NEED OF GRADING CAPACITORS IN CIRCUIT BREAKERS IN EHV SYSTEM
The Grading capacitors are the capacitors (Typical value of around 500 Pico farads) which are positioned parallel with the interrupting units of the circuit breakers. Before judging the necessity of grading capacitors, let us discuss the importance of these capacitor units across interrupting unit of the circuit breaker and what are the consequences of neglecting them. What is the purpose of Grading Capacitors? Let's examine a 400 kv Transmission line linking two substations via a circuit breaker at each end. The purpose of this transmission line is to facilitate the bidirectional power transfer between Busbars of these substations. Suppose if there is a grounded fault on this line (May be a single phase or two phase or three phase fault) somewhere between the two substations.The relays situated at both ends of the line will detect this fault and will trip the breakers accordingly.Now,with the breaker open,One end of the circuit breaker is grounded via the transmission line...