Dear All,
Can anybody please tell me which value(saturated or unsaturated) of sub-transient reactance(Xd") we take for the calculation of fault current of the system?

Answer Posted / sarmadahmed

Fault current calculations are usually done to find the rating of protection equipment. For this we need the maximum fault current. Since unsaturated machines has lower value of sub-transient reactance, we should use unsaturated sub transient reactance for the calculations.

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