Doble Engineering - Testing Rectifier Transformers - Presentation

TESTING RECTIFIER-TRANSFORMERS Long Pong, Doble Engineering Pierre Leblanc, Alcoa Hugo Simard, Rio Tinto Alcan ABSTRACT Maintenance and Diagnostic in aluminum smelter plant are challenging because the finance losses can be very high when the smelting process is unexpectedly interrupted. We can work on one unit at a time and the unit must be returned back in service when another unit has a problem. Therefore it is not practical to disconnect the transformer from the rectifier for routine maintenance test. Rectifier Transformers come typically in various configurations, as shown in Table 1, and have more complex secondary connections than a power transformer, see Figure 1c. In the field it is impractical to disconnect the transformer from the rectifier for routine maintenance testing. This leads the testers to use different test procedure in the field, in the factory or among themselves. As a result the test data can not be compared easily or at worst, can become meaningless. This paper will cover Doble test procedures (Overall, Excitation and Doble Turn Ratio) and data analysis of the rectifier-transformers in Table 1 with consideration of both the technical needs and the field difficulties. Four case studies and the typical test results will be included. It is the hope of the authors that the proposed test procedures can be used as a standard test in the factory and in the field.

Table 1 Typical Configurations of Rectifier Transformers

#

HV

LV

Figure

Case Study

Overall Excitation Ratio

1

∆

∆∆

2b

I. Alcoa-Mt Holly





2

Y

∆∆

2d

3

Y

Y∆

3

4

YY

∆Y

4

5

∆Y

∆∆

5

III. RTA-Laterriere 



6

∆

Y−Y Y−Y

6b

IV. RTA-Arvida





7

Y

Y−Y Y−Y

6c

II. RTA-Alma

© 2012 Doble Engineering Company -79th Annual International Doble Client Conference All Rights Reserved



a) Overall View

b) LV Terminals as they go through the building Wall

c) LV Terminals other side of the Building Wall

Fuji Rectifier-Transformer Figure 1

© 2012 Doble Engineering Company -79th Annual International Doble Client Conference All Rights Reserved 2-26

TEST PROCEDURE As shown in Table 1, most rectifier-Transformers are 3-winding units and thus a three-winding transformer test plan should be used. In order to simplify the test procedure, the windings are identified as following: High Voltage winding is HV, First LV winding is LV1, Second LV winding is LV2 and Third LV or Tertiary winding is LVT. The LV1 should be the one shown on the left on the nameplate vector diagram. If the two LV windings are connected together, the overall insulation of these two windings will be identified as LV.

LV Interconnection Figure 2 For a routine test, the same standard tests recommended for a power transformer are also recommended for rectifier-transformer. These tests are Overall Insulation, Bushing, Surge Arrester and Excitation tests. The test procedure and data interpretation are also the same with the following exceptions: 1.

At the LV winding side, the rectifier can stay connected but isolated from pot line by DC disconnect switches; because a tremendous effort required to disconnect the secondary windings.

2.

If the two LV windings have an interconnection bus between the rectifiers as shown in red of Figure 2, then these two windings should be tested as one winding in a routine test.

3.

In order to obtain a representative measurement of the LV winding insulation, the surge capacitors on the bus bars between LV winding and rectifier must be disconnected during testing, see Figure 2.

4.

The neutral bushing H0 can be left open and floating if it is far away from the phase bushings and it causes more trouble to be shorted to the phase bushings, see Figure 4.

The details of test procedures and connections are in the Appendix I and II, and the nameplates are in Appendix III. In the Factory, the rectifier-transformer should be tested as 3-winding transformer if it has three windings electrically separate. During commissioning, the rectifier-transformer should be tested with and without the rectifier connected. At delivery site, the rectifier transformer should be tested as it was in the factory condition, i.e. as three winding transformer without the rectifier connected. This will check the transformer condition as received and the test results should be kept for diagnostic test baseline. After connecting the rectifier, the rectifier transformer should be retested and the test results should be kept for routine test baseline. The test with rectifier connected should be done as a three winding transformer if there is no rectifier interconnection, otherwise it should be tested as a two winding transformer.

