

2.2

2S1-2S3

5.0

5.0

5.0

3S1-3S2

2.5

2.5

2.2

3S1-3S3

5.1

5.1

5.1

4S1-4S2

2.2

2.4

2.2

4S1-4S3

5.1

5.0

5.1


R-Phase (M-Ohm)

Y-Phase (M-Ohm)

B-Phase (M-Ohm)

Pry-Earth

4000

4000

4000

Pry-Sec1 (1a)

4000

4000

4000

Pry-Sec2 (2a)

4000

4000

4000

Pry-Sec3 (3a)

4000

4000

4000

Pry-Sec4 (4a)

4000

4000

4000


R-Phase (M-Ohm)

Y-Phase (M-Ohm)

B-Phase (M-Ohm)

Sec1-Earth

200

200

200

Sec2-Earth

200

200

200

Sec3-Earth

200

200

200

Sec4-Earth

200

200

200

Sec1-Sec2 (1a-2a)

200

200

200

Sec2-Sec3 (2a-3a)

200

200

200

Sec3-Sec4 (3a-4a)

200

200

200

Sec4-Sec1 (4a-1a)

200

200

200


Page 10


CT#5, Transformer#2 Side Date:10/10/09, Friday. R-Sl.no. OC 2373/1/3/08, Y-Sl.no. OC 2373/1/18/08, B-Sl.no. OC 2373/1/4/08 Secondary Winding Resistance (DM3540A Multimeter) Terminal

R-Phase (Ohm)

Y-Phase (Ohm)

B-Phase (Ohm)

1S1-1S2

1.9

2.3

2.1

1S1-1S3

4.3

4.1

4.0

2S1-2S2

1.9

2.2

2.0

2S1-2S3

4.8

4.3

4.2

3S1-3S2

2.1

2.1

2.3

3S1-3S3

4.3

4.3

4.1

4S1-4S2

2.0

2.1

2.1

4S1-4S3

4.1

4.1

4.0


R-Phase (M-Ohm)

Y-Phase (M-Ohm)

B-Phase (M-Ohm)

Pry-Earth

5000

5000

5000

Pry-Sec1 (1a)

5000

5000

5000

Pry-Sec2 (2a)

5000

5000

5000

Pry-Sec3 (3a)

5000

5000

5000

Pry-Sec4 (4a)

5000

5000

5000


R-Phase (M-Ohm)

Y-Phase (M-Ohm)

B-Phase (M-Ohm)

Sec1-Earth

200

200

200

Sec2-Earth

200

200

200

Sec3-Earth

200

200

200

Sec4-Earth

200

200

200

Sec1-Sec2 (1a-2a)

200

200

200

Sec2-Sec3 (2a-3a)

200

200

200

Sec3-Sec4 (3a-4a)

200

200

200

Sec4-Sec1 (4a-1a)

200

200

200


Page 11


Precaution • • •

:

Safety of the experimenter, the first preference. Never start Meggering if both the terminals is being caught by performer Always discharge by connecting the terminal to earth so that the experimenter is free of shock.

Conclusion

:

From this test it is proved that there isn't any leakage or short circuit connection from primary to earth through the casing. Neither is the secondary windings touching the casing or with each other nor the primary winding is in contact with the secondary windings. The Potential transformer is perfectly right.


Page 12

CT Ratio Check

CT Ratio Check CT#1 CT#2 CT#3 CT#4 CT#5

: CT on Tie line Side : CT on Transformer I Side : CT on Bus Coupler Side : CT on Jemina Line Side : CT on Transformer II Side

Aim

: Ratio Test on various Current Transformers.

Objective

:

To check the ratio of primary to secondary current under loaded condition and compare with the name plate rating. Theory

:

Current transformers (CTs) of all sizes and types find their way into substations to provide the current replicas for metering, controls, and protective relaying. CT performance is characterized by ratio correction factor (turns ratio error), saturation voltage, phase angle error, and rated burden. Bushing CTs are installed in power equipment. They are toroidal, having a single primary turn (the power conductor), which passes through their center. The current transformation ratio results from the number of turns wound on the core to make up the secondary. More than one ratio is often provided by tapping the secondary winding at multiple turn's ratios. The core cross-sectional area, diameter, and magnetic properties determine the CT's performance. Metering CTs are designed with core cross-sections chosen to minimize exciting current effects and are allowed to saturate at fault currents. Larger cores are provided for protection CTs where high current saturation must be avoided for the CT to faithfully reproduce high currents for fault sensing. The exciting current of the larger core at low load is not considered important for protection.

Core#1 : Metering. Core#2 : Protection (Over Current, Earth fault, Differential). Core#3 : Bus bar Protection. Core#4 : Bus Bar Protection Zone


Page 13

CT Ratio Check Instruments used: Sl. no

Description

Specification

Quantity

1

Auto Transformer

0-260V, 50Hz

1

2

Loading Transformer

230V,50Hz-7.5KVA, 1V/T

1

3

Multimeter

AC/DC, Analog, Multi-range

1

4

Clamp leaker

DC-10A, Motwane

1

5

Clamp meter

Kyoritsu, DCM, Model 2002

1

6

Connecting wires

-----------------------------------------

7

1-Ф Supply

230V, 50Hz

Remarks

APR 1

Circuit diagram:

Current Transformer

Clamp meter

1-Ф Supply

Auto Transformer

Loading Transformer

Junction Box Figure 2 Experimental set up for CT Ratio check

Clamp Leaker NB: Never open the secondary terminal of CT when primary is connected.


Page 14

CT Ratio Check Procedure

:

1. Set up the experiment as shown in the circuit diagram. 2. Make the connections in the junction box so as to get the CT ratio 300/1A. Connect the first terminal and the middle one so that we get the ratio 300/1A i.e. 1S1-1S2, 2S1-2S2, etc. Never leave any CT secondary open. 3. Load the primary with certain percentage of full load current. Increase the load current in steps of 25%, 50%, 75% and 100% of the rated primary current. Observe it on the clamp meter held on the primary side. 4. With the help of clamp leaker measure the current on the secondary side, on each core and note down the readings. 5. Put off the power supply and then make the connections in junction box so as to get 600/1A CT ratio. Connect first terminal and the last terminal i.e. 1S1-1S3, 2S1-2S3, etc. 6. Load the primary with 12.5%, 25%, 37.5% and 50% of the rated primary current and check the values on the clamp meter. 7. With the help of clamp leaker, measure the current in each core i.e. secondary side. For simplicity note down the readings for half core first and then go for full tap readings. 8. Repeat step 1-7 for other two phases also. Precaution i. ii. iii. iv.

:

Safety the first priority. Never open the secondary terminal of the Current Transformer while it is on loaded condition. Make the connections tight. To avoid over heating of the primary connections, give 100% primary input for the lowest tap and 50% primary input for the full tap.

Results

:

The results are being tabulated for each current transformer. The actual ratio given on the name plate is 300-600/1A. The ratio replicates the name plate rating when the applied load current approaches the name plate rating. The errors are more when 12.5% and 25% of the total load current is applied. However as we apply more and more towards the actual load value, the ratio is almost near the actual ratio. The accuracy of CT is expressed in terms of its ratio from its true ratio. This is called ratio error and is expressed as; %

100

Is=Secondary current, Ip=Primary current


Page 15

CT Ratio Check 1. CT#1, Tie Line Side (Incomer #1) CT# 1, 1S1-1S2, 300/1A Date: 22/10/09, Thursday, 4:40pm, Sunny. R-Sl.no. OC 2373/1/5/08, Y-Sl.no. OC 2373/1/12/08, B-Sl.no. OC 2373/1/10/08 % of Rated Applied Secondary Current (A) Primary Primary R-phase Y-phase B-phase Current (A)

Current (A)

(A)

25% 50% 75% 100%

75 150 225 300

0.24 0.49 0.75 1.00

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.11 0.24 0.36 0.50

25% 50% 75% 100%

75 150 225 300

0.24 0.50 0.75 1.00

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.10 0.23 0.36 0.49

25% 50% 75% 100%

75 150 225 300

0.24 0.50 0.75 1.00

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.10 0.24 0.35 0.49

25% 50% 75% 100%

75 150 225 300

0.24 0.50 0.74 1.00

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.11 0.23 0.36 0.49

Ratio

% error

(A)

Ratio

312.50 4.17% 0.23 326.09 306.12 2.04% 0.48 312.50 300.00 0.00% 0.74 304.05 300.00 0.00% 1.00 300.00 CT# 1, 1S1-1S3, 600/1A 681.82 13.64% 0.11 681.82 625.00 4.17% 0.23 652.17 625.00 4.17% 0.36 625.00 600.00 0.00% 0.49 612.24 CT# 1, 2S1-2S2, 300/1A 312.50 4.17% 0.23 326.09 300.00 0.00% 0.48 312.50 300.00 0.00% 0.73 308.22 300.00 0.00% 0.99 303.03 CT# 1, 2S1-2S3, 600/1A 750.00 25.00% 0.11 681.82 652.17 8.70% 0.23 652.17 625.00 4.17% 0.35 642.86 612.24 2.04% 0.48 625.00 CT# 1, 3S1-3S2, 300/1A 312.50 4.17% 0.23 326.09 300.00 0.00% 0.49 306.12 300.00 0.00% 0.73 308.22 300.00 0.00% 0.98 306.12 CT# 1, 3S1-3S3, 600/1A 750.00 25.00% 0.10 750.00 625.00 4.17% 0.23 652.17 642.86 7.14% 0.35 642.86 612.24 2.04% 0.48 625.00 CT# 1, 4S1-4S2, 300/1A 312.50 4.17% 0.23 326.09 300.00 0.00% 0.48 312.50 304.05 1.35% 0.73 308.22 300.00 0.00% 0.98 306.12 CT# 1, 4S1-4S3, 600/1A 681.82 13.64% 0.10 750.00 652.17 8.70% 0.23 652.17 625.00 4.17% 0.35 642.86 612.24 2.04% 0.48 625.00

% error

(A)

Ratio

% error

8.70% 4.17% 1.35% 0.00%

0.22 0.49 0.74 1.00

340.91 306.12 304.05 300.00

13.64% 2.04% 1.35% 0.00%

13.64% 8.70% 4.17% 2.04%

0.10 0.23 0.36 0.49

750.00 652.17 625.00 612.24

25.00% 8.70% 4.17% 2.04%

8.70% 4.17% 2.74% 1.01%

0.23 0.48 0.74 1.00

326.09 312.50 304.05 300.00

8.70% 4.17% 1.35% 0.00%

13.64% 8.70% 7.14% 4.17%

0.10 0.23 0.36 0.49

750.00 652.17 625.00 612.24

25.00% 8.70% 4.17% 2.04%

8.70% 2.04% 2.74% 2.04%

0.23 0.48 0.74 1.00

326.09 312.50 304.05 300.00

8.70% 4.17% 1.35% 0.00%

25.00% 8.70% 7.14% 4.17%

0.10 0.23 0.36 0.49

750.00 652.17 625.00 612.24

25.00% 8.70% 4.17% 2.04%

8.70% 4.17% 2.74% 2.04%

0.23 0.49 0.74 0.99

326.09 306.12 304.05 303.03

8.70% 2.04% 1.35% 1.01%

25.00% 8.70% 7.14% 4.17%

0.10 0.23 0.36 0.48

750.00 652.17 625.00 625.00

25.00% 8.70% 4.17% 4.17%


Page 16

CT Ratio Check 2. CT#2, Transformer#1 Side (Incomer #1) CT# 2, 1S1-1S2, 300/1A Date: 22/10/09, Thursday, 4:55pm, Sunset. R-Sl.no. OC 2373/1/15/08, Y-Sl.no. OC 2373/1/9/08, B-Sl.no. OC 2373/1/1/08 % of Rated Applied Secondary Current (A) Primary Primary R-phase Y-phase B-phase Current (A)

Current (A)

(A)

25% 50% 75% 100%

75 150 225 300

0.24 0.50 0.75 1.00

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.11 0.23 0.36 0.49

25% 50% 75% 100%

75 150 225 300

0.24 0.50 0.75 1.00

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.11 0.23 0.35 0.48

25% 50% 75% 100%

75 150 225 300

0.24 0.50 0.75 1.00

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.11 0.23 0.36 0.49

25% 50% 75% 100%

75 150 225 300

0.24 0.50 0.75 1.00

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.11 0.23 0.36 0.49

Ratio

% error

(A)

Ratio


% error

(A)

Ratio

% error

0.00% 0.00% 0.00% 0.00%

0.24 0.50 0.75 1.00

312.50 300.00 300.00 300.00

4.17% 0.00% 0.00% 0.00%

13.64% 4.17% 4.17% 0.00%

0.11 0.23 0.36 0.49

681.82 652.17 625.00 612.24

13.64% 8.70% 4.17% 2.04%

0.00% 0.00% 0.00% 0.00%

0.24 0.50 0.75 1.00

312.50 300.00 300.00 300.00

4.17% 0.00% 0.00% 0.00%

13.64% 4.17% 4.17% 2.04%

0.11 0.24 0.36 0.49

681.82 625.00 625.00 612.24

13.64% 4.17% 4.17% 2.04%

0.00% 0.00% 0.00% 0.00%

0.24 0.51 0.75 1.01

312.50 294.12 300.00 297.03

4.17% -1.96% 0.00% -0.99%

13.64% 4.17% 4.17% 2.04%

0.11 0.24 0.36 0.49

681.82 625.00 625.00 612.24

13.64% 4.17% 4.17% 2.04%

4.17% 0.00% 0.00% 0.00%

0.24 0.50 0.75 1.01

312.50 300.00 300.00 297.03

4.17% 0.00% 0.00% -0.99%

13.64% 4.17% 4.17% 2.04%

0.11 0.24 0.36 0.49

681.82 625.00 625.00 612.24

13.64% 4.17% 4.17% 2.04%


Page 17

CT Ratio Check 3. CT#3, Bus Coupler Side

% of Rated Primary Current (A)

CT# 3, 1S1-1S2, 300/1A Date: 23/10/09, Friday, 9:50am, Sunny. R-Sl.no. OC 2373/1/7/08, Y-Sl.no. OC 2373/1/8/08, B-Sl.no. OC 2373/1/6/08 Applied Secondary Current (A) Primary R-phase Y-phase B-phase Current (A)

(A)

25% 50% 75% 100%

75 150 225 300

0.23 0.49 0.75 1.00

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.11 0.23 0.36 0.49

25% 50% 75% 100%

75 150 225 300

0.24 0.48 0.74 0.99

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.11 0.22 0.36 0.49

25% 50% 75% 100%

75 150 225 300

0.23 0.49 0.75 1.00

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.11 0.24 0.36 0.50

25% 50% 75% 100%

75 150 225 300

0.24 0.49 0.73 0.99

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.11 0.23 0.35 0.48

Ratio

% error

(A)

Ratio

326.09 8.70% 0.23 326.09 0.49 306.12 306.12 2.04% 0.75 300.00 300.00 0.00% 1.00 300.00 300.00 0.00% CT# 3, 1S1-1S3, 600/1A 681.82 13.64% 0.11 681.82 0.24 625.00 652.17 8.70% 0.36 625.00 625.00 4.17% 612.24 2.04% 0.49 612.24 CT# 3, 2S1-2S2, 300/1A 312.50 4.17% 0.23 326.09 0.49 306.12 312.50 4.17% 0.75 300.00 304.05 1.35% 1.00 300.00 303.03 1.01% CT# 3, 2S1-2S3, 600/1A 681.82 13.64% 0.11 681.82 681.82 13.64% 0.23 652.17 0.36 625.00 625.00 4.17% 612.24 2.04% 0.49 612.24 CT# 3, 3S1-3S2, 300/1A 326.09 8.70% 0.24 312.50 0.50 300.00 306.12 2.04% 0.75 300.00 300.00 0.00% 1.00 300.00 300.00 0.00% CT# 3, 3S1-3S3, 600/1A 681.82 13.64% 0.11 681.82 0.23 652.17 625.00 4.17% 625.00 4.17% 0.36 625.00 0.49 612.24 600.00 0.00% CT# 3, 4S1-4S2, 300/1A 0.23 326.09 312.50 4.17% 0.49 306.12 306.12 2.04% 0.74 304.05 308.22 2.74% 303.03 1.01% 1.00 300.00 CT# 3, 4S1-4S3, 600/1A 681.82 13.64% 0.11 681.82 0.23 652.17 652.17 8.70% 0.36 625.00 642.86 7.14% 0.49 612.24 625.00 4.17%

% error

(A)

Ratio

% error

8.70% 2.04% 0.00% 0.00%

0.23 0.49 0.74 0.99

326.09 306.12 304.05 303.03

8.70% 2.04% 1.35% 1.01%

13.64% 4.17% 4.17% 2.04%

0.10 0.23 0.35 0.48

750.00 652.17 642.86 625.00

25.00% 8.70% 7.14% 4.17%

8.70% 2.04% 0.00% 0.00%

0.23 0.49 0.74 0.99

326.09 306.12 304.05 303.03

8.70% 2.04% 1.35% 1.01%

13.64% 8.70% 4.17% 2.04%

0.11 0.23 0.35 0.48

681.82 652.17 642.86 625.00

13.64% 8.70% 7.14% 4.17%

4.17% 0.00% 0.00% 0.00%

0.23 0.49 0.74 1.00

326.09 306.12 304.05 300.00

8.70% 2.04% 1.35% 0.00%

13.64% 8.70% 4.17% 2.04%

0.10 0.23 0.35 0.48

750.00 652.17 642.86 625.00

25.00% 8.70% 7.14% 4.17%

8.70% 2.04% 1.35% 0.00%

0.23 0.49 0.74 0.99

326.09 306.12 304.05 303.03

8.70% 2.04% 1.35% 1.01%

13.64% 8.70% 4.17% 2.04%

0.10 0.23 0.35 0.48

750.00 652.17 642.86 625.00

25.00% 8.70% 7.14% 4.17%


Page 18

CT Ratio Check 4. CT#4, Jemina Line Side (Incomer#2) CT# 4, 1S1-1S2, 300/1A Date: 22/10/09, Thursday, 6:00pm, Dark. R-Sl.no. OC 2373/1/14/08, Y-Sl.no. OC 2373/1/2/08, B-Sl.no. OC 2373/1/16/08 % of Rated Applied Secondary Current (A) Primary Primary R-phase Y-phase B-phase Current (A)

Current (A)

(A)

25% 50% 75% 100%

75 150 225 300

0.24 0.50 0.76 1.01

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.11 0.24 0.36 0.49

25% 50% 75% 100%

75 150 225 300

0.24 0.50 0.76 1.01

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.11 0.24 0.36 0.50

25% 50% 75% 100%

75 150 225 300

0.24 0.50 0.76 1.01

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.11 0.24 0.36 0.49

25% 50% 75% 100%

75 150 225 300

0.24 0.50 0.76 1.01

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.11 0.25 0.36 0.49

Ratio

% error

(A)

Ratio

312.50 4.17% 0.23 326.09 300.00 0.00% 0.49 306.12 296.05 -1.32% 0.74 304.05 297.03 -0.99% 1.00 300.00 CT# 4, 1S1-1S3, 600/1A 681.82 13.64% 0.11 681.82 625.00 4.17% 0.23 652.17 625.00 4.17% 0.35 642.86 612.24 2.04% 0.50 600.00 CT# 4, 2S1-2S2, 300/1A 312.50 4.17% 0.24 312.50 300.00 0.00% 0.50 300.00 296.05 -1.32% 0.76 296.05 297.03 -0.99% 1.02 294.12 CT# 4, 2S1-2S3, 600/1A 681.82 13.64% 0.10 750.00 625.00 4.17% 0.24 625.00 625.00 4.17% 0.36 625.00 600.00 0.00% 0.50 600.00 CT# 4, 3S1-3S2, 300/1A 312.50 4.17% 0.24 312.50 300.00 0.00% 0.50 300.00 296.05 -1.32% 0.75 300.00 297.03 -0.99% 1.01 297.03 CT# 4, 3S1-3S3, 600/1A 681.82 13.64% 0.11 681.82 625.00 4.17% 0.24 625.00 625.00 4.17% 0.36 625.00 612.24 2.04% 0.50 600.00 CT# 4, 4S1-4S2, 300/1A 312.50 4.17% 0.24 312.50 300.00 0.00% 0.50 300.00 296.05 -1.32% 0.75 300.00 297.03 -0.99% 1.01 297.03 CT# 4, 4S1-4S3, 600/1A 681.82 13.64% 0.11 681.82 600.00 0.00% 0.24 625.00 625.00 4.17% 0.36 625.00 612.24 2.04% 0.50 600.00

% error

(A)

Ratio

% error

8.70% 2.04% 1.35% 0.00%

0.23 0.49 0.74 0.99

326.09 306.12 304.05 303.03

8.70% 2.04% 1.35% 1.01%

13.64% 8.70% 7.14% 0.00%

0.11 0.23 0.36 0.49

681.82 652.17 625.00 612.24

13.64% 8.70% 4.17% 2.04%

4.17% 0.00% -1.32% -1.96%

0.24 0.50 0.75 1.00

312.50 300.00 300.00 300.00

4.17% 0.00% 0.00% 0.00%

25.00% 4.17% 4.17% 0.00%

0.11 0.24 0.36 0.49

681.82 625.00 625.00 612.24

13.64% 4.17% 4.17% 2.04%

4.17% 0.00% 0.00% -0.99%

0.24 0.50 0.75 1.01

312.50 300.00 300.00 297.03

4.17% 0.00% 0.00% -0.99%

13.64% 4.17% 4.17% 0.00%

0.11 0.23 0.35 0.50

681.82 652.17 642.86 600.00

13.64% 8.70% 7.14% 0.00%

4.17% 0.00% 0.00% -0.99%

0.24 0.50 0.75 1.00

312.50 300.00 300.00 300.00

4.17% 0.00% 0.00% 0.00%

13.64% 4.17% 4.17% 0.00%

0.11 0.24 0.35 0.49

681.82 625.00 642.86 612.24

13.64% 4.17% 7.14% 2.04%


Page 19

CT Ratio Check 5. CT#5, Transformer#2 Side (Incomer#2)

