Why is distance protection better than overcurrent protection?

In over current protection, protection is based on a curve. The higher the fault current, the shorter the breaking time and vice versa. Meaning, fault at distance 2 km (higher current) is protected quicker than a fault at 5 km(lower fault current).

What is distance protection in transmission lines?

Distance Protection is a Non-unit System of Protection, which measures the Impedance between the Relay Location and the point where the fault is incident and compares it with the Set Value. If the measured Impedance is less than the Set Value , the Relay operates and Isolates the Faulty Section.

Is distance protection directional?

Because, impedance is a complex number, the distance protection is inherently directional. The first quadrant is the forward direction i.e. impedance of the transmission line to be protected lies in this quadrant. However, if only magnitude information is used, non-directional impedance relay results.

Which distance relay is most affected by the power surge?

The effect of power surges on impedance relay is greater than that of mho relay and lesser than that of reactance relay. As the area of reactance relay occupying on the R-X diagram is large, it is largely affected by the power surges compared to other types of distance relays.

What is working principle of distance relay?

The major principle of distance relay is it functions depending on the distance of fault in the transmission line. Its operation depends on the impedance between the point of fault and the point where the relay is installed. The impedance at that particular point becomes the operating quantity for the relay.

What is the advantage of the distance relay over current relay?

Advantages of Distance Relay Over Overcurrent Relay Distance relays are mostly chosen than of overcurrent relays due to the reason that these will not be easily impacted by the variations in short-circuit current magnitude whereas overcurrent relays are easily affected.

In what way is distance protection superior to overcurrent protection for the protection of transmission lines?

Distance relays are preferred to overcurrent reIays because they are not nearly so much affected by changes in short-circuit-current magnitude as overcurrent relays are, and, hence, are much less affected by changes in generating capacity and in system configuration.