FOUR CASE STUDIES Field Test Results – Alcoa in Mt Holly, SC The tests were performed on the rectifier transformer (S/N# AN69051T11) made by Fuji in 1979 and located at Alcoa aluminum plant in Mt Holly, SC with system configuration as shown in Figure 3 and 26b with rectifier interconnection. The Table 2 is the test results from the factory without the rectifier connected and from the routine tests as a two-winding transformer with the rectifier connected on June 9 th, 2011. Table 3 is test results from the experimental tests as a three-winding transformer with the rectifier connected on January 24 th, 2012. © 2012 Doble Engineering Company -79th Annual International Doble Client Conference All Rights Reserved 3-26

System Configuration Figure 3

Table 2 Overall Test as 2-Winding Transformer – Alcoa in Mt Holly, SC on 06/09/2011 Without rectifier With Rectifier & With Rectifier & Rectifier With Surge Cap Without Surge Cap Contribution Insulation (Factory) in 1980 %PF Cap(pF) %PF Cap(pF) %PF Cap(pF) Cap(pF) CH+CHL 0.25 17,200 0.35 17,155 0.33 17,159 CH 8,450 0.53 8,376 0.53 8,371 8,750 0.28 8,779 0.13 8,786 CHL CL+CHL 0.23 15,000 0.35 5,971,794 1.94 23,385 8,385 6,250 0.35 5,962,622 2.93 14,609 8,359 CL 0.18 8,774 0.13 8,784 CHL CH+CL 0.36 15300 Observations (Table 2): 1.

In the factory, there were only three tests done (CH+CHL, CL+CHL and CH+CL) without the rectifier connected and the two LV windings were tied together and tested as one winding. Calculations were performed to obtain the individual components (CH, CHL and CL).

2.

In the field, there was no opportunity to test the transformer without the rectifier connected. The insulation capacitance compared well between the factory and field tests on the HV side, but not on the LV side due to the presence of the rectifier insulation.

3.

Based on the factory CL, the contribution of the rectifier insulation was calculated to be 8 359pF, which is about 1.3 times the LV winding insulation.

4.

Since the rectifier insulation is bigger than LV winding insulation, the dry type insulation will contribute more watt losses. This will make the power factor higher as shown in [1]. There was no baseline or reference data with rectifier presence, so it was difficult to rate this data. However according to [1], the %PF of the dry type insulation can be up to 3%. In the future when more data is collected, this will improve the acceptance criteria.

5. If the surge capacitors were not disconnected, their values (6uF) overwhelm the LV test results and LV winding insulation (0.0014uF) would be masked. Basically see only the capacitor condition as shown in Table 2. The power factor with the surge capacitor is much lower than the power factor without surge capacitor.


Table 3 Overall Test Results as 3-winding Transformer– Alcoa in Mt Holy, SC on 01/24/2012 Test Insulation kV %PF Cap(pF) Note 10 CH + CHL1 0.90 12,797 =CH+CHL-CHL2 10 CH 0.72 8,380 = CH in 2-winding 10 CHL1 0.53 4,417 ≈ CHL/2 = (8,786 / 2) 0.049 CL1 + CL12 2.78 12,274,610 Rectifier conducting 0.049 CL1 4.86 7,405 ≈ CL/2 = (14,609 / 2) 0.049 CL12 2.06 12,268,740 Rectifier conducting 0.049 =CL+CHL-CL1CL2 + CHL2 3.51 11,597 CHL1 0.049 CL2 4.81 7,207 ≈ CL/2 = (14,609 / 2) 0.049 CHL2 1.02 4,378 ≈ CHL/2 = (8,786 / 2) Observations (Table 3): 1.

The test results are consistent between the two-winding tests and three-winding tests, i.e. the insulation components, either individual or combined system, are tested with the similar value.

2.

“CHL1 is similar to CHL2” and “CL1 is similar to CL2” suggest the two LV windings are constructed identically and mounted one on top another.

3.

The CHL1 and CHL2 capacitances are significant values; this suggests no shielding between the HV and LV windings.

4.