% of Rated Primary Current (A)

CT# 5, 1S1-1S2, 300/1A Date: 23/10/09, Friday, 10:20am, Sunny. R-Sl.no. OC 2373/1/3/08, Y-Sl.no. OC 2373/1/18/08, B-Sl.no. OC 2373/1/4/08 Applied Secondary Current (A) Primary R-phase Y-phase B-phase Current (A)

(A)

25% 50% 75% 100%

75 150 225 300

0.23 0.49 0.74 1.00

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.11 0.23 0.36 0.49

25% 50% 75% 100%

75 150 225 300

0.23 0.48 0.74 0.99

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.10 0.23 0.35 0.49

25% 50% 75% 100%

75 150 225 300

0.23 0.49 0.74 0.99

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.10 0.23 0.36 0.48

25% 50% 75% 100%

75 150 225 300

0.23 0.49 0.74 0.99

12.5% 25.0% 37.5% 50.0%

75 150 225 300

0.10 0.23 0.36 0.48

Ratio

% error

(A)

Ratio


% error

(A)

Ratio

% error

4.17% 2.04% 0.00% -0.99%

0.23 0.49 0.74 1.00

326.09 306.12 304.05 300.00

8.70% 2.04% 1.35% 0.00%

13.64% 4.17% 4.17% 2.04%

0.10 0.23 0.35 0.49

750.00 652.17 642.86 612.24

25.00% 8.70% 7.14% 2.04%

8.70% 2.04% 1.35% 1.01%

0.23 0.49 0.74 1.00

326.09 306.12 304.05 300.00

8.70% 2.04% 1.35% 0.00%

13.64% 8.70% 4.17% 4.17%

0.11 0.23 0.36 0.49

681.82 652.17 625.00 612.24

13.64% 8.70% 4.17% 2.04%

8.70% 2.04% -1.32% 1.01%

0.23 0.49 0.74 0.99

326.09 306.12 304.05 303.03

8.70% 2.04% 1.35% 1.01%

25.00% 8.70% 4.17% 2.04%

0.11 0.23 0.36 0.49

681.82 652.17 625.00 612.24

13.64% 8.70% 4.17% 2.04%

8.70% 2.04% 1.35% 2.04%

0.23 0.49 0.74 1.00

326.09 306.12 304.05 300.00

8.70% 2.04% 1.35% 0.00%

13.64% 8.70% 4.17% 2.04%

0.11 0.23 0.36 0.50

681.82 652.17 625.00 600.00

13.64% 8.70% 4.17% 0.00%


Page 20

CT Ratio Check Conclusion

:

From this experiment, it is proved that the name plate ratio replicates the field test report. However the name plate ratio matches the field test ratio at 100% of the actual load current for lowest tap. For the full tap 50% of the actual load current was provided. The ratio came close to name plate rating at the 50% of the full load current. From this I conclude had we applied the full load current we will be getting exact replicate of the name plate rating. We couldn't apply full load current on 600/1A tap as the primary wire was getting heated up. More or less the obtained results are correct. The ratio error of a CT depends on its exciting current. When the primary current increases, the CT tries to produce corresponding secondary current, and this needs a greater secondary emf, core flux density and exciting current. A stage comes when any further increase in primary current is almost wholly absorbed in an increased exciting current and thereby the secondary current hardly increases at all. At this stage CT becomes saturated. Thus the ratio error depends on saturation. An accuracy of 2-3% of the CT is desirable for distance and differential relays, where as for many other relays, a higher percentage can be tolerated. When the primary current increases, at a certain value the core commences to saturate and the error increases. The value of current at which the error reaches a specified error limit is known as its 'Accuracy Limit Primary Current' or saturation current. The ratio of accuracy limit primary current and the rated primary current is known as rated accuracy limit factor (ALF) or saturation factor, the standard value of which are 5,10,15,20 & 30.


Page 21

Ratio Test of CVT & PT

Ratio Test of CVT and PT CVT#1 CVT#2 PT#1 PT#2

: Capacitive Voltage Transformer (Tie Line side) : Capacitive Voltage Transformer (Jemina side) : Potential Transformer of Bus (Transformer#1 side) : Potential Transformer of Bus (Transformer#2 side)

Aim

:

¾ To find the ratio of primary voltage to the subsequent secondary voltage and then compare with the given ratio in the name plate rating. Objective

:

To measure the voltage of three cores of each phase on the secondary winding and check if the ratio is alright upon doubling the applied voltage on primary side.

Instrument used Sl. no Description

Specification

Quantity Remarks

1

Auto Transformer

0-260V, 50Hz

1

2

Transformer

230V-3000V, 50Hz

1

3

Multimeter


1

4

Multimeter

DM3540A (Motwane)

1

5

Connecting wires

---------------------------------------------

6

1-Ф Supply

230V, 50Hz

APR 1

Theory : Potential transformers are used to reduce the system voltage level low enough to suit the ratings of protective relays. The voltage rating of protective relay is usually 110V. The % error is given by; %

100

Where K= Nominal voltage ratio, Vs= Secondary voltage and Vp=Primary voltage. The accuracy of PTs used for meters and instruments is only important at normal system voltage where as PTs used for protection requires errors to be limited over a wide range of voltages under faulty conditions. This may be about 5-150% of nominal voltage.


Page 22


Test applied to / experimental set up;

Circuit diagram Capacitive Voltage Transformer

1‐Ф, 230V, 50Hz Supply

Secondary Voltage Measurement

AVΩ Meter

Variac 0-260V, 50Hz

Transformer 230-3000V, 50Hz

Figure 3 Experimental setup for ratio test of PT and CVT


Page 23


Procedure: 1. 2. 3. 4.

Set up the connection as shown below. Connect one wire from HV side of transformer to the top of CVT. Connect the other to the earth. Adjust the voltage from the auto transformer so that 1KV is available on the secondary side of transformer which is shown on the voltmeter. (In fact we are applying 1KV to the primary winding of CVT). 5. Connect a multimeter (Voltmeter) to the core 1, core 2 and core 3 of each phase of CVT upon the application of 1KV to the primary and note down the reading. 6. Repeat the same for other two phases. 7. Repeat step 4 so that we get 2KV on the secondary side of the transformer and follow step 5 and step 6. Results:

CVT#1, Tie Line Side

Primary (V) 1000V Ratio % Error 2000V Ratio % Error

Date:12/10/09, Monday, 11:00am, Sunny. R-Sl.no.30309003, Y-Sl.no.30209002, B-Sl.no. 30209003 Secondary (V) R-Phase Y-Phase B-Phase Core1 Core2 Core3 Core1 Core2 Core 3 Core1 Core2 Core 3 1.640 1.648 1.648 1.680 1.640 1.648 1.680 1.650 1.640 610 607 607 595 610 607 595 606 610 1.7% 1.17% 1.17% -0.83% 1.7% 1.17% -0.83% 1.0% 1.7% 3.27 3.30 3.40 3.27 3.13 3.30 3.27 3.13 3.13 612 606 588 612 639 606 612 639 639 2.0% 1.0% -2.0% 2.0% 6.5% 1.0% 2.0% 6.5% 6.5%

CVT#2, Jemina Line

Primary (V) 1000V Ratio % Error 2000V Ratio % Error

Date:13/10/09, Tuesday, 10:30am, Sunny. R-Sl.no.30309001, Y-Sl.no.30309002, B-Sl.no. 30309004 Secondary (V) R-Phase Y-Phase Core1 Core2 Core3 Core1 Core2 Core 3 Core1 1.647 1.647 1.647 1.641 1.642 1.641 1.611 607 607 607 609 609 609 620 1.17% 1.17% 1.17% 1.5% 1.5% 1.5% 3.33% 3.256 3.255 3.258 3.216 3.216 3.218 3.194 614 614 613 622 622 622 626 2.33% 2.33% 2.17% 3.67% 3.67% 3.67% 4.33%


B-Phase Core2 1.631 613 2.17% 3.191 626 4.33%

Core 3 1.631 613 2.17% 3.194 626 4.33%

Page 24


Bus PT#1 (Transformer#1 side) Date:19/10/09, Monday, 11:35am, Sunny. R-Sl.no. OP 2373/1/7/08, Y-Sl.no. OP 2373/1/3/08, B-Sl.no. OP 2373/1/4/08 Secondary (V) R-Phase Y-Phase B-Phase Primary (V) Core1 Core2 Core3 Core1 Core2 Core 3 Core1 Core2 1.709 1.706 1.706 1.670 1.670 1.724 1.701 1.682 1000V 585 586 586 599 599 580 588 595 Ratio -2.5% -2.33% -2.33% -0.17% -0.17% -3.33% -2.0% -0.83% % Error 3.29 3.29 3.29 3.25 3.26 3.26 3.30 3.30 2000V 608 608 609 615 614 614 606 606 Ratio 1.3% 1.3% 1.5% 2.5% 2.33% 2.33% 1.0% 1.0% % Error

Core 3 1.681 595 -0.83% 3.30 606 1.0%

Bus PT#2 (Transformer#2 side) Date:19/10/09, Monday, 11:35am, Sunny. R-Sl.no. OP 2373/1/5/08, Y-Sl.no. OP 2373/1/6/08, B-Sl.no. OP 2373/1/8/08 Secondary (V) R-Phase Y-Phase B-Phase Primary (V) Core1 Core2 Core3 Core1 Core2 Core 3 Core1 Core2 Core 3 1.75 1.75 1.75 1.78 1.78 1.78 1.70 1.74 1.74 1000V 571 571 571 562 562 562 588 575 575 Ratio -4.83% -4.83% -4.83% 6.3% 6.3% 6.3% 2.0% 4.17% 4.17% % Error 3.30 3.31 3.31 3.37 3.37 3.37 3.38 3.38 3.38 2000V 606 604 604 594 594 594 592 592 592 Ratio 1.0% 0.67% 0.67% -1.0% -1.0% -1.0% -1.3% -1.3% -1.3% % Error Observation: 1. From the result obtained the ratio of primary to secondary voltage is within the range 607-626 where as the actual ratio are 600. The experimented ratio is slightly greater than the actual value. 66000/√3 600 110/√3 There is slight error which may be because of the inaccuracy of voltage applied from the transformer. However the results are fairly correct.


Page 25


Precaution: • • • •

Safety of the experimenter, the first preference. Always take the reading after it reaches a stable value. Always avoid parallax error while noting the reading. Always give proper connection to CVT and to earth.

Conclusion: From this test it is seen that the ratio of primary to secondary voltage is fairly correct with maximum of 6.5% error. For Lab test an error of ±5% is the accepted while for the field test an error of ±15% is accepted. The error can be eliminated by using more accurate meter, and applying the accurate voltage. Since the analog meter was used for noting the reading on the primary side, may be exact voltage wasn’t applied, parallax error might have introduced in the process. However the result doesn’t deviate much from the exact value thus the name plate rating is ok.


Page 26

KPV Test of Current Transformer

Knee Point Voltage Test (KPV Test) of Current Transformer CT #1 CT#2 CT#3 CT#4 CT#5

: Incoming line CT (Tie Line) : CT on Transformer I side : Bus Coupler CT : Incoming line #2 CT (Jemina Line) : CT on Transformer II Side

Aim

: Knee Point Voltage Testing of Current Transformers.

Objective

:

This test should confirm that at any case the saturation point shouldn’t lie before 100% of KPV. It may occur at 110% or higher, doesn’t matter but saturation point shouldn't occur before 100% of the KPV. If saturation point occurs before 100% of KPV then the relays will operate before reaching its set value (100%) which is not desirable. To find the saturation point of CT i.e. at what point of voltage it get saturated. Compare the obtained saturation point with that of the name plate rating. Theory

:

Knee point voltage is the point on the graph obtained between voltage and current beyond which the current rise is very sharp when voltage in increased slightly. When the applied voltage is increased in steps the current also rises in certain step. When the knee point voltage is reached then the current shoots up beyond its normal increasing step. Therefore in this test we see whether the KPV given on the name plate is correct or not. If the saturation point is reached before the actual KPV then the relays are going to trip before fault occurs. In fact the relays should trip upon reaching KPV or later. Therefore for proper coordination and tripping or relays KPV should be checked accurately. Since minimum KVP at lowest tap is provided for core 3 &4 of CT, so we test KPV for only these cores. V

KPV

0

I


Page 27


Instrument used: Sl. no Description

Specification

Quantity

1

Auto Transformer

0-260V, 50Hz

1

2

Transformer

230V-3000V, 50Hz

1

3

Multimeter


1

4

Clamp leaker

DC-10A, Motwane

1

5

Connecting wires

---------------------------------------------

6

1-Ф Supply

230V, 50Hz

Remarks

APR 1

Name plate rating

Procedure: 1. Set up the connection as shown below. 2. Apply certain percentage of Knee point Voltage to Core #3 and Core #4 and then note down the readings as shown by clamp leaker. 3. Repeat the same step for other two phases. 4. Compare the readings.


Page 28


Test applied to/ experimental set up

:

Current Transformer #1 Sl.No. 2373/1/5/08 Sl.No. 2373/1/12/08 Sl.No. 2373/1/10/08 Current Transformer #3 Sl.No. 2373/1/7/08 Sl.No. 2373/1/8/08 Sl.No. 2373/1/6/08

Clamp leaker

1‐Ф, 230V, 50Hz Supply

Junction box AVΩ Meter

Variac 0-260V, 50Hz

Transformer 230-3000V, 50Hz

Figure 4 KPV Testing of Current Transformer


Page 29


Technical terms: : Minimum Knee Point Voltage at lowest Tap = 325V

Name plate rating

There are two tapping in each core of CT. Therefore in this case lowest tap refers to the tapping between one end and the middle point. So at full tapping the Knee Point Voltage will be the double of the KPV of lowest tap.

P1

P2 Primary

1S1

1S2

Lowest Tap (325V)

1S3 2S1 2S2 2S3 3S1 3S2 3S3 4S1 4S2

4S3

Full Tapping (650V)

KPV for Core#3 and Core#4 Knee Point Voltage is available for only core #3 and core #4. This is because these cores are specifically designed for protection class core. For protection class core, saturation of current is very important and need to protect the equipment from over current. Whenever the current reaches its saturation point, relay should trip off. Therefore these cores have Knee point Voltage, before which saturation shouldn’t occur. Accuracy rating for Core#1 and Core#2 However this is not the case with core#1 and core#2. These cores are specifically designed for metering purposes, where accuracy is of much importance. If saturation point exists for these cores then when the current increases beyond certain value, the meter will stop reading, in fact the meter should record whatever the amount of current drawn. Therefore these cores are rated at 0.2 class of accuracy. For half the winding of each core, the rated KPV is 325V therefore for full winding the rated KPV is 650V. More the number of turns, greater will be the voltage and lesser will be the current, thereby the ratings 325V, 60mA and 650V, 30mA. If the saturation point is reached, CT will make humming sound and must be avoided.


Page 30


Results

:

1. Incoming Tie line CT, CT#1 CT# 1, 3S1-3S2, 325V, 60mA at Vk/2 Date: 19/10/09, Monday, 3:30pm, Sunny. R-Sl.no. OC 2373/1/5/08, Y-Sl.no. OC 2373/1/12/08, B-Sl.no. OC 2373/1/10/08 % of KPV Applied Voltage (V) R-phase (mA) Y-phase (mA) B-phase (mA) 7.31 8.22 7.79 25% 81.25 10.99 12.43 12.08 50% 162.50 16.31 20.34 19.45 75% 243.75 100%

325.00

29.98

40.00

36.70

110%

357.50

45.90

71.00

67.80

CT# 1, 3S1-3S3, 650V, 30mA at Vk/2 25% 50% 75%

162.50 325.00 487.50

3.65 5.55 7.46

3.97 6.31 9.69

3.76 5.91 8.88

100%

650.00

11.93

18.55

15.39

110%

715.00

15.79

25.77

23.10

CT#1, 4S1-4S2, 325V, 60mA at Vk/2 25% 50% 75% 100% 110%

81.25 162.50 243.75 325.00 357.50

7.54 11.95 17.14 31.26 53.90

8.25 12.74 19.55 42.50 70.30

8.34 13.16 20.42 39.50 72.60

For demonstration of saturation current, 400V was being applied to B-phase and the current was observed to be 215mA. See the graph. CT#1, 4S1-4S3, 650V, 30mA at Vk/2 25% 50% 75% 100% 110%

162.50 325.00 487.50 650.00 715.00

3.79 5.40 8.00 13.13 18.33

4.06 6.27 8.83 15.67 24.03


4.33 6.45 8.70 17.12 24.59

Page 31


2. CT Transformer 1 side, CT #2 CT# 2, 3S1-3S2, 325V, 60mA at Vk/2 Date: 19/10/09, Monday, 4:20, Sunny. R-Sl.no. OC 2373/1/15/08, Y-Sl.no. OC 2373/1/9/08, B-Sl.no. OC 2373/1/1/08 % of KPV

Applied Voltage (V)

R-phase (mA)

Y-phase (mA)

B-phase (mA)

25%

81.25

7.26

7.60

8.29

50%

162.50

11.36

12.43

13.22

75%

243.75

18.38

18.04

19.90

100%

325.00

35.00

31.84

35.5

110%

357.50

49.90

46.80

50.80

CT# 2, 3S1-3S3, 650V, 30mA at Vk/2 25%

162.50

3.73

3.91

3.89

50%

325.00

6.42

5.72

6.85

75%

487.50

8.73

8.40

8.72

100%

650.00

15.05

14.47

15.68

110%

715.00

22.05

20.11

22.23

CT#2, 4S1-4S2, 325V, 60mA at Vk/2 25%

81.25

7.43

7.38

8.41

50%

162.50

11.29

11.01

13.96

75%

243.75

17.65

16.43

21.43

100%

325.00

29.39

26.27

39.50

110%

357.50

55.8

49.40

63.30

CT#2, 4S1-4S3, 650V, 30mA at Vk/2 25%

162.50

3.85

3.77

4.20

50%

325.00

5.72

6.54

6.67

75%

487.50

8.88

8.31

10.35

100%

650.00

14.20

13.14

17.72

110%

715.00

20.06

19.46

22.87


Page 32


3. CT on Bus Coupler, CT #3 CT# 3, 3S1-3S2, 325V, 60mA at Vk/2 Date: 19/10/09, Monday, 4:45pm, Sunset. R-Sl.no. OC 2373/1/7/08, Y-Sl.no. OC 2373/1/8/08, B-Sl.no. OC 2373/1/6/08 % of KPV

Applied Voltage (V)

R-phase (mA)

Y-phase (mA)

B-phase (mA)

25%

81.25

7.29

7.09

7.24

50%

162.50

11.83

11.66

11.26

75%

243.75

17.84

17.21

17.14

100%

325.00

32.8

32.9

37.30

110%

357.50

46.2

58.6

54.30

CT# 3, 3S1-3S3, 650V, 30mA at Vk/2 25%

162.50

3.38

3.29

3.47

50%

325.00

5.53

5.37

5.36

75%

487.50

7.80

7.85

8.03

100%

650.00

13.65

13.53

14.42

110%

715.00

19.66

22.66

20.47

CT#3, 4S1-4S2, 325V, 60mA at Vk/2 25%

81.25

7.84

7.53

8.09

50%

162.50

12.66

11.82

13.23

75%

243.75

19.88

18.50

19.64

100%

325.00

37.50

40.4

36.80

110%

357.50

60.00

64.40

59.60

CT#3, 4S1-4S3, 650V, 30mA at Vk/2 25%

162.50

3.66

3.32

3.79

50%

325.00

5.82

5.44

6.10

75%

487.50

8.86

8.43

8.66

100%

650.00

16.11

15.76

16.73

110%

715.00

23.83

23.75

24.76


Page 33


4. CT on Jemina Line CT #4 CT# 4, 3S1-3S2, 325V, 60mA at Vk/2 Date: 22/10/09, Thursday, 10:20am, Sunny. R-Sl.no. OC 2373/1/14/08, Y-Sl.no. OC 2373/1/2/08, B-Sl.no. OC 2373/1/16/08 % of KPV

Applied Voltage (V)

R-phase (mA)

Y-phase (mA)

B-phase (mA)

25%

81.25

7.53

7.61

7.66

50%

162.50

11.73

12.03

12.20

75%

243.75

17.89

17.89

18.57

100%

325.00

36.3

34.4

33.3

110%

357.50

69.2

55.1

52.0

CT# 4, 3S1-3S3, 650V, 30mA at Vk/2 25%

162.50

3.25

3.39

3.43

50%

325.00

5.38

5.50

5.51

75%

487.50

8.22

8.26

8.23

100%

650.00

15.33

14.27

14.64

110%

715.00

22.20

19.20

20.25

CT#4, 4S1-4S2, 325V, 60mA at Vk/2 25%

81.25

7.38

7.65

7.30

50%

162.50

11.65

11.88

11.17

75%

243.75

17.18

17.80

15.24

100%

325.00

35.7

37.60

28.35

110%

357.50

55.4

51.30

47.6

CT#4, 4S1-4S3, 650V, 30mA at Vk/2 25%

162.50

3.47

3.49

3.29

50%

325.00

5.33

5.48

5.18

75%

487.50

7.91

8.17

7.43

100%

650.00

14.23

14.81

12.34

110%

715.00

20.36

20.98

17.01


Page 34


5. CT on Transformer#2 side, CT#5 CT# 5, 3S1-3S2, 325V, 60mA at Vk/2 Date: 22/10/09, Thursday, 10:50am, Sunny. R-Sl.no. OC 2373/1/3/08, Y-Sl.no. OC 2373/1/18/08, B-Sl.no. OC 2373/1/4/08 % of KPV

Applied Voltage (V)

R-phase (mA)

Y-phase (mA)

B-phase (mA)

25%

81.25

6.90

7.76

7.84

50%

162.50

10.92

11.90

11.48

75%

243.75

16.12

18.35

15.54

100%

325.00

29.52

36.5

28.31

110%

357.50

45.2

67.6

40.6

CT# 5, 3S1-3S3, 650V, 30mA at Vk/2 25%

162.50

3.29

3.59

3.50

50%

325.00

5.36

5.78

5.24

75%

487.50

7.90

8.93

7.64

100%

650.00

13.66

16.17

12.44

110%

715.00

18.49

23.70

16.45

CT#5, 4S1-4S2, 325V, 60mA at Vk/2 25%

81.25

6.82

6.59

7.90

50%

162.50

10.70

10.39

11.55

75%

243.75

15.96

14.82

16.91

100%

325.00

28.41

25.06

31.20

110%

357.50

45.7

38.3

53.4

CT#5, 4S1-4S3, 650V, 30mA at Vk/2 25%

162.50

3.23

3.20

3.44

50%

325.00

5.12

5.06

5.43

75%

487.50

8.03

7.32

7.85

100%

650.00

13.36

11.55

13.62

110%

715.00

18.02

15.27

19.44


Page 35


Graphical Analysis for CT#1, 4S1-4S2, 325V, 60mA, B-phase

KPV Curve Characteristic 450 400

400 357.5

350

Voltage (V)

325 300 250

243.75

200 KPV Curve

162.5

150 100

81.25

50 0 0

50

100

150

200

250

Current (mA) CT#4, 4S1-4S3, 650V, 30mA at Vk/2, R-Phase

KPV Curve Characterstics 800 715

700 650

Voltage (V)

600 500

487.5

400 325

300 200

KPV Curve

162.5

100 0 0

5

10

15

20

25

Current (mA)


Page 36


Precaution • • • •

:

Safety of experimenter and the teams the first priority. Always take the readings after it has settled to a particular value. Make sure that no heavy equipment like welding machines, are operating from the same source from which testing is being done. Always note the name plate reading and then perform the experiment.

