Transient Performance of Capacitive Voltage Transformers

The transient response of the voltage on the secondary is investigated with following changes in the model. Two instants of switching are considered. Instrument transformers are the integral components of power systems .Capacitive Voltage Transformers (CVTs) are widely used for protection, metering and control applications. The work presents the modeling of CVT by its equivalent circuit. A 420kV CVT is considered with a line to ground fault on the primary side. Another kind of transient response called ferro resonance is also studied. Three types of ferro resonance suppression circuits (FSCs) are considered to dampen the behavior due to ferro resonance The parameters of these FSCs are discussed. The impedance, power characteristics of these FSCs with variation of frequency are studied. Furthermore, using metal oxide varistors are used to improve the performance of the FSCs.The two switching instants in presence of FSC are also evaluated .The effect of FSCs on the transient response of CVTs are presented in this work. The effect of magnetizing current of intermediate voltage transformer on the transient response is also simulated.