The rectifier interconnection causes the rectifier to conduct at as low as 50V during the inter-LV windings CL12 test were performed. The test set would trip if test performed at higher voltage. The large CL12 capacitance indicates that the rectifier starts to conduct.

5.

Because of the rectifier interconnection, this transformer should be routine tested as 2-winding transformer.

Excitation Tests The tests were performed as regular delta winding test, i.e. between phases with the third phase grounded and guarded. The test results are in Table 4.

Table 4 Excitation Test – Rectifier Transformer in Mt Holly, SC H1 - H2 Test kV 6.004

mA 162

Watts 1262

H2 - H3 X L

mA 67

Watts 569

H3 - H1 X L

mA 134

Watts 1082

X L

IRauto G

Observations (Table 4) 1.

The test results are all inductive (L) and typical for a three phase core form type transformer. The expected pattern of the current and watt is two Highs and one Lower (HLH).


Lessons Learned 1.

To avoid the masking phenomenon, the insulation systems need to be tested separately.

2.

This transformer has three electrically separate windings, so should be tested as three-winding transformer in factory and repeat those tests at the receipt in the field for condition check and retested with rectifier connected as two-winding transformer because of the rectifier interconnection.

3.

The data analysis is performed based on the oil filled transformer insulation for the HV side. For the LV side with rectifier, the dry type insulation limit can be used as reference.

Field Test Results– Rio Tinto Alcan (RTA)’s Alma Plant The tests were not done as planned, however after inspecting the installation the followings are our observations:

H1, H2, H3 Bushings H0 Bushing

Spare Rectifier Transformer in Alma Figure 4 Field Observations 1. The HV phase bushings are in the enclosure duct and the H0 bushing was outside on the other corner of the transformer. This bushing arrangement does not allow the short-circuit to include the neutral bushing. 2. The rectifiers have the interconnection, so this transformer should be routinely tested as 2winding transformer when the rectifiers still connected, but the surge capacitors need to be disconnected for testing.


Field Test Results– Rio Tinto Alcan (RTA)’s Laterrière Plant The tests were performed on the rectifier transformer (S/N#289805) located at RTA aluminum plant in Laterrière, Quebec (Canada) and made by TTI in 1988 with system configuration as shown in Figures 5 and 29 in Appendix for detail nameplate. This unit is twin transformers in the same tank; the only common electrical point is the HV terminals internally connected together. This configuration allows the routine tests be done as three-winding transformer.

Laterrière Rectifier Transformer Figure 5 Overall Test The Table 5 shows the test results in the repair shop in 2011, during the commissioning tests after repair without rectifier connected and during the routine tests as three-winding transformer with the rectifier connected. Table 5 Overall Test Results as 3-Winding Transformer– RTA in Laterrière, QC Repair on site At repair shop Commissioning without rectifier without rectifier Test with rectifier Rectifier (04/18/2007) (10/20/2011) (10/31/2011) Insulation kV Contribution %PF Cap(pF) %PF Cap(pF) %PF Cap(pF) CH + CHL1 10 0.36 34,525 0.28 34,384 0.33 34,607 CH 10 0.36 34,038 0.27 33,895 0.28 34,200 CHL1 10 0.32 484 0.26 477 0.33 401 CL1 + CL12 0.5 0.32 22,832 0.24 22,736 0.36 28,591 5,855 CL1 0.5 0.32 22,680 0.23 22,587 0.32 28,438 5,851 CL12 0.5 0.09 151 0.12 150 0.08 152 CL2 + CHL2 0.5 0.34 23,119 0.23 23,020 0.36 28,756 5,736 CL2 0.5 0.34 22,718 0.23 22,622 0.38 28,271 5,649 CHL2 0.5 0.34 401 0.3 397 0.27 484 86 © 2012 Doble Engineering Company -79th Annual International Doble Client Conference All Rights Reserved 7-26


For this type of configuration (no rectifier interconnection), test should be always performed as threewinding transformer either with or without rectifier connected.

2.

The test results are consistent among the three tests in repair on site, at repair shop or during commissioning.

3.

