Relay Protection State Evaluation of Smart Substation Based on Fuzzy Comprehensive Evaluation and Improved D-S Theory

To make an accurate evaluation for relay protection state of smart substation under more and more operation information, a twice modeling evaluation method is presented about relay protection state. Characteristic indexes system of relay protection device is built and expected values of various characteristic indexes and state classification of device are given by this method. Considering fuzziness of various factors for evaluation result, fuzzy comprehensive evaluation is utilized to established elementary evaluation model by studying membership functions and determination methods of weighting factors of different type data. By introducing improved D-S theory, the framework of information fusion evaluation about relay protection is studied, elementary evaluation results are further fused and evaluation model is once again built. Case study shows that this method can significantly distinguish the different states of relay protection, obtain specific evaluation conclusion, overcome evaluation result invalidations of traditional D-S theory under evidence conflict and avoid evaluation result uncertainties of different fuzzy comprehensive evaluation methods because of the lack of information.