An induction type overcurrent relay giving inverse-time operation with a definite minimum time characteristic is shown in Fig. 3.25. It consists essentially of an ac energy meter mechanism with slight modification to give required characteristics. The relay has two electromagnets. The upper electromagnet has two windings, one of these is primary and is connected to […]
Operation of Induction Type Overcurrent Relay | Electrical Engineering
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Phase Comparators and Its Types | Devices | Electrical Engineering
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Phase comparison technique is the most widely used technique for all practical directional, distance, differential and carrier relays. In a phase comparator, the operation of the relay takes place when the phase relation between two inputs S1 and S2 varies within certain specified limits. Both inputs must exist for an output to occur; ideally, operation […]
Negative Phase Sequence Relay and Its Types | Electrical Engineering
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Whenever there is an unbalanced circuit, the unbalanced currents will have a negative phase sequence component. A negative phase sequence (or phase unbalance) relay is essentially provided for the protection of generators and motors against unbalanced loading that may arise due to phase-to-phase faults. Essentially such a relay has a filter circuit which is responsive […]
Distance Relays and Its Classification | Devices | Electrical Engineering
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In this article we will discuss about distance relays and its classification. Introduction to Distance Relays: Distance protection is the name given to the protection, whose action depends upon the distance of the feeding point to the fault. The time of operation of such a protection is a function of the ratio of voltage and […]
Induction Type Directional Relays | Devices | Electrical Engineering
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In this article we will discuss about induction type directional relays used in an electric circuit. Induction Type Directional Power Relay: The non-directional relay can operate for fault flow in either direction. In order to achieve operation for the fault flowing in a specific direction, it is necessary to add a directional element to the […]
Differential Relays and Its Types | Devices | Electrical Engineering
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Differential protective relaying is the most positive in selectivity and in action. It operates on the principle of comparison between the phase angle and magnitudes of two or more-similar electrical quantities. Comparing two electrical quantities in a circuit by means of differential relays is simple in application and positive in action. For example, in comparison […]
Impedance Relay: Operation and Types | Devices | Electrical Engineering
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It is noteworthy here that in electrical engineering, the term ‘impedance’ can be applied to resistance alone or reactance alone, or a combination of the two. In protective relaying terminology, however, an impedance relay has a characteristic that is different from that of a relay responding to any component of impedance and therefore, the “impedance […]
Static Relays: Need and Limitations | Devices | Electrical Engineering
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In this article we will discuss about:- 1. Meaning of Static Relays 2. Need for Static Relays 3. Essential Components 4. Advantages 5. Limitations. Contents: Meaning of Static Relays Need for Static Relays Essential Components of Static Relays Advantages of Static Relays Limitations of Static Relays 1. Meaning of Static Relays: A static relay refers […]
Classification of Static Relays | Devices | Electrical Engineering
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Static relays are classified according to the type of the measuring unit or comparator as follows: 1. Electronic Relays 2. Transductor (Magnetic Amplifier Relays) 3. Rectifier Bridge Relays 4. Transistor Relays 5. Hall Effect Relays 6. Gauss Effect Relays. 1. Electronic Relays: These were the first to be developed in the series of static relays. […]
Static Distance Relays and Its Characteristics | Electrical Engineering
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Distance relays are characterised by having two input quantities proportional to the voltage and current at a particular point in the power system, referred to as the relaying point. Ideal static distance relays have characteristics independent of actual magnitudes of voltage and current but dependent only on their ratio and phase angle between them. The […]