Abstract
In this paper, a quick solving method in an expert-system is developed for selecting switching devices suitable in private electric power distribution systems by modeling the inference processes of engineers who design the protection coordination. The engineers efficiently and quickly select switching devices by taking into account of the nature of rules and deal with time-current characteristic curves of switching devices by some clusters. In order to simulate these engineer's treatments, we classify the rules regarding the over-current protection into three groups. The first group is independent of the characteristic curves of switching devices. Second and third group consist of the rules for determining the lower and upper bounds of the solution, respectively. The inference engine of our prototype system is improved by adding a new function to understand a cluster of characteristic curves of switching devices.
This classification of rules brings about the reduction of the application frequency of rules in our expert system and makes it possible to construct a quick inference system. This conception could be applied to the similar problems dealing with numerical data and curves.
