Electromagnetic induction relays are the most widely used relays for protective relaying purposes involving only ac quantities. These relays operate on the simple principle of split-phase induction motor. Actuating force is developed on a moving element, that may be a disc or other form of rotor of non-magnetic current-conducting material (such as aluminium), by the […]
Electromagnetic Induction Relays and Its Structure | Electrical Engineering
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Comparators: General Equation and Analysis | Electrical Engineering
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The application of a particular relay is governed by its characteristics and other factors such as accuracy, operating time, reliability, burden, method of setting adjustment etc. The function of a protective relay is to sense any abnormal condition in the system and send a signal to the breaker which in turn isolates the faulty section […]
Amplitude Comparators and Its Types | Devices | Electrical Engineering
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Amplitude comparator compares the amplitudes of two (or more) input quantities. The phase angle between the quantities under comparison (inputs) is not recognized or noticed by the amplitude comparator. If the two input signals are S1 and S2 (say S1 the operating and S2 restraining), the amplitude comparator gives positive output only if – S2/S1 […]
Classification of Overcurrent Relays | Devices | Electrical Engineering
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Depending upon the time of operation, overcurrent relays may be categorized as: 1. Instantaneous Overcurrent Relay 2. Inverse-Time Overcurrent Relay 3. Definite Time Overcurrent Relay 4. Inverse Definite Minimum Time (IDMT) Relays 5. Very Inverse Relay 6. Extremely Inverse Relay. 1. Instantaneous Overcurrent Relay: An instantaneous overcurrent relay is one in which no intentional time […]
Operation of Induction Type Overcurrent Relay | Electrical Engineering
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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 […]
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 […]