The IEEE defines protective relays as: “relays whose function is to detect defective lines or apparatus or other power system conditions of an abnormal or dangerous nature and to initiate appropriate control circuit action ”. Relays detect and locate faults by measuring electrical quantities in the power system which are different during normal and … [Read more...] about Classification or Types of Protective Relays
The terms ‘Switchgear’ and ‘Motor Control Centres’ are used in general to describe combinations of enclosures, busbars, circuit breakers, power contactors, power fuses, protective relays, controls and indicating devices.Read more about switchgear here What is Switchgear? | Features, Components and ClassificationThe standards used in Europe often refer to IEC60050 for … [Read more...] about What are Motor Control Centres?
The use of overcurrent relays is the simplest and cheapest type of line protection. Three types of overcurrent relays are used: Inverse time delay overcurrent (TDOC) relays, Instantaneous overcurrent relays, Directional overcurrent relays. In general, overcurrent relays are difficult to implement where coordination, selectivity, and speed are important. They … [Read more...] about Overcurrent Relays for Transmission Line Protection
In this post, we will explain Instantaneous, Inverse Time and Definite Time Lag Relays and their characteristics. An important characteristic of a relay is its time of operation. By ‘the time of operation’ is meant length of the time from the instant when the actuating element is energized to the instant when the relay contacts are closed. Sometimes it is desirable and … [Read more...] about Instantaneous, Inverse Time and Definite Time Lag Relays
Most of the relays used in the power system operate by virtue of the current and/or voltage supplied by current and voltage transformers connected in various combinations to the system element that is to be protected. Through the individual or relative changes in these two quantities, faults signal their presence, type and location to the protective relays. Having … [Read more...] about Basic Relays – Electromagnetic Attraction and Induction Relays