Conclusion

:

From this experiment it is proved that the saturation point of current doesn’t occur below 100% of KPV. In fact it occurs beyond 110% of the rate KPV. Therefore this equipment is safe to use. If the saturation point occurs before 100% of KPV then the relays connected to it will operate under normal conditions also. When the saturation point occurs, the current rises to a very high value, crossing the set point of relays which makes it to trip off, thus protecting the equipments. This will allow only permissible amount of current to flow through the equipments.


Page 37

Surge Monitor Testing

Date Day Time Weather

: 13/10/09 : Tuesday : 5:45pm : Sunset

Surge Monitor Testing Aim

: To check the deflection in the surge monitor.

Objective

: To find out whether the surge monitor is working or not.

Instrument Used

:

Sl. no.

Description

1

Megger

2

Connecting Wires

Specification 1KV, 0-200Mohms, Waco, Sl. no. 91611 ----------------------------------

Quantity

Remarks

1 APR

Test applied to/ Test set up;

Model : SM‐T2B‐3R Sl.No. 5300

Lightening Arrester

Surge Monitor

Megger

Figure 5 Surge Monitor Testing


Page 38

Surge Monitor Testing

Procedure: 1. Connect positive terminal of the Megger to the top portion of the surge monitor as shown above. 2. Connect the other terminal to the earth terminal. 3. Start Meggering Observation: • •

When voltage (1KV) was applied to the surge monitor by Meggering, the pointer inside the surge monitor started deflecting. In some case the pointer didn’t deflect indicating that the monitor is not working.

Precaution • • •

:

Safety of the experimenter, the first priority. Never start Meggering if both the terminals is being caught by performer Always discharge by connecting the terminal to earth so that the experimenter is free of shock.

Conclusion

:

From this test we can know whether the surge monitor is working or not. If there is no deflection then it is proved that the surge monitor is not working and need to be replaced. If the indicator inside the surge monitor starts to deflect upon the application of voltage then it is proved that the surge monitor is working.


Page 39

SF6 Circuit Breaker Testing

SF6 Circuit Breaker Testing CB#1 CB#2 CB#3 CB#4 CB#5

: Circuit Breaker on Incomer#1 (Tie Line) : Circuit Breaker on Transformer#1 side : Circuit Breaker on Bus Coupler Side : Circuit Breaker on Incomer#2 (Jemina Line) : Circuit Breaker on Transformer#2 side

Aim

: Testing of SF6 Circuit Breaker.

Objective

:

¾ To find out the Alarm 'Loss of SF6' at 20ºC. ¾ To find out the General Lock out SF6 at 20ºC. ¾ To find the closing and opening time of SF6 Circuit Breaker. Theory

:

The Nominal pressure of SF6 gas at 20ºC is 6.0 bars. When the loss of SF6 gas occurs below certain set value it gives an alarm indicating less SF6 gas. So we need to attend to it by refilling. If we fail to attend to the alarm, then when the pressure of SF6 gas falls further, then Lock out of SF6 occurs. At this point the circuit breaker neither opens nor closes i.e. it remains in deadlock position.


Page 40


Instruments used Sl. no 1

:

Description SCOT M3K Time Interval Meter

2

Multimeter

3

Refrigerant Leak Detector

Circuit diagram

Specification Model no. 2100.02W.166, T&M Pvt. Ltd., Pune India. Digital Multimeter DM3540A, Motwane Model CPS LS790B, Sl.No. 581964, USA Made

Quantity

Remarks

1 Set 1 1

:

To Circuit Breaker Junction Box Red : (3, 4, 5) Yellow : 17 Green : 7 for trip 1 and 12 for trip 2

DC +ive, CB Coil Source C +ive, CB Close Coil terminal T +ive, CB Source Trip Coil terminal Source

Master Earthing (Double Earthing)

Figure 6 SF6 Circuit Breaker Testing SCOT M3K Timer


Page 41


SF6 Breaker Testing with the Testing Equipment of BPC ( Circuit Breaker Operational Analyzer Model 2406 HISAC, Sl. no. 3290-009).

R

Y

B

Master Earthing (Double Earthing)

To Circuit Breaker Junction Box

Power Supply

Figure 7 SF6 Circuit Breaker Testing with Circuit Breaker Operational Analyzer

NB: The terminals from the kit are to be connected as given in the earlier diagram and the wires refer the same definition.


Page 42


Procedure

:

PART-I 1. Connect the SF6 gas pipe to the breaker and start filling up the gas. 2. Fill up till the pressure reaches 1.0bar. 3. Check all the pipes and SF6 breaker for any leakage with the help of Refrigerant Leak Detector. If leakage is there, then it makes continuous beeping sound. To find the exact leak area, apply shampoo foam over the area. Wherever the pore is, the bubble becomes big and burst out. 4. Leave the Breaker at 1.0bar for few hours. If leakage is there, the pressure falls down. 5. If there is no leakage then fill up the breaker with SF6 gas at 6.0bars. 6. At certain pressure (5.0 bars approx.) general lock out SF6 will occur. The multimeter connected across alarm (X1-4, K11-A1) and trip contact (X1-4, K10-A1) will make continuity sound. 7. Increase the pressure until it reaches certain point (5.3bars approx.) when the multimeter connected across alarm and trip contact stops making continuity sound. This is the Alarm Loss of gas pressure. 8. Still fill up the breaker with SF6 gas until the pressure reaches 6.0bars and disconnect it. PART-II 1. Set up the experiment with SCOT M3K Time Interval Meter. 2. Connect the RYB terminals at the top and middle (make and break) points and plug it to the SCOT M3K Time Interval Meter. 3. Connect two ground wires so as to have effective earthling. If one fails other will work. 4. Connect the control cable with the Circuit Breaker a. Red one is DC +ive and it is the CB coil source. DC signals flows from Breaker to the SCOT M3K Time Interval Meter. Connect it to X1-3, 4, and 5. b. The command (Close command and Trip command) that we give flows to the CB through the other two wires. c. The yellow wire is C +ive and it is the close coil terminal. The close command that we punch goes through this cable to operate the CB. Connect it to X1-17. d. Green wire is T +ive and is the Trip coil terminal. The trip command that we punch passes through this wire to trip the CB. Connect it to X-7. 5. Supply AC power to the motor so that it energizes the spring. When spring compresses to its set position, the limit switch disconnects the AC supply and the motor stops, thus the spring is charged. 6. Give the close, open-1 and close/open command consecutively with simultaneous recording of the time (ms). 7. Change the green terminal to X1-12 and give open-2 command and note down the readings.


Page 43


Results

: 25/10/2009, Sunday, Sunny. 66KV Circuit Breaker SF6 gas filling Pressure Density Monitor Status.

Sl. No.

Temperature (ºC)

2009/IND/03/6059

20

2009/IND/03/6060

20

2009/IND/03/6061

20

2009/IND/03/6058

20

2009/IND/03/6062

20

Trip Contact X1-4 K10-A1 X1-4 K10-A1 X1-4 K10-A1 X1-4 K10-A1 X1-4 K10-A1

Lockout gas pressure (bar) kg/cm2 5.1

Leakage

5.2

OK

5.0

OK

5.2

OK

5.0

OK

X1-4 K11-A1 X1-4 K11-A1 X1-4 K11-A1 X1-4 K11-A1 X1-4 K11-A1

Loss of SF6 gas pressure (bar) 5.3

Status found Leakage

5.4

OK

5.3

OK

5.4

OK

5.3

OK

Sl. No.

Motor Sl. No.

Close Coil (Ω)

Trip Coil 1(Ω)

Trip Coil 2(Ω)

2009/IND/03/6059

-

50.0

50.0

50.0

2009/IND/03/6060

289-087

50.4

50.3

50.6

2009/IND/03/6061

289-349

48.5

50.1

50.6

2009/IND/03/6058

289-436

50.9

50.2

50.0

2009/IND/03/6062

289-543

49.7

49.7

50.1


Status found

Alarm Contact

Page 44


Test Result of SF6 Circuit Breaker Location Serial Number Date of Testing Feeder Name Rated Voltage Rated Current Phase R Y B

: Bus Coupler Side. Type : 3AP1FG : 2009/IND/03/6061. Make : SEIMENS : 26/10/2009, 9:45am, Sunny. STC : 40KA : CB3 : 145KV : 3150A Closing/Opening Time Close (ms) Open-1 (ms) Open-2(ms) C/O(ms) 59 33 30 29 58 34 31 31 59 33 33 33 Coil Resistance Coil Resistance (Ω) Close coil 48.5 Trip Coil-1 50.1 Trip Coil-2 50.4


: Transformer#2 Side. Type : 3AP1FG : 2009/IND/03/6062. Make : SEIMENS : 26/10/2009, 10:25am, Sunny. STC : 40KA : CB5 : 145KV : 3150A Closing/Opening Time Close (ms) Open-1 (ms) Open-2(ms) C/O(ms) 57 32 30 33 57 32 30 33 57 32 30 33 Coil Resistance Coil Resistance (Ω) Close coil 49.7 Trip Coil-1 49.7 Trip Coil-2 50.1


Page 45



: Transformer#1 Side. Type : 3AP1FG : 2009/IND/03/6058. Make : SEIMENS : 26/10/2009, 11:00am, Sunny. STC : 40KA : CB2 : 145KV : 3150A Closing/Opening Time Close (ms) Open-1 (ms) Open-2(ms) C/O(ms) 60 33 33 31 59 34 34 30 62 32 32 30 Coil Resistance Coil Resistance (Ω) Close coil 50.9 Trip Coil-1 50.2 Trip Coil-2 50.0


: Incomer#1 Tie Line Side. Type : 3AP1FG : 2009/IND/03/6060. Make : SEIMENS : 26/10/2009, 11:20am, Sunny. STC : 40KA : CB1 : 145KV : 3150A Closing/Opening Time Close (ms) Open-1 (ms) Open-2(ms) C/O(ms) 57 33 34 34 58 32 33 31 59 32 33 33 Coil Resistance Coil Resistance (Ω) Close coil 50.4 Trip Coil-1 50.3 Trip Coil-2 50.6


Page 46



Result • • •

: The rated time for closing is 50±8 ms; therefore the value that we obtained is within the range. The rated opening time is 30±4 ms; therefore the value we obtained is within the permissible limit. The rated close-open time is 30±10 ms; therefore the value we obtained is within the normal range.

Precaution • • • •

: Incomer#2 Jemina Line Side. Type : 3AP1FG : 2009/IND/03/6059. Make : SEIMENS : 28/12/2009, 4:15pm, Sunny. STC : 40KA : CB4 : 145KV : 3150A Closing/Opening Time Close (ms) Open-1 (ms) Open-2(ms) C/O(ms) 59.0 28.8 60.4 29.8 57.4 30.0 58.0 31.0 58.2 29.6 58.4 30.4 Coil Resistance Coil Resistance (Ω) Close coil 48.9 Trip Coil-1 49.0 Trip Coil-2 49.0

:

Safety the first priority. Always take the steady value. Connect the wires properly and tightly. Note down the readings properly.

Conclusion

:

From this field test I came to learn that the results are correct and the SF6 circuit breaker is safe to use. Of course one SF6 circuit breaker on Jemina side had leakage therefore it was replaced and tested. Rests of the circuit breaker are working fine. Sometimes the tripping coil gets burned often as in case of Jemina line circuit breaker, the reason being the flow of continuous current, low resistance of the coil and appearance of high voltage across its terminal. For resistance check, apply voltage across the terminals for 15s and then check the current obtained and cross check with the actual value.


Page 47

Transformer Winding Resistance

Transformer Winding Resistance Aim

: To find out the Winding Resistance of Transformer and of its respective CTs.

Objective

:

• • •

To check the winding resistance of Transformer in R, Y and B phase on HV side. To check the winding resistance on LV side at Tap # 9. To check the winding resistance of WTICT, NCT and LV phase CT.

Theory : There are three current transformers in 20MVA Transformer viz. winding temperature indicator current transformer (WTICT), Neutral current transformer (NCT) and LV phase current transformers. WTICT is connected to the bellow heater in the WTI. When transformer is loaded the current flows through the CT and flows through the heater coil, thereby the temperature indicated by WTI becomes the winding oil temperature and the winding temperature. In no load condition the WTI temperature and the OTI temperature are same as indicated in the dehydration curve. NCT is located below the neutral point in secondary winding and for each LV phases there is CT. Tap # 9 is normal position with turn's ratio two, so whenever we do normal test we take tap # 9. For this test we simply use Ohm's law. Transformer 1 Sl. no. 21067/1 WTICT

: 350/5A, CL-5, 20VA.

NCT

: Core (i), 400/1A, 5P10, 10VA Core (ii), 400/1A, 5P10, 10VA Core (iii), 400/1A, CL-PS, Vk ≥ 800V. Imag ≤ 100mA at Vk, RCT ≤ 1.5Ω LV Phase CT Core (i), 400/1A, 5P10, 10VA. Core (ii), 400/1A, 5P10, 10VA Core (iii), 400/1A, CL-PS, Vk ≥ 800V. Imag ≤ 100mA at Vk, RCT ≤ 1.5Ω Connections: WTICT (15, 16). NCT (18, 19, 20). LV R-Ph CT (21, 22, 23), LV Y-Ph CT (24, 25, 26), LV B-Ph CT (27, 28, 29). 15-2WS7, 16-2WS8 17-2WS9

18-2S1, 2S2 19- 2S3, 2S4 20- 2S5, 2S6 21- 2US1, 2US2 22- 2US3, 2US4 23- 2US5, 2US6

24- 2VS1, 2VS2 25- 2VS3, 2VS4 26- 2VS5, 2VS6 27- 2WS1, 2WS2 28- 2WS3, 2WS4 29- 2WS5, 2WS6


Page 48


Instruments used

:

Sl. no Description

Specification

1

AVΩ Meter

2

Multimeter

3

Connecting wires

Circuit diagram

Motwane Digital Multimeter DM3540A, Motwane ---------------------------------------------

Quantity

Remarks

1 1 APR

:

N.B: Part I and II refers to connections of different experiment. Figure 8 Measurement of Transformer winding resistance


Page 49


Procedure

:

1. Disconnect the earth terminal from the neutral point. 2. Position the tap at 01. 3. Connect a wire to the R-phase (incoming) whose end will be connected to +ive supply and connect a wire from the other end and connect it to voltmeter. 4. Connect a wire to the Y-phase (incoming) whose end will be connected to -ive supply and connect a wire from the other end and connect it to voltmeter. 5. Connect an ammeter to the negative wire. 6. Switch on the power supply and note down the readings on voltmeter and ammeter. 7. Calculate the resistance from the values observed. 8. Increase the tap to next level and repeat step 1 to7. 9. Repeat the above step for Y-B and B-R phases. 10. For LV side repeat the above step for R-N, Y-N, B-N and B-Y, however here we need not change the tapings. Just position at the normal tap. 11. To find the winding resistance of CT connect ohmmeter across respective terminals i.e. 15,16,17,18,19,20,21,22,23,24,24,25,26,27,28 and 29 in our case. 12. Record the reading. Result : Transformer 1, Sl. No. 21067/1 Date: 3/11/09, 11:00am, Sunny. Tap Position 01 02 03 04 05 06 07 08 09b 10 11 12 13 14 15 16 17

R-Y Phase Current Voltage (A) (V) 4.40 4.00 4.48 3.98 4.42 3.96 4.42 3.91 4.50 3.88 4.50 3.88 4.52 3.85 4.59 3.82 4.60 3.79 4.69 3.78 4.70 3.77 4.79 3.75 4.80 3.72 4.85 3.70 4.90 3.68 4.95 3.65 5.00 3.62

Resistance (mΩ) 909.09 888.39 895.93 884.62 862.22 862.22 851.77 832.24 823.91 805.97 802.13 782.88 775.00 762.89 751.02 737.37 724.00

Tap Position 17 16 15 14 13 12 11 10 09b 08 07 06 05 04 03 02 01

Y-B Phase Current Voltage (A) (V) 4.90 3.57 4.81 3.59 4.79 3.61 4.71 3.63 4.68 3.65 4.61 3.68 4.60 3.71 4.52 3.73 4.50 3.74 4.49 3.77 4.41 3.79 4.40 3.82 4.38 3.84 4.31 3.86 4.29 3.88 4.22 3.90 4.20 3.92

Resistance (mΩ) 728.57 746.36 753.65 770.70 779.91 798.26 806.52 825.22 831.11 839.64 859.41 868.18 876.71 895.59 904.43 924.17 933.33


Page 50


Tap Position 01 02 03 04 05 06 07 08 09b 10 11 12 13 14 15 16 17

TB No. 18 19 20 TB No. 21 22 23 24 25 26 27 28 29

Transformer 1, Sl. No. 21067/1 Date: 3/11/09, 11:00am, Sunny. B-R Phase LV Side Tap # 9 Current Voltage Resistance Current Voltage Resistance Phase (A) (V) (mΩ) (A) (V) (mΩ) 4.42 3.80 859.73 R-N 3.59 0.2794 77.83 4.49 3.79 844.10 4.53 3.78 834.44 Y-N 7.30 0.5730 78.49 4.49 3.77 839.64 4.61 3.75 813.45 B-N 7.30 0.5730 78.49 4.69 3.73 795.31 4.71 3.71 787.69 B-Y 6.40 0.9960 155.63 4.78 3.69 771.97 4.80 3.66 762.50 4.84 3.65 754.13 4.89 3.64 744.38 4.93 3.62 734.28 In LV side, the Line resistance is double to that of 4.99 3.60 721.44 Phase Resistance. 5.01 3.57 712.57 5.06 3.55 701.58 5.12 3.52 687.50 5.19 3.49 672.45 Transformer 1, Sl. No. 21067/1. WTICT Neutral CT (NCT) Wire Code 2S1-2S2

Resistance (Ω)

2S3-2S4 2S5-2S6 LV Phase CTs Wire Code Resistance (Ω) 2US1-2US2 2US3-2US4 2US5-2US6 2VS1-2VS2 2VS3-2VS4 2VS5-2VS6 2WS1-2WS2 2WS3-2WS4 2WS5-2WS6

TB No. 15 16 16 17 15 17

Wire Code Resistance (Ω) 2WS7 2WS8 2WS8 2WS9 2WS7 2WS9

For WTICT we have to do with pair of wires alternatively.


Page 51


Transformer 2, Sl. No. 21067/2 Date: 4/11/09, 12:40pm, Sunny. Tap Position 01 02 03 04 05 06 07 08 09b 10 11 12 13 14 15 16 17

Tap Position 01 02 03 04 05 06 07 08 09b 10 11 12 13 14 15 16 17

R-Y Phase Current Voltage (A) (V) 3.62 3.150 3.68 3.130 3.70 3.110 3.62 3.090 3.76 3.060 3.79 3.037 3.80 3.018 3.85 2.998 3.90 2.977 3.95 2.974 3.99 2.952 4.00 2.930 4.01 2.905 4.05 2.880 4.10 2.850 4.12 2.030 4.19 2.000

Y-B Phase Resistance Tap Current Voltage Resistance (mΩ) Position (A) (V) (mΩ) 870.17 01 3.63 3.175 874.66 3.69 3.150 850.54 02 853.66 840.54 03 3.70 3.130 845.95 853.59 04 3.71 3.110 838.27 813.83 05 3.74 3.090 826.20 3.79 3.070 801.32 06 810.03 794.21 07 3.80 3.050 802.63 3.81 3.030 778.70 08 795.28 763.33 09b 3.84 3.000 781.25 752.91 10 3.89 2.990 768.64 739.85 11 3.90 2.960 758.97 3.92 2.940 732.50 12 750.00 724.44 13 3.97 2.915 734.26 3.99 2.892 711.11 14 724.81 695.12 15 4.00 2.869 717.25 4.02 2.844 492.72 16 707.46 4.09 2.813 477.33 17 687.78 Transformer 2, Sl. No. 21067/2 Date: 4/11/09, 12:00am, Sunny. B-R Phase LV Side Tap # 9 Current Voltage Resistance Current Voltage Resistance Phase (A) (V) (mΩ) (A) (V) (mΩ) 3.58 3.190 891.06 R-N 4.32 0.352 81.48 3.60 3.170 880.56 3.62 3.140 867.40 Y-N 4.35 0.353 81.15 3.68 3.110 845.11 3.70 3.110 840.54 B-N 4.32 0.354 81.94 3.78 3.060 809.52 3.79 3.040 802.11 B-Y 4.00 0.644 161.00 3.81 3.008 789.50 3.80 3.004 790.53 3.81 2.982 782.68 3.85 2.957 768.05 3.89 2.934 754.24 In LV side, the Line resistance is double to that of 3.90 2.905 744.87 Phase Resistance. 3.94 2.877 730.20 3.98 2.852 716.58 4.00 2.822 705.50 4.02 2.794 695.02


Page 52


Transformer 2, Sl. No. 21067/2. Neutral CT (NCT) Wire Code Resistance (Ω) 2S1-2S2 2.6 2S3-2S4 2.4 2S5-2S6 2.6 LV Phase CTs Wire Code Resistance (Ω) 2US1-2US2 3.5 2US3-2US4 2.3 2US5-2US6 2.6 2VS1-2VS2 2.4 2VS3-2VS4 2.5 2VS5-2VS6 2.8 2WS1-2WS2 1.2 2WS3-2WS4 2.4 2WS5-2WS6 2.4

TB No. 18 19 20 TB No. 21 22 23 24 25 26 27 28 29

WTICT TB No. 15 16 16 17 15 17

Wire Code Resistance (Ω) 2WS7 2.6 2WS8 2WS8 1.7 2WS9 2WS7 1.9 2WS9

For WTICT we have to do with pair of wires alternatively.

