What is directional overcurrent 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 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 directional and non directional protection?
In power systems relays are used to detect abnormal conditions. For example, over current, under voltage, fault conditions etc. 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.
What do directional overcurrent relays typically protect?
Overcurrent directional relays can be set to trip for faults in the forward direction, which will protect the equipment in front of the relay. Or they can also be set to trip for faults behind the relay in the reverse direction.
How does a directional overcurrent protection device work?
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 does directional overcurrent relaying ( 67 ) mean?
Abstract– Directional overcurrent relaying (67) refers to relaying that can use the phase relationship of voltage and current to determine direction to a fault. There are a variety of concepts by which this task is done. This paper will review the mainstream methods by which 67 type directional decisions are made by protective relays.
How is directional overcurrent used to detect earth faults?
It is not the best protection to detect earth faults. Directional overcurrent is the calculation of the difference between the phase angle of the current and the phase angle of the voltage.
Which is an example of a directional overcurrent?
Directional overcurrent is the calculation of the difference between the phase angle of the current and the phase angle of the voltage. To oversimplify, if the voltage and current vectors point the same way, it’s probably forward, and if they point in opposite directions, the fault is probably reverse.