“CHL1 is similar to CHL2” and “CL1 is similar to CL2” suggest the two LV windings are constructed identically and mounted one on top another.

4.

The CHL1 and CHL2 capacitances are small values; this suggests an existing shield between the HV and LV windings.

5.

The insulation of rectifier system represents 5800pF, which is about only 25% the LV winding insulation. The influence of this dry type insulation is low.

6.

With rectifier connected, testing the LV winding at 1kV would decrease the watt loss to a negative value, but test at 0.5kV produced the test results compared with factory test. The LV winding is rated 535.5V Y (L-N).

Excitation Tests The tests were performed between phases with the third phase grounded and guarded. The test results are in Table 6.

Table 6 Excitation Test Results – Rectifier Transformer in Laterrière, QC H1 – H3 Test kV 8

mA 224

Watts 1254

H2 – H1 X L

mA 182

Watts 1065

H3 – H2 X L

mA 175

Watts 1032

X L

Observations (Tables 6 and 7) The test results are all inductive (L) and the pattern is one high and two lows (HLL), which is not the typical pattern for three phase core form transformer. This pattern can be expected, because there are two HV windings with two different configurations Delta and Wye, and internally connected together as shown in Figure 30; and the tests were performed phase-to-phase with the third phase grounded and guarded. The test results will be the total of the two HV windings combined as described in Table 7. The two outer phases contribute the high value (H) and the middle phase is the lower value (L). Furthermore the two windings have zigzag segments for phase shifting; these segments for phase shifting; these segments will contribute as two high (h) and one lower (l) values in the same way as the main windings

Table 7 Excitation Test Pattern– Rectifier Transformer in Laterrière, QC Phase A (H1-H3) B (H2-H1) C (H3-H2)

HV Delta H+h L+h H+l

HV Wye H+h+H+l L+h+ H+h H+l+L+h

Total 3H+2h+l H+2L+3h 2H+L+h+2l

Results Highest Lower Lowest


Doble Turn Ratio Two methods were tried out. The first method was the standard method (1) and the second method (2) was modified to neutralize the phase shifting effect. The test results are in Table 8.

Table 8 Doble Ratio Test on Rectifier Transformer in Laterrière, QC Winding

NP Ratio

Method

H-L1 (S) Y-D

42.96

H-L2 (R) D-D

74.40

1 2 1 2

H1-H3/ X1-X3

H2-H1/ X2-X1

H3-H2/ X3-X2

85.72 56.55 73.25 81.36

104.74 56.61 77.10 81.36

80.48 56.67 72.20 81.43

Max %Cv 0.11% 0.05%

Notes Inconsistent Consistent Inconsistent Consistent


The test results are not comparable with the nameplate ratio. This can be expected due to the zigzag winding segments as described in [4] and requires a correction factor or three phase source for ratio test to obtain the nameplate ratio.

2.

The standard method (#1) used for standard transformer produces different ratios among phases due to the zigzag winding in different core leg and the flux distribution unequal in other “not under tested” legs.

3.

The modified method (#2) produces a consistent ratio among phases. This method can be used for condition monitoring or diagnostic to detecting a problem in a winding. Any deviation of a measured ratio should indicate a problem and prompt an investigation as described in [5] that recommends the use of Coefficient of Variation (%Cv) for analysis.

4.

We did not have opportunity to perform all the test and analysis for this configuration transformer and hope to complete it in the second part of the study.

Lessons Learned 1.

For this transformer, we can use the criteria of data analysis of the regular oil filled transformer for Overall tests.

2.

Test should be performed at the rated voltage of the system or below.


Field Test Results– Rio Tinto Alcan (RTA) in Arvida Plant

Arvida Rectifier Transformer Figure 6 Overall Test The Table 9 shows the test results from historical data in 2007 and the experiment tests on 10/28/2011 as twowinding transformer with the rectifier connected. The intention of the 10/28/2011 test was to try the three-winding configuration, but the surge capacitors could not be disconnected because of access limitation.