Precautions : • • •

Safety of experimenter the first priority. Always adjust the DC voltage level as per the ranges of the meters used. Avoid parallax error.

Conclusion

:

From this field test, the winding resistances of CTs are below 1.5Ω. As indicated on the name plate rating. The winding resistance of NCT, LV Phase CTs and WTICT are permissibly correct.


Page 53

Transformer Testing

Transformer Testing (IR Check, Ratio Check, Magnetizing Balance Check, Magnetizing Current Check, Vector Group Check) Aim 1. 2. 3. 4. 5.

: To check the 'Insulation Resistance' of the Transformer. To check the 'Ratio of HV-LV winding'. To check the 'Magnetizing Balance' or 'Core Balance'. To check the 'Magnetizing Current'. To check the 'Vector Group'.

Objectives

:

¾ To find out the insulation resistance between HV-Earth, LV-Earth and HV-LV terminals and to ensure there is no leakage to earth i.e. continuity check. ¾ To ensure that the turns ratio for each tapping is in accordance to the name plate rating. ¾ To ensure that the magnetic balance is not disturbed. ¾ To observe the no load magnetizing current. ¾ To ensure the vector group DYN 11. Theory

:

I.

Insulation Resistance Test Insulation resistance of a two-winding transformer insulation system, HV to ground, LV to ground, and HV to LV is determined with a Megger type of instrument. Historically, insulation resistance measurements are also made to assess the amount of moisture in transformer insulation. However, the measurement of insulation dissipation factor has shown to be a better indicator of the overall condition of insulation in a power transformer.

II.

Ratio Test The purpose of this test is to ensure that all windings have the correct number of turns according to the design. Since the transformer is equipped with a load tap changer (LTC), ratio tests is also carried out at the various positions of the tap changer(s). The objective of ratio tests at different tap positions is to ensure that all winding taps are made at the correct turns and that the tap connections are properly made to the tap changing devices. ANSI/IEEE general standard [1] requires that the measured voltage ratio between any two windings be within ± 0.5% of the value indicated on the nameplate. To verify this requirement, ratio tests are performed in which the actual voltage ratio is determined through measurements. Ratio tests can be made by energizing the transformer with a low AC test voltage and measuring the voltage induced in other windings at various tap settings, etc. In each case the voltage ratio is calculated and compared to the voltage ratio


Page 54

Transformer Testing

indicated on the transformer's nameplate. More commonly, Transformer Turns Ratio (TTR) test sets are used for making the tests. III.

Magnetizing Balance Test This test is performed to ensure that the HV and LV windings are not displaced from its original 120º displacement from respective phases.

In this, two phase supply is applied to one of the winding and the induced voltages on the other two windings are measured. The voltage applied on the windings should be the sum of the voltage induced on other two windings. If the phase displacements are correct then the flux distribution on each winding will also be proportionate i.e. upon repeating the applied voltage to other phases too, the sum of induced voltages should be equal to the applied voltage. In the readings one will see the maximum value being in the diagonal. In case of LV side which is star connected, magnetic balance test ensures that the windings are not displaced with respect to the neutral point. If windings are displaced from each other then we say neutral is displaced, which means some currents are flowing in the neutral point (Earth Fault). By KCL, current flowing in the neutral point should be zero at balanced condition however practically it is not true. Therefore in order to satisfy this condition neutral point is grounded so that any current flowing through neutral point goes to earth. Here too the diagonal characteristic is observed. IV.

Magnetizing Current Check This test ensures that the magnetizing current under no load condition doesn’t exceed 4% of the rated current. When voltage is applied to the exciting or primary winding of the transformer, a magnetizing current flows in the primary winding which produces the flux in the core. The flow of flux in magnetic circuits is analogous to the flow of current in electrical circuits. The magnetizing current is required to magnetize the winding and the core.


Page 55

Transformer Testing

Magnetizing Current

V.

Vector Group Check This test is from the design point of consideration and is required to check the vector group indicated on the name plate of the transformer. There are various vector groups and in our case the transformer is Dy11. Some of the typical examples are as follows.

The vector diagram for Dy11 is shown below.

30° Lag or +30°

Here, RYB forma an equilateral triangle. R-b=R-y, Y-b=Y-y, R-Y=R-N+Y-N, B-y is the shoot point.

Dy11

This confirms the Dy11 vector group test.


Page 56

Transformer Testing

Instrument required : Sl. no

Description

1

Motorized Megger

2

Multimeter

3

Clamp Leaker

Specification 5KV, 0-10000MΩ, Sl. no. 850302, WACO Digital Multimeter DM3540A, Motwane DC-10A, Motwane

4

Testing Board

MCB C16 attached, handmade

5

Connecting wires

2.5 sq.mm

6

Transformer

Sl. no 21067/1, 20MVA

1

7

3-Ф Supply

415V, 50Hz

1

8

AVΩ Meter

AC/DC Range

1

9

Screw Driver

-type

1

Circuit diagram

Quantity

Remarks

1 1 1 1

See picture

APR

:

Figure 9 Various testing on Transformer


Page 57

Transformer Testing

Procedure I.

:

Insulation Resistance Check a. Connect wires from HV, LV and Earth terminals. b. Use 5KV Motorized Megger with external power supply. c. Connect HV and Earth terminals to the Megger. Switch on the power supply and note down the readings indicated on the Megger at 15th and 60th seconds. d. Switch off the Megger and discharge the current in the lines used by shorting the terminals to avoid risk of shock. e. Connect LV and Earth terminals to the Megger. Switch on the power supply and note down the readings indicated on the Megger at 15th and 60th seconds. f. Repeat step d. g. Connect HV and LV terminals to the Megger. Switch on the power supply and note down the readings indicated on the Megger at 15th and 60th seconds. h. Repeat step d. i. Calculate R15/R60 and then tabulate the readings.

II.

Ratio Test a. Connect the circuit diagram as in the figure above. b. Disconnect the neutral from Earth terminal. c. Apply 3-Ф power from nearby BMK to the connection board. d. Since the transformer has 17 taps, begin one by one. e. Positioning the tap at 01, check the voltage at HV side, LV side (line as well as phase voltage) and note down the readings. f. Increase the tap to next level and then repeat step 'e'. g. Repeat step 'f' till the highest tap. h. Tabulate the readings for further analysis.

III.

Magnetizing Balance Check (Core Balance), Tap # 9b. a. The experiment continues from above tests. b. Make sure that the table for recording data is made sequentially. c. Switch on the power supply and always work offline. d. Remove the HV B-phase out and then measure the voltage on HV lines and LV side (Line as well as phase voltages). e. Remove the HV R-phase out and then measure the voltage on HV lines and LV side (Line as well as phase voltages). f. Remove the HV Y-phase out and then measure the voltage on HV lines and LV side (Line as well as phase voltages). Switch off the power supply. g. Record the data sequentially and correctly. h. Observe the characteristic of the readings on the table.


Page 58

Transformer Testing

IV.

V.

Magnetizing Current Check (No load current), Tap # 9b. a. Reconnect every connection as shown in the circuit diagram. b. Switch on the power supply but while changing the connections switch it off. c. Disconnect the R-phase on HV side and then measure the current on R-phase itself. Record the voltage on R-Y phase too. Use Clamp leaker. d. Reconnect R-phase and disconnect the Y-phase on HV side. Measure the current on Y-phase itself. Record the voltage on Y-B phase too. Use Clamp leaker. e. Reconnect Y-phase and disconnect the B-phase on HV side. Measure the current on B-phase itself. Record the voltage on Y-B phase too. Use Clamp leaker. f. Disconnect HV side and give the supply to LV terminals. g. Use clamp leaker to measure the current in the lines. h. Disconnect the r-phase on LV side and then measure the current on r-phase itself. Record the voltage on r-y phase too. i. Reconnect r-phase and disconnect the y-phase on LV side. Measure the current on y-phase itself. Record the voltage on y-b phase too. j. Reconnect y-phase and disconnect the b-phase on LV side. Measure the current on b-phase itself. Record the voltage on b-r phase too. k. Observe the readings very carefully such that the magnetizing current is not less than 4% of the actual rated current in both the cases. Vector Group Check, Tap # 9b. a. Reconnect every connection as shown in the circuit diagram. b. Here we need to check the name plate rating. The vector Group is Dy11 so we need to prove this. Refer the vector diagram given in theory. c. Short the R-phase of HV and LV terminals. d. Apply voltage on HV side. e. Check the voltage R-Y, Y-B, B-R, R-n, Y-n, R-b, R-y, Y-b, Y-y, B-b and B-y terminals. f. Check if the results are matching with that given in theory.

Precautions : 1. Safety of experimenter the first priority. 2. While Meggering, always discharge the current to avoid shock. 3. Always switch off the power supply when connecting the circuit to avoid spark. Insulation Resistance Values of Power Transformers (MΩ) Class Winding Temperatures °C 33-132KV 20°C 30°C 40°C 50°C 60°C 70°C R15 450 300 200 140 60 40 R60 900 600 400 280 120 50 R60-Value of IR at 60sec & R15 at 15 sec. after the application of test voltage of Megger Courtesy: Installation, commissioning and maintenance of electrical equipment, Tarlok Singh


Page 59

Transformer Testing

Result

: TRANSFORMER # 1, Sl. no 21067/1

Transformer Testing, Sl. No. 21067/1 Date : 30/10/2009, 12:00pm, Sunny. Insulation Resistance (IR) Check by 5KV Motorized Megger (MΩ) Terminals IR-R60 IR-R15 R15/R60 HV-Earth 10000+∞ 10000 1 HV-LV 10000+∞ 5000 0.5 LV-Earth 10000+∞ 8000 0.8 Transformer Testing, Sl. No. 21067/1 Magnetizing Balance Check (Tap #9) or Core Balance Ф-out R-Y(V) Y-B(V) B-R(V) r-y(V) y-b(V) b-r(V) r-n(V) y-n(V) b-n(V) B 416.0 318.0 98.3 213.5 65.4 148.1 120.0 93.1 28.5 R 216.7 417.0 201.6 184.5 180.1 10.19 62.5 121.3 59.9 Y 81.4 335.4 416.0 78.4 219.6 145.2 23.96 97.3 121.4 Transformer Testing, Sl. No. 21067/1 Magnetizing Current Check (Tap # 9) or No Load Current HV Side LV Side Applied Applied Ф-out Current (mA) Ф-out Current (mA) Voltage(V) Voltage (V) r-y 417.0 r-ph 9.63 R R-Y 417.0 R-ph 3.50 r y-b 415.0 y-ph 6.30 Y Y-B 415.0 Y-ph 2.46 y B B-R 416.0 B-ph 2.49 b-r 416.0 b-ph 9.82 b Transformer Testing, Sl. No. 21067/1 Vector Group Check (Tap # 9), Dy11 Terminals Voltage(V) R-Y 416.0 Y-B 417.0 B-R 417.0 R-N 121.8 Y-N 300.0 R-b=R-y, B-b 261.0 Y-b=Y-y, B-y 475.0 R-Y=R-N+Y-N, R-b 208.2 B-y is the shoot point. Dy11 R-y 208.5 These conditions are found correct. Y-b 259.4 Y-y 259.4


Page 60

Ratio Test of Transformer

Ratio Test of Transformer # 1, Sl. no 21067/1 Tap

HV (∆) Side (Volts)

LV (Star) Side (Volts)

Actual Ratio

Ratio Rph Yph Bph

VRY

VYB

VBR

v ry

v yb

v br

v rn

v yn

v bn

HV/LV

01

415

415

415

189.6

191.9

189.3

109.4

110.1

110.3

2.20

2.19

2.16

02

413

416

416

190.8

193.3

191.2

110.6

111.2

111.4

2.18

2.16

03

415

415

416

193.3

194.6

193.6

111.9

112.6

112.8

2.15

04

413

417

415

195.3

197.3

196.9

113.4

114.0

114.2

05

415

416

415

198.1

199.5

198.2

114.8

115.4

06

417

415

416

200.3

201.3

200.4

116.1

07

415

416

417

202.9

204.5

203.4

08

415

416

417

205.7

206.6

9b

414

415

416

208.0

10

417

417

418

11

418

416

12

414

13

% Error Rph

Yph

Bph

2.19

-0.45%

-1.82%

-0.45%

2.15

2.18

-0.92%

-1.38%

0.00%

2.15

2.13

2.15

0.00%

-0.93%

0.00%

2.13

2.11

2.11

2.11

-0.94%

-0.94%

-0.94%

115.6

2.10

2.09

2.09

2.09

-0.48%

-0.48%

-0.48%

116.9

116.9

2.08

2.08

2.06

2.08

-0.00%

-0.96%

0.00%

117.7

118.3

118.3

2.05

2.05

2.03

2.05

-0.00%

-0.98%

0.00%

206.2

119.5

119.6

119.9

2.03

2.02

2.01

2.02

-0.49%

-0.99%

-0.49%

209.2

208.5

120.6

121.2

121.3

2.00

1.99

1.98

2.00

-0.50%

-1.00%

0.00%

210.0

212.3

211.5

122.0

122.5

122.3

1.98

1.99

1.96

1.98

+0.51%

-1.01%

0.00%

417

213.2

215.0

214.3

123.6

124.4

124.5

1.95

1.96

1.93

1.95

+0.51%

-1.03%

0.00%

416

418

215.7

217.3

216.8

125.3

125.5

126.2

1.93

1.92

1.91

1.93

-0.52%

-1.04%

0.00%

414

415

416

218.9

220.3

219.7

126.9

127.4

127.7

1.90

1.89

1.88

1.89

-0.53%

-1.05%

-0.53%

14

417

417

416

221.9

223.3

222.7

129.0

129.2

129.5

1.88

1.88

1.87

1.87

0.00%

-0.53%

-0.53%

15

414

416

417

225.0

227.6

226.0

130.9

131.0

131.40

1.85

1.84

1.83

1.85

-0.54%

-1.08%

0.00%

16

415

416

417

228.4

230.9

228.4

132.7

133.2

133.6

1.83

1.82

1.80

1.83

-0.55%

-1.64%

0.00%

17

414

415

416

232.1

233.6

232.7

134.5

134.8

135.2

1.80

1.78

1.78

1.79

-1.11%

-1.11%

-0.56%


Page 61

Transformer Testing

TRANSFORMER # 2, SL. No. 21067/2 Transformer Testing, Sl. No. 21067/2 Date : 4/11/2009, 10:00am, Sunny. Insulation Resistance (IR) Check by 5KV Motorized Megger (MΩ) Terminals IR-R60 IR-R15 R15/R60 HV-Earth 6000 10000 1.67 HV-LV 5000 10000 2.00 LV-Earth 9000 10000 1.11 Transformer Testing, Sl. No. 21067/2 Magnetizing Balance Check (Tap #9) or Core Balance Ф-out R-Y(V) Y-B(V) B-R(V) r-y(V) y-b(V) b-r(V) r-n(V) y-n(V) b-n(V) B 421.0 349.0 72.60 223.3 81.6 142.0 121.7 101.7 21.03 R 209.0 422.0 213.1 182.5 183.4 477 60.0 121.8 61.40 Y 60.20 356.0 421 85.8 223.9 138.5 17.78 103.2 120.8 Transformer Testing, Sl. No. 21067/2 Magnetizing Current Check (Tap # 9) or No Load Current HV Side LV Side Applied Applied Ф-out Current (mA) Ф-out Current (mA) Voltage(V) Voltage(V) r-y 422.0 r-ph 11.0 R R-Y 422.0 R-ph 3.90 r y-b 421.0 y-ph 6.50 Y Y-B 423.0 Y-ph 2.00 y B B-R 423.0 B-ph 2.20 b-r 423.0 b-ph 11.0 b Transformer Testing, Sl. No. 21067/1 Vector Group Check (Tap # 9), Dy11 Terminals Voltage(V) R-Y 420.0 Y-B 421.0 B-R 423.0 R-N 122.10 Y-N 299.0 R-b=R-y, B-y 475.0 Y-b=Y-y, R-Y=R-N+Y-N, R-b 210.5 B-y is the shoot point. R-y 211.4 Dy11 These conditions are found correct. Y-b 261.6 Y-y 261.3


Page 62

Ratio Test of Transformer

Ratio Test of Transformer # 2, Sl. no 21067/2 Tap

HV (∆) Side (Volts)

LV (Star) Side (Volts)

Actual Ratio

Ratio Rph Yph Bph

VRY

VYB

VBR

v ry

v yb

v br

v rn

v yn

v bn

HV/LV

01

422

421

422

191.6

190.9

191.0

110.9

111.3

110.7

2.20

2.20

2.21

02

421

423

423

194.1

193.6

193.4

112.2

112.5

112.0

2.18

2.17

03

425

422

422

196.7

195.5

195.6

113.5

113.7

112.5

2.15

04

423

427

423

198.9

198.4

198.3

114.8

115.0

113.6

05

424

421

422

201.2

200.4

200.3

116.1

116.2

06

421

423

422

203.5

202.3

201.6

117.4

07

422

423

420

206.1

205.3

205.3

08

422

422

421

208.3

207.4

9b

422

422

421

210.6

10

423

421

422

11

421

422

12

422

13

% Error Rph

Yph

Bph

2.21

+0.11%

+0.24%

+0.43%

2.18

2.19

-0.51%

+0.23%

+0.33%

2.16

2.16

2.16

+0.50%

+0.40%

+0.35%

2.13

2.13

2.15

2.13

-0.16%

+1.04%

+0.15%

115.9

2.10

2.11

2.10

2.11

+0.35%

+0.04%

+0.33%

117.8

117.3

2.08

2.07

2.09

2.09

-0.54%

+0.53%

+0.64%

118.9

119.2

118.5

2.05

2.05

2.06

2.05

-0.12%

+0.51%

-0.21%

207.3

120.1

120.4

119.9

2.03

2.03

2.03

2.03

-0.20%

+0.23%

+0.04%

210.1

209.9

121.6

121.8

121.4

2.00

2.00

2.01

2.01

+0.19%

+0.43%

+0.29%

213.2

212.6

212.8

123.3

123.4

123.1

1.98

1.98

1.98

1.98

+0.20%

+0.01%

+0.16%

422

216.2

215.3

215.6

124.9

125.0

124.7

1.95

1.95

1.96

1.96

-0.14%

+0.52%

+0.38%

422

421

219.1

218.2

218.4

126.6

126.7

126.2

1.93

1.93

1.93

1.93

-0.20%

+0.21%

-0.12%

422

422

422

222.2

220.6

220.3

128.3

128.4

128.0

1.90

1.90

1.91

1.92

-0.04%

+0.68%

+0.82%

14

421

423

422

225.0

224.1

223.4

130.0

130.1

129.7

1.88

1.87

1.89

1.89

-0.47%

+0.40%

+0.48%

15

422

422

421

228.4

227.1

227.5

131.9

132.0

131.5

1.85

1.85

1.86

1.85

-0.13%

+0.44%

+0.03%

16

422

422

419

231.7

230.5

230.4

133.6

133.7

133.3

1.83

1.82

1.83

1.82

-0.47%

+0.04%

-0.62%

17

423

422

422

219.1

233.7

234.1

135.5

135.6

135.0

1.80

1.93

1.81

1.80

+7.26%

+0.32%

+0.15%


Page 63

Transformer Testing

Result: • • • •

•

The field testing of the ratio of HV/LV at various tapings is found correct with slight errors. The phase voltage of secondary is also found to be 1/√3 times that of line voltage. The actual ratio at normal tap is 2 i.e. 66/33KV. It is observed in the magnetizing balance check that the maximum voltage exists across the diagonal element for HV and LV phase voltage. NB: If the diagonal characteristics holds true for the phase voltages at LV side then it is true for HV side. Further Vector Group check will also hold true. The vector group check for Dy11 also proved the equations or the vector characteristic given.

Conclusion: From the above field test it is proved that the results obtained are tallying with the name plate ratings. Ratios at various taps are correct with some errors. The windings at the core are also balanced at 120° from each other. The magnetizing current as observed during the field test is far below 4% of the actual rated current. No load current should not exceed above 4% of the actual rated current. It is observed that in the Y phase the current is comparatively less. The reason being, the Y phase winding lies at the middle so the flux gets distributed equally to other windings too thereby resulting in low currents. Whereas in other case very less flux gets to the third winding (see the fig. below). The vector group is found to be Dy11. There are a total of about 63 vector group, some of which are given at the theory portion.


Page 64

Dehydration, Filtration and Testing of Transformer Oil

Transformer Oil Testing Aim

: Dehydration & filtration of Transformer oil in the Transformer.

