What does a directional power relay do?

The directional relay means the relay operates for the specific direction of the actuating quantity in the circuit. The directional power relay operates when power in the circuit flows in the specific direction.

In what conditions is it necessary to use directional protection?

It is necessary to use it in the following conditions: in a system with several sources. in closed loop or parallel-cables systems. in isolated neutral systems for the feedback of capacitive current. and to detect an abnormal direction of flow of active or reactive power (generators)

Why must directional relay be used on a ring main system?

Such relays are called as directional overcurrent relays. They are used in distribution system or subtransmission system where ‘ring main’ configuration is used to provide more reliability of service. Cost of this relaying scheme is higher than ‘non-directional’ overcurrent due to additional cost of VT.

What do you mean by directional relay?

Definition: A protection relay in which the tripping decision is dependent in part upon the direction in which the measured quantity is flowing.

How directional relay is used in generator protection?

The voltage-and-current-directional relay has two armature coils. Such a relay, for example, controls the closing and opening of a circuit breaker in the circuit between a d-c generator and a bus to which another source of voltage may be connected, so as to avoid motoring of the generator.

What is the difference between directional and non directional relays?

The relay operates when the fault current exceeds the pickup current. For Directional Over current relay, the fault current can flow in both the directions through the relay either forward or reverse, depending upon fault location.

What is the difference between the reverse power relay and the directional relay?

The directional relay will respond to any type of current, real or reactive. The reverse power relay, normally used in generator protection, responds to current drawn by a motor or generator (or resistor) that is producing work, as opposed to current that supports a magnetic field.

What is an NC relay?

A: NO, NC refer to the relay being de-energized or powered off. So, to have “open to alarm” condition, the NO contact would be used for this. NC means normally-closed contact. NO means normally-open contact. When the relay coil is de-energized, NC contact becomes open, and NO contact closes.