Table 9 Overall Tests Results - Rectifier Transformer in Arvida, QC Insulation

Test kV

Historical Data (2007) %PF

CH + CHL CH CHL(UST)

10 10 10

0.81 1.14 0.55

Cap (pF)

Routine Test (2011) %PF

Cap(pF)

0.99 1.64 0.77

9,986 2,038 7,941

9,940 2,030 7,910


Any attempt to test the LV winding with surge capacitor connected resulted in tripping the test set. So we could perform the test only on HV winding similar as in the previous routine test.

Excitation Tests The tests were performed in the same way as the standard delta winding excitation test, i.e. between phases with the third phase grounded and guarded. The test results are in Table 10.

Table 10 Excitation Test Results – Rectifier Transformer in Arvida, QC H1 - H2 Test kV 3

mA 816.23

Watts 5048.1

H2 - H3 X L

mA 999.79

Watts 6384.5

H3 - H1 X L

mA 1068.8

Watts 6354

X L


The test results are all inductive (L) and the pattern is normal of 2 highs and lower, because the HV winding is a regular delta winding. © 2012 Doble Engineering Company -79th Annual International Doble Client Conference All Rights Reserved 10-26

Lessons Learned: 1.

The surge capacitors should be relocated for easy access to be disconnected for testing the LV winding.

2.

This transformer has three electrically separate windings and no rectifier interconnection, so should be tested as three-winding transformer if the surge capacitors can be disconnected.

CONCLUSION AND RECOMMENDATION The purpose of this paper was to demonstrate the best test procedure for rectifier transformer with consideration of the physical installation complexity. To that end, the case studies show clearly that different test procedures will provide different test results, will limit their usefulness and allow us to conclude the following: 1.

2.

For Overall test, the rectifier transformers should be tested according to the number of electrically separate windings. Most of them are three winding transformers, in this case they should be tested as: a.

In the factory, tested as three-winding transformer;

b.

At the delivery site, tested as in factory condition;

c.

After connected to the rectifiers, tested as three-winding transformer if there is no rectifier interconnection; or as two-winding transformer if there is the rectifier interconnection.

d.

The power factor or watt loss should be similar as the oil filled transformer, with the exception of the LV side when connected to rectifier. The power factor of the combined LV winding and rectifier is expected to be higher.

The excitation tests should be performed in the same way as the regular power transformer. The test results should be: a.

The current and watt loss pattern will also be two high and one low (regular pattern) if the HV winding has no zigzag or phase-shifting winding segment.

b.

The zigzag winding segment will alter the current/watt pattern to one high and two lowers. The two lowers may be different depending the zigzag winding.

3.

The test procedures in Appendix I and II should be used to obtain a consistent test results.

4.

The Doble turns ratio and the leakage reactance tests were not completed in this work, are required more field testing and analysis for future publication.

ACKNOWLEDGEMENTS The authors would like to thank Mr. Francis Thibault, RioTinto-Alcan, for assisting in the field works and provide all test results and the information for the rectifier transformers in Rio Tinto Alcan plants.

REFERENCES [1] Jill C. Adee and William L. Bailey, “Power-Factor Testing of Ventilated and Non-Ventilated Dry-Type Transformers (A Review)”, Proceedings of the Sixty-Sixth Annual International Conference of Doble Clients, 1999, Sec. 8-18 [2] Long Pong, “Review Negative Power Factor Test Results and Case Study Analysis,” Minutes of the Sixty Ninth Annual International Conference of Doble Clients, 2002 – 13B [3] Doble Test Procedure – Chapter 1, General “Introduction To Doble Testing", Copyright © 2000, Doble Engineering Company. © 2012 Doble Engineering Company -79th Annual International Doble Client Conference All Rights Reserved 11-26

[4] Norbert Gilbert, “Doble Turns Ratio for Transformers with Zigzag Winding Configurations” Minutes of the 73rd Annual International Conference of Doble Clients, 2006 – T-4 [5] Long Pong, Kate Brady and Martin Gamache “Ratio and Saturation Curve Testing On Current Transformer Installed on Power Apparatus,” Minutes of the 77th Annual International Conference of Doble Clients, 2010 – BIIT-

