What are relay protection devices?
In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. The need to act quickly to protect circuits and equipment often requires protective relays to respond and trip a breaker within a few thousandths of a second.
What does a protection relay do?
The purpose of the protection relay is to detect a problem, ideally during its initial stage, and to either eliminate or significantly reduce damage to personnel and/or equipment.
What is a mechanical relay?
Mechanical relays consist of a coil (electromagnet) and contacts. The coil is activated when the proper voltage is applied and current is running through it. Once the coil is activated, it exerts a force on the common (COM) contact which moves it, connecting it with the normally open (NO) contact.
How are protective relays used in Electrical Engineering?
Protective relay. In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected.:4 The first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as over-current, over-voltage,…
What are the different types of power system relays?
This impedance or corresponding distance is called the reach of relay. Power system protection relays can be categorized into different types of relays. Types of protection relays are mainly based on their characteristic, logic, on actuating parameter and operation mechanism.
How are protective relays used in hydroelectric power plants?
Electromechanical protective relays at a hydroelectric generating plant. The relays are in round glass cases. The rectangular devices are test connection blocks, used for testing and isolation of instrument transformer circuits.
What happens when an electromechanical relay is activated?
When an electromechanical Relay is activated, bounce occurs at the contact site. Bounce creates a window of time where the load circuit is flickering between open and closed, a condition which may need to be considered in load design. Isolation voltage is another area where Electromechanical Relays are limited.