# GATE 2016 EE (SET 1) Q20

20. The magnitude of three phase fault currents at buses A and B of a power system are $$10pu and 8pu$$, respectively. Neglect all resistances in the system and consider the pre-fault system to be unloaded. The pre-fault voltage at all buses in the system is $$1.0pu$$. The voltage magnitude at bus B during a three phase fault at bus $$A is 0.8pu$$. The voltage magnitude at bus A during a three phase at bus B, in pu, is _________?

Solution:

Voltage at bus B after 3 phase fault at $$A = 0.8pu$$

$$V_{B}=V_{prefault}-Z_{12}\times I_{f}$$

$$0.8=1.0-Z_{12}\times 8$$

$$Z_{12}=0.025pu$$

$$V_{A}=1.0-(0.025\times 10)$$

$$V_{A}=0.75pu$$

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