ABSTRACT
This chapter introduces an Expert System (ES) for optimal coordination of directional overcurrent relays (DOCR) in meshed networks. It is based on Rules only (IF–Then–Rule Structure), thus there is no need for introducing an initial solution, additional auxiliary variables, and an objective function because minimization is innately included by setting the time dials to a minimum and increasing their values gradually. Accordingly, it has inherent immunity from trapping in a local minimum, and the problem of the miscoordination of DOCR, which may arise due to rounding off the continuous-time dial settings, is avoided. The Facts and the Knowledgebase (Rules) of the developed ES are represented on a personal computer by making use of the expert system shell, CLIPS (C Language Implementation Production System). The developed ES-based protection coordination is tested and validated by applying it to different case studies, then the obtained results are compared with those results obtained by applying a traditional optimization technique on the same studied cases, the comparison results showed the efficiency of the developed ES in setting the DOCR optimally.
