Answer / sathish n p

Take an example let tr rating is 2500KVA, 11KV/415v

TO calculate maximum loading on primary side
2500 X 10^3=1.732 X 11 X 10^3 X I

I=131.01Amps
Similarly Secondary side
2500 X 10^3=1.732 X 415 X I

I=3478 Amps

Answer / debashis

For determining the optimum loading of a transformer we need
to determine the load for which my copper loss would be equal to my iron loss.

At this point the loss would be at its minimum level and hence
the efficiency would be maximum.

Remember Iron loss is independent of load and copper loss depends on the load.

Answer / elminshawy

Sorry Vikadeny
But how it is optimum if I bought a 100MVA transformer and
I only loaded it to 50MVA or 70MVA ?

for optimum loading of transformers please refer to IEC
standard (60354 Loading guide for oil-immersed power
transformers )

Answer / rajendran

I think question refers to the optimum loading at which the
efficiency of the transformer is more/maximum...


if it is like that then we can refer the loading curves
provided by the manufacturer of the transformer....

generally as a thumbrule the optimum loading point is
around 85 to 95 percent of the capacity..

Answer / vikadent

As a rule of thumb, the optimum loading is between 50% to 70
% and my reference is Electrical installation guide by
Schneider and this is the range where the losses are minimum
inside the transformer.

Answer / khalid hussain shaikh

POWER=1.732*VOLTAGE*CURRENT*POWER FACTOR
HERE POWER=2500KVA
VOLTAGE=11 KV
POWER FACOR AS STANDARD=0.85
I=?
I=2500KVA/1.732*11KV*0.85
KV CANCELLED EACH DENOMINATOR AND NUMARATOR,
I=2500/1.732*11*0.85
I=154 AMP (11 KV SIDE)
I=2500 KVA/1.732*415 V*0.85
V CANCELLED EACH DENOMINATOR AND NUMARATOR
I=2500 K/610.963
I=4.091 KA
I=4091 AMP

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TRAFO 1. WHY BREATHER IS USED. 2. WHY OIL GOES DOWN IN CONSERVATOR TANK. 3. WHY WE ARE TAKING OIL SAMPLE TAKING FROM BOTTOM OF TRANSFORMER. 4. HOW TO CHECK IR VALUE OF TRANSFORMER. 5. WHY OLTC HAVING BUCHHOLZ TRIP ONLY; WHY NO ALARM. 6. OFF LOAD TAP CHANGER OPERATION PROCEDURE. 7. TR. SHUTDOWN / ISOLATION PROCEDURE. 8. WHEN THREE TRS. IN PARALLEL, ONE TR. IS NOT SHARING THE LOAD – WHAT IS REASON AND WHAT YOU WILL DO. 9. WHY TR. HAS OLTC IN HV SIDE. 10. WHAT IS % IMPEDANCE. 11. WHY TR. RATING IN MVA. 12. WHAT IS VECTOR GROUP IN TR. 13. CONDITION FOR PARALLEL OPERATION OF TRS. 14. WHAT IS TERTIARY WINDING. WHERE IT WILL BE. 15. IF TR. TRIP ON BUCHHOLZ OR TAP CHANGER RELAY, WHAT YOU WILL DO. 16. DIFFERENCE BETWEEN OIL TEMP. AND WINDING TEMP. PROTECTION 17. HOW WINDING TEMP. IS MEASURED IN CAST RESIN TR. 18. DIFFERENT TYPES OF FAULTS IN TR. Trafo - Page-1 of 2 19. WHAT HAPPENS WHEN TR. CHARGED FROM LV. 20. WHAT WILL YOU DO IF MEGGER READING SHOWS ZERO BETWEEN LV WINDING AND EARTH. 21. CAN WE INTERCHANGE BUCHHOLZ RELAY OF MAIN TANK AND OLTC TANK. 22. IF THE LINE BETWEEN BREATHER AND CONSERVATOR TANK 23. LOCKED, WHAT WILL HAPPEN DURING LOAD CYCLE. 24. WHAT IS THE FUNCTION OF OIL SEAL IN BREATHER. 25. WHAT ARE LOCATIONS FOR BUCHHOLZ RELAY FIXED IN POWER TR. 26. WHAT ARE CHECKS IN POWER TR. DURING MAINTENANCE. 27. WHAT IS IMPORTANT WHEN WE CHECK OLTC OPERATION DURING MAINTENANCE. Trafo - Page 2 of 2

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