单相短路时220kV变压器中性点过电压及避雷器并联棒间隙的动作特性仿真试验研究

Research on the Breakdown Characteristics of Parallel Rod Gap of Arrester and Neutral Point Overvoltage Under Single-phase Short Circuit of 220kV Transformer by Simulation and Test

为了明确一起相同位置,不同相别发生单相接地故障时,仅有一次造成对侧220 kV主变中性点间隙击穿的原因,利用EMTP电磁暂态程序,分别计算了2起单相接地故障下,对侧220 kV主变中性点的暂态过电压。分析了影响中性点过电压的因素,最后,仿真研究了单相接地故障下,中性点避雷器与间隙并联的动作特性,试验验证了仿真的有效性。研究表明:暂态电压波由电缆进入架空线,是造成连接在架空线处所有不接地变压器中性点电压抬高的主要原因;单相短路下,只要中性点电压超过间隙的击穿电压,间隙优先避雷器动作。

In order to clarify the reason for the breakdown of the neutral point gap of the opposite 220 kV main transformer only once when a single-phase ground fault occurs in the same position and different phases, the temporary over-voltage of the neutral point of the opposite 220 kV main transformer under two single-phase ground faults is calculated by EMTP electromagnetic transient program. The factors that affect the over-voltage of the neutral point are analyzed. Finally, the action characteristics of the parallel connection between the neutral point arrester and the gap are studied by simulation, and the effectiveness of the simulation is verified by experiments. The research shows that the transient voltage wave entering the overhead line from the cable is the main reason for the rise of the neutral point voltage of all ungrounded transformers connected to the overhead line;in case of single-phase short circuit, as long as the neutral point voltage exceeds the breakdown voltage of the gap, the gap takes precedence over the action of the arrester.