Assessment of Capacitor Voltage Transformer Affect On Distance Relay

A capacitor voltage transformer (CVT) comprises a capacitor voltage divider connected to an iron-core voltage transformer. The capacitor voltage transformer is used in the transmission and distribution circuit for stepping down voltages for metering or protection. The performance of the capacitor voltage transformer described in this dissertation is assessed by computer simulation. The simulation tools MATLAB and PSCAD/EMTDC were used. Various types of fault have been made to investigate the transient response of the CVT. It can be seen that as the location of the fault becomes more remote the period of oscillation becomes longer. The results obtained indicate that the CVT transient behaviour is controlled by the sum of the stack capacitances, the shape and parameters of the ferroresonance suppression circuits and the point on wave at which the fault occurs. Experiment results are presented in this dissertation. The objective of the experiment is to investigate the effect on the performance of a distance relay of the CVT transient response. From the results obtained we can see that the CVT transient will slow down the relay for in zone faults. The type of fault applied in this experiment is single phase to ground. x