What is 3 step distance protection?
In three stepped distance protection, the relay is set for protection of line in three steps with suitable time delay between each step for back up. In this project to design three stepped distance relay, one quadrilateral relay and two reactance relays are used.
Why distance relay is used?
A 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 operates in response to changes in the ratio of measured current and voltage.
What are zones of distance protection?
It is set at 150% of the Protected Line lenghth or 100% of the Protected Line Length plus the 50% of the shortest Adjoning Line Length, whichever is the Less. It is set in such a way, so that the Zone 2 of he Adjacent lines do not overlap, so as avoid loss of Discrimination.
What are main problems with distance relaying scheme?
The major problem to the distance relay is to measure correct impedance from relaying point to fault point when series capacitor remains in fault path.
What are the advantages of distance protection?
Selective and dependable tripping for line faults without the need for a pilot channel, as well as simple time coordination of distance relays across the system, are great advantages of distance protection.
Where is distance relay used?
Distance relays are generally used for phase-fault primary and back-up protection on subtransmission lines, and on transmission lines where high-speed automatic reclosing is not necessary to maintain stability and where the short time delay for end-zone faults can be tolerated.