Highest Prospective Short Circuit Current Isc which a typical oil immersed Transformer can feed in case of Short Circuit fault is as given bellow:
Considering, Infinite Utility Source at Transformer primary :
| Transformer Parameters | 2500 KVA | 2000 KVA | 1600 KVA | 1250 KVA | 1000 KVA | 630 KVA | 500 KVA | 400 KVA | 315 KVA | 250 KVA |
|---|---|---|---|---|---|---|---|---|---|---|
| Line Voltage Volts | 433 | 433 | 433 | 433 | 433 | 433 | 433 | 433 | 433 | 433 |
| Impedance % z | 6.25 | 6.25 | 6.25 | 5 | 5 | 4.5 | 4.5 | 4.5 | 4.5 | 4.5 |
| Trafo Full Load Current FLA Amps | 3334 | 2667 | 2133 | 1667 | 1333 | 840 | 667 | 533 | 420 | 333 |
| Trafo Isc KA | 53 KA | 43 KA | 34 KA | 33 KA | 27 KA | 19 KA | 15 KA | 12 KA | 9 KA | 7 KA |
| Trafo LV side Main Circuit Breaker In Amps | 4000 A | 3200 A | 2500 A | 2000 A | 1600 A | 1000 A | 800 A | 630 A | 630 A | 400 A |
| CB In Panel Rating At 45*C Ambient Room Temperate | 3500 A | 2900 A | 2300 A | 1800 A | 1500 A | 900 A | 700 A | 550 A | 550 A | 350 A |
Considering, 500 MVA Utility Source at Transformer Primary :
| Transformer Parameters | 2500 KVA | 2000 KVA | 1600 KVA | 1250 KVA | 1000 KVA |
|---|---|---|---|---|---|
| Utility MVA | 500 | 500 | 500 | 500 | 500 |
| Line Voltage Volts | 433 | 433 | 433 | 433 | 433 |
| Impedance % z | 6.25 | 6.25 | 6.25 | 6.25 | 6.25 |
| Trafo Full Load Current FLA Amps | 3334 | 2667 | 2133 | 1667 | 1333 |
| Trafo MVA | 40 | 32 | 25.6 | 20 | 16 |
| Short Circuit MVA | 37 | 30.1 | 24.4 | 19.2 | 15.5 |
| Fault Short Circuit KA | 49.4 KA | 40.1 KA | 32.5 KA | 25.6 KA | 20.7 KA |
What is Short Circuit?
Short Circuit is a fault which allows the current to flow through its unintended path with very low impedance, which results into excessive current flow through the path.
What is Transformer Impedance?
Transformer Impedance is the % of voltage drop required on primary side to feed full load current on secondary side, this drop is due to winding resistance and leakage reactance of the Transformer.