Optimal coordination of directional over current relays using evolutionary programming

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Title:

Optimal coordination of directional over current relays using evolutionary programming

ÎÄÕ±àºÅ:

1673-4785(2009)06-0549-12

×÷Õß:

M. Geethanjali£¬ S. Mary Raja Slochanal

Author(s):

M. Geethanjali£¬ S. Mary Raja Slochanal

Department of Electrical and Electronics Engineering, Thiagarajar College of Engineering, Maduraiª²625015, India

Keywords:

power system protection;  protection coordination;  directional over current relay;  evolutionary programming;  optimization technique

·ÖÀàºÅ:

TP18

DOI:

10.3969/j.issn.1673-4785.2009.06.014

ÎÄÏ×±êÖ¾Âë:

A

Abstract:

Co-ordination of directional over current relays (DOCR) requires the selection and setting of relays so as to sequentially isolate only that portion of the power system where an abnormality has occurred. The problem of coordinating protective relays in electrical power systems consists of selecting suitable settings such that their fundamental protective function is met, given operational requirements of sensitivity, selectivity, reliability and speed. Directional over current relays are best suited for protection of an interconnected sub-station transmission system. One of the major problems associated with this type of protection is the difficulty in coordinating relays. To insure proper coordination, all the main/back up relay pairs must be determined. This paper presents an effective algorithm to determine the minimum number of break points and main/back up relay pairs using relative sequence matrix (RSM). A novel optimization technique based on evolutionary programming was developed using these main/back up relay pairs for directional over current relay coordination in multi-loop networks. Since the problem has multi-optimum points, conventional mathematics based optimization techniques may sometimes fail. Hence evolutionary programming (EP) was used, as it is a stochastic multiª²point search optimization algorithm capable of escaping from the local optimum problem, giving a better chance of reaching a global optimum. The method developed was tested on an existing 6 bus, 7 line system and better results were obtained than with conventional methods.