Objective

:

1. To remove the moisture present in the core, windings, tank, radiator and the conservator tank. 2. To check the insulation resistance (IR Value) of the Transformer using Megger and observe the reading. 3. Check the Breakdown Voltage value (BDV) of the dehydrated oil. Theory : After the erection of Transformer at site, dehydration and filtration of oil is very important. Here 'Transformer Oil Conditioning Machine' is used. There are two outlets in this machine; one is used as incoming oil source and the other acts as outgoing source. After connecting one pipe to the transformer tank and the other to the oil barrel start the machine and fill the transformer with oil. Don’t fill it fully; as transformer oil gets heated its volume expands. Now connect both pipes to transformer where one draws oil from the transformer and the other pumps in the dehydrated oil coming from the Transformer oil conditioning machine. There are moistures present in core and windings. When the oil is heated, by virtue of core and windings being immersed in the oil, it gets heated. As a result of this the moisture present, in the core and windings vaporize out and gets mixed with the oil. This oil is then passed into the oil conditioning machine. The oil passes through 'degassing chamber' in two stages where the oil is set to flow in the form of fountain. When this process happens the moisture is sent out from the oil which is then sucked by the vacuum pump. The oil further passes through heater and filter vessel where the oil gets heated and gets filtered of carbon deposits, dirt, sludge, etc. particles. The oil is again pumped in the transformer. It heats the core and the process continues. During the process of Transformer Oil Conditioning, check the IR value of the transformer every after one hour. Theoretically the Megger value should come down and then rise up until it attains a stable value. When it attains stable value for multiple Meggering then it shows that the oil is dehydrated. Then collect sample oil for BDV test. The BDV value shouldn’t come below 60KV. While Meggering we go with checking the insulation resistance value of primary-earth, secondary-earth and primary-secondary winding (see fig. 1). The theory behind is as follows; Primary-Earth : Basically we are observing the change in the characteristics of the insulation resistance between primary winding and the earth. The IR value of primary to earth will be high before conditioning. When the conditioning of the oil is started the moisture gets removed and the value comes down. Upon further conditioning the IR value will go up indicating that there is no conduction path from primary to earth. Secondary-Earth : Here we are checking the insulation resistance between secondary winding and the earth terminal. The same characteristic should be observed as described above.


Page 65


Primary-Secondary : The insulation resistance of primary-secondary is observed. Upon heating, dehydrating and filtering, the IR value should come down and the rise up until it attains a stable value. Thus moisture is indicated, vaporized and removed out.

IR Value Pry-Earth IR Value Pry-Sec

IR Value Sec-Earth

Fig. 1

IR Value

Sample Graph

0

Time


Page 66


Instruments used: Sl. no 1

Description Transformer oil conditioning machine

2

Multimeter

3

Motorized Megger

4

Connecting wires

Specification Sl. no. 1043421, Supply 415V, 165.2KW, 238Amperes. Digital Multimeter DM3540A, Motwane 5KV, 0-10000MΩ, Sl. no. 850302, WACO 2.5 sq.mm

Quantity

Remarks

1 Set 1 1 APR

Circuit diagram Transformer Oil Conditioning Machine

HV

LV

Earth

Motorized Megger

Internal diagram

Figure 10 Conditioning of Transformer Oil


Page 67


Procedure

:

PART I 1. Connect the pipes at respective inlet and outlet of the Transformer oil conditioning machine. 2. Connect the other end to the oil drum and the inlet to the 'Top Oil Filter Valve' of the transformer tank. 3. Start the machine and fill up the transformer to certain level but not fully so that when at peak temperature of the oil the volume expanded will not overflow the oil from the transformer. 4. When heating the oil, please observe the source load and the load that the one heater absorbs. (In our case the source load was 130A whereas each heater consumes 80A. There are three heaters, so we were bound to switch on only one heater.) 5. Now for dehydration and filtration, connect the pipe connecting the oil drum to the 'Bottom Oil Filter Valve' of the transformer tank. 6. Start the machine with one heater being switched on. 7. Disconnect the earth terminal from the neutral point. Start Meggering with HV-Earth, LV-Earth and HV-LV and record the reading every one hour until the readings comes down and rise up to attain a stable value. N.B The process may go on for two to three days. Then put off the heater and cool the oil with machine under running condition. 8. Take the oil sample (two bottles) for Breakdown Voltage test. The average of six readings obtained should be above 60KV. This ends the dehydration and filtration test. PART II (BDV Test) 1. 2. 3. 4. 5. 6.

Arrange the BDV testing kit (Automatic Oil Test Set OTS100AF/Megger) Wash the oil container thoroughly with oil form one bottle. Pour the oil sample from other bottle and place it in the testing kit. Adjust the space between the electrodes to 2.5mm. Keep it idle for 15minutes so that the oil sample settles down. Set the standard to IEC 156 1995 and then press the button to apply voltage.

Precaution

:

¾ Safety of the experimenter the first priority. ¾ Make sure not to fill the transformer tank fully so that the oil will not overflow when heated at peak temperature. ¾ Drying of a transformer must be done under continuous and competent supervision. ¾ Careful observation of temperature is essential during drying as high temperature can result in damage to the insulation. ¾ No sparks or smoking should be allowed in the vicinity of a transformer being dried.


Page 68


Results

: Dehydration and Filtration of Transformer Oil Transformer #1, 20MVA, 66/33KV, Sl. no. 21067/1.

27/10/2009

26/10/2009

Date

IR by 5KV Motorized Motor (MΩ)

Temperature (ºC)

Time

HV-Earth

LV-Earth

HV-LV

Machine oil

OTI

WTI

11:56am 1:25pm

10000 10000

10000 10000

8000 10000

35 38

34 38

31 38

2:30pm

10000

10000

10000

42

39

40

3:30pm

10000

10000

10000

51

46

45

5:18pm

10000

10000

10000

52

48

47

6:20pm

10000

10000

10000

56

51

50

7:25pm

10000

10000

10000

60

54

52

10:30pm

8000

8000

8000

60

56

54

12:30am 2:35am

8000 7000

8000 7000

8000 7000

60 60

57 57

55 55

4:30am

7000

7000

7000

60

57

55

6:30am

7000

7000

7000

60

57

55

8:30am

7000

7000

7000

60

57

55

9:30am

7000

8000

9000

60

58

58

10:30am

8000

10000

10000

60

59

59

11:30am

9000

10000

10000

60

59

59

12:30am

7000

9000

10000

60

59

59

1:30pm

7000

9000

10000

60

60

60

2:30pm

7000

9000

10000

60

60

60

3:30pm

8000

10000

10000

60

60

60

4:30pm

8000

10000

10000

60

60

60

5:30pm

8000

10000

10000

60

59

60

6:30pm

8000

10000

10000

60

59

60

7:30pm

8000

10000

10000

60

59

60

8:30pm

8000

10000

10000

60

59

60

9:30pm

8000

10000

10000

60

59

60

10:30pm

8000

10000

10000

60

59

60

11:30pm

8000

10000

10000

60

59

60


Remarks

With the help of thermostat the maximum temperature was fixed at 60˚C. 4:20pm, interruption, oil overflow from breather. 5:12pm, Machine started after draining the oil.

Date/Time

Page 69


Time

HV-Earth

LV-Earth

HV-LV

Machine oil

OTI

WTI

12:30am 1:30am 2:30am 3:30am 4:30am 5:30am 6:30am 7:30am 8:30am 9:30am 10:30am 11:30am 12:30pm 2:30pm 3:30pm 4:30pm 5:30pm 6:30pm

8000 8000 8000 8000 8000 8000 8000 8000 8000 8000 8000 8000 8000 10000 10000 10000 10000 10000

10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000

10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000

60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60

59 59 59 59 59 59 59 59 59 59 59 59 59 56 55 54 54 52

60 60 60 60 60 60 60 60 60 60 59 59 59 56 56 56 55 54

Remarks

1:30pm, interruption, Supply went off. 2:10pm, Machine started.

Date

28/10/2009

Date/Time

Dehydration and Filtration of Transformer Oil Transformer #1, 20MVA, 66/33KV, Sl. no. 21067/1. IR by 5KV Motorized Motor Temperature (ºC) (MΩ)

Radiator 1 2 3 4 5 6 7 8 9 10

Open (Time) 10:15am 11:00am 12:30pm 1:30pm 2:40pm 3:10pm 3:40pm 4:10pm 5:10pm 6:10pm

Radiators Close (Time) Remarks 10:50am 11:40am All radiators opened on 28/10/2009 at 1:30pm 6:30pm. Heater switched off and cooling 2:40pm of the oil started with machine under 3:10pm running condition. Machine stopped at 29/10/2009 at 9:45am. Oil sample taken 3:40pm for BDV Test at SMD, Semtokha. 4:10pm OLTC Filtration started at 4:00pm till 4:40pm 6:00pm on 29/10/2009. 5:40pm 6:30pm


Page 70


Breakdown Voltage Test of the Sample Oil Taken from Transformer#1. Date: 29/10/2009, 10:55am at Semtokha. Experimenter: Pema Jampel. Equipment : Automatic Oil Test Set (OTS100AF/Megger) Readings 1st Reading 2nd Reading 3rd Reading 4th Reading 5th reading 6th Reading

Time (Minutes) 5 2 2 2 2 2 Average = 75.2KV

Graphical Analysis

BDV(KV) 84.8 77.4 69.8 58.1 76.7 84.4

:

Transformer Oil Characteristic Curve HV-Earth 12000

10000

IR Value

8000

6000 Transformer Oil Characteristic Curve

4000

2000

6:30pm

3:30pm

11:30am

8:30am

5:30am

2:30am

11:30pm

8:30pm

5:30pm

2:30pm

11:30am

8:30am

2:35am

7:25pm

3:30pm

11:56am

0

Time


Page 71


Transformer Oil Characteristic Curve LV‐Earth 12000

IR Value

10000 8000 6000 4000

Transformer Oil Characteristic Curve LV‐Earth

2000

11:56am 3:30pm 7:25pm 2:35am 8:30am 11:30am 2:30pm 5:30pm 8:30pm 11:30pm 2:30am 5:30am 8:30am 11:30am 3:30pm 6:30pm

0

Time

Transformer Oil Characteristic curve HV-LV 12000 10000

IR Value

8000 6000 TransformerOil Characteristic curve HV-LV

4000 2000

11:56am 3:30pm 7:25pm 2:35am 8:30am 11:30am 2:30pm 5:30pm 8:30pm 11:30pm 2:30am 5:30am 8:30am 11:30am 3:30pm 6:30pm

0

Time


Page 72


Dehydration and Filtration of Transformer Oil Transformer #2, 20MVA, 66/33KV, Sl. no. 21067/2.

1/11/2009

31/10/2009

30/10/2009

Date

IR by 5KV Motorized Motor (MΩ)

Temperature (ºC)

Time

HV-Earth

LV-Earth

HV-LV

Machine oil

OTI

WTI

1:00pm

10000

10000

10000

-

38

38

2:00pm

10000

10000

10000

42

40

42

3:00pm

10000

10000

10000

43

40

42

4:00pm

10000

10000

10000

44

43

44

5:00pm

10000

10000

10000

50

48

49

6:00pm

10000

10000

10000

55

53

54

7:00pm

8000

8000

8000

57

54

55

8:00pm

8000

7000

8000

60

55

56

9:00pm

8000

7000

8000

60

56

57

10:00pm

8000

7000

8000

60

56

57

11:00pm

8000

7000

8000

60

56

57

12:00am

7000

7000

7000

60

56

57

1:00am

7000

7000

7000

60

57

58

2:00am

7000

7000

7000

60

57

58

3:00am

7000

7000

7000

60

57

58

4:00am

7000

7000

7000

60

58

58

5:00am

7000

7000

7000

60

59

59

6:00am

7000

7000

7000

60

60

60

7:00am

6000

7000

7000

60

61

61

8:00am

6000

7000

7000

60

62

62

9:00am

6000

7000

7000

60

62

62

10:00am

6000

7000

7000

60

62

62

11:00am

6000

7000

7000

60

62

62

12:00pm

7000

8000

8000

60

63

63

1:00pm

7000

8000

8000

60

63

63

2:00pm

7000

8000

8000

60

63

63

3:00pm

7000

8000

8000

60

63

63

4:00pm

8000

9000

9000

60

63

63

Remarks

1:00pm, Filtration started with all radiators open. All radiators closed at 3:00pm on 31/10/09.

Date/Time


Page 73


Time

HV-Earth

LV-Earth

HV-LV

Machine oil

OTI

WTI

5:00pm 6:00pm 7:00pm 8:00pm 9:00pm 10:00pm 11:00pm 12:00am 1:00am 2:00am 3:00am 4:00am 5:00am 6:00am 7:00am 8:00am 9:00am 10:00am 11:00am 12:00pm 1:00pm 2:00pm 3:00pm 4:00pm 5:00pm 6:00pm

8000 8000 8000 8000 8000 8000 8000 8000 9000 9000 9000 9000 9000 9000 9000 9000 9000 9000 10000 10000 10000 10000 10000 10000 10000 10000

9000 9000 9000 9000 9000 9000 9000 9000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000

9000 9000 9000 9000 9000 9000 9000 9000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000 10000

60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60

63 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 61 61 61 60 60 55

63 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 62 61 61 61 60 60 55


Remarks

All Radiator s opened at 4:30pm, 2/11/09 for cooling. Machine stopped at 4:00pm, 3/11/09

3/11/2009

2/11/2009

1/11/2009

Date

One pair of Radiators opened and closed after every one hour subsequently. Started at 11:00am till 4:30pm.

Date/Time

Dehydration and Filtration of Transformer Oil Transformer #2, 20MVA, 66/33KV, Sl. no. 21067/2. IR by 5KV Motorized Motor Temperature (ºC) (MΩ)

Page 74


Breakdown Voltage Test of the Sample Oil Taken from Transformer#2. Date: 3/11/2009, 10:45am at Semtokha. Experimenter: Pema Jampel. Equipment : Automatic Oil Test Set (OTS100AF/Megger) Readings 1st Reading 2nd Reading 3rd Reading 4th Reading 5th reading 6th Reading

Time (Minutes) 5 2 2 2 2 2 Average = 77.50KV

BDV(KV) 67.9 71.9 79.8 87.9 72.8 84.7

Transformer Oil Curve HV‐Earth 12000

IR Value (MΩs)

10000

8000

6000

Transformer Oil Curve HV‐Earth

4000

2000

1:00pm 4:00pm 7:00pm 10:00pm 1:00am 4:00am 7:00am 10:00am 1:00pm 4:00pm 7:00pm 10:00pm 1:00am 4:00am 7:00am 10:00am 1:00pm 4:00pm

0

Time


Page 75


Transformer Oil Characteristic Curve LV‐Earth 12000

IR Value (MΩs)

10000 8000 6000 Transformer Oil Characteristic Curve LV‐Earth

4000 2000


0

Time

Transformer Oil Characteristic Curve HV‐LV 12000

IR Value (MΩs)

10000 8000 6000 4000

Transformer Oil Characteristic Curve HV‐LV

2000


0

Time


Page 76


Breakdown values of Transformer Oil with 4mm gap between 13mm diameter spheres. Oil Temp. °C 30 40 50 60 70 BDV KV 35 38 40 45 50 Courtesy: Installation, commissioning and maintenance of electrical equipment, Tarlok Singh. Conclusion

:

From the graphical analysis it shows that the IR value decreases, and rise to a stable value thus indicating that the moisture from the core and the oil is removed. Further the BDV test clearly shows that the breakdown voltage is very good. Therefore dehydration and filtration of transformer oil is completed.


Page 77

Winding Resistance and Ratio Check of CT & PT

Winding Resistance and Ratio Check of 33kv CT & PT Panel 1 CT (Outgoing Feeder) Panel 2 CT (Outgoing Feeder) Panel 3 CT & PT (Outgoing Feeder) Panel 4 CT (Incomer 2) Panel 5 CT (Bus Coupler) Panel 6 Panel 7 CT (Incomer 1) Panel 8 CT (Outgoing Feeder) Panel 9 CT (Outgoing Feeder) Panel 10 CT (Outgoing Feeder) Aim

: 300-150/1-1-1A : 300-150/1-1-1A : 300-150/1-1-1A, 33kV/√3/110/√3. : P1:-400-200/1-1A & P2:-400-200/1-1A, 33kV/√3/110/√3 : 400-200/1-1A : Adapter Feeder has no CT : P1:-400-200/1-1A & P2:-400-200/1-1A, 33kV/√3/110/√3 : 300-150/1-1-1A, 33kV/√3/110/√3 : 300-150/1-1-1A : 300-150/1-1-1A

: Testing of Current and Potential Transformer of 33KV side Panel.

Objectives : • To check the secondary winding resistance of CT and PT • To check the ratio of primary to secondary current of various cores under loaded condition and compare with the name plate rating. • To check the Insulation Resistance value of Potential Transformer. Theory : Current transformer and Potential Transformer are used for metering and protection. The Current Transformer used here have two ratio i.e. 150/1A and 200/1A. Both the incomers have used the ratio of 200/1A while the outgoing feeders have used 150/1A. The reason being, since the LV current of each Transformer is 349.91A each phase will be carrying 116.366A therefore keeping the ratio at 400/1A will mar the accuracy that is why 200/1A have been selected as the CT ratio. There are three outgoing feeder for each Transformer which will be carrying the total current from the Transformer. Here too, at the maximum, each feeder will be able to carry a load of 116.366A therefore we set the CT ratio to 150/1A instead of 300/1A. However there is every possibility that one feeder may be lightly loaded and the other heavily loaded where by the loading may cross over 150A. For this reason the CT ratio 300/1A should also be checked so that it can be put to use in the above mentioned case. The CT of outgoing feeders has three cores of which core 3 is spare core and has been shorted. CT secondary should never be left open. For the same power when current is stepped down from 300 to 1A, the voltage will rise by that many times. Core 1 has been used for metering while core 2 is used for protection. The incomers have four cores. Core 1 is used for metering, Core 2 for protection, Core 3(PS) is used for Restricted Earth Fault Protection and Core 4 is used for differential protection. Incomers have two CT connected in series, each CT containing two cores thereby four cores in total.


Page 78


Instruments Used Sl. no

:

Description

Specification

Quantity

1

Auto Transformer

0-260V, 50Hz

1

2

Loading Transformer

230V,50Hz-7.5KVA, 1V/T

1

3

Multimeter

1

4

Multimeter

1

5

Clamp leaker

AVΩ meter Digital Multimeter DM3540A, Motwane DC-10A, Motwane

6

Clamp meter


1

7

Connecting wires

-----------------------------------------

8

1-Ф Supply

230V, 50Hz

Remarks

1 APR 1

Circuit diagram

P1

1S1

P2

1S3 2S1

2S3

3S1

3S3

Ωm

DMM Pictorial View DMM

PT

Figure 11 Winding Resistance Check of 33kv CT & PT


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CT Ratio Check

R

Y

B

1-Ф Supply

After giving the supply, measure the current in the ammeter wire and the over current protection panel wire with the help of Clamp Leaker.

Figure 12 Ratio Check of 33kv CT

Procedure

:

PART I (Winding Resistance Test) 1. Remove the earth terminal from three phase of PT from the lower side of the box. Make sure there is no connection from the PT to earth. 2. Using the Multi meter as ohmmeter and measure the winding resistance of the respective secondary windings and of respective phases 3. For measuring the winding resistance of CT, connect the multimeter (as ohm meter) terminal to the respective secondary terminals of the Current Transformer. 4. Tabulate the reading and compare with the standard/manufacturer value.


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PART II (Ratio Test) 1. Collect the required instrument for performing the test. 2. Connect the secondary end of the loading transformer to the CT terminals. 3. Connect an Auto transformer (Variac) to provide supply to the loading transformer with varying loading. 4. Connect the Auto Transformer to a single phase supply. 5. Put a Clamp Meter to the wire connecting the CT terminals form the loading transformer. 6. Increase the current in steps of 25%, 50% and 100% of the actual rated current and check the value on the secondary terminals respectively. 7. Repeat step 6, for other ratio too. 8. Repeat step 2-7 for other phases also. Precaution • • • • •

:

Safety the first priority. Never leave the secondary terminal of CT open. Always short it if not in use. Make the connections tight. Always remember the approximate value that should come on secondary. If the value doesn’t tally then check the connections. Take the readings properly and do not manipulate the reading.

Results

:

The results are being tabulated for each current transformer and potential transformer. The actual ratio given on the name plate are 300-150/1-1-1A and 400-200/1-1A. The error limits doesn’t cross over 15%. Therefore the results are correct.


