Abstract
In this paper, we proposed the method judging whether transmission system is radial system or loop system using simple set theory. And we proposed the method judging whether power device's operation causes of blackout or not. Using proposed method, we developed automatic judgement system of radial system for preventing power device's wrong control in SCADA. Finally, we simulated a variety of case study using SCADA simulator with developed system, and verified reliability of the result and performance of developed system.