Non indirectional induction overcurrent relay construction. The relay is designed to operate when the actuating quantity equals, or exceeds, its pickup value. Because of its low pickup, this device is basically a reverse power relay. Jun 27, 1972 an induction disc type relay according to claim 1, wherein said disc is mounted on a shaft having a bias spring provided therefor to impart a bias torque to said disc in one of said directions. Included in the relay are two sets of shading coils and reluctance paths responsive to the same input signal for applying the. Induction disc type relay mainly consists of one rotating disc.
Electromagnetic relay working types of electromagnetic relays. These relays work on the principle of the induction motor or an energy meter. Apr 26, 2018 as shown in figure below, this structure contains two separate coils on two different magnetic circuits, each of which produces one of the two necessary fluxes for driving the rotor, which is also a disc. Induction disc typeelectromagnetic force causes mechanical operation of relayfixed operating characteristic static relay. Various features of construction of an induction relay are shown in fig. It con sists of a steel ball resting between two hemispherical cup jewels, one fixed in the. This article analyzes the overtravel in induction disc overcurrent relays. Jul 31, 2015 this makes, torque per va of this relay is about three times more than that of induction disc type relay with a cshaped electromagnet. Behavior of induction disc overcurrent relays as a. An induction disc type relay according to claim 2, including a singular input coil mounted on said core structure to which said input signal is applied.
Closeup of an inductiontype overcurrent unit, showing the disc rotor and drag magnet. An induction relay essentially consists of a pivoted aluminium disc placed in two alternating magnetic fields of the same frequency but displaced in time and space. The three primary aims of overcurrent electrical protection are. This relay is also called earth leakage induction type relay. In these relays, a metallic disc is allowed to rotate between the two electromagnets. Power relays cw,cwc, cwd, cwp, cwp1 electromechanical.
Rotating disc laser type if shaft movement is not detected, starting is aborted. If magnetic saturation of the poles can be avoided by designing, the operating characteristics of the relay can be made linear and accurate for a wide range of operation. Personnel injury protection equipment damage protection coordination and proper discrimination of operation. The operating voltage of the relay adjusted by proper tap setting and by proper selection of voltage ratio of potential transformers. Induction type overcurrent relays used in power system. Analysis of overtravel in induction disc overcurrent relays.
This principle says, a torque is produced by two phase displaced fluxes, which is proportional to the product of their magnitude and. Included in the relay are two sets of shading coils and reluctance paths responsive to the same input signal for. Both relay types are frequently provided in one relay case and are actuated by the same current. As shown in figure below, this structure contains two separate coils on two different magnetic circuits, each of which produces one of the two necessary fluxes for driving the rotor, which is also a disc. The electromagnetic relay operates on the principle of a splitphase induction motor. The cap15b relay is a threephase, highspeed induction cup power relay that is similar to the. The type cw relay is a single phase induction type relay providing overpower or reversepower protection for electrical equipment or circuits. The second unit is an induction disk, ac operated, adjustable timing unit. Application the type cv relays are singlephase induction disc type relays operating either on under or over voltage or both. In the shaded pole relay the main flux is split into two fluxes displaced in time and. The protective relay is the device that responds to signals from the transducers by quickly initiating or allowing a control action to be implemented in order to prevent damage to the faulted equipment and to restore service as soon as possible. Conversely, ten induction disc relays of the same model will have identical functionality that is rather limited compared to their digital counterparts.
Model was successfully verified with experimental results. The number of poles in the protective relay depends upon the number of winding to be accommodated. Aug 31, 2018 the induction disc type relay is based on the same principle as that of an ammeter or a volt meter, or a wattmeter or a watt hour mater. The relay time dial assembly can be removed, cleaned and reinstalled by the following procedure. On the relay, the moving element rotor is usually a metal disk, although. When i test induction disc relay type is the pickup. Induction type relay construction detail electrical concepts. The outofphase fluxes thus produced in the air gap causes a contact closing torque. In induction disc type of relays, disc is the moving element on which the moving contact of relay is fixed whereas in the case of induction cup the contact is. Basic relays electromagnetic attraction and induction relays. Any intermediate curves can be obtained by interpolation since the adjustment is continuous.
Behavior of induction disc overcurrent relays idor is analyzed. Principle of induction type relays electrical concepts. Different types of relays used in protection system and their. When i test induction disc relay type is the pickup value. Gnana swathika types of protective relay electromagnetic or electrothermal static microprocessor based.
Inaccuracies due to the calibrated knob for the dial are considered. This relay can be four pole or eight pole depending on the number of windings accommodated. The initial force is developed on the moving element that may be disc or another form of the rotor of the nonmagnetic moving element. Here, an aluminum or copper disc is placed between the poles of an. The operating characteristics of the more commonly used protective relays are described in this section. However, in general, there is the usual inverse it relationship, with.
The figure below shows the constructional of nondirectional induction type overcurrent relay. With limited functionality and identical operating characteristics for around 100 years, you would think that we have all agreed on the right way to test an induction disc relay. Here, an aluminum or copper disc is placed between the poles of an ac magnet which. An induction type relay is a splitphase induction motor with contacts. Old style protection relays relied on induction disc electromechanical type relays.
