Directional relay working principle

1. How does directional relay work?
2. What is the construction and working principle of directional relay?
3. What is the principle of directional protection?
4. Where is directional relay used?
5. What does directional relay respond to?
6. What are the 3 main parts of a relay?
7. What is the difference between reverse power relay and directional relay?
8. What are the three types of relays?
9. What are the problems of directional relays?
10. What are the disadvantages of directional relay?
11. What is the angle of directional relay?
12. What is directional protection relay?
13. What is the difference between reverse power relay and directional relay?
14. What are the problems in directional relay?
15. What is difference between directional and non directional OC relay?
16. Which distance relay is directional relay?
17. What are the 3 main parts of a relay?

How does directional relay work?

The directional relays permit tripping only for a certain direction of current flow, and the other relays determine (1) if it is a short circuit that is causing the current to flow, and (2) if the short circuit is near enough so that the relays should trip their circuit breaker.

What is the construction and working principle of directional relay?

Construction of Induction Type Directional Relay :

It consists of an aluminum (metallic) disc which rotates freely in between two electromagnets. The central limb of the upper electromagnet consists of winding called potential coil. The potential coil is connected to the system voltage through a potential transformer.

What is the principle of directional 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.

Where is directional relay used?

Answer: Directional overcurrent relay is used for the protection of ring main distribution lines. Ring main distribution lines are the lines that exists in a interconnected system with two or more sources.

What does directional relay respond to?

Directional relays can respond to positive sequence, negative sequence, or zero sequence inputs. This should be a consideration when applying directional relays at locations where zero-sequence voltage is minimal.

What are the 3 main parts of a relay?

A relay contains a coil, an armature, and at least one pair of contacts. Current flows through the coil, which functions as an electromagnet and generates a magnetic field. This pulls the armature, which is often shaped as a pivoting bracket that closes (or opens) the contacts.

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

P RINCIPLE OF R EVERSE POWER R ELAY A reverse power relay is a directional relay that is used to monitor the power flow from generator (running in parallel with another generator or the utility) and in case of abnormal condition take appropriate action.

What are the three types of relays?

The three main types of relays are electromechanical, solid-state, and reed.

What are the problems of directional relays?

Directional relays use voltage as the polarizing quantity. When three-phase faults occur close to the relay bus, the available voltage becomes nearly zero and this creates a problem in estimation of the fault direction. The capacitor coupling voltage transformer subsidence transients add to this problem.

What are the disadvantages of directional relay?

Disadvantages or demerits:

The directional feature is absent in electromagnetic relays. Requires periodic maintenance and testing unlike static relays. Relay operation can be affected due to ageing of the components and dust, pollution resulting in spurious trips.

What is the angle of directional relay?

The directional element is “quadrature” polarized, meaning the A-phase relay uses A-phase current and VBC voltage. The relay is built such that the angle of maximum torque occurs for phase current lagging the unity power position by 45 degrees or leading the quadrature voltage by 45 degrees.

What is directional protection relay?

(protection) Relay: equipment used to monitor one or more electrical variable (current or voltage), generally to detect a fault and to control the opening of a circuit breaker.

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

P RINCIPLE OF R EVERSE POWER R ELAY A reverse power relay is a directional relay that is used to monitor the power flow from generator (running in parallel with another generator or the utility) and in case of abnormal condition take appropriate action.

What are the problems in directional relay?

The problem with directional relays is the cost imposition related to relaying changes and installing the necessary equipment such as voltage transformers. In [23], instead of using the voltage for finding the direction of current flow, the negative component of the current is used.

What is difference between directional and non directional OC 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.

Which distance relay is directional relay?

The relay is called Mho relay because its characteristic is a straight line, when plotted on an admittance diagram. It is inherently a directional relay as it detects the fault only in the forward direction.

What are the 3 main parts of a relay?

A relay contains a coil, an armature, and at least one pair of contacts. Current flows through the coil, which functions as an electromagnet and generates a magnetic field. This pulls the armature, which is often shaped as a pivoting bracket that closes (or opens) the contacts.