ABSTRACT
In high voltage substations, there are different kinds of conductors close to one another, such as high voltage buses, current transformers, potential transformers, carrier couplers, bushing, control cables, substation ground conductors, and equipment ground connections. The control cables are used to carry potential transformer outputs, current transformer outputs, circuit breaker control signals, relaying, and other communication signals. Increasingly, electronic equipment is used in switchyards and control houses. The induced voltage produced inside a substation can couple into low voltage control cables and electronic equipment unless it is suitably protected. Parallel conductors exhibit both mutual inductance and capacitance. Since the power conductors carry relatively large currents and operate at higher voltages as compared to control cables, power frequency voltages may appear on the control cables through this coupling and cause considerable noise problems. In addition, if care is not taken to ground the system properly, ground currents at these frequencies
may be coupled with the instrumentation and control system resistively, capacitively, or inductively, producing nuisance trips [1-3]. This chapter deals with the calculation of the induced voltages in the control cables due to switching and lightning surges. In the presence of shunt capacitor banks in the substation, the magnitude and frequency of the switching surges increase.