The time curves for the new design ifc relay are similar. The electrical protective relay can be broad, classified into two categories i electromagnetic relay and ii static relay. Application the type cv relays are singlephase induction disc type relays operating either on under or overvoltage or both. The torque is produced in the disc by the interaction of one of the magnetic fields with the currents induced in the disc by the other. They have earned a welldeserved reputation for accuracy, dependability, and reliability. In induction relay the deflecting torque is produced by the eddy currents in an aluminium or copper disc by the flux of an ac electromagnet. It is not intended for use as a fault protective relay.
Power system ii lab manual jis college of engineering. The watthour structure type relay works as an electromagnetic induction type of watthour a meter so named, after it. Induction cup relay working principle construction and types. The relay has a high torque movement combined with low burden and low overshoot. United states ssins no 6830 nuclear regulatory commission. Inductiontype relays are the most widely used protective relaying where ac quantities are involved.
Cwc and cwp the type cwc and cwp relays are induction disc type relays used for directional ground fault protection on grounded neutral power systems. Based on experimental results, obtained from tests on three relays from different manufacturers, it is verified that the equivalent overtravel time can be considered constant for a wide range of settings in the device. A model of idor as a function of the frequency is developed. The induction cup structure relay works on similar principle of an induction disc relay. The induction type relays are also called magnitude relays. A curve is shown for each numerical setting of the time dial scale. Sep 01, 2018 as we said earlier, the working principle of induction cup relay, is same as the induction motor. Type cdg 11 overcurrent and earthfault relay general description a nondirectional heavily damped induction disc relay which has an adjustable inverse timecurrent characteristic with a definite minimum time. Record time dial position as found in your application.
These relays are applied as a voltage fault detector operating in conjunction with other protective relays. Depending on the type of rotor whether a disc or a cup, the relay is known as an induction disc or an induction cup relay. The force is developed by the interaction of electromagnetic fluxes with eddy current, that is induced in the rotor by these. Westinghouse induction type overcurrent and directional overcurrent relays i contacts j t1rf. According to the principle of operation and construction, the relay may be classified such as the electromagnetic attraction type, electromagnetic induction type, electrodynamic type, moving coil type, electrothermal.
With relay oriented so that the disc is level, rotate the disc to the point the contacts just make. Actuating force is developed in a movable element that may be a disc or other form of rotor of nonmagnetic currentconducting material by the interaction of electromagnetic fluxes with eddy currents that are induced in the rotor by these fluxes. The voltage unit operates on the inductiondisc principal. Braking due to magnetic fluxes created by operative current is considered. An induction disc type relay adapted to apply to an induction disc a rotational torque proportional to an input so that an operating output is produced at the expiration of a predetermined time dependent on the magnitude of the input after the application of the input. Electromagnetic relay working types of electromagnetic. Induction cup relay work in same principle of induction disc relay. Apr 26, 2018 an induction type relay is a splitphase induction motor with contacts. Induction motor damage curves motor thermal limit curve ieee 620, ieee guide for the presentation of thermal limit curves for squirrel cage induction machines rotor temperature limits during starting stator temperature limits during running. This relayis similar to model iac77aa described in geh2059 except. The torque is produced in the disc by the interaction of one of the magnetic fields with. A rotating magnetic field is produced by different pairs of field poles. Induction relays are available in many variations to provide accurate pickup and timecurrent responses for a wide range of simple or complex system.
Every induction disc type relay works on the same well known ferraries principle. Doesnt have moving partstrip output is of attracted armature typeoperating qty is generated by discrete analog generally electronic componentsselectable operating characteristic numeric. In four poles design both pair of poles are supplied from same current transformers secondary, but phase difference between the currents of two pole pairs is 90 deg. Closeup of an induction type overcurrent unit, showing the disc rotor and drag magnet. The basis construction of this relay is just like four poles or eight pole induction motor. This is the first generation oldest relaying system and they have been in use for many years. Shadedpole induction 51 element overcurrent relay setting 50 elements. This is done by inserting an inductor in series with coil. In induction disc type of relays, disc is the moving element on which the moving contact of relay is fixed whereas in the case of induction cup the contact is fixed on the cup. Here, an aluminum or copper disc is placed between the poles of an ac magnet which produces an alternating flux. The relay energized by voltage to be monitored via potential transformers. It is provided with one operating winding and two restraining windings without taps. The most commonly used type of relay is the inverse definite with minimum time lag relay idmt in which inverse characteristic plus definite time characteristic.
In this section we will consider only the latter two aspects. In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected 4 the first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as overcurrent, overvoltage, reverse power flow, overfrequency, and underfrequency. Induction cup relay modern induction cup relays have 4 or more poles the relays can be responsive to voltage and current the double actuating quantity relay can be responsive to both voltage and current the operating time characteristics depends on the type of structure modern induction cup relay may have an operating time. This relay in nothing but one version of induction disc relay. Ca generator differential relay is a single phase, induction disc type with inverse timing characteristics. Microsoft powerpoint ieee sf motor protection fundamentals. Relay model iac9oaa is an extremely inverse time characteristic induction disk time overcurrent relay with torque control. Behavior of induction disc overcurrent relays as a function. Visit principle of induction type relay to know about the working principle. Feb 03, 2018 this is a demonstration of the working of an induction disc relay. Current from the secondary induces an electromagnetic field which exerts a force on the disc.
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