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PT WINDING RESISTANCE Date:15/10/09, Sunday, Sunny. Panel 3, Outgoing Feeder, Type: OG001 (W013), Breaker rating 1250A. Terminal R: 09/34228 (Ω) Y: 09/34224 (Ω) B: 09/34218 (Ω) 1a-1n 0.9 0.9 0.9 2a-2n 0.9 0.8 0.9 Panel 8, Outgoing Feeder, Type: OG001 (W013), Breaker rating 1250A. Terminal R: 09/34220 (Ω) Y: 09/34227 (Ω) B: 09/34229 (Ω) 1a-1n 0.8 0.9 0.8 2a-2n 0.8 0.8 0.9 Panel 7, Incomer 1, Type: IC002 (W003), Breaker rating 1250A. Terminal R: 09/34221 (Ω) Y: 09/34223 (Ω) B: 09/34225 (Ω) 1a-1n 0.9 0.8 0.8 2a-2n 0.8 0.9 0.9 Panel 4, Incomer 2, Type: IC001 (W008), Breaker rating 1250A. Terminal R: 09/34226 (Ω) Y: 09/34219 (Ω) B: 09/34222 (Ω) 1a-1n 0.8 0.7 0.7 2a-2n 0.8 0.8 0.8

CT WINDING RESISTANCE (400-200/1-1A) Panel 4, Incomer 2, Type: IC001 (W008), Breaker rating 1250A, 17/11/09. P2 Terminal R: 09/24606 (Ω) Y: 09/24607 (Ω) B: 09/24609 (Ω) 1S1-1S2 3.6 3.5 3.5 1S1-1S3 6.8 6.6 6.7 2S1-2S2 3.6 3.6 3.7 2S1-2S3 6.7 6.8 6.7 P1 Terminal R: 09/24602 (Ω) Y: 09/24603 (Ω) B: 09/24601 (Ω) 1S1-1S2 3.8 3.8 3.8 1S1-1S3 7.2 7.2 7.2 2S1-2S2 8.3 8.5 8.5 2S1-2S3 16.2 16.8 16.3 Panel 7, Incomer 1, Type: IC002 (W003), Breaker rating 1250A. P2 Terminal R: 09/24611(Ω) Y: 09/24608 (Ω) B: 09/24610 (Ω) 1S1-1S2 3.5 3.5 3.5 1S1-1S3 6.6 6.6 6.5 2S1-2S2 3.6 3.5 3.5 2S1-2S3 6.7 6.7 6.6 P1 Terminal R: 09/24604(Ω) Y: 09/24605 (Ω) B: 09/24597 (Ω) 1S1-1S2 3.8 3.8 3.8 1S1-1S3 7.2 7.2 7.2 2S1-2S2 8.3 8.4 8.5 2S1-2S3 15.8 16.4 16.4


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CT WINDING RESISTANCE (300-150/1-1-1A) Date: 17/11/2009, Tuesday, Sunny. Panel 1, Outgoing Feeder, Type: OG002 (W013), Breaker rating 1250A. Terminal R: 09/24596(Ω) Y: 09/24580 (Ω) B: 09/24590 (Ω) 1S1-1S2 3.4 3.4 3.3 1S1-1S3 6.4 6.2 6.1 2S1-2S2 6.1 6.1 6.2 2S1-2S3 11.7 11.6 11.5 3S1-3S2 3.3 3.2 3.5 3S1-1S3 6.2 6.0 6.4 Panel 2, Outgoing Feeder, Type: OG002 (W013), Breaker rating 1250A. Terminal R: 09/24583 (Ω) Y: 09/24579 (Ω) B: 09/24585 (Ω) 1S1-1S2 3.3 3.4 3.4 1S1-1S3 6.2 6.2 6.3 2S1-2S2 5.9 6.1 6.0 2S1-2S3 11.3 11.7 11.6 3S1-3S2 3.3 3.4 3.3 3S1-1S3 6.2 6.2 6.1 Panel 3, Outgoing Feeder, Type: OG001 (W013), Breaker rating 1250A. Terminal R: 09/24582 (Ω) Y: 09/24593 (Ω) B: 09/24594 (Ω) 1S1-1S2 3.3 3.3 3.4 1S1-1S3 6.1 6.1 6.3 2S1-2S2 6.2 6.1 6.1 2S1-2S3 11.7 11.7 11.6 3S1-3S2 3.3 3.3 3.3 3S1-1S3 6.3 6.2 6.1 Panel 5, Bus Coupler, Type: BC001 (W013), Breaker rating 1250A. Terminal R: 09/24600 (Ω) Y: 09/24599 (Ω) B: 09/24598 (Ω) 1S1-1S2 3.8 3.7 8.1 1S1-1S3 7.2 7.1 15.7 2S1-2S2 8.2 8.1 3.7 2S1-2S3 15.9 15.6 7.1 Panel 8, Outgoing Feeder, Type: OG001 (W013), Breaker rating 1250A.17/11/09. Terminal R: 09/24592 (Ω) Y: 09/24591 (Ω) B: 09/24586 (Ω) 1S1-1S2 3.2 3.4 3.2 1S1-1S3 6.1 6.2 6.1 2S1-2S2 6.0 6.2 6.1 2S1-2S3 11.7 11.7 11.7 3S1-3S2 3.4 3.3 3.2 3S1-1S3 6.3 6.2 6.1


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Panel 9, Outgoing Feeder, Type: OG002 (W013), Breaker rating 1250A.17/11/09. Terminal R: 09/24581 (Ω) Y: 09/24587 (Ω) B: 09/24595 (Ω) 1S1-1S2 3.4 3.3 3.4 1S1-1S3 6.3 6.2 6.3 2S1-2S2 6.2 6.1 6.1 2S1-2S3 11.7 11.6 11.7 3S1-3S2 3.3 3.4 3.2 3S1-1S3 6.1 6.2 6.2 Panel 10, Outgoing Feeder, Type: OG002 (W013), Breaker rating 1250A.17/11/09. Terminal R: 09/24589 (Ω) Y: 09/24584 (Ω) B: 09/24588 (Ω) 1S1-1S2 3.2 3.2 3.3 1S1-1S3 6.1 6.2 6.2 2S1-2S2 6.1 6.1 6.1 2S1-2S3 11.6 11.5 11.7 3S1-3S2 3.3 3.3 3.3 3S1-1S3 6.2 6.2 6.0

PT RATIO CHECK (33kV/√3/110/√3) Date:15/10/09, Sunday, Sunny. Panel 4, Incomer 2, Type: IC001, Breaker rating 1250A. Sl. No. R: 09/34228, Y: 09/34224, B: 09/34218 Secondary (V) Primary (V) R-Phase Y-Phase B-Phase Core1 Core2 Core1 Core2 Core1 Core2 0.741 0.797 0.741 0.734 0.741 0.744 222.50 300.27 279.17 300.27 303.13 300.27 299.06 Ratio 0.09 -6.94 0.09 1.04 0.09 -0.31 % Error Panel 3, Outgoing Feeder, Type: OG001 (W013), Breaker rating 1250A. Sl. No. R: 09/24582, Y: 09/24593, B: 09/24594 Secondary (V) Primary (V) R-Phase Y-Phase B-Phase Core1 Core2 Core1 Core2 Core1 Core2 0.734 0.734 0.737 0.737 0.737 0.737 219.40 298.91 298.91 297.96 297.96 297.96 297.96 Ratio -0.36 -0.36 -0.68 -0.68 -0.68 -0.68 % Error Panel 7, Incomer 1, Type: IC002, Breaker rating 1250A. Sl. No. R: 09/24611, Y: 09/24608, B: 09/24610 Secondary (V) Primary (V) R-Phase Y-Phase B-Phase Core1 Core2 Core1 Core2 Core1 Core2 0.737 0.737 0.736 0.737 0.739 0.739 219.60 297.96 297.96 298.37 297.96 297.16 297.16 Ratio -0.68 -0.68 -0.54 -0.68 -0.95 -0.95 % Error


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Panel 8, Outgoing Feeder, Type: OG001, Breaker rating 1250A. Sl. No. R: 09/24592, Y: 09/24591, B: 09/24586 Secondary (V) Primary (V) R-Phase Y-Phase B-Phase Core1 Core2 Core1 Core2 Core1 Core2 0.731 0.733 0.734 0.733 0.733 0.733 218.90 299.45 298.64 298.23 298.64 298.64 298.64 Ratio -0.18 -0.45 -0.59 -0.45 -0.45 -0.45 % Error

CT RATIO CHECK Panel 1 CT Station Feeder, 1S1-1S2, 150/1A: Metering. Date: 24/11/2009, Tuesday, Sunny. R-Sl.no. 09/24596, Y-Sl.no. 09/24580, B-Sl.no. 09/24590 Applied Primary Current (A)

R-phase

Secondary Current (A) Y-phase

B-phase

(A)

Ratio

% error

(A)

Ratio

% error

(A)

Ratio

% error

50 75 150

0.32 0.50 1.01

156.25 150.00 148.51

4.17% 0.00% -0.99%

0.36 0.49 1.03

138.89 153.06 145.63

-7.41% 2.04% -2.91%

0.34 0.52 1.00

147.06 144.23 150.00

-1.96% -3.85% 0.00%

50 75 150

0.32 0.50 1.01

0.36 0.51 1.00

138.89 147.06 150.00

-7.41% -1.96% 0.00%

0.33 0.50 1.02

151.52 150.00 147.06

1.01% 0.00% -1.96%

0.15 0.24 0.49

333.33 312.50 306.12

11.11% 4.17% 2.04%

0.33 0.50 1.02

151.52 150.00 147.06

1.01% 0.00% -1.96%

0.15 0.24 0.49

333.33 312.50 306.12

11.11% 4.17% 2.04%

151.52 147.06 150.00

1.01% -1.96% 0.00%

Panel 1 CT, 2S1-1S2, 150/1A: Protection. 156.25 150.00 148.51

4.17% 0.00% -0.99%

0.34 0.50 1.01

147.06 150.00 148.51

-1.96% 0.00% -0.99%

Panel 2 CT Outgoing Feeder, 1S1-1S2, 150/1A: Metering. R-Sl.no. 09/24583, Y-Sl.no. 09/24579, B-Sl.no. 09/24585 50 75 150

0.33 0.50 1.02

50 75 150

0.15 0.23 0.49

50 75 150

0.33 0.51 0.99

50 75 150

0.15 0.23 0.49

151.52 150.00 147.06

1.01% 0.00% -1.96%

0.34 0.49 1.02

147.06 153.06 147.06

-1.96% 2.04% -1.96%

Panel 2 CT, 1S1-1S3, 300/1A: Not Used. 333.33 326.09 306.12

11.11% 8.70% 2.04%

0.15 0.24 0.48

333.33 312.50 312.50

11.11% 4.17% 4.17%


1.01% -1.96% 1.01%

0.32 0.49 1.02

156.25 153.06 147.06

4.17% 2.04% -1.96%


11.11% 8.70% 2.04%

0.15 0.24 0.49

333.33 312.50 306.12

11.11% 4.17% 2.04%


0.33 0.50 1.14

151.52 150.00 131.58

1.01% 0.00% -12.28%

0.33 0.50 1.01

151.52 150.00 148.51

1.01% 0.00% -0.99%

0.33 0.51 1.00


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Panel 3 CT, 1S1-1S3, 300/1A: Not Used. 50 75 150

0.15 0.24 0.50

50 75 150

0.33 0.51 1.03

333.33 312.50 300.00

11.11% 4.17% 0.00%

0.16 0.24 0.50

312.50 312.50 300.00

4.17% 4.17% 0.00%

0.14 0.24 0.50

357.14 312.50 300.00

19.05% 4.17% 0.00%

0.33 0.50 1.00

151.52 150.00 150.00

1.01% 0.00% 0.00%

0.15 0.23 0.49

333.33 326.09 306.12

11.11% 8.70% 2.04%

0.50 1.01 -

200.00 198.02 -

0.00% -0.99% -

0.24 0.50 0.75

416.67 400.00 400.00

4.17% 0.00% 0.00%

0.50 1.01 -

200.00 198.02 -

0.00% -0.99% -

0.24 0.49 0.75

416.67 408.16 400.00

4.17% 2.04% 0.00%

0.49 1.01 -

204.08 198.02 -

2.04% -0.99% -

0.23 0.49 0.74

434.78 408.16 405.41

8.70% 2.04% 1.35%

0.50 1.00 -

200.00 200.00 -

0.00% 0.00% -

0.24 0.50 0.74

416.67 400.00 405.41

4.17% 0.00% 1.35%


1.01% -1.96% -2.91%

0.33 0.50 1.01

151.52 150.00 148.51

1.01% 0.00% -0.99%


0.15 0.24 0.50

333.33 312.50 300.00

11.11% 4.17% 0.00%

0.16 0.24 0.50

312.50 312.50 300.00

4.17% 4.17% 0.00%

Panel 4 CT Incomer 2, 1S1-1S2, 200/1A: Metering. P1 R-Sl.no. 09/24602, Y-Sl.no. 09/24603, B-Sl.no. 09/24601 P2 R-Sl.no. 09/24606, Y-Sl.no. 09/24607, B-Sl.no. 09/24609 100 200 300

0.49 1.01 -

100 200 300

0.24 0.50 0.75

100 200 300

0.49 1.01 -

100 200 300

0.24 0.49 0.75

100 200 300

0.49 1.01 -

100 200 300

0.24 0.49 0.75

204.08 198.02 -

2.04% -0.99% -

0.50 1.02 -

200.00 196.08 -

0.00% -1.96% -


4.17% 0.00% 0.00%

0.24 0.50 0.75

416.67 400.00 400.00

4.17% 0.00% 0.00%

Panel 4 CT, 2S1-1S2, 200/1A: Protection. 204.08 198.02 -

2.04% -0.99% -

0.49 1.01 -

204.08 198.02 -

2.04% -0.99% -


4.17% 2.04% 0.00%

0.24 0.49 0.75

416.67 408.16 400.00

4.17% 2.04% 0.00%

Panel 4 CT, 3S1-3S2, 200/1A: REF. 204.08 198.02 -

2.04% -0.99% -

0.49 1.01 -

204.08 198.02 -

2.04% -0.99% -


4.17% 2.04% 0.00%

0.23 0.49 0.74

434.78 408.16 405.41

8.70% 2.04% 1.35%

Panel 4 CT, 4S1-4S2, 200/1A: Differential Protection. 100 200 300

0.48 1.01 -

100 200 300

0.24 0.49 0.75

208.33 198.02 -

4.17% -0.99% -

0.49 1.01 -

204.08 198.02 -

2.04% -0.99% -


4.17% 2.04% 0.00%

0.24 0.50 0.74

416.67 400.00 405.41

4.17% 0.00% 1.35%


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Panel 5 CT Bus Coupler, 1S1-1S2, 200/1A: Metering. R-Sl.no. 09/24600, Y-Sl.no. 09/24599, B-Sl.no. 09/24598 100 200 300

0.49 1.00 -

204.08 200.00 -

2.04% 0.00% -

0.49 1.00 -

204.08 200.00 -

2.04% 0.00% -

0.49 1.00 -

204.08 200.00 -

2.04% 0.00% -

0.24 0.50 0.74

416.67 400.00 405.41

4.17% 0.00% 1.35%

0.49 1.00 -

204.08 200.00 -

2.04% 0.00% -

0.24 0.49 0.74

416.67 408.16 405.41

4.17% 2.04% 1.35%

0.50 1.03 -

200.00 194.17 -

0.00% -2.91% -

0.24 0.49 0.75

416.67 408.16 400.00

4.17% 2.04% 0.00%

0.51 1.02 -

196.08 196.08 -

-1.96% -1.96% -

0.24 0.49 0.75

416.67 408.16 400.00

4.17% 2.04% 0.00%

0.51 1.02 -

196.08 196.08 -

-1.96% -1.96% -

0.23 0.48 0.74

434.78 416.67 405.41

8.70% 4.17% 1.35%

200.00 198.02 -

0.00% -0.99% -


0.24 0.50 0.74

100 200 300

0.49 1.00 -

100 200 300

0.23 0.49 0.75

416.67 400.00 405.41

4.17% 0.00% 1.35%

0.24 0.49 0.75

416.67 408.16 400.00

4.17% 2.04% 0.00%

Panel 5 CT, 2S1-1S2, 200/1A: Protection. 204.08 200.00 -

2.04% 0.00% -

0.49 1.00 -

204.08 200.00 -

2.04% 0.00% -


8.70% 2.04% 0.00%

0.24 0.49 0.75

416.67 408.16 400.00

4.17% 2.04% 0.00%

Panel 7 CT Incomer 1, 1S1-1S2, 200/1A: Metering. P1 R-Sl.no. 09/24604, Y-Sl.no. 09/24605, B-Sl.no. 09/24597 P2 R-Sl.no. 09/24611, Y-Sl.no. 09/24608, B-Sl.no. 09/24610 100 200 300

0.50 1.00 -

100 200 300

0.24 0.49 0.75

200.00 200.00 -

0.00% 0.00% -

0.50 1.00 -

200.00 200.00 -

0.00% 0.00% -


4.17% 2.04% 0.00%

0.24 0.49 0.75

416.67 408.16 400.00

4.17% 2.04% 0.00%

Panel 7 CT, 2S1-1S2, 200/1A: Protection. 100 200 300

0.49 1.00 -

100 200 300

0.24 0.49 0.75

204.08 200.00 -

2.04% 0.00% -

0.51 1.02 -

196.08 196.08 -

-1.96% -1.96% -


4.17% 2.04% 0.00%

0.24 0.49 0.74

416.67 408.16 405.41

4.17% 2.04% 1.35%

Panel 7 CT, 3S1-3S2, 200/1A: REF. 100 200 300

0.49 1.00 -

100 200 300

0.24 0.48 0.74

204.08 200.00 -

2.04% 0.00% -

0.50 1.01 -

200.00 198.02 -

0.00% -0.99% -


4.17% 4.17% 1.35%

0.23 0.47 0.73

434.78 425.53 410.96

8.70% 6.38% 2.74%

Panel 7 CT, 4S1-4S2, 200/1A: Differential Protection. 100 200 300

0.49 1.00 -

204.08 200.00 -

2.04% 0.00% -

0.50 1.01 -

200.00 198.02 -

0.00% -0.99% -


0.50 1.01 -

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Panel 7 CT, 4S1-4S3, 400/1A: Not Used. 100 200

0.24 0.49

300

0.79

416.67 408.16 379.75

4.17% 2.04% 5.06%

0.24 0.49 0.75

416.67 408.16

4.17% 2.04%

400.00

0.00%

0.24 0.49

416.67 408.16

4.17% 2.04%

400.00

0.00%

0.33 0.49 1.01

151.52 153.06 148.51

1.01% 2.04% -0.99%

0.14 0.23 0.48

357.14 326.09 312.50

19.05% 8.70% 4.17%

0.33 0.49 1.00

151.52 153.06 150.00

1.01% 2.04% 0.00%

0.14 0.23 0.48

357.14 326.09 312.50

19.05% 8.70% 4.17%

0.34 0.49 1.01

147.06 153.06 148.51

-1.96% 2.04% -0.99%

0.15 0.24 0.50

333.33 312.50 300.00

11.11% 4.17% 0.00%

0.34 0.49 1.01

147.06 153.06 148.51

-1.96% 2.04% -0.99%

0.15 0.24 0.49

333.33 312.50 306.12

11.11% 4.17% 2.04%

0.75


0.33 0.50 1.01

151.52 150.00 148.51

1.01% 0.00% -0.99%

0.33 0.50 1.00

151.52 150.00 150.00

1.01% 0.00% 0.00%


0.15 0.24 0.50

333.33 312.50 300.00

11.11% 4.17% 0.00%

0.15 0.23 0.49

333.33 326.09 306.12

11.11% 8.70% 2.04%


0.33 0.49 1.01

151.52 153.06 148.51

1.01% 2.04% -0.99%

0.33 0.50 0.99

151.52 150.00 151.52

1.01% 0.00% 1.01%


0.16 0.24 0.49

312.50 312.50 306.12

4.17% 4.17% 2.04%

0.16 0.24 0.49

312.50 312.50 306.12

4.17% 4.17% 2.04%


0.33 0.50 1.01

151.52 150.00 148.51

1.01% 0.00% -0.99%

0.32 0.50 1.01

156.25 150.00 148.51

4.17% 0.00% -0.99%


0.15 0.24 0.49

50 75 150

0.33 0.50 1.01

333.33 312.50 306.12

11.11% 4.17% 2.04%

0.15 0.23 0.48

333.33 326.09 312.50

11.11% 8.70% 4.17%


1.01% 0.00% -0.99%

0.32 0.50 1.01

156.25 150.00 148.51

4.17% 0.00% -0.99%


0.15 0.24 0.49

333.33 312.50 306.12

11.11% 4.17% 2.04%

0.15 0.24 0.49

333.33 312.50 306.12

11.11% 4.17% 2.04%


Page 88



0.34 0.50 1.01

147.06 150.00 148.51

-1.96% 0.00% -0.99%

0.33 0.50 1.00

151.52 150.00 150.00

1.01% 0.00% 0.00%

0.33 0.50 1.00

151.52 150.00 150.00

1.01% 0.00% 0.00%

0.15 0.23 0.50

333.33 326.09 300.00

11.11% 8.70% 0.00%

0.32 0.50 1.01

156.25 150.00 148.51

4.17% 0.00% -0.99%

0.15 0.24 0.49

333.33 312.50 306.12

11.11% 4.17% 2.04%


0.15 0.24 0.50

333.33 312.50 300.00

11.11% 4.17% 0.00%

0.15 0.24 0.50

333.33 312.50 300.00

11.11% 4.17% 0.00%


0.33 0.50 1.01

151.52 150.00 148.51

1.01% 0.00% -0.99%

0.33 0.50 1.00

151.52 150.00 150.00

1.01% 0.00% 0.00%


0.15 0.24 0.49

333.33 312.50 306.12

11.11% 4.17% 2.04%

0.15 0.24 0.49

333.33 312.50 306.12

11.11% 4.17% 2.04%

INSULATION RESISTANCE CHECK OF PT Phase R Y B Phase R Y B Phase R Y B Phase R Y B

IR Check of Incomer 2 PT, Panel 4 (1kV Megger), MΩ Pry-Earth Pry-Sec1 Pry-Sec2 Sec1-Sec2 Sec1-Earth 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 IR Check of Incomer 1 PT, Panel 7 (1kV Megger), MΩ Pry-Earth Pry-Sec1 Pry-Sec2 Sec1-Sec2 Sec1-Earth 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 IR Check of Outgoing Feeder, Panel 8 (1kV Megger), MΩ Pry-Earth Pry-Sec1 Pry-Sec2 Sec1-Sec2 Sec1-Earth 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200 IR Check of Outgoing Feeder, Panel 3 (1kV Megger), MΩ Pry-Earth Pry-Sec1 Pry-Sec2 Sec1-Sec2 Sec1-Earth 200 200 200 200 200 200 200 200 200 200 200 200 200 200 200


Sec2-Earth 200 200 200 Sec2-Earth 200 200 200 Sec2-Earth 200 200 200 Sec2-Earth 200 200 200

Page 89


Phase R Y B Phase R Y B Phase R Y B Phase R Y B Phase R Y B Phase R Y B Phase R Y B Phase R Y B Phase R Y B

IR Check of 33kV Circuit Breaker, Panel 1 (Motorized 5kV Megger), MΩ Upper arm - Earth Lower arm - Earth Upper arm - Lower arm 10000 10000 3000 10000 10000 5000 10000 10000 5000 IR Check of 33kV Circuit Breaker, Panel 2 (Motorized 5kV Megger), MΩ Upper arm - Earth Lower arm - Earth Upper arm - Lower arm 10000 10000 10000 10000 10000 10000 10000 10000 10000 IR Check of 33kV Circuit Breaker, Panel 3 (Motorized 5kV Megger), MΩ Upper arm - Earth Lower arm - Earth Upper arm - Lower arm 10000 10000 10000 10000 10000 10000 10000 10000 10000 IR Check of 33kV Circuit Breaker, Panel 4 (Motorized 5kV Megger), MΩ Upper arm - Earth Lower arm - Earth Upper arm - Lower arm 10000 10000 10000 10000 10000 10000 10000 10000 10000 IR Check of 33kV Circuit Breaker, Panel 5 (Motorized 5kV Megger), MΩ Upper arm - Earth Lower arm - Earth Upper arm - Lower arm 10000 10000 10000 10000 10000 10000 10000 10000 10000 IR Check of 33kV Circuit Breaker, Panel 7 (Motorized 5kV Megger), MΩ Upper arm - Earth Lower arm - Earth Upper arm - Lower arm 10000 10000 10000 10000 10000 10000 10000 10000 10000 IR Check of 33kV Circuit Breaker, Panel 8 (Motorized 5kV Megger), MΩ Upper arm - Earth Lower arm - Earth Upper arm - Lower arm 10000 10000 10000 10000 10000 10000 10000 10000 10000 IR Check of 33kV Circuit Breaker, Panel 9 (Motorized 5kV Megger), MΩ Upper arm - Earth Lower arm - Earth Upper arm - Lower arm 10000 10000 10000 10000 10000 10000 10000 10000 10000 IR Check of 33kV Circuit Breaker, Panel 2 (Motorized 5kV Megger), MΩ Upper arm - Earth Lower arm - Earth Upper arm - Lower arm 10000 10000 10000 10000 10000 10000 10000 10000 10000


Page 90


Conclusion : From this field test, it confirms that the secondary winding resistances are within its permissible value. The CT and PT Ratio also match with the name plate rating. The Insulation Resistance value also shows good insulation. The CT ratios have been checked for every core and for both the ratio. Thus we hereby conclude that the equipment has no defect and can be put to use.


