## Answers

Oct 03, 2020 - 02:16 AM

For the terminal fault of the generator the short circuit current keeps changing with respective time.

Since synchronous machine has variable reactance, calculation at any instant requires a formula

involving time as one of the variables. Usually for the sake of simplicity, the reactance is considered

fixed over the time interval for which the fault current is calculated .

Please refer the below formula

Here reactance, voltage is in p.u and t in seconds

In this case if you need to calculate the final steady state short curcuit currrent, You can use Isc=E/Xd and multiply with your acutal rated current to get the actual short circuit current.

Since synchronous machine has variable reactance, calculation at any instant requires a formula

involving time as one of the variables. Usually for the sake of simplicity, the reactance is considered

fixed over the time interval for which the fault current is calculated .

Please refer the below formula

Here reactance, voltage is in p.u and t in seconds

In this case if you need to calculate the final steady state short curcuit currrent, You can use Isc=E/Xd and multiply with your acutal rated current to get the actual short circuit current.

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