Explain distance protection relay
A distance relay is a fundamental device that trips the circuit breaker in the event of a fault. In low rating power systems circuits, the relay itself can trip the circuit, without the circuit breaker. … Based on the impedance of the transmission line, the relay operates.
Distance protection relay finds fault distance on transmission line by V/I method. If the fault is nearer, the fault current is more. If the fault is farther, the fault current is less. Accordingly, the relay is set. There are 3 zones of protection. 1st zone is the actual line to be protected. 2 Nd zone is the longest line from CT of the protected line. 3rd zone is beyond. 1st zone is set at 85 percent of line impedance.
Distance relay is a type of protection relay most often used for transmission line protection. Distance relays measure the impedance from the installation side to the fault location and operate in response to changes in the ratio of measured current and voltage. The basic principle of distance protection involves the division of the voltage at the relaying point by the measured current. … If the measured impedance is less than the reach point impedance, it is assumed that a fault exists on the line between the relay and the reach point. distance relay is a fundamental device that trips the circuit breaker in the event of a fault. In low rating power systems circuits, the relay itself can trip the circuit, without the circuit breaker. … Based on the impedance of the transmission line, the relay operates.