Page 91

Testing of XLPE Cables (High POT Test)

HIGH POT TEST (CABLE HV TEST) Aim

: Testing of XLPE Cables.

Objective

:

• • •

To check the Insulation Resistance Value of the cables. To check the withstand voltage of the cable. To check the value of leakage current flowing out from the cable to ground.

Theory : High POT Test or Cable HV Test or High Pressurized Test, anyone one may say but all these are same. Such tests are performed to know the IR value of the insulation and the leakage current flowing into the ground. This test can be done with AC as well as DC. In fact this test should be done with AC but wherever possibility doesn’t exist we go for DC supply. This test will also confirm whether the cable will be able to withstand the desired voltage. Cables have a capacitive effect so when we apply AC voltage, it will allow the current the pass through without any hindrance but blocks the DC therefore the current will be quite high (in terms of amperes), so such current will trip. But the testing kit is meant to measure current in terms of miliamperes. If we go for DC then the current required for charging the capacitor will be very less which tallies with our testing kit. Therefore we convert the AC supply to DC supply with the help of Rectifier and the current limiting resistor and supply the voltage. DC voltage is root 2 times the AC voltage. Since the capacitor remains charged once the voltage is applied it is necessary to discharge the capacitor after finishing the experiment in order to avoid shock. Discharge it to ground with discharge rod. While doing for Bus Section we use AC voltage since here we do not have capacitive effect. The conductors are rectangular copper plates. If dust and moisture is present then the spark will occur before actual withstand voltage is applied. In such case we will have to clean and heat the surrounding of the conductor and then do the test. While doing the experiment one may notice that the pointer of the AVΩ meter keeps on fluctuating indicating the presence of dust. As we increase the voltage beyond 30KV, hissing sound occurs indicating the inception of Corona. While increasing the voltage the air around the conductor also gets ionized and if moisture is present around then the voltage gets discharged through the conducting medium (moisture) to the ground. While discharging the cable after the test, if the discharge is high then it indicates the capacitive effect is more indicating longer cables thereby more leakage and weaker insulation. Better the insulation and shorter the length of the cable, lesser will be the discharge (spark). The leakage current should be within 10-15mA.


Page 92


Instruments Used

:

Sl. No.

Description

1

HV Testing Transformer

2 3

Rectifier Current limiting Resistor

4

High Voltage Tester

5 6

Motorized Megger AVΩ Meter

Experimental diagram B

Y

Specification I/p: 0-250V, O/p: 0-36KV, 1-Ф, 50Hz, Sl. no. H-2640. Sl. no. H-2638.

Remarks Prayog Electricals Pvt. Ltd. Bombay

I/p: 220/250V, O/p: 0-36KV, 1-Ф, 50Hz, Sl. no. H-2640. 5kV, AC input. µA and mA range

Prayog Electricals Pvt. Ltd. Bombay

:

Current Limiting Resistor

R

Rectifier

1‐Ф Supply

High Voltage Transformer

E

1‐Ф Supply High Voltage Tester

AVΩ Meter

Figure 13 High POT Test (CABLE HV TEST)


Page 93


Procedure : PART I (Before HV Test) 1. Collect the required testing instrument as per the requisition table. 2. Clean thoroughly the dust and dirt from the conductors to be tested and heat the area so that the place is moisture free. 3. Connect Megger to R-earth phase and supply the power. Note the value of resistance after reaching a steady value. 4. Repeat step 2 for Y phase and B phase. 5. Check the Megger value for phase to phase. PART II 1. Short any two phases (say Y & B) with earth terminal. Leave the other phase (say R) unconnected. 2. Connect the terminal from the HV Transformer to R phase. 3. Switch on the power supply. 4. Gradually increase the voltage up to 40kV DC and keep it for 5 minutes. 5. Check the leakage current in the ammeter connected to the HV Transformer. 6. Note down the reading. 7. Repeat step 1-6 Y and B phase too. 8. For Bus section where bare conductors is there, use AC voltage for 1 minute. PART III 1. After completing Part I & II, then Connect Megger to R-earth phase and supply the power. 2. Observe the IR value after the meter pointer attains a steady value. 3. Connect Megger to Y-Earth and supply the power. 4. Repeat step 3 for B-Earth terminals. 5. Check the Megger value for phase to phase i.e. R-Y, Y-B & B-R. 6. Note down the readings carefully. Precautions : 1. Safety the first priority. 2. When high voltage is being injected don’t allow anyone to stand nearby the testing kit. 3. Make sure no one is there on the equipment on which test is being carried out. 4. Forget not, to keep one person guarding the other end of cable so that no one comes nearby the cable under test. 5. Always increase the voltage gradually. If sparking occurs, it is due to moisture and dust, so make the area clean and dry. 6. After completing the test always discharge the charge from the cable with the help of discharge rod before touching it with bare hand.


Page 94


HIGH POT TEST (CABLE HV TEST): Cable between Transformer 1 and 33kV Panel 7. Date: 26/11/2009, 10:40am, Location: Inside the room. Temperature : 12°C IR Check of Cable ( 5KV Motorized Megger) Terminals

Before HV Test (MΩ)

After HV Test (MΩ)

R-Earth

10000

10000

Y-Earth

10000

10000

B-Earth

10000

10000

R-Y Phase

10000

10000

Y-B Phase

10000

10000

B-R Phase

10000

10000

40 KV DC applied to the Cable under Test for 5 minutes Terminals

Leakage Current (µA)

R- Y+B+Earth

10

Y- R+B+Earth

10

B- Y+R+Earth

10

HIGH POT TEST (CABLE HV TEST): Cable between Transformer 2 and 33kV Panel 4. Date: 26/11/2009, Location: Inside the room. Temperature : 12°C IR Check of Cable ( 5KV Motorized Megger) Terminals



R-Earth

10000

10000

Y-Earth

10000

10000

B-Earth

10000

10000

R-Y Phase

10000

4500

Y-B Phase

10000

5000

B-R Phase

10000

4000



R- Y+B+Earth

10

Y- R+B+Earth

7

B- Y+R+Earth

37


Page 95


HIGH POT TEST (CABLE HV TEST): Outgoing Cable from Panel 1. Date: 26/11/2009, 11:30am, Location: Inside the room. Temperature : 13°C IR Check of Cable ( 5KV Motorized Megger) Terminals



R-Earth

10000

10000

Y-Earth

10000

10000

B-Earth

10000

10000

R-Y Phase

10000

10000

Y-B Phase

10000

10000

B-R Phase

10000

10000



R- Y+B+Earth

10

Y- R+B+Earth

10

B- Y+R+Earth

10

BUS TEST (100X10 SQ.MM) SECTION 2 Date: 26/11/2009, Location: Inside the room. IR Check of Bus, Section 2 ( 5KV Motorized Megger) Terminals



R-Earth

10000

10000

Y-Earth

10000

10000

B-Earth

10000

10000

R-Y Phase

10000

10000

Y-B Phase

10000

10000

B-R Phase

10000

10000

40 KV AC applied to the Bus under Test for 1 minute. Terminals

Leakage Current (mA)

R- Y+B+Earth

2

Y- R+B+Earth

2

B- Y+R+Earth

2


Page 96


BUS TEST (100X10 SQ.MM) SECTION 1 Date: 26/11/2009, Location: Inside the room. IR Check of Bus, Section 1 ( 5KV Motorized Megger) Terminals



R-Earth

10000

10000

Y-Earth

10000

10000

B-Earth

10000

10000

R-Y Phase

10000

10000

Y-B Phase

10000

10000

B-R Phase

10000

10000

40 KV AC applied to the Bus under Test for 1 minute. Terminals

Leakage Current (mA)

R- Y+B+Earth

3

Y- R+B+Earth

5

B- Y+R+Earth

4 (Trip at 30kV)

HIGH POT TEST (CABLE HV TEST): Outgoing Cable from Panel 9. Date: 16/12/2009, 4:45pm, Location: Inside the room. Temperature : 13°C IR Check of Cable, 3x150sq.mm. ( 5KV Motorized Megger) Terminals



R-Earth

10000

10000

Y-Earth

10000

10000

B-Earth

10000

10000

R-Y Phase

10000

10000

Y-B Phase

10000

10000

B-R Phase

10000

10000



R- Y+B+Earth

8

Y- R+B+Earth

8

B- Y+R+Earth

6


Page 97


HIGH POT TEST (CABLE HV TEST): Outgoing Cable from Panel 8. Date: 16/12/2009, Location: Inside the room. Temperature : 13°C IR Check of Cable, 3x150sq.mm. ( 5KV Motorized Megger) Terminals



R-Earth

10000

10000

Y-Earth

10000

10000

B-Earth

10000

10000

R-Y Phase

10000

10000

Y-B Phase

10000

10000

B-R Phase

10000

10000

40 KV DC applied to the Bus under Test for 5 minutes. Terminals


R- Y+B+Earth

4

Y- R+B+Earth

15

B- Y+R+Earth

15

HIGH POT TEST (CABLE HV TEST): Outgoing Cable from Panel 2. Date: 16/12/2009, Location: Inside the room. Temperature : 13°C IR Check of Cable, 3x150sq.mm. ( 5KV Motorized Megger) Terminals



R-Earth

10000

10000

Y-Earth

10000

10000

B-Earth

10000

10000

R-Y Phase

10000

10000

Y-B Phase

10000

10000

B-R Phase

10000

10000

40 KV DC applied to the Bus under Test for 1 minute. Terminals


R- Y+B+Earth

6

Y- R+B+Earth

8

B- Y+R+Earth

10


Page 98


Observation

:

While the experiment is under test, one will observe the inception of corona above 30kV/cm2. Hissing sound will be noticed indicating the inception of corona. Some sparking sound may be heard indicating the presence of dust particles. If moisture is present then the voltage trips off through spark before reaching the set voltage as it happened for B-phase of Bus Section 1. So we heated the area with halogen lamp, cleaned the conductor thoroughly and performed the test which gave better result. While Meggering, initially the pointer moves towards zero indicating the capacitance of the cable being charged i.e. the current is drawn to charge the capacitance of the cable so no current flows through the cable. However after the capacitive effect of the cable, the current passes through cable thus indicating the IR value. For Long cables the pointer may stick at zero for longer time indicating greater capacitance however the pointer will rise slowly. Conclusion

:

The result shows very good IR value of the cable and bus section. The leakage current found is very less ranging in micro amperes while the normal leakage current comes in 10-15mA. For better result the conductors should be free from dust particles and moisture free. However our results have good IR values and lesser leakage current indicating the stability of cable under the desired voltage. Therefore the cables are good and healthy.


Page 99

Inverse Definite Minimum Time (IDMT) Relay Test

Relay Testing (Over Current Protection) Aim

: Testing of Inverse Definite Minimum Time (IDMT) and Earth Fault Relay of 33KV Vacuum Circuit Breaker.

Objective ¾ ¾ ¾ ¾

:

Find out the trip time of IDMT Relay under Normal condition. Find out the trip time of IDMT Relay under High Set condition. Find out the trip time of Earth Fault IDMT under Normal Condition. Find out the trip time of Earth Fault IDMT under High Set Condition.

Theory : An over current protection device protects the circuit by opening the device when the current reaches a value that will cause an excessive or dangerous temperature rise in conductors. The time it takes for an over current protection device (OCPD) to open is inversely proportional to the magnitude of the fault current. Thus, the higher the ground-fault current, the less time it takes for the OCPD to open and clear the fault. Inverse Definite Minimum Time Over current (IDMT) relay gives inverse-time current characteristics at lower values of the fault current and definite-time characteristics at higher values of the fault current (Used in distribution line). Here we set the current and Trip time at a particular value and then injects higher current and note the Trip time obtained. The field test should confirm that the trip time obtained should not be greater than the set time. According to British standards, the following are the important characteristics of over current relays.

Figure 14 Inverse-Time, Very-Inverse Time and Extremely-Inverse Time characteristics.


Page 100


Instruments Used Sl. no

:

Description

1

Relay Test Set

2

Clamp Leaker

Specification 230V, 50Hz, 0-1-5-10-25-100A, 0-99.99S,0-9.999S DC-10A, Motwane

3

Connecting Wires

APR

4

Power Supply

230V, 50Hz

Quantity 1

Remarks Shruti Electronics Kolkata

1 1

Circuit Diagram:

Back View of the Relay. Connected in order to check the time from the relay test set as well as

X1 TB R=15, Y=19, B=23, N=27

Power Supply

Figure 15 Testing of IDMT Relays


Page 101


Procedure : 1. Set up the experiment as given above with the relay test set. 2. Set the 'Time Setting' of the relay as per the desired value and find out the calculated trip time. 3. Set the 'Current Setting' of the relay as per the desired value. 4. Connect the wires from the relay test set to the 'Terminal Box' so as to obtain R-Y or Y-B or B-R respectively. 5. To compare the time noted by the relay and the relay test set, connect the terminals from the relay test set to the relay as shown in the figure above. 6. Now inject a bit higher current through the relay test set so as to provide fault and see the trip time obtained. 7. After the fault has been injected note the tripping time and the LED indication. 8. Follow this procedure for O/C IDMT, O/C High Set, Earth Fault IDMT and Earth Fault High Set conditions. 9. Repeat the same for other relays too. Results

:

The result shows that the 'Trip Time Obtained' is always lesser than the 'Calculated Trip Time' indicating that the relays will operate faster. At the most the tripping time of the relay should not be greater than that of the calculated trip time. In case of high set conditions the relay should trip instantaneously, therefore we set the time to zero. The term 'High Set' is used for very fast relays with operating time less than 0.1s. IDMT Over current relays gives inverse-time current characteristics at lower values of fault current and definite time characteristics at higher values of fault current. Generally, an inverse-time characteristic is obtained if the value of PSM is below 10. For the value of PSM between 10 and 20, the characteristics tend to become a straight line i.e. towards a definite time characteristics.


Page 102


Over Current Protection (Inverse Definite Minimum Time, IDMT) Relay Date: 22/11/2009, Feeder Name: Station Feeder (Panel 1). Type: 7SJ600, Sl. No. BF0904106790. Rated Voltage: 60, 110,125 V DC. 1. Over current IDMT (Ip) Phase

Current Setting(A)

Injected Current(A)

Time Setting(s)

Calculated Trip Time(ms)

Trip Time Obtained(ms)

LED Indication

R-Y

1

2

0.15

1500

1300

1,2

Y-B

1

2

0.15

1500

1300

1,2

B-R

1

2

0.15

1500

1310

1,2

2. Over current High Set (I >>) Phase

Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

4

4

0

0

30

1

Y-B

4

4

0

0

30

1

B-R

4

4

0

0

30

1

3. Earth Fault IDMT (Iep) Phase

Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

0.2

0.4

0.15

1500

1190

1,3

Y-B

0.2

0.4

0.15

1500

1190

1,3

B-R

0.2

0.4

0.15

1500

1000

1,3

4. Earth Fault High Set(Ie>>) Phase

Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

2

2

0

0

60

1,4

Y-B

2

2

0

0

50

1,4

B-R

2

2

0

0

60

1,4


Page 103


Over Current Protection (Inverse Definite Minimum Time, IDMT) Relay Date: 22/11/2009, Feeder Name: OG002 (Panel 2). Type: 7SJ600, Sl. No. BF0904106791. Rated Voltage: 60, 110,125 V DC. 1. Over current IDMT (Ip) Phase

Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

1

2

0.15

1500

1260

1,2

Y-B

1

2

0.15

1500

1360

1,2

B-R

1

2

0.15

1500

1200

1,2


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

4

4

0

0

20

1

Y-B

4

4

0

0

30

1

B-R

4

4

0

0

30

1


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

0.2

0.4

0.15

1500

1200

1,3

Y-B

0.2

0.4

0.15

1500

1200

1,3

B-R

0.2

0.4

0.15

1500

1200

1,3


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

2

2

0

0

20

1,4

Y-B

2

2

0

0

20

1,4

B-R

2

2

0

0

20

1,4


Page 104



Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

1

2

0.15

1500

1270

1,2

Y-B

1

2

0.15

1500

1300

1,2

B-R

1

2

0.15

1500

1250

1,2


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

4

4

0

0

30

1

Y-B

4

4

0

0

50

1

B-R

4

4

0

0

50

1


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

0.2

0.4

0.15

1500

1230

1,3

Y-B

0.2

0.4

0.15

1500

1220

1,3

B-R

0.2

0.4

0.15

1500

1230

1,3


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

2

2

0

0

60

1,4

Y-B

2

2

0

0

60

1,4

B-R

2

2

0

0

60

1,4


Page 105


Over Current Protection (Inverse Definite Minimum Time, IDMT) Relay Date: 22/11/2009, Feeder Name: IC001 (Panel 4). Type: 7SJ600, Sl. No. BF0904106789. Rated Voltage: 60, 110,125 V DC. 1. Over current IDMT (Ip) Phase

Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

1

2

0.2

2000

1830

1,2

Y-B

1

2

0.2

2000

1850

1,2

B-R

1

2

0.2

2000

1910

1,2


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

4

4

0.03

300

60

1,4

Y-B

4

4

0.03

300

50

1,4

B-R

4

4

0.03

300

60

1,4


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

0.2

0.4

0.2

2000

1680

1,3

Y-B

0.2

0.4

0.2

2000

1700

1,3

B-R

0.2

0.4

0.2

2000

1780

1,3


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

2

2

0.03

300

70

1,4

Y-B

2

2

0.03

300

60

1,4

B-R

2

2

0.03

300

30

1,4


Page 106


Over Current Protection (Inverse Definite Minimum Time, IDMT) Relay Date: 22/11/2009, Feeder Name: BC001 (Panel 5). Type: 7SJ600, Sl. No. BF0904106792. Rated Voltage: 60, 110,125 V DC. 1. Over current IDMT (Ip) Phase

Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

1

2

0.2

2000

1880

1,2

Y-B

1

2

0.2

2000

1900

1,2

B-R

1

2

0.2

2000

1980

1,2


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

4

4

0

0

60

1,4

Y-B

4

4

0

0

50

1,4

B-R

4

4

0

0

60

1,4


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

0.2

0.4

0.2

2000

1700

1,3

Y-B

0.2

0.4

0.2

2000

1700

1,3

B-R

0.2

0.4

0.2

2000

1700

1,3


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

2

2

0

0

60

1,4

Y-B

2

2

0

0

50

1,4

B-R

2

2

0

0

60

1,4


Page 107


Over Current Protection (Inverse Definite Minimum Time, IDMT) Relay Date: 22/11/2009, Feeder Name: IC002 (Panel 7). Type: 7SJ600, Sl. No. BF0904106787. Rated Voltage: 60, 110,125 V DC. 1. Over current IDMT (Ip) Phase

Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

1

2

0.2

2000

1790

1,2

Y-B

1

2

0.2

2000

1840

1,2

B-R

1

2

0.2

2000

1830

1,2


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

4

4

0.03

300

60

1,4

Y-B

4

4

0.03

300

50

1,4

B-R

4

4

0.03

300

50

1,4


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

0.2

0.4

0.2

2000

1900

1,3

Y-B

0.2

0.4

0.2

2000

1940

1,3

B-R

0.2

0.4

0.2

2000

1920

1,3


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

2

2

0.03

300

60

1,4

Y-B

2

2

0.03

300

50

1,4

B-R

2

2

0.03

300

60

1,4


Page 108



Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

1

2

0.15

1500

1490

1,2

Y-B

1

2

0.15

1500

1400

1,2

B-R

1

2

0.15

1500

1450

1,2


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

4

4

0

0

20

1,4

Y-B

4

4

0

0

30

1,4

B-R

4

4

0

0

20

1,4


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

0.2

0.4

0.15

1500

1320

1,3

Y-B

0.2

0.4

0.15

1500

1300

1,3

B-R

0.2

0.4

0.15

1500

1300

1,3


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

2

2

0

0

60

1,4

Y-B

2

2

0

0

60

1,4

B-R

2

2

0

0

60

1,4


Page 109



Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

1

2

0.15

1500

1380

1,2

Y-B

1

2

0.15

1500

1470

1,2

B-R

1

2

0.15

1500

1440

1,2


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

4

4

0

0

30

1,4

Y-B

4

4

0

0

30

1,4

B-R

4

4

0

0

20

1,4


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

0.2

0.4

0.15

1500

1260

1,3

Y-B

0.2

0.4

0.15

1500

1300

1,3

B-R

0.2

0.4

0.15

1500

1320

1,3


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

2

2

0

0

30

1,4

Y-B

2

2

0

0

30

1,4

B-R

2

2

0

0

20

1,4


Page 110



Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

1

2

0.15

1500

1300

1,2

Y-B

1

2

0.15

1500

1340

1,2

B-R

1

2

0.15

1500

1370

1,2


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

4

4

0

0

20

1,4

Y-B

4

4

0

0

30

1,4

B-R

4

4

0

0

30

1,4


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

0.2

0.4

0.15

1500

1300

1,3

Y-B

0.2

0.4

0.15

1500

1320

1,3

B-R

0.2

0.4

0.15

1500

1300

1,3


Current Setting(A)

Injected Current(A)

Time Setting(s)



LED Indication

R-Y

2

2

0

0

20

1,4

Y-B

2

2

0

0

30

1,4

B-R

2

2

0

0

20

1,4


Page 111


Precautions : I. II. III.