BIOGRAPHY Long Pong has been employed at Doble Engineering since 2000, and currently works as a Senior Principal Engineer in the Client Service Department. He has amassed 24 years of experiences in condition assessment, electrical testing/repair and project management of Generation, Transmission and Distribution apparatuses. In the last eight years, Mr. Pong has published twenty-six technical papers pertaining to condition assessment, troubleshooting and new test techniques of power electrical apparatus. Before joining Doble, he was employed at Alcan-Énergie Électrique and Hydro-Quebec. He is IEEE member, and has been a CEA (Canadian Electrical Association) member and a registered professional engineer in North Carolina. He obtained his Bachelor of

Pierre LeBlanc has been employed at Alcoa since 1998 and currently works as a Power Engineer and Substation Supervisor. He has been involved in industrial equipment maintenance for the last 21 years. He specialized on the last 4 years working essentially on medium voltage equipment including regulating and rectifier transformers systems. For the 14 years with Alcoa, he has worked as Reliability Engineer assigned to many department including the substation. Prior to working on the aluminum industry, he was employed for 7 years at Quebec Cartier Mining as a maintenance, project engineer and Lineman supervisor. He also worked 3 years at the engineering firm BBA, and 3 years in the Combat System Engineer program for the Canadian Navy. He is IEEE member, was in the OIQ for 15 years. He obtained his Bachelor of Electrical Engineering from Laval University in Quebec, Canada, in 1985.

Hugo Simard, P.E., obtained his Bachelor of Electrical Engineering from University of Québec in Chicoutimi, Canada, in 1997. He has been working for Rio Tinto Alcan for the last fifteen years and is responsible for providing the technical support to transformer and DC substation of aluminum plant.


APPENDIX I Specific Test Procedures 3-Winding Transformer at Alcoa Plant in Mt. Holly, SC Overall Tests Table 11 Overall Tests of Rectifier-Transformer as Three-Winding ChoiceofLV Cables

#Line 1 2 3 5 6 7 9 10 11

Voltage (kV) 10 10 10 0.5 0.5 0.5 0.5 0.5 0.5

HV Cable

Red LVLead

Blue LVLead

Fig.

HV

LV1

LV2

8

LV1

HV

LV2

9

LV2

HV

LV1

10

Test Mode

Measure

Guard-B Guard-RB UST-R Guard-B Guard-RB UST-R Guard-B Guard-RB UST-R

CH+CHL1 CH CHL1 CL1+CL12 CL1 CL12 CL2+CHL2 CL2 CHL2

CHL2

HV

CHL1

CH

LV1

CL12

CL1

LV2 CL2

Tank & Core

Three-Winding Insulation System Figure 7

Overall Test Connection on LV1 Figure 9

Overall Test Connection on HV Figure 8



2-Winding Transformer at Alcoa Plant in Mt. Holly, SC Overall Tests Table12 Overall Tests of Rectifier-Transformer as 2-Winding #Line 1 2 3 5 6 7

Voltage (kV) 10 10 10 0.5 0.5 0.5

HV Cable

LV Lead

Fig.

HV

LV

12

LV

HV

13

Test Mode

Measure

GND Guard-RB UST-RB GND Guard-RB UST-RB

CH+CHL CH CHL CL+CHL CL CHL

CHL2

HV

CHL1

CH

LV1

CL12

CL1

LV2 CL2

Tank & Core



\ Overall Test Connection on LV Figure 13


3-Winding Transformer at Rio Tinto Alcan Plant in Laterriere, QC Overall Test

A. Overall Tests on HV winding (Lines 1, 2, 3)

B. Overall Tests on S Winding, LV1 (Lines 5, 6, 7

C. Overall Tests on R Winding, LV2, (Lines 9, 10, 11) Overall Test Connections Figure 14 Table 13 Overall Tests Test Line

Test Mode

Measured

1 2 3 5 6 7 9 10 11

Guard-B Guard-RB UST-R Guard-R Guard-RB UST-B Guard-B Guard-RB UST-R

CH+CHLS CH CHLS CLS+CLSLR CLS CLSLR CLR+CHLR CLR CHLR

HV Cable

Red LV Lead

Blue LV Lead

Fig.

