Fault-clearing surge

Effect of line transposition—sound circuit voltage, (a) Untransposed, (b) Transposed. 

Effect of an opening resistor on a fault-clearing overvoltage, (a) No resistor, (b) Opening resistor. 

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It is a common practice to classify the fault-clearing surge not as a closing surge but as a fault surge since it occurs as a consequence of a fault. 

Figure 2.31 shows an example of a fault-clearing surge. The maximum overvoltage is observed to be 1.5 pu, which is greater than that of the 1.32 pu fault surge in Figure 2.26. The overvoltage increases to about 1.6 pu in the two phase-to-ground fault cases and to about 2.0 pu in the three phase-to-ground fault cases.

Reduction of surge overvoltages by an insertion resistor. I closing surge, a resistor insertion. b resistor off. a resistor insertion, residual voltage. II fault-clearing surge, (a) Model circuit. 

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