the effect of voltage transformers and the coupling capacitor voltage transformers (ccvt) on distance protection performance

Distance relays rely on accurate voltage and current signals to correctly determine if a fault is within their zone of protection, as determined by the impedance reach setting. the current signal provided to the relay comes from a current transformer (ct), which is a simple device consisting of a steel core and wire wrapped around that core. at high voltage levels, the voltage signal typically comes from a capacitor voltage transformer (cvt), which is more complicated and less reliable than a ct. although a cvt is more complex than a ct, very little additional attention is typically given to monitor the performance of a cvt. to study the effects of voltage transformer with coupled capacitor, a small network with two stations and with two switches on both sides of the communication transmission line was considered. cvt was used on the circuit breaker b1 side and vt was used on the circuit breaker b2 side. and the faults at different distances from the transmission line between two stations and in different states were modeled in pscad software and the output curve of the software includes voltage, current, residual current and the function of the distance relay was obtained when the fault occurred. and by comparing the results of the output curves of the software, it was concluded that by applying a slight delay in the operation of the relay zones, the distance protection operation error can be avoided due to the presence of cvt.