In order that current should flow without causing excessive heating or voltage drop, the relay contacts should have low contact resistance, be clean and smooth, be of sufficient size and proper shape.
Answer : Overheating of relay contacts or contact born out is due to slow making and breaking of load circuit contacts, foreign matter on the contact surface, too low contact pressure.
Answer : The contacts of high voltage switches used in power system are submerged in oil. The main purpose of the oil is to extinguish the arc.
Answer : The voltage appearing across the contacts after opening of the circuit breaker is called recovery voltage.
Description : In the induction type directional over current relay, when a short-circuit occurs in the circuit (A) power flows in reverse direction (B) power flows in normal direction (C) directional power element does not operate (D) over current element is not energized
Answer : In the induction type directional over current relay, when a short-circuit occurs in the circuit power flows in reverse direction
Answer : The under voltage relay can be used for generators, busbars, transformers, motors.