Under Reach of Distance Relay

A distance relay is said to under reach when the impedance seen by relay due to fault is more than the relay setting value even though the fault point is within the protected zone of line. This means that reach of relay has decreased from the setting value. Therefore, percentage under reach can be defined … Read more Under Reach of Distance Relay

Effect of Load Encroachment on Distance Protection

For discussing the effect of Load Encroachment on Distance Protection, we make a steady state model of Transmission Line as shown in figure below. In the figure Vi is Sending End voltage and Vj is Receiving End voltage. Power Pij+jQijis flowing in the direction shown in figure. We know that,   Pij – jQij= VixI … Read more Effect of Load Encroachment on Distance Protection

Outfeed and Infeed Effect

We will discuss here the Outfeed and Infeed Effect and its implication on Distance protection. Consider the operation of distance relay R1 for a fault F close to remote bus on line BC as shown in the figure below. Therefore fault current will be feed by Source G1, G2 and G3. Therefore, IBF= IAB + … Read more Outfeed and Infeed Effect

Distance Protection Philosophy

Distance protection is a non-unit system of protection offering considerable economic and technical advantages. Unlike phase and neutral over current protection, the key advantage of distance protection is that its fault coverage of the protected circuit is independent of source impedance variations. Let us take an example of this to understand how distance protection is … Read more Distance Protection Philosophy