The overcurrent relays, even though simplest of all types of electromechanical relays, are the most difficult static relays. This is because the induction disc characteristics of the overcurrent relays (inverse characteristics) are not amenable to simple mathematical analysis.
Based on the relay operating characteristics, overcurrent relays can be classified into three groups: definite current or instantaneous, definite time, and inverse time.
Overcurrent relay protection is given at B, C, D and E, that is, at the infeed position of each part of the electrical power system. Each relay protection device comprises a definite-time delay overcurrent protection relay in which the trip of the current sensitive element starts the time delay device.Classification of protective relays. According to the relays operating characteristics, the relay may be classified as follows:-1) Solenoid type: In this type of relay, an iron core or plunger is moved into the solenoid coil. 2) Attracted armature type: This type of relay is connected in a circuit and this type of relay operate when the current of the circuit increase beyond the normal.Overcurrent relaying is the simplest and cheapest type of protection used for protection of lines, transformers, generators and motor. Overcurrent relays Types Based on operating time characteristics, normally defined by the time vs.
An Introduction to Relay Definitions And Terminology. operation of the relay, for example, current for an overcurrent relay, voltage for a voltage relay, phase angle for a directional relay, time for. Relay contact notations are given in the following order: 1. Poles 2. Throws 3.Read More
Impedance Type Distance Relay Definition: The relay whose working depends on the distance between the impedance of the faulty section and the position on which relay installed is known as the impedance relay or distance relay. It is a voltage controlled equipment.Read More
Relay coordination study and analysis is performed to make sure that safety operation of the system are functioning correctly and to avoid the nuisance tripping, as protection is a major concern in any industry and they rely on protective devices for the same.Read More
What Is a Relay and How It Works? 1 Applications of Relays 2 Classification of Relays 3 1. Electromagnetic Relays 3 1.1 Attraction Type Electromagnetic Relays 4 1.2 Induction Type Relays 5 1.3 Latching and Non-Latching Relays 8 2. Solid State or Electronic Relays 9 2.1 Reed Relay Coupled SSR 9 2.2 Transformer-Coupled SSRs 10 2.3 Photo-Coupled.Read More
Overcurrent Relay Coordination for Phase and Earth faults using ETAP Proceedings of 7 th IRF International Conference, 27 April-2014, Pune, India, ISBN: 978-93-84209-09-4 58 b. make sure that the relay farthest from the source has current settings equal to or less than the relays.Read More
Understand Relay Specifications to Get the Most Out of Your Switching System Relay specifications aren't simply numbers on a data sheet-you need to take them seriously. Operating a relay used outside of its specifications can severely shorten its life and cause switching system failures and even potentially damage the UUT (Unit Under Test).Read More
The time-current characteristic curve is different for inverse time, definite time, and instantaneous relays. You can use combinations of curve types to achieve the design requirements. I commonly use inverse-time, definite-time, and instantaneous elements, all on the same relay. Inverse time overcurrent relays: Slow to trip at low currents.Read More
Differential relay operates when the phase difference in two or more than two identical quantities crosses the predetermined value. Differential relay is another type of relay which is used for protection against faults related to current and voltage in the device. This is the most prevalent and successful method to protect the circuit.Read More
Relay classification, Principle of different types of electromagnetic relay. General equation of phase and magnitude comparators, Duality of comparators, Electromagnetic relays, over current relays Directional relays, Distance relay- impedance, Reactance and Mho type, Differential relays. MODULE-II (10 HOURS).Read More
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.Read More