Distance relay is used for the protection of transmission line & feeders In a distance relay, instead of comparing the local line current with the current at far end of line, the relay compares the local current with the local voltage in the corresponding phase or suitable components of them
Principle of operation of distance relay
1. The basic principle of measurement involves the comparison of fault current seen by the relay with the voltage at relaying point; by comparing these two quantities.
2. It is possible to determine whether the impedance of the line up to the point of fault is greater than or less than the predetermined reach point impedance
There are two types of torques
Types of distance relay Distance relays are classified depending on their operating characteristic in the R-X plane
• Impedance Relay
• Mho Relay
• Reactance Relay
