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?
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Answer / yegneswaran
Saturated machines will have lesser reactance compares to unsaturated ones...
Hence, fault current is more while saturated subtransient reactance taken into account...
We should consider saturated subtransient reactance while calculating fault current value.
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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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