Summary of Research on Relay Protection in Active Distribution Networks
Distribution network relay protection is the key to ensure the safe and stable operation of the distribution network.With the connection of large-scaled distributed generators to power grid,the traditional three-stage current protection and fault ranging technology of distribution network meet challenges.Distribution network has many branches,short lines,and timing er-rors,making it difficult for many protection methods to meet the requirements for relay protection of the distribution network.This paper firstly introduces the impact of parallel operation of distributed power supply and energy storage equipment on dis-tribution network relay protection,classification of distributed power supply,and focuses on the control mode of inverter-type distributed power supply and its fault output characteristics.Secondly,the classification of industrial frequency quantity protec-tion is reviewed.In single-ended quantity protection,the improvement of traditional three-stage current protection into adaptive directional current protection is an important research direction.In the double-ended two protections,longitudinal differential protection is one of the effective measures to improve the rapidity and selectivity,but the existence of branches along the line and the unsynchronisation of each strategy device in the distribution network lead to the difficulties of the practicality of the dif-ferential protection.The protection method using multiple information has a large amount of data processing and a high depend-ence on the communication system,which is generally applied to the backup protection scheme in practical engineering.Then the principle of transient protection and fault ranging methods in active distribution networks are briefly summarised.Finally,the challenges faced by the existing protection methods are pointed out,and the future research directions are prospected.
distribution networkdistributed generationrelay protectionfault characteristicslongitudinal differential protection
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