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0 04-05-2012 Issue for Construction

A 30-01-2012 Issue for Approval B.M.SHIM D.W.SHIN S.H.HYUN

REV. DATE DESCRIPTION DSGN CHKD APPD

PROJECT :

TWO(2) x 500 MW MONG DUONG 1 THERMAL POWER PLANT

EMPLOYER :

CONSULTANT :

CONTRACTOR :

DESIGNED BY DATE TITLE :

B.M.SHIM 30-01-2012CALCULATION

FORGENERATOR TRANSFORMER SIZING

CHECKED BY DATE

D.W.SHIN 30-01-2012

APPROVED BY DATE PROJECT NUMBER DOCUMENT NUMBER REV.

S.H.HYUN 30-01-2012 ADB/MD1-TPIP/EPC150911 MD1-0-E-505-06-00001 0

FOR CONSTRUCTION

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MONG DUONG POWER STATION PH.1Calculation for Generator Transformer Sizing Rev. 0

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CONTENTS

1.0 PURPOSE ............................................................................................................................... 1

2.0 CODE & STANDARD .......................................................................................................... 1

3.0 SITE CONDITIONS .............................................................................................................. 1

4.0 CALCULATION CRITERIA ............................................................................................... 1

5.0 GIVEN DATA FOR GENERATOR TRANSFORMER SIZING ..................................... 2

6.0 CALCULATION FOR GENERATOR TRANSFORMER SIZING ................................ 2

7.0 DECISION OF GENERATOR TRANSFORMER SIZING ............................................. 3

ATTACHMENT#1 HEAT BALANCE DIAGRAMS

ATTACHMENT#2 TRANSFORM SIZING CALCULATION

ATTACHMENT#3 LOADING GUIDE FOR OIL IMMERSED POWER TRANSFORMER

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1.0 PURPOSE

This calculation is prepared to determine and verify the capacity of generator transformer

(525kV/21kV) for Mong Duong Thermal Power Plant Phase 1 Project in Vietnam .

2.0 CODE & STANDARD

IEC 60076: Power Transformers

3.0 SITE CONDITIONS

The site climatic conditions and the site design conditions are as follows :

a) Absolute minimum air temperature : -0.2

b) Absolute maximum air temperature : 39.5

c) Ambient design temperature : 39.5

d) Humidity range : 18-92%

4.0 CALCULATION CRITERIA

To calculate transformers sizing, the following points are considered.

a) The load for the Unit Auxiliary Transformer will not be considered.

b) The capacity of generator transformer will be capable for the operating power factorrange of 0.85 lagging to 0.9 leading at the generator terminals.

c) The maximum generator output based on the maximum turbine output(VWO condition)is considered as follows ;

- Output : 551.500 MW (Refer to Attachment #1)- Voltage : 21 kV 5% , 50 Hz- Current : 15,162.3 Amperes- Power Factor : 0.85 Lagging

d) Generator transformer voltage ratings are as follows ;

- High voltage : 525.0 kV WYE with grounded neutral- Low voltage : 21.0 kV DELTA

e) Generator transformer will be operated at its ODAF rating under most condition.

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5.0 GIVEN DATA FOR GENERATOR TRANSFORMER SIZING

a) The generator will be operated with max. continuous rating 648.82 MVA (551.500 MWat power factor 0.85 lagging).

DescriptionOperating Condition

(Case : VWO) Remark

Ambient Air Temperature 34.5 C

Refer to Heat

Balance Diagrams

(Attachment #1)

Cooling Water Temperature 30.5 C

Relative Humidity 85.0 %

Power Factor 0.85 lagging

Power at the Generator Terminal 551.500 MW

b) The generator will be operated in any of the following power factor ranges ;

- Case I : 0.90 P.F Leading- Case II : 1.0 P.F- Case III : 0.85 P.F Lagging

6.0 CALCULATION FOR GENERATOR TRANSFORMER SIZING

The generator output based on the maximum turbine output(VWO condition) is calculated asfollows ;

- Power factor 0.90 Leading :

MVA = 551.500 / 0.9 = 612.778 MVA at 39. 5C amb. temp.

- Power factor 1.0 :

MVA = 551.500 / 1.0 = 551.500 MVA at 39. 5C amb. temp.

- Power factor 0.85 Lagging :

MVA = 551.500 / 0.85 = 648.824 MVA at 39. 5C amb. temp.

The capacity of generator transformer will be sized to cover the generator output at the powerfactor ranges of 0.85 lagging to 0.9 leading as calculated above and therefore, generatortransformer capacity at 39. 5C amb. temp should be :

618.906 MVA or above @ 0.90P.F. Leading

557.015 MVA or above @ 1.0P.F.

655.312 MVA or above @ 0.85P.F. Lagging

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MONG DUONG POWER STATION PH.1Calculation for Generator Transformer Sizing Rev. 0

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The rated capacity of transformer has been selected as 660MVA(based on ODAF) at theambient temperature 39.5C, which has the output capabilities by ambient temperature aslisted below. Also, this capacity will satisfy to have minimum 1% margin for generator outputfor all ambient temperature condition as shown in Attachment #2.

Ambient Temperature -0.2C 34.5C 39.5C

Transformer Capacity[MVA] 842.1 682.8 660

* Note) The transformer capacity is calculated as per the loading factor at the differentambient temperatures. (Refer to the attachment #3, IEC 60354 Loading Guide for Oil-immersed Power Transformers, 3.3 Normal continuous Loading Table 6. Acceptable loadfactor for continuous duty K24 at different ambient temperatures (ON, OF and OD cooling)).

7.0 DECISION OF GENERATOR TRANSFORMER SIZING

Because the capacity of transformer means a value of input power to transformer, the capacityof generator transformer should be equal or larger than the output of generator.

Based on the calculation results given above, the capacity of the generator transformer isselected as below;

660MVA(220MVA x 3), ODAF, 525/21 kV

Z=14.5% @660MVA

On Load Tap Changer on HV side : 17% with 1.3% steps

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Attachment #2 Transformer Sizing Calculation

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GENERATOR TRANSFORMER SIZING CALCULATION

1. GENERATOR RATING BASED ON 34.5Deg.C 2.TRANSFORMER IMPEDANCE DGEN MVA PF MW %z 14.50%648.8235 0.85 551.5 X/R RATIO

551.5000 1 551.5 TOLERANCE 7.5%612.7778 0.9 551.5 MARGIN 101%

3.CALCULATION

MW MVAR MVAGOUT(P) GOUT(Q) TIN(M) TIN(M)*1.01

0.85 551.5 341.8 648.824 655.31181 551.5 0.0 551.500 557.0150

0.9 551.5 -267.1 612.778 618.90560.85 551.5 341.8 648.824 655.3118

1 551.5 0.0 551.500 557.01500.9 551.5 -267.1 612.778 618.90560.85 551.5 341.8 648.824 655.3118

1 551.5 0.0 551.500 557.01500.9 551.5 -267.1 612.778 618.9056

Temp Deg. Generator Output

MWGOUT(P)

PFTR Input(TIN(M)) Considering Marg

(MVA)

34.5 551.500

39.5 551.500

-0.2 551.500

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Attachment #3

Loading Guide for Oil-Immersed Power Transformers (IEC 60354)

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