HV

S

R

14A

S

HV

R

14B

R

HV

S

14C

Test Results: The power factor of HV winding should be 0.5% or below, however the power factor of LV windings can be higher due to the rectifier insulation. © 2012 Doble Engineering Company -79th Annual International Doble Client Conference All Rights Reserved 15-26

Excitation Test A. Excitation Test on H1-H2

B. Excitation Test on H2-H3

C. Excitation Test on H3-H1

Excitation Test Connections Figure 15 Table 14 Excitation Tests Test # 1 2 3

Test Mode UST-R UST-R UST-R

HV cable H1 H2 H3

Red LV lead H3 H1 H2

Ground None None None

Test Results: The pattern of test results is expected to be three different values: High, Medium and Low in the currents and watt losses due to the zigzag windings


Doble Turns Ratio Test TTR

A) True Capacitance Test, CTrue

B) Ratio Test on H1-H3/S1-S3

C) Ratio Test on H1-H3/R1-R3 Doble Ratio Test Connections Figure 16


Table 15 Doble Ratio Tests Test Line 1 2 3 4 5 6

Ratio H1-H3/ S1-S3 H2-H1/ S2-S1 H3-H2/ S3-S2 H1-H3/ R1-R3 H2-H1/ R2-R1 H3-H2/ R3-R2

HV Cable

TTR-Cap + LV Lead

Ground

Figure

H1

S1

H3, S3

16b

H2

S2

H1, S1

H3

S3

H2, S2

H1

R1

H3, R3

H2

R2

H1, R1

H3

R3

H2, R2

16c

Test Results The measured turn ratio may not compare to the nameplate ratio due to the zigzag winding


Doble Turns Ratio Test – Method 2

TTR Capacitor S3

S2

S1

H1 H2 H3

R1

R2

R3

Ground Lead

A) True Capacitance Test, CTrue

B) Ratio Test on H1-H3/S1-S3

S3

S2

S1

H1 H2 H3

R1

R2

R3

C) Ratio Test on H1-H3/R1-R3 Doble Ratio Test Connections Figure 17


Table 16 Doble Ratio Tests Test Line 1 2 3 4 5 6

Ratio H1-H2/ S3-S12 H2-H3/ S1-S23 H3-H1/ S2-S13 H1-H3/ R1-R3 H2-H1/ R2-R1 H3-H2/ R3-R2

HV Cable

TTR-Cap + LV Lead

H1

S3

H2

S1

H3

S2

H1

R1

H2

R2

H3

R3

Ground H2, S1, S2 H3, S2, S3 H1, S1, S3 H3, R2, R3 H1, R1, R3 H2, R1, R2

Figure 17b

17c

Test Results The measured turn ration may not compare to the nameplate ratio due to the zigzag winding. But they should compare well among the phases.


APPENDIX II General Test Procedures Overall Test For Rectifier Transformer without Interconnection Table 17 Overall Tests of Rectifier-Transformer as Three-Winding Choice of LV

#Line

Cables

Voltage

HV

Red

Blue

(kV)

Cable

LVLead

LVLead

Fig.

Test Mode

Measure

Guard-B

CH+CHL1

Guard-RB

CH

1

10

2

10

3

10

UST-R

CHL1

5

0.5

Guard-B

CL1+CL12

6

0.5

Guard-RB

CL1

7

0.5

UST-R

CL12

9

0.5

Guard-B

CL2+CHL2

10

0.5

Guard-RB

CL2

11

0.5

UST-R

CHL2



HV

LV1

LV2

LV1

HV

HV

LV2

LV2

LV1

18

19

20




Bushing Tests Table 18 Tests of Bushings Test # 1 2 3

kV 10 10 10

C1 LV Lead H1-Tap H2-Tap H3-Tap

HV Cable H1 H2 H3

Test Mode UST-R UST-R UST-R

kV 0.5 0.5 0.5

HV Cable H1-Tap H2-Tap H3-Tap

A) C1 Test Connection

C2 LV Lead H1 H2 H3

Test Mode Guard-R Guard-R Guard-R

b) C2 Test Connection

Typical Test Connection of a Bushing Figure 22

Surge Arrester Test Connection Table 19 Testing of Arrestor Test# 1 2 3

kV 10 10 10

HV Cable H1 H2 H3

Test Mode GST-GND GST-GND GST-GND


Excitation Test: All other windings are open-circuited. Table 20 Excitation Tests HV Y without H0 Y withH0 Delta

