基于高阻并联避雷器接地方式的柔性直流配电网保护方法

针对柔性中压直流配电网系统直流线路单极接地故障检测困难的问题,提出一种高阻并联避雷器接地的新型接地方式及其包含自适应放大系数的保护策略。首先讨论了现有的柔性直流配电网接地方式的优缺点,提出了基于联结变压器中性点经高阻并联避雷器的新型接地方式。然后通过理论推导分析了新型接地方式在交直流侧接地故障下的过电压机理和故障特征,根据不同故障下的电压电流特性,提出了相应的直流线路保护策略,实现了差动保护在直流配电网发生故障时准确快速地进行故障识别和故障选线。最后以仿真实例验证了新型接地方式的有效性和所提出的保护方法的可靠性。

Protection Method of Flexible DC Power Distribution Network Based on Grounding Mode with High Resistor and Arrester in Parallel

To solve the difficult problem of monopolar grounding fault detection in flexible medium-voltage DC power distribution network, this paper proposes a new grounding mode with high resistor and arrester in parallel and a protection strategy including adaptive amplification factor. Firstly, advantages and disadvantages of the existing grounding modes in flexible DC distribution network are discussed. A new grounding mode with high resistor and arrester in parallel via the neutral point of the coupling transformer is proposed. Secondly, the overvoltage mechanism and fault characteristics of the new grounding mode are analyzed by theoretical derivation with AC/DC grounding faults. According to voltage and current characteristics in different fault conditions, the DC line protection strategy is developed. It realizes the accurate and rapid fault identification of differential protection with faults in DC network. Finally, the effectiveness of the new grounding mode and the reliability of the proposed protection method are verified by simulation example.