220 kV变压器中性点接地方式改造后相关设备的安全校核分析

Safety Checking and Analysis of Relevant Equipment after Transformation of Neutral Point Grounding Mode of 220 kV Transformer

摘要:

为限制方山电厂近区发生非对称故障时500 kV泸州变电站220 kV系统短路电流，需对电厂主变压器中性点接地方式进行改造，将电厂2台主变压器中性点分别通过接地小电抗器和1套隔直装置接地。文中通过仿真模拟电厂近区不同接地故障，电厂2台主变压器采用不同接地方式，分别得出主变压器中性点、接地小电抗器、隔直装置等设备的暂态电压和短路电流，验证电厂2台主变压器接地中性点分别通过接地小电抗器和1套隔直装置接地时，相关设备不会出现电压、电流超限而威胁设备的安全。同时，对线路、发电机、主变压器相关保护的影响进行了分析，对是否引发谐振进行了评估。

Abstract:

In order to limit the short-circuit current of 220 kV system of 500 kV Luzhou substation when an asymmetric fault occurs in the near area of Fangshan power plant, the neutral point grounding mode of main transformer in the power plant needs to be modified. The neutral points of two main transformers in the power plant are grounded through small grounding reactors and a set of neutral DC current blocking device respectively. Through the simulation calculation and analysis, the different grounding faults in the near area of the power plant are simulated, and the transient voltage and short-circuit current of the neutral point of main transformer, small grounding reactor, neutral DC current blocking device and other equipment are obtained under different grounding modes of the two main transformers. It is verified that when the neutral points of the two main transformers are grounded through a small grounding reactor and a set of neutral DC current blocking device, the relevant equipment does not have excessive voltage and current that threaten the equipment security. Meanwhile, the impact on the related protections of line, generator and main transformer is also analyzed, and whether the resonance is triggered or not is evaluated.