(Protection) Relay Guides

(Protection) Relay Guides

Knowledge of the expert

The relay is a well known and widely used component. Applications range from classic panel built control systems to modern inrefaces between control microprocessors and their power circuits or any application where reliable galvanic separation is required between different circuits.

Altough considered to be a relatively simple component, the electromechanical relay and its technology is complex and often misundestood.

History of relay

The earliest electrical relays were developed in the 1830s, as people began to recognize that such switches could be extremely useful. Historically, electrical relays were often made with electromagnets, which continue to be used today, although for some applications solid state relays are preferred. They key difference between electromagnetic and solid state options is that electromagnetic relays have moving parts, and solid state relays do not.

Electromagnets also conserve more energy than their solid state counterparts do.


Usage of relay

One of the reasons an electrical relay is such a popular tool for electricians and engineers is that it can control electrical output which is higher than the electrical input it receives. In the example discussed above, if the ignition connected directly to the battery, heavy duty insulated wiring would be needed to connect the steering column to the battery, and the ignition switch would also need to be much more robust.

By using a relay, relatively lightweight wiring can be used, saving space and increasing vehicle safety.

A variety of circuits can be connected to an electrical relays. Relays can be used as amplifiers for electrical energy, as in the car example, and they can also connect to things like alarm switches, activating when a circuit is broken to trigger an alarm.

Many electrical failsafe systems utilize electrical relays which turn on or off in response to things like a current overload, irregular current, and other issues which may arise.

These electrical relays trip to shut the system down until the problem can be addressed.

All documents, EE software and EE books are free to download.

Protection Relays

No.DescriptionDownload
1Relay Selection Guide
2Distance Relay Fundamentals
3Line Protection With Distance Relays
4Electrical Relay Diagram and P&ID Symbols New
5The philosophy of protective relaying New
6The Art and Science of Protective Relaying
7Protective Relaying – Principles and Applications
8Transmission Line Protection Principles New

Relay book

No.DescriptionDownload
1Introduction
2Relays – General
3Electromechanical Relays
4Contact System
5Magnetic System – Coil
6Mechanical Components
7Handling and Use in Production
8Quality Aspects
9Standards
10Electronics in and around Power Relays
11Relay definitions

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Page edited by E.C. (Google).



17 Comments


  1. syed aijaz mohiuddin
    Sep 13, 2014

    HI,
    please, can u give me the details of dry type transformer for the maintenance point of view.and also the over -under voltage relay…feeder protection relays..
    thanking you..


  2. iman ramang
    Aug 19, 2014

    As i know for Voltage Drop maximum allowable on VAC is 5%


  3. Moloi
    Jun 12, 2014

    What is the recommended voltage drop in Alternating Current{AC} and Direct current {DC}


  4. hadi218
    Jul 12, 2013

    Thanks for information


  5. Avinash
    Feb 26, 2013

    can any one share “pilot protective relaying by walter Elmore” or “Numerical Differential Protection by Gerhard Zeigler”
    Thanks

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