What are protective relays used for?

What are protective relays used for?

Protective relays are one of the critical components of the electrical power grid that serve to detect defective equipment or other dangerous or intolerable conditions and can either initiate or permit switching or simply provide an alarm to provide a safer, more reliable delivery system.

What are the two types of relays?

Types of Relays – A Thomas Buying Guide

• Relays are electrically operated switches.
• Electromechanical relays have an electromagnetic coil and a mechanical movable contact.
• Solid-state relays are solid-state electronic components that do not have any moving components, which increases their long-term reliability.

What are the different types of protective relays?

Basic classification of protective relays includes:

• Electromagnetic Relays: Armature. Induction cup / induction disc.
• Static Relays: Analog input signals are processed by solid state devices.
• Digital / Numerical Relays: Uses programmable solid state devices based on digital signal processing.

How a protective relay is different from a circuit breaker?

Relays are controlling devices whereas Circuit Breakers are switching devices. A Relay can divert signals between two different electric circuits, whereas circuit breaker can only stop or flow the current in the circuit. A Relay won’t be able to prevent the arc.

What type of protective relay is used in induction motor?

Thermal overload relay is commonly used for motor overload protection. Both act to open the motor circuit and therefore to disconnect the motor from the source of supply. HRC fuses provide very rapid short circuit protection.

What is a thermal relay?

A relay that opens or closes contacts with a bending mechanism as a result of the difference in the expansion coefficients of a bimetal, which is heated by the current. The thermal relay switches a magnetic contactor to protect a motor from overload.

What are the 5 applications of relay?

Applications of Relays in Electronic Circuits

• Relay Drive by Means of a Transistor.
• Relay Drive by Means of SCR.
• Relay Drive from External Contacts.
• LED Series and Parallel Connections.

What are the fundamental requirements of protective relay?

Functional Requirements of Protection Relay

• Reliability. The most important requisite of protective relay is reliability.
• Selectivity. The relay must be operated in only those conditions for which relays are commissioned in the electrical power system.
• Sensitivity.
• Speed.
• Switchgear.
• Protective Gear.
• Station Battery.

Is a relay a circuit protection device?

Relay acts as a switching or protecting device which gives a signal to the circuit breaker of arrival of any fault in the circuit, as the prescribed safe limit is crossed by the circuit. It is controlled by the low power signal.