Admin Table of Contents
- 1 What is a directional power relay?
- 2 What is directional over current protection?
- 3 What are the features of a directional relay?
- 4 What is directional and non directional relays?
- 5 How do you use a directional power relay?
- 6 What is the purpose of a directional overcurrent relay?
- 7 How does a directional overcurrent power relay work?
- 8 How does a directional relay identify the zone of Operation?
- 9 How is the forward and reverse of a relay determined?
What is a directional power relay?
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. The relay has two windings, one acts as voltage coil while other as current coil, similar to a wattmeter.
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 are the main features of the directional relays?
Directional relays must have the following features:
- high speed of operation;
- high sensitivity;
- ability to operate with low values of voltage;
- adequate short-time thermal rating;
- burden must not be excessive; and.
- there should be no voltage creep and current creep.
What are the features of a directional relay?
Answer: Directional relay must have the following features :
- High speed operation.
- High sensitivity.
- Advocate short time.
- Thermal rating.
- Ability to operate with low values of voltage burden must not be excessive and.
- There should be no voltage and current creep.
What is directional and non directional relays?
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. For example, breaker at generator end. Directional Relay: Directional relay operates when the fault is driving power to flow in particular direction.
Which relay does not require separate directional element?
In case of multi-terminal line the first zero of the distance relay is set to reach 80 to 90%of the distance from the nearest terminal. 140. The impedance relay does not have directional features.
How do you use a directional power relay?
The directional (or reverse) power relay operates when the power through the relay will be reversing i.e. generator supply to the network fails and the power from the other sources in the system try to feed the power to this unit in the reverse direction.
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.
Why is directional overcurrent protected?
Directional overcurrent protection schemes were replaced with line impedance relays (21) to prevent a situation like this from occurring. This relay’s primary purpose is to trip for faults on the transmission line, not for faults somewhere else on the system, as would happen here.
How does a directional overcurrent power relay work?
Directional overcurrent relays (67) respond to excessive current flow in a particular direction in the power system. The relay typically consists of two elements. One is a directional element, which determines the direction of current flow with respect to a voltage reference.
How does a directional relay identify the zone of Operation?
The directional relays identify the zone of operation with the help of polarising voltage and characteristic angle. Directional relays needed reference voltage to identify the direction of currents. This is the voltage taken from Potential Transformers.
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.
How is the forward and reverse of a relay determined?
Forward and reverse are typically determined by the normal flow of current into the relay, so be sure to confirm the CT connections before you make any assumptions. Incorrectly determining forward and reverse is an easy mistake to make.