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The principle is to grade the operating times of the relays in such a way that the relay closest to the fault spot operates first. Said Salim Palayi Assistant Executive Engineer Electrical Division, Manjeri K.S.E.B Limited salimpalayi@yahoo.com Basics of Over Current Protection 01/09/20151 2. •We are to discuss the application of the time graded protection on –Radial feeder –Parallel feeder –Ring feeder Protection of radial feeder •The main characteristic of the radial feeder is that power can flow in one direction only from generator to supply end of the load line. Such non unit type protections don’t have pilots. Differential Protection; 1.

The relay time current characteristic is inverse over a significant time range and it tends to definite time after saturation. The feeder cod be in the form of a transmission line, short, medium or long, or this could be a distribution circuit. It is remarkably effective with ground faults due to its steep characteristics.

… As for example, differential protection is said to be a unit protective system; whereas current time graded overcurrent protection or distance protection are said to be non-unit protective systems.
Overcurrent relays coordination using MATLAB model A. Akhikpemelo1*, M ... and long sub transmission lines protection.

Pilot relaying protection. The first group of non unit type of protection includes time graded over current protection; current graded over current protection and distance protection.

What is time grading, current grading and time-current grading overcurrent protection for transmission lines?

Information provided by Woodward Governor Company is believed to be correct and reliable. XI1-I – Time overcurrent relay (Januar 2007) Manual XI1-I (Revision New) Woodward Manual XI1-I GB 2 TD_XI1-I_01.07_GB_Rev.New Woodward Governor Company reserves the right to update any portion of this publication at any time. methods available for the protection of transmission and distribution lines [69]. - 2766608 Time-graded Protection. The various methods of protecting the feeders are: 1. A straightforward way of obtaining selective protection is to use time grading. Effect Assessment of TCSC on Algerian Transmission Line Protected by IDMT Directional Overcurrent Relay. ... time will be lesser [19]. 2. Basics of overcurrent protection 1. 3. Over current and its causes In an electric power system, over current or excess current is a situation where a larger than intended electric current exists through a conductor, leading to … Distance protection. It can be graded for a very large . Over current protection. Reliability:- Reliability is the ability of a protective system to work properly during the period for which it is in service.

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