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Note for Switch Gear & Protective Devices - SGPD by mahaveer singh

  • Switch Gear & Protective Devices - SGPD
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  • Electrical Engineering
  • B.Tech
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Mahaveer Singh
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Er.Mahaveer singh Contactno:8387057001,8005829571, Mahaveers024gmail.com Btech 5sem/3rdyear electrical MITS JADAN PALI History of Relay ⚫ The static relay is the next generation relay after electromechanical type. ⚫ The Solid Static relays was first introduced in 1960’s. ⚫ The term ‘static’ implies that the relay has no moving mechanical parts in it. ⚫ Compared to the Electromechanical Relay, the Solid Static relay has longer life-span, decreased noise when operates and faster respond speed. ⚫ Static relays were manufactured as semiconductor devices which incorporate transistors, ICs, capacitors, small microprocessors etc. ⚫ all The static relays have been designed to replace almost the functions which were being achieved earlier by electromechanical relays. Measuring principles :⚫ The working principle of the Solid Static relays is similar to that of the Electromechanical Relay which means the Solid Static relays can perform Electromechanical Relay can perform. tasks that the

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The ⚫ Solid Static devices instead of relays use analogue magnetic coils and electronic mechanical components to create the relay characteristics. The measurement is carried out by static circuits ⚫ consisting of comparators, level detectors, filter etc while in a conventional electromagnetic relay it is done by comparing operating torque (or force) with restraining torque (or force). The relaying quantity such as voltage/current is rectified ⚫ and measured. When the quantity under measurement attains certain welldefined value, the output device is triggered and thereby the circuit breaker trip circuit is energized. In a solid state relay, the incoming voltage and current ⚫ waveforms are monitored by analog circuits, not recorded or digitized. The analog values are compared to settings made by ⚫ the user via potentiometers in the relay, and in some case, taps on transformers. Though this relay has a microprocessor, it lacks the attributes of a digital/numeric relay, and hence the term “microprocessor relay” is not a clear term. Function of Relay :⚫ Early versions used discrete devices such as transistors and diodes in conjunction with resistors, capacitors,

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inductors, etc., but advances in electronics enabled the use of linear and digital integrated circuits in later versions for signal processing and implementation of logic functions. ⚫ While basic circuits may be common to a number of relays, the packaging was still essentially restricted to a single protection function per case, while complex functions required several cases of hardware suitably interconnected. In some cases, relay burden is reduced, making for reduced CT/VT output requirements. In a static relay there is no armature or other moving element and response is developed by electronic, magnetic or other components without mechanical motion. Basler Electric BE1-27 Solid State Protective Relay, Over/Under Voltage A relay using combination of both static and electromagnetic units is also called a static relay provided that static units accomplish the response. Additional electromechanical relay units may be employed in output stage

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as auxiliary relays. A protective system is formed by static relays and electromechanical auxiliary relays. The performance of static relay is better than electromagnetic relays as they are fast acting and accuracy of measurement is better than electromagnetic relay. The constraint in static relay is limited function/features. In the last decade, some microprocessors were introduced in this relay to achieve the functions like: 1. Fuse failure features 2. Self check feature 3. Dead Pole detection and 4. Carrier aided protection feature Operation of Relay The essential components of static relays are shown in figure below. ⚫ The output of CT and PT are not suitable for static components so they are brought down to suitable level by auxiliary CT and PT. Then auxiliary CT output is given to rectifier. ⚫ Rectifier :- rectifies the relaying quantity i.e., the output from a CT or PT or a Transducer. ⚫ The rectified output is supplied to a measuring unit comprising of comparators, level detectors, filters, logic

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