Station Transformer Sizing Report for Arar

TCE CONSULTING ENGINEERS LIMITED

33/4.16kV STATION TRANSFORMER

30421007-3CL-00006P0A

SHEET i OF i

SIZING REPORT

SAUDI ELECTRICITY COMPANY EASTERN OPERATING AREA Dammam, Saudi Arabia GENERATION EXPANSION OF ARAR POWER PLANT (CONTRACT NO :30421007/00)

DESIGN BASIS FOR 33/4.16kV STATION TRANSFORMER SIZING TRANSFORMER SIZING DOCUMENT NO. : 30421007-3CL-00006-P0A

JULY 2004

ENGINEERING CONSULTANT TCE CONSULTING ENGINEERS LIMITED 73/1, ST. MARK’S ROAD BANGALORE 560 001 INDIA

CONTRACTOR: AL-TOUKHI COMPANY FOR INDUSTRY & TRADING P.O. BOX 497, RIYADH 11411, KINGDOM OF SAUDI ARABIA ARABIA TEL. 00966-1-4633660 : FAX. 00966–1-4631150

P0A 29-07-2004

DG

SR

REV NO . DATE

PREPARED BY

CHECKED BY

FILENAME : Station Transformer sizing report for Arar.doc

CLEARED BY

APPROVED BY TCE FORM 032 R1

TCE CONSULTING ENGINEERS LIMITED

30421007-3CL-00006P0A


CONTENTS SHEET i OF i

SIZING REPORT

CONTENTS

CLAUSE No.

DESCRIPTION

PAGE No.

1.0

INTRODUCTION

1

2.0

OBJECT

2

3.0

REFERENCES

3

4.0

ASSUMPTIONS / CONSIDERATIONS

4

5.0

SIZING CALCULATION

5

6.0

CONCLUSIONS

7

ISSUE A FILE NAME: F120R1

FORM NO. 120 R1

TCE CONSULTING ENGINEERS LIMITED 30421007-3CL-00006P0A


WRITEUP SHEET 1 OF 8

SIZING REPORT

1.0

INTRODUCTION:

1.1

Al-Toukhi company for Industry & Trading has been awarded turnkey contract for Open Cycle Gas Turbine based CPS expansion project at Arar of Saudi Electric Company-Eastern Operation Area (SEC-EOA), Saudi Arabia.

1.2

The project consists of design, engineering, procurement, installation, testing and commissioning of two (2) Nos. 60.16MW @ 50 ?C, PG7121 (EA) model Gas Turbine Generator unit of GE make along with associated Generator Transformer and other balance of plant electromechanical equipment.


FORM NO. 120 R1




SIZING REPORT

2.0

OBJECT:

2.1

The object of this report is to determine the following :

2.1.1

The rating of Station Transformers, T401 & T402 required to feed the GT Starting Motors & Station Auxiliary loads and to provide backup power supply to Unit Auxiliary Switchgears for proposed Gas Turbine Unit#7 and Unit#8 to be installed at Arar Central Power Station, Saudi Arabia.


FORM NO. 120 R1




SIZING REPORT

3.0

REFERENCES:

3.1

Document No 30421007-3CL-0003-POA- Station & Unit Auxiliary Transformer sizing report.

3.2

Key One Line Diagram: Drawing No.30421007-E3-00001-P0A.


FORM NO. 120 R1




SIZING REPORT

4.0

ASSUMPTIONS/CONSIDERATIONS:

The following assumptions are made for purpose of Station Transformer sizing calculations. 4.1

A power factor of 0.85 and an efficiency of 0.95 has been considered for GT starting motor.

4.2

As per SEC-EOA’s clarification vide A40 of clarification set No 04 dated 10th Dec 2003, starting of only one GTG starting motor has been considered at a time.

4.3

An overall margin of minimum 10% is considered on Station Auxiliary loads at 480V Station Switchgear over and above the base load kVA rating. This is to take into account variations in the estimates during detailed engineering and for future addition of loads.

4.4

The final rating of the transformer will not be less than the rating indicated in the Technical proposal.

4.5

For Station Transformer sizing, the following conditions are considered.

4.5.1

Under normal conditions, each Station Transformer will feed the station loads connected to its bus section with the bus coupler in open condition.

4.5.2

During failure of one ST, the other ST will feed the entire 4.16kV Switchgear loads. Under this condition, outage of two UAT’s and starting of one 4.16kV Starting motor is considered, such that the ST will be feeding the starting motor, entire station loads and two Unit auxiliary Switchgear loads.


