Study On Protection Technology In Distribution Network With Distributed Generation

With the high quality requirements of power consumers, especially after severalpower outages around the world in recent years, centralized power grid presents itsshortcomings in the guarantee of reliability and power quality. What’s more, energyresources and environmental protection are the prerequisites of sustainabledevelopment, with the circumstance of energy shortage nowadays, distributedgeneration has been well developed because of its apparent advantages, for example,cleanliness, low cost on resources of power transmission and distribution as well asthe operation expense, high power reliability. However, running with distributedgeneration, the configuration of distribution network will be changed and theninfluences the allocation of relay protection and the settings of operation value. Thepower flow, direction, duration and strength of fault current all will change.This paper first introduces the basic principle and mathematical model ofdifferent types of distributed generation, and the output characteristics of photovoltaicpower generation and super capacitor are simulated in Matlab/Simulink.To analyze the effect of distributed generation on relay protection in distributionnetwork, the traditional distribution network protection scheme are introduced, andthen constructs a distribution network model with distributed generation, analyzes theinfluence on current protection of main feeder, reclosing and conventional branch lineprotection after distributed generation synchronization. Influence mainly include thatsome protection scope changes, reclosing failure, abnormal movements of protectioncomponents and so on. It puts forward a method for determining the access capacityof distributed generation which is based on current protection constraints, and thecorrectness of theoretical analysis are verified by simulation examples.Finally, it puts forward the centralized direction longitudinal protection schemeto improve the traditional distribution network protection scheme, and the automaticreclosing device is adjusted.