Test# 1 2 3 1 2 3 1 2 3

HV Y without H0 Figure 23

kV 10 10 10 10 10 10 10 10 10

HV Cable H1 H2 H3 H1 H2 H3 H1 H2 H3

LV Lead H2 H3 H1 H0 H0 H0 H2 H3 H1

Ground H3 H1 H2

HV Y with H0 Figure 24

Test Mode UST UST UST UST UST UST UST UST UST

Connection Fig.22

Fig.23

Fig.24

HV Delta Figure 25


APPENDIX III Rectifier Transformer Nameplate H2

H1

H2

V1

Z2

X2

H3

H1

U1P X2P V1P Y2P W1P Z2P

X2N U1N Y2N V1N Z2N W1N

H3

U1

W1

Y2

b) Rectifier-Transformer #1

a) Physical Layout

Manufacturer Year Capacity (MVA) Voltage (kV) HV/LV1; LV2 Configuration Class

Fuji 1979 34.28 MVA 35.2/0.638; 0.638 D/ D D FA

c) Rectifier-Transformer #2 Fuji Rectifier-Transformer at Alcoa in Mt Holly, SC Figure 26


H1

H0

H1

H2

R2 R1

H3

R2N R4N R6N R2P R4P R6P

H0 H3

R3 R6

H

a) Physical Layout

R5

R4

R1N R3N R5N R1P R3P R5P

b) Electrical Diagram Manufacturer Year Capacity (MVA) Voltage (kV) HV/LV1; LV2 Configuration Class

ABB 2010 137 42.39/1.127; 1.138 Y/Y D OFAF

ABB Rectifier-Transformer #3 at RTA in Alma, QC Figure 27 H1

H1 H0

H0

H2

H3 2U

H3 3V

LV1

2V

H LV2 Y

X 2W 3U

a) Physical Layout

b) Electrical Diagram Manufacturer Year Capacity (MVA) Voltage (kV) HV1, HV2 / LV1, LV2 Configuration Class

ABB 2003 70.9 42.41 / 1.127, 1.138 YY/DY OFAF

ABB Rectifier-Transformer #4 Figure 28


3W

H3 H2 H1

S3 h12

R2

h13 R1

S1

∆ (LV1)

S2

h22

H1

Y∆

S1

R3 h11

S2

h23

h21

H2

∆ (LV2)

S3 R1

a) Electrical Diagram

R2

H3

R3

a) Physical Layout

Manufacturer Year Capacity (MVA) Voltage (kV) HV1, HV2 / LV1, LV2 Configuration Class

TTI 1988 91.73 69/0.924; 0.924 DY/DD ONAN/ODAF

TTI Rectifier-Transformer #5 at RTA in Laterriere, QC Figure 29 H1

H2

N1

A2

A3

H3

N1

H2

A4

A1

N2

A5

A6 A5 A4 A3 A2 A1 B1 B2 B3 B4 B5 B6

H1

B3

H3

A6 B2

N2

B1

B4 B5

b) Electrical Diagram – Rectifier-Transformer #6

a) Physical Layout

A3

H2

H1

B6

N1 A2

H3

A1

A5

B3

A4 B1 A6

N2 B2

B5

c) Electrical Diagram – Rectifier-Transformer #7 Manufacturer Year Capacity (MVA) Voltage (kV) HV / LV1, LV2 Configuration Class

B4

CWC 1941 7.5 13.2/0.624; 0.624 D / Y-Y Y-Y ONAN/ONAF

Westinghouse Rectifier-Transformers at RTA in Arvida Figure 30 © 2012 Doble Engineering Company -79th Annual International Doble Client Conference All Rights Reserved 26-26

B6

Doble Engineering - Testing Rectifier Transformers - Presentation

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