effect of Emerging Transients

In the low voltage and medium voltage circuits; Current chopping in C.B., energy in inductance 1/2 Li sq. gets transferred to capacitance 1/2 CV sq. giving overvoltages.

In capacitor banks, cable charging circuits etc.; Restrike in circuit breaker giving overvoltages.

For EHV lines and auto reclosures; travelling waves to and fro; can cause switching surges.

Requirements for machines which are subject to overspeed or loss of load are predominant over the general considerations of system over voltage which can be permissible to the tune of 10 %