Directional Relays: Selective protection cannot be achieved with time graded overcurrent protection systems in ring or loop systems as well as in radial circuits with two end power supply. A directional feature is incorporated in…
Time Current Relay Application: Time Current Relay Application - Overcurrent and earth fault protective gear can be made discriminative by grading the operating times of successive devices. The pickup currents are adjusted in such a…
Instantaneous Overcurrent Relays: If the relay operates instantly without any intentional time delay, this characteristic can generally be satisfied by a relay of the non-polarized attracted armature type. This relay has a special advantage of…
Overcurrent Relay Characteristics: The operating time of all Overcurrent Relay Characteristics tends to become asymptotic to a definite minimum value with increase in the value of current. This is inherent in electromagnetic relays due to…
General Equation for Electromagnetic Relay: It has already been shown that when not more than two quantities are involved, the equation for the characteristic of the relay at the threshold of operation under steady state…
Comparator Equation in Power System Protection: Comparator Equation in Power System Protection - Taking a very general case to cover the complete range of conventional relay characteristics, let S1Â and S2 be the two input signals…
Relay Design and Construction: The Relay Design and Construction is normally divided into the following stages: Selection of the operating characteristics. Selection of proper construction. Design of the contact movement from the point of view…
Induction Relay Torque Equation: In Induction Relay Torque Equation, Two magnetic fluxes Φ1 and Φ2 differing in time phase penetrate through a disc. These alternating fluxes induce emfs e1 and e2 in the disc which lag their…
Types of Electromagnetic Relays: There are two principal Types of Electromagnetic Relays: Attracted armature type; and Induction type. (a) Attracted Armature Type: This includes plunger, hinged armature, balanced beam and moving iron polarized relays. These…
Relay Classification in Power System Protection: There are various types of Relay Classification in Power System Protection. Normally the actuating quantity is an electrical signal, although sometimes the actuating quantity may be pressure or temperature.…