FORM NO. 120 R1




SIZING REPORT

5.0

SIZING CALCULATION :

5.1

Calculation of load during starting of one 4.16kV GT Starting motor with 100% base load on 4.16kV Switchgear:

5.1.1

Maximum Load to be fed from one Station Transformer during starting of one GT Starting motor with 100% base load on 4.16kV Switchgear

5.1.2

Maximum Base load on 4.16kV switchgear =

=

Starting kVA of GT Starting motor + Base load in kVA on 4.16kV Switchgear

1765kVA

(Refer to Page 2 of 2, Annexure-II of Doc.No.30421007-3CL-00003P0A: Station and Unit Auxiliary transformers sizing report ) Considering 10 % margin, Base load = 1765 x 1.1 = 1941.5 kVA 5.1.3

The input kVA of Starting motor is calculated considering efficiency & power factor. Starting motor rating =

663 kW at a Power factor of 0.85 and an efficiency of 0.95

(As per preliminary load list. This rating would be confirmed with Sub Vendor) Starting Motor kVA

= 663 / 0.85x0.95 = 821 kVA

As per Cl.No.6.10.05.B.3, Page 214 of 336 of PTS-1022, the locked rotor currents at rated voltage shall not exceed 550% of the full load current. (the actual starting current of GT motor would be verified with Sub vendor) Hence, kVA of the motor during starting

= 5.5 x full load kVA = 5.5 x 821 = 4515.5 kVA


FORM NO. 120 R1




SIZING REPORT

5.1.4

Hence, maximum Load to be fed from one Station Transformer during starting of one GT Starting motor with 100% base load on 4.16kV Switchgear

=

Starting kVA of GT Starting motor + Base load in kVA on 4.16kV Switchgear

=

1941.5 + 4515.5

=

6457 kVA

5.2

Calculation of load during running of one 4.16kV GT Starting motor with 100% base load on 4.16kV Switchgear:

5.2.1

Maximum Load to be fed from one Station Transformer during running of one GT Starting motor with 100% base load on 4.16kV Switchgear

5.2.2

Maximum Base load on 4.16kV switchgear =

=

Running kVA of GT Starting motor + Base load in kVA on 4.16kV Switchgear

1765kVA

(Refer to Page 2 of 2, Annexure-II of Doc.No.30421007-3CL-00003P0A: Station and Unit Auxiliary transformers sizing report ) Considering 10 % margin, Base load = 1765 x 1.1 = 1941.5 kVA 5.2.3

Running load required for Starting Motor

= 663 / 0.85x0.95 = 821 kVA

5.2.4

Hence, maximum Load to be fed from one Station Transformer during running of one GT Starting motor with 100% base load on 4.16kV Switchgear

=

Running load in kVA of GT Starting motor + Base load in kVA on 4.16kV Switchgear

=

1941.5 + 821

=

2762.5 kVA ISSUE A

FILE NAME: F120R1

FORM NO. 120 R1




SIZING REPORT

5.3

The minimum kVA rating of Station Transformer shall be such that:

5.4

i)

it shall be able to deliver the running load required continuously.

ii)

For the starting period of one GT Starting motor, the Station Transformer shall be able to meet the load kVA requirement without exceeding the permissible temperature rises.

iii)

during starting of GT Starting motor, Voltage dip shall be limited to 12.5% as per clause 4.03 of PTS-1022 Page No. 90 of 336.

As per Cl.No.5.2.4 above, the minimum Station Transformer rating shall be 2763kVA to meet the full load requirements. However, as per clause 3.03.2 of PTS-1022, Page No. 37 of 336, 7500kVA transformer is the minimum rating required. Hence, kVA rating of Station Transformer selected = 7500kVA.

5.5

As can be seen, 7500kVA rated transformer is meeting the requirements of Cl.No.5.3 (i) & (ii) above. Also, voltage dip during motor starting is observed to be 6% as per System studies conducted which is well within the limit of the allowable 12.5%.

6.0

CONCLUSION:

6.1

The final selected ratings for Station Transformers are tabulated below : Sl.No.

Parameter

Unit

1

Rating

kVA

2

Voltage load)

3

%Impedance

%

4

Vector Group

-

5

Cooling Type

-

6

Indoor / Outdoor

-

ratio

(No

kV

ST

Reference

As per Cl No.5.0 above As per Cl No.3.03.2 33/4.16 of PTS-1022 As per Cl No.3.03.2 8 of PTS-1022 As per Cl No.3.03.2 Dyn1 of PTS-1022 As per Cl No.3.03.2 ONAN of PTS-1022 As per Cl No.3.03.2 Outdoor of PTS-1022 7500


FORM NO. 120 R1




SIZING REPORT

Sl.No.

Parameter

7

Dry type type

8

/Oil

filled

Tap changer

Unit

ST

-

Oil Filled

-

Off circuit tap Changer +/- 5%

Reference

As per Cl No.3.03.2 of PTS-1022 As per Cl No.3.03.2 of PTS-1022

Where, ST : - Station Transformer


FORM NO. 120 R1

Station Transformer Sizing Report for Arar

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