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Three – phase to ground fault takes place at locations F1 and F2 in the system shown in the figure If the fault takes place at location F1, then the voltage and the current at bus A are VF1 and IF1 respectively. If the fault takes place at location F2, then the voltage and the current at bus A are VF2 and IF2 respectively. The correct statement about voltages and currents during faults at F1 and F2 is

Three – phase to ground fault takes place at locations F1 and F2 in the system shown in the figure If the fault takes place at location F1, then the voltage and the current at bus A are VF1 and IF1 respectively. If the fault takes place at location F2, then the voltage and the current at bus A are VF2 and IF2 respectively. The correct statement about voltages and currents during faults at F1 and F2 is Correct Answer V<sub>F1</sub> lags I<sub>F1</sub> and V<sub>F2</sub> leads I<sub>F2</sub>

When fault takes place at F1

[ alt="F1 Vijay Ravi 27.08.21 D1" src="//storage.googleapis.com/tb-img/production/21/08/F1_Vijay_Ravi_27.08.21_D1.png" style="width: 351px; height: 120px;">

Both generator 1 and generator 2 are supplying the fault current.

The voltage at bus A is due to generator 2 the angle of the generator is zero so that the voltage at A is negative.

Hence VF1 lags IF1 

Ix fault current will be Ix∠90° 

IF1 = - Ix = (1∠180°) Ix∠-90° 

IF1 = Ix∠90° 

Therefore VF1 lags IF1

When fault takes place at F2

[ alt="F1 Vijay Ravi 27.08.21 D2" src="//storage.googleapis.com/tb-img/production/21/08/F1_Vijay_Ravi_27.08.21_D2.png" style="width: 349px; height: 117px;">

Both generator 1 and generator 2 are supplying the fault current.

The voltage at bus A is due to generator 1 the angle of the generator is δ and it is positive so that the voltage angle at bus A is also positive

Hence VF2 leads IF2

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