Abstract :
Current transformers (CT) designed for protective relaying applications with secondary current ratings substantially lower than 5 A offer advantages when lead resistance tends to predominate over the relay burden. The lower current rating may allow the use of a smaller wire size or a smaller CT core as well as providing improved transient performance. With the longer lead runs associated with EHV stations, and the advent of low-burden solid-state relays, the picture has become favorable for such lower current rating, and their advantages and disadvantages are considered. Also addressed are working voltage levels, open-circuit voltages, noise sensitivity, circuit breaker interchangeability, relay stocking requirements, and CT costs
Keywords :
current transformers; power transformers; relay protection; CT; EHV stations; circuit breaker; costs; current transformers; lead resistance; noise sensitivity; open-circuit voltages; power transformers; protective relaying; relay burden; relay protection; relay stocking; secondary current rating; transient performance; voltage levels; Circuit breakers; Circuit noise; Current transformers; Noise level; Protective relaying; Relays; Solid state circuits; Transformer cores; Voltage; Wire;
