Optimization of Relay Protection Configuration for Photovoltaic Power

This paper analyzes the existing protection configuration of major electrical equipment in photovoltaic power stations and identifies poor selectivity and long operating delays. It proposes an optimized scheme that adds zero-sequence directional overcurrent protection to the low-voltage-side branches of the main transformer. For collector lines, the scheme uses short-delay directional instantaneous overcurrent protection with undervoltage blocking and short-delay zero-sequence instantaneous overcurrent protection as the primary protection. It also adds zero-sequence directional overcurrent protection to the grounding transformer. Analysis and calculations show that the proposed scheme improves system reliability and protection selectivity and facilitates the economical operation of photovoltaic power stations.