How does directional protection determine the direction of current?
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 the directional property can be introduced in an over current relay?
In order to achieve the operation of the relay in the forward direction, a directional feature is added to the overcurrent relay by adding a directional relay to the overcurrent relay, such a relay will respond to fault flow in a particular direction.
What is the job of directional over current 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 over current protection?
Directional Overcurrent Protection (ANSI 67) Due to its ability to detect the direction of a short-circuit current, directional overcurrent protection helps to protect an installation against short-circuit currents that could circulate in both directions through the circuit breaker.
What are the difference between directional relay and non directional relay?
Directional relays are designed to locate or sense the fault in a particular direction only, it will not sense fault if fault occurs in opposite direction. While non directional relays don’t have directional features & will sense the fault in both directions.
Why are directional overcurrent relays used for transmission line protection?
Directional Overcurrent Relays The overcurrent relaying is made directional to provide relay coordination between all the relays that can see a given fault. Otherwise, the coordination is often too difficult if not impossible.
In what conditions 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.
How do you test a directional relay?
Directional Overcurrent Relay Test Plan Summary
- Connect all currents and voltages.
- Choose the fault type to apply.
- Apply nominal balanced three-phase voltages.
- Cut the fault voltage in half.
- Raise the fault current more than 110% of the pickup setting.
Why do we use directional relay in power system protection?
Directional Earth Fault Relay is used to protect the transformer/generator/alternator from over current fault. The relay sense the fault current in only one direction, the relay does not operate when the current in opposite direction.
What is relay characteristic angle?
Relay Characteristic Angle: RCA The characteristic angle is the phase angle by which reference or polarising voltage is adjusted such that the directional relay operates with maximum sensitivity. Characteristic Angle is also called Directional angle as it decides the direction of operation of the relay.
What are the various overcurrent protective schemes?
3.2 Overcurrent protection scheme. The overcurrent protection scheme is used to protect the distribution lines of electric grids integrated with DER. This protection scheme is further classified into two categories, the phase overcurrent protection and the ground overcurrent protection.
What is induction type directional power relay?
This Induction Type Directional Power Relay operates when power in the circuit flows in a specific direction Unlike a non-directional overcurrent relay, a directional power relay is so designed that it obtains its operating torque by the interaction of magnetic fields derived from both voltage and current source of the …