Switching and Power Frequency Transients in EHV Systems A Review and Case study

Overvoltages caused by transients are important in a power system as they cause stresses on electrical equipment. Majority of power system failures are directly or indirectly related to transient problems rather than steady state operation. The insulation level of each element in a power system is governed by the transient voltages originating as a result of lightning, short circuits and switching actions. In contrast to lightning, switching overvoltages originates on the system and is inherently measured in terms of the system voltage.

With the adoption of 400 kV voltages and above, it was clear that switching surges created in the system would determine the cost and strength of the major insulations to ground. This paper gives an insight to the electromagnetic transient phenomenon - switching and power frequency overvoltages and case study results of simulation for these overvoltages for a typical Indian 765 kV system.