Safety, the first priority. Refer the drawings correctly. Avoid loose connections.

Conclusion : From this test it is proved that the operating time of the relay is within its range. The operating time doesn’t exceed the set time. For the entire outgoing feeder, the high set condition the time set is zero so that the relay acts as instantaneous relay and trips off as soon as the fault occurs. While in case of incomers, the time has been set to 0.03 so that this relays acts only after the relays of the outgoing feeder trips off. In any case the trip time obtained is lesser than the time set, thus indicating that the relays will clear the fault within the set time.


Page 112

System Stability Testing

Stability Testing Report Aim

: To confirm the stability of the total system.

Objective

:

• • • • •

To check if the ratio of CT on primary and secondary are correct. To check if there is any connections left out. To check if the connections are done correctly. To check if the line is continuous. To check if the relay scheme is functioning or not.

Theory : This test is the last test done before charging the transformer. This test ensures that every work done till now is stable. By applying certain amount of current on the primary of the CT we check the current on the secondary side. By knowing the ratio of CT, we can find out the secondary currents, which have to be traced till the relay panel and control panel. If the same current exists then the system is stable. However sometimes we don’t get it. We may get different secondary current, and then the connections have to be checked as the wire may be connected mistakenly to other device. If there is any open circuit then we won't get current at the end of the circuit. While performing this test one has to be thorough with the CT ratio of various equipments so that when we get different values we will be able to know by calculation whose secondary current is flowing. And also before checking one should know by calculation what value of current should we get at that point. In fact this is the final test, here we know every result but we are assuring that result by practically performing the test. Often there will be wrong connections and open circuit. For this we apply known value of current in the primary side of CT. We trace the secondary current through CT junction box, Control panel (Metering circuit) and relay panel (distance protection and bus bar protection). We also check the secondary CT current at Transformer Junction box and follow up till its control panel where we check currents in MW, MVAR, MWT, MVART, ATY, TVM, ASS, IC TB (Incoming TB) and O/C and E/F relay. We also trace it in Relay panel where differential and bus bar protection are done. After the system is found good then for the functioning of the relay we knowingly apply some fault to the system such as changing the polarity of the connections and restricted earth fault. Then we observe whether the relay are working and check the currents in the relay panel. The panel should show abnormal current in the line of fault.


Page 113


Instruments used

:

Sl. no Description

Specification

Quantity

1

Clamp Meter


1

2

Clamp Leaker

1

3

Multimeter

4

3-Ф D Supply

DC-10A, Motwane Digital Multimeter DM3540A, Motwane 415V, 50 Hz

5

Connecting wires

---------------------------------------------

Circuit diagram

Remarks

1 1 APR

:

Figure 16 System Stability Testing


Page 114


Procedure

:

PART I- System Check 1. 2. 3. 4. 5. 6.

Set up connection as given in the diagram above. Short the LV winding of the transformer. Close all the isolator. All the line should be connected so that loading can be done. Supply 3-Ф currents to the current transformer as given in the figure. With the help of clamp meter check the current in the primary side of CT. With the help of clamp leaker observe the current on the secondary terminal at the transformer. Check whether the current observed is as per the ratio or not. If the current doesn’t match then find out by calculation whose secondary current it is and accordingly change the connection. 7. Then follow the line terminals at Control panel and check the current at metering core (MW, MVAR, MWT, MVART, TVM, and ASS). Check the value for correctness at the spot. 8. Follow the line at relay panel for O/C, E/F and differential protection. 9. If everything is ok then apply earth fault at R-phase, Y-phase and B-phase and observe the readings at the panel. The current will abnormal wherever the fault is. 10. Check all the panel readings by applying fault at each phase. Compare the result obtained with the CT ratio.

PART II - NCT Test by applying Restricted Earth Fault. 1. 2. 3. 4. 5.

Open circuit the LV winding and remove the earth connection from the neutral point. Don’t load the CT. Short any two HV phases say R-Y. Connect a wire to r-phase at LV side and bring out the terminal. Connect an auto transformer to r-n at LV side and further connect the auto transformer to 1-Ф source. 6. Clutch the neutral wire with clamp meter and supply 10A current from the auto transformer. 7. With the help of Clamp leaker check the current on Transformer Junction box (NCT). It should reflect almost 25mA. 8. Trace this current till control and relay panel. NB: - Shorting means we are applying fault current purposefully so that neutral gets displaced. Actually neutral should have zero current but here we are supplying current in neutral so that restricted earth fault occurs. We trace this fault current at transformer junction box till the relay panel.


Page 115


Results

CTJB X1-1 X1-2 X1-3 X1-7,8,9

: System Stability Check, Incomer 1, Tie Line side (Tie Line-Transformer 1-RP & CP) Date: 1/11/2009, Sunday, Sunny. Primary Current: R=14.37A, Y=14.65A, B=14.71A. CT Secondary Current Check. CT Ratio 600/1A. Core 1(mA) Core 2(mA) Core 3(mA) Core 4(mA) CTJB CTJB CTJB 600/1A 600/1A 600/1A 600/1A R= 24.21 X2-1 R= 24.21 X3-7 R= 24.21 X4-7 R= 24.29 Y= 24.12 X2-2 Y= 24.21 X3-8 Y= 24.43 X4-8 Y= 24.29 B= 24.25 X2-3 B= 24.21 X3-9 B= 24.41 X4-9 B= 24.29 N=0.00 X2-7,8,9 N=0.00 X3-1,2,3 N=0.00 X4-1,2,3 N=0.00

Actual current (mA) 23.95 24.42 24.52 0.00

INC TB X1-5-D11= 24.34 X1-6-D31=24.38 X1-7-D51=24.33 X1-8-D71=00.00

MW(mA) (600-300)/1A D13=24.36 D33=24.43 D53=24.47 D71=00.00

Control Panel 1 (CP1), Metering, Core # 1 MVAR(mA) MWT(mA) MVART(mA) ATY(mA) (600-300)/1A (300)/1A (300)/1A (300)/1A D15=24.36 D17=24.39 D19=24.33 D35=24.47 D37=24.36 D37A=24.36 D39=24.33 D55=24.51 D57=24.19 D57=24.30 D71=00.00 D71=00.00 D71=00.00 -

TVM(mA)

ASS(mA)

D21=24.31 D41=24.36 D61=24.36 D71=00.00

D23=24.15 D43=24.17 D63=24.19 D71=00.00

Ammeter (mA) 24.49 24.41 24.52 00.00

INC TB (mA) X1-5=A111=24.41 X1-6=A131=24.49 X1-7=A151=24.48 X1-8=A171=00.00

Relay Panel 1 (RP1). Distance (Core # 4), O/C & E/F Protection (Core # 2). 21 Distance Relay(mA) INC CT TB(mA) 67 Relay(mA) HV Side A112=Q1=24.41 X1-9=A211=24.41 A213(R)=24.45 A132=Q3=24.49 X1-10=A231=24.49 A283(Y)=24.45 A152=Q5=24.48 X1-11=A251=24.48 A253(B)=24.47 A172=Q7=00.00 X1-12=A271=00.00 A273(N)=00.00


Page 116


Relay Panel 3 (RP3), Bus Bar Protection, Core # 3 I/C TB (Incoming Terminal Box) (mA) Bus Bar Summation CT 1T1 (mA) X1-1-2=1B111=24.39 1B113=24.39 X1-1-3=1B131=24.54 1B133=24.54 X1-1-4=1B151=24.51 1B153=24.31 X1-1-1=1B171=00.00 1B173=00.00

CTJB X1-1 X1-2 X1-3 X1-4,5,6

Core 1(mA) 300/1A R= 48.38 Y= 48.35 B= 48.41 N=0.00

System Stability Check, Transformer 1 side Date: 1/11/2009, Sunday, Sunny. Primary Current: R=14.37A, Y=14.65A, B=14.71A. CT Secondary Current Check. Core 2(mA) Core 3(mA) CTJB CTJB CTJB 300/1A 600/1A X2-1 R= 48.33 X3-7 R= 24.22 X4-1 X2-2 Y= 48.36 X3-8 Y= 24.21 X4-2 X2-3 B= 48.36 X3-9 B= 24.25 X4-3 X2-4,5,6 N=0.00 X3-1,2,3 N=0.00 X4-4,5,6

Core 4(mA) 300/1A R= 48.35 Y= 48.33 B= 48.34 N=0.00

Actual current (mA) (300/1A) 47.90 48.33 49.03 0.00

INC TB X1-5-D11= 48.37 X1-6-D31= 48.87 X1-7-D51= 48.61 X1-8-D71= 00.00

MW(mA) (600-300)/1A D13= 48.37 D33= 48.60 D53= 48.80 D71= 00.00

Control Panel 2 (CP2), Metering, Core # 1 MVAR(mA) MWT(mA) MVART(mA) ATY(mA) (600-300)/1A (300)/1A (300)/1A (300)/1A D15= 48.70 D17= 48.33 D19= 48.51 D35= 48.70 D37= 48.70 D37= 48.33 D39 = 48.30 D55= 48.70 D57= 48.73 D57= 48.33 D71= 00.00 D71= 00.00 D71= 00.00 -


TVM(mA)

ASS(mA)

D21= 48.56 D41= 48.55 D61= 48.55 D71= 00.00

D23= 48.90 D43= 48.80 D63= 48.00 D71=00.00

Page 117


Relay Panel 2 (RP2). Differential Protection (Core # 4), 300/1A. INC TB (mA) Differential Relay 87(mA) HV Side X1-1=A311= 48.43 A312= 47.90 X1-2=A331= 48.44 A332= 47.80 X1-3=A351= 48.44 A352= 47.70 X1-4=A371= 00.00 A372= 00.00 Relay Panel 3 (RP3), Bus Bar Protection, Core # 3 I/C TB (Incoming Terminal Box) (mA) Bus Bar Summation CT 2T1 (mA) X1-2-2=2B111=24.31 2B111=24.45 X1-2-3=2B131=24.96 2B133=24.40 X1-2-4=2B151=24.36 2B153=24.42 X1-2-1=2B171=00.00 2B173= 00.00 TVM : Tri Vector Meter ASS

: Ampere Selector Switch

MW

: Megawatt

MVAR: Megavars ATY : Refers to Transducer in Ammeter


Page 118


CTJB X1-1 X1-2 X1-3 X1-4,5,6

System Stability Check, Transformer 2 side ( Tie Line- Bus coupler- Transformer 2-RP & CP) Date: 6/11/2009, Friday, Sunny. Primary Current: R=13.33A, Y=13.33A, B=13.28A. Sec. current : r=26.55mA, y= 26.44mA, b=26.44mA CT Secondary Current Check (Transformer 2 Side). CT Ratio 600-300/1-1A. Actual current Core 1(mA) Core 2(mA) Core 3(mA) Core 4(mA) CTJB CTJB CTJB (mA) 300/1A 300/1A 600/1A 300/1A 600/1A 300/1A 1S1R= 44.41 X2-1 2S1R= 44.40 X3-7 3S3R= 22.20 X4-1 4S1R= 44.41 22.22 44.43 1S1Y= 44.42 X2-2 2S1Y= 44.31 X3-8 3S3Y= 22.22 X4-2 4S1Y= 44.43 22.22 44.43 1S1B= 44.42 X2-3 2S1B= 44.33 X3-9 3S3B= 22.19 X4-3 4S1B= 44.31 22.13 44.27 1S2N= 00.00 X2-4,5,6 2S1N= 00.00 X3-1,2,3 3S1N= 00.00 X4-4,5,6 4S2N= 00.00 0.00 0.00

INC TB X1-5 D11= 43.71 X1-6 D31= 43.41 X1-7 D51= 44.11 X1-8 D71= 00.00

MW(mA) (600-300)/1A D13= 43.31 D33= 44.33 D53= 44.26 D71= 00.00

Control Panel 5 (CP5), Metering, Core # 1 (300/1A) MVAR(mA) MWT(mA) MVART(mA) TVM(mA) (600-300)/1A (300)/1A (300)/1A D15= 44.41 D17= 44.13 D19= 44.1 D21= 44.33 D35= 43.23 D37= 44.26 D37= 44.31 D41= 44.31 D55= 44.31 D57= 44.29 D57= 44.33 D61= 44.36 D71= 00.00 D71= 00.00 D71= 00.00 D71= 00.00

ASS(mA) D23= 44.40 D43= 44.36 D63= 44.32 D71= 00.00

Ammeter (mA) Ammeter check found ok. Selector switches operating properly.

Relay Panel 5 (RP5). Differential Protection (Core # 4), O/C & E/F Protection (Core # 2). O/C & E/F Protection Differential Protection INC TB (mA) HV Terminal, Relay 87(mA) INC CT TB(mA) HV Terminal, Relay67(mA) X1-1=A311= 44.31 A312= 24.41 X1-9=A313= 44.30 A315(R)= 44.30 X1-2=A331= 44.31 A332= 24.49 X1-10=A333= 44.40 A335(Y)= 44.40 X1-3=A351= 44.31 A352= 24.48 X1-11=A353= 44.30 A355(B)= 44.30 X1-4=A371= 00.00 A372= 00.00 X1-12=A373= 00.00 A375(N)= 00.00


Page 119


Relay Panel 3 (RP3). Bus Bar Differential Protection (Core # 3), 600/1A. INC TB (mA) Bus Bar Summation CT 5T1 (mA) X1-5-2=5B111= 22.33 5B113= 47.90 X1-5-3=5B131= 22.26 5B133= 47.80 X1-5-4=5B151= 22.36 5B153= 47.70 X1-5-1=5B71= 00.00 5B73= 00.00 Relay Display check ok. BB differential ICT o/p check by polarity reverse of anyone CT found ok.

CTJB X1-1 X1-2 X1-3 X1-4,5,6

System Stability Check, Bus Coupler side ( Tie Line- Bus coupler-RP & CP) Date: 6/11/2009, Friday, Sunny. Primary Current: R=13.33A, Y=13.33A, B=13.28A. Sec. current : r=26.55mA, y= 26.44mA, b=26.44mA CT Secondary Current Check (Bus Coupler). CT Ratio 600-300/1-1A. Actual current Core 1(mA) Core 2(mA) Core 3(mA) Core 4(mA) CTJB CTJB CTJB (mA) 600/1A 600/1A 600/1A 600/1A 1S1R= 22.21 X2-1 2S1R= 22.13 X3-7 3S3R= 22.33 X4-7 4S3R= 22.21 22.22 1S1Y= 22.00 X2-2 2S1Y= 22.16 X3-8 3S3Y= 22.26 X4-8 4S3Y= 22.30 22.22 1S1B= 22.31 X2-3 2S1B= 22.19 X3-9 3S3B= 22.21 X4-9 4S3B= 22.26 22.13 1S3N= 00.00 X2-4,5,6 2S3N= 00.00 X3-1,2,3 3S1N= 00.00 X4-1,2,3 4S1N= 00.00 0.00

Relay Panel 3 (RP3). Bus Bar Protection, 600/1A Bus Bar Protection Zone A, Core 3, 600/1A Bus Bar Protection Zone B, Core 4, 600/1A INC TB (mA) Bus Bar Summation CT 3T1 (mA) INC CT TB(mA) Bus Bar Summation CT 1T2 (mA) X1-3-2=3B111B= 22.26 3B113= 22.21 X1-3-6=3B111A= 22.31 3B113A= 22.26 X1-3-3=3B131B = 22.21 3B133= 22.22 X1-3-7=3B131A = 22.83 3B133A= 22.25 X1-3-4=3B151B = 22.27 3B153= 22.21 X1-3-8=3B151A = 22.30 3B153A= 22.26 X1-3-1=3B71B = 00.00 3B73= 00.00 X1-3-5=3B71A = 00.00 3B73A= 00.00 Core 1 is spare, shorted secondary cores at CTJB. Primary current check as relay displayed found ok. O/p current from ICT found developed when CT polarity was reversed=ok.


Page 120


Relay Panel 3 (RP3). O/C & E/F Protection, 600/1A. INC TB (mA) Relay 50/51 (mA) X11-1=A111= 22.33 A113= 22.19 X11-2=A131= 22.31 A133= 22.23 X11-3=A151= 22.36 A153= 22.24 X11-4=A171= 00.00 A173= 00.00 • • •

All inbuilt CT secondary output check of Transformer 1 & 2 found ok. Neutral CT secondary output check up to panel REF Relay end found ok. WTICT secondary output check found ok. Stability Testing, 27/11/09, Differential Relay 87. Transformer 1, RP2. NORMAL CONDITION Primary Current: R=10.30A, Y=10.30A, B=10.30A HV Side Relay 87(mA)

LV Side Relay 87(mA)

A312(R)=36.90

A212(R)=59.60

A332(Y)=37.00

A232(Y)=60.20

A352(B)=37.20

A252(B)=59.80

A372(N)=00.00

A283(N)=00.07

Connect Phase-Earth fault to any of the HV line, so that fault gets injected and check the differential current. Differential Relay 87. FAULT CONDITION (B-phase on HV side shorted to earth) HV Side Relay 87(mA)


A312(R)=36.60

A212(R)= 59.40

A332(Y)=37.10

A232(Y)= 59.80

A352(B)=37.10

A252(B)= 59.20

A372(N)= 39.80

A283(N)= 00.05

Differential Relay 87. FAULT CONDITION (Y-phase on LV side shorted to earth) HV Side Relay 87(mA)


A312(R)= 36.80

A212(R)= 59.40

A332(Y)= 37.00

A232(Y)= 59.90

A352(B)= 37.10

A252(B)= 59.60

A372(N)= 00.02

A283(N)= 00.15


Page 121


Stability Testing, 27/11/09, Differential Relay 87. Transformer 2, RP5. NORMAL CONDITION Primary Current: R=10.50A, Y=7.30A, B=8.20A HV Side Relay 87(mA)


A312(R)= 36.40

A212(R)= 58.80

A332(Y)= 36.40

A232(Y)= 59.10

A352(B)= 36.70

A252(B)= 59.20

A372(N)= 00.02

A283(N)= 00.07

Connect Phase-Earth fault to any of the HV line, so that fault gets injected and check the differential current. Differential Relay 87. FAULT CONDITION (B-phase on HV side shorted to earth) HV Side Relay 87(mA)


A312(R)= 36.40

A212(R)= 58.80

A332(Y)= 36.50

A232(Y)= 59.00

A352(B)= 54.90

A252(B)= 59.00

A372(N)= 39.70

A283(N)= 00.07

Differential Relay 87. FAULT CONDITION (Y-phase on LV side shorted to earth) HV Side Relay 87(mA)


A312(R)= 36.50

A212(R)= 58.80

A332(Y)= 36.40

A232(Y)= 59.10

A352(B)= 36.80

A252(B)= 59.20

A372(N)= 00.02

A283(N)= 00.11

Restricted Earth Fault (REF) Test NCT Ratio 400/1A, Transformer 1 NCT Ratio 400/1A, Transformer 2 Applied current in primary :- 10A Applied current in primary :- 9.91A I/C 1 33KV Side (Neutral Current) :- 24.83mA I/C 2 33KV Side (Neutral Current) :- 21.70mA HV side RP2 (Neutral Current) :- 20.84mA HV side RP5 (Neutral Current) :- 29.70mA HV Terminal NCT :- 25.56mA LV Terminal NCT :- 25.69mA


Page 122


Precaution 1. 2. 3. 4.

:

Safety, the first priority. While taking reading, make sure the reading is the correct one. If the reading doesn’t tally the CT ratio then check the connections. Always note the steady value of the meter.

Conclusion

:

From the result obtained above it is confirmed that the pre commissioning test for the substation is completed and the substation is ready for Test Charge. The result tallies with the CT ratio and the connections have been checked. This is the last Pre-Commissioning Check done on the system. The System Stability has been found healthy and wherever necessary the connections have been checked.


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Reference Ram, Badri & Vishwakarma, D.N. (2008). Power System Protection and Switchgear. New Delhi : Tata McGraw-Hill Publishing Company Limited. Singh, Tarlok (2007). Installation, Commissioning and Maintenance of Electrical equipment. Myers S.D, Kelly J.J & Parrish R.H (1981).A Guide to Transformer Maintenance. Akron, Ohio. Transformer Maintenance Institute. Dorf, Richard C (2000). The Electrical Engineering Handbook. Boca Raton. CRC Press LLC. Laughton M.A & Warne D.J (2003).Electrical Engineer's Reference Book. Jordan Hill, Oxford, Burlington. Reed Educational and Professional Publishing Limited. Grigsby L.L (2001). The Electrical Power Engineering Handbook. Boca Raton, Washington. CRC Press LLC. Whitaker, Jerry C (1999). AC Power System Handbook. Boca Raton, Washington. CRC Press LLC.

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Testing and Commissioning Report of Olakha Substation

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