Directional overcurrent protection devices can achieve this requirement, albeit at extra cost. Directional IEDs determine the direction of the fault current by measuring the voltage with a voltage transformer as well as the current with a current transformer, and establishing the phase difference.
What is directional over current protection?
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. … Traditionally, three phase relays and one ground relay have been used to protect a feeder or a transmission line.
What is the difference between directional and nondirectional relay?
Non Directional relay: When there is fault in power system, power flows through fault. Non directional relays operate irrespective of direction of flow of current. … Directional Relay: Directional relay operates when the fault is driving power to flow in particular direction. It senses the direction of current flowing.
What is the purpose of a directional overcurrent relay?
Directional overcurrent relays are normally used on incoming line circuit breakers on buses which have two or more sources. They are connected to trip an incoming line breaker for fault current flow back into the source, so that a fault on one source is not fed by the other sources.
What is a 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.
In what condition is it necessary to use directional protection?
Earth fault directional protection is sensitive to the direction of flow of the current to earth. It is necessary to install this type of protection equipment whenever the phase to earth fault current is divided between several earthing systems.
What is non-directional earth fault?
Basic protection of busbars and feeders in utility substations and industrial power distribution systems. Not active product since 2009. The directional or non-directional earth-fault relay REJ 517 is a secondary relay which is connected to the voltage and current transformers of the object to be protected.