The Function Of Protective Relaying

The function of protective relaying is to cause the prompt removal from service of any element of a power system when it suffers a short circuit, or when it starts to operate in any abnormal manner that might cause damage or otherwise interfere with the effective operation of the rest of the system. The relaying equipment is aided in this task by circuit breakers that are capable of disconnecting the faulty element when they are called upon to do so by the relaying equipment.

Circuit breakers are generally located so that each generator, transformer, bus, transmission line, etc., can be completely disconnected from the rest of the system. These circuit breakers must have sufficient capacity so that they can carry momentarily the maximum short-circuit current that can flow through them, and then interrupt this current; they must also withstand closing in on such a short circuit and then interrupting it according to certain prescribed standards.

Fusing is employed where protective relays and circuit breakers are not economically justifiable. Although the principal function of protective relaying is to mitigate the effects of short circuits, other abnormal operating conditions arise that also require the services of protective relaying. This is particularly true of generators and motors.

Title:The Philosophy Of Protective Relaying
Download:Right here | Get Download Updates | Get Technical articles

The Philosophy Of Protective Relaying

Shape Up Your Knowledge //

Want to be a better electrical engineer? Subscribe to professional technical articles. Sharpen up your knowledge in field of electrical engineering now!

Subscribe Now

Page edited by E.C. (Google).


  1. Vladimir Gurevich
    Feb 06, 2015

    Dear Sir/Madam,

    I would like suggest for your and your colleagues attention the information about my new book:

    Cyber and Electromagnetic Threats in Modern Relay Protection

    You can order the book:

    online from CRC Press web site or by E-mail:

    in USA:
    Tel: 800-272-7737, Fax: 800-374-3401

    outside of USA:
    Tel: 561-994-0555, Fax: 561-989-9732

    Sincerely yours,

    Dr. Vladimir Gurevich

  2. hossein
    Mar 09, 2014

    Hello,your site is very great.Thank you.

Leave a Comment

Tell us what you're thinking... we care about your opinion!