Functions of protective relay: 1. a) Majority carriers Microprocessor-based relays are typically three-phase devices. 2. Which of the following is not a kind of relay on the basis of constructional feature Moving iron type Static Induction Current 2. b. This impedance between the relay and the fault depends on the electrical distance between them. Restoring force in an electromagnetic relay is produced by Magnet Spring Actuator Beam 3. C37.2. source of supply , trip coil of the circuit breaker and relay stationary contacts are connected in series connection. This makes a single microprocessor-based relay capable of performing the same functions that would require several electromechanical or solid-state relays. Protective Relays. Instrument transformers generally fall into one of two broad categories: The loads on instrument transformers, such as relays and meters, are known as burdens to distinguish them from power system loads. Second part , secondary winding of C.T is connected in series with relay operating coil. Solid-state electronic relays are typically available in single-phase or three-phase versions. Protective Relay. Generally, there are two configurations 1 VA and 5 VA relay. It is an electrical device designed to initiate the isolation of a part of the electrical installation, or to operate an alarm signal, in the event of abnormal condition or a fault. A current transformer consists of a coil toroidally-wound around a ferromagnetic core. The IEEE standard function numbers are given in Table 1. Protective relays can monitor large AC currents by means of current transformers (CT’s), which encircle the current-carrying conductors exiting a large circuit breaker, transformer, generator, or other devices. b) The saturation voltage VCE for germanium transistor is more than silicon transistor. It acts just like a ‘ silence guard’, when any fault occurred in a system, the relay operates to close the trip circuit of the breaker and the breaker disconnects the faulty circuit. Protective relays are classified by function. Learn about power engineering and HV/MV/LV substations. The protective relay also includes to current transformer, voltage transformer, trip circuits, Secondary circuit, auxiliary relays, and time delay relays. d. In the transformer-coupled type of solid-state relay, a minimal amount of DC current is provided to the primary winding of the transformer using a converter of type DC to AC. Third part is the tripping circuit which may be either a.c and d.c . The content is copyrighted to EEP and may not be reproduced on other websites. THE INFORMATION PROVIDED IN THE APPENDICES SUPERCEDES THAT IN THE MAIN PORTION OF THIS BOOK. Multiple Choice Question (MCQ) of Electronics page-16:226. Multiple Choice Question (MCQ) of Electronics page-15:211. Now describe , how the relay disconnects the faulty circuit . Protective relay in MV applications. Tell us what you're thinking... we care about your opinion! The pickup values may be adjusted … e) Holes and electrons simultaneously, Classification or types of protective relays. A protective relay is a device which initiates the circuit breaker to cut the faulty circuit from the healthy system. The supplied current is then transformed to AC type and stepped up to make the SSR to function along with the triggering circuit. This reliable control power is most often provided by a DC battery system, although AC UPS-based systems are also encountered. Dangerous overloads may be due to external faults or the internal ones. A protective zone is the separate zone which Es established around each system element. What does protective relay provide? Definition of Protective Relay. In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. For relaying applications in industrial facilities, CT ratios are typically 50:5-4000:5. While electromechanical and solid-state electronic relays typically incorporate one relay function per device, microprocessor-based relays usually encompass many functions in one device. The conduction in JEFT is always by the However, they do require “reliable” control power to maintain operation during abnormal system conditions. b) Minority carriers Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these functions are performed by digital instruments still called protective relays. A relay is automatic device which senses an abnormal condition of electrical circuit and closes its contacts. - Published on 17 Nov 15. a. B. As a more accurate alternative, manufacturer-published CT excitation curves may be used to determine the current transformer accuracy. Result complete the tripping circuit of the breaker and making the circuit breaker open. To make circuit representations easier, each function has been defined and assigned a number by IEEE Std. d) Inner and bound electrons are always present in the semiconductor. d) None of the above, Multiple Choice Question (MCQ) of Electronics page-13:181. Table 1 – Commonly used protective relay device function numbers, Table 2 – Commonly used suffix letters applied to protective relay function numbers, Reference // System Protection by Bill Brown, P.E., Square D Engineering Services, Please send all new information of any type relay, I love this job If possible I will do again, Mr Edvard thanks for the information is very good. In essence, a CT may be thought of as a conventional transformer with one primary turn. Close the contacts when the actuating quantity attains a certain predetermined value. This condition will cause the CT to saturate, significantly changing the ratio and thus the accuracy of the measurement. Mounting investments in the transmission & distribution networks to replace the old equipment is expected to be a major factor expected to … For example, 87T denotes a transformer differential relay, 51N denotes a residual ground time-overcurrent relay, 87B denotes a bus differential relay, etc. c) PUT c) The saturation voltage VCE for silicon transistor is same as that for germanium. The following is a summary of protective relay functions and their appropriate protection element tests. Relays detect and locate faults by measuring electrical quantities in the power system which are different during normal and intolerable conditions. ... Relay contacts may be open-air pads of metal alloy, mercury tubes, or even magnetic reeds, The actuating quantity of an overcurrent relay is a current. Protective relays are devices that are connected to instrument transformers to receive input signals and to circuit breakers to issue control commands for opening or closing. The time of operation of such protection is a function of the ratio of voltage and current, i.e., impedance. D. Earth any stray voltage Digital protective relays were in their infancy during the late 1960s. Hence , a heavy current  flow through the relay coil, causing the relay to operate by closing its contacts. Edvard. It is a phenomenal compilation of important studies that explore the competitive landscape, segmentation, geographical expansion, and revenue, … A. Provide additional safety to the circuit breaker in its operation. Current transformers in the United States typically have 5A rated secondaries, with primary ratings from 10-40,000 A and larger. a) Semiconductors It helps you. OPERATION INDICATORS Generally, a protective relay is provided with an indicator that shows when the relay has operated to trip a circuit breaker. An electrical device designed to detect some specified condition in a power system, and then command a circuit breaker either to trip or to close in order to protect the integrity of the power system, is … C57.13. d) Electrons An overcurrent relay can be either of two types: instantaneous or time-delay type. There are three parts in the relay circuit :-. To remove the component which is behaving abnormally by closing the trip circuit of the circuit breaker or to buzzer an alarm. The magnetic field generated by the current through the conductor causes current to flow in the coil. 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