35kV配电网中性点经小电阻接地的改造方案分析

针对南京路变电站35kV系统电容电流过大、中性点经消弧线圈接地暴露出的问题,制定了两种经小电阻接地的改造方案,采取在变压器角形接线侧增加Z型接地变和中性点电阻的方式。根据南京路变电站35kV侧为双母线接线且需并列运行的特点,对Z型接地变的设置方案及容量选择、运行操作等方面需注意的问题进行了探讨,对经小电阻接地的主变压器差动保护的几种配置方案进行了分析比较,提出了一种新的适合小电阻接地系统的主变压器差动保护方案。

Analysis of improving scheme for neutral grounding via low resistance in 35 kV distribution network

The capacitive current level in 35kV system of Nanjing road substation is too high, and the neutral grounding via arc suppression coil is liable to cause some problems. According to this situation, there are two improving schemes about grounded-neutral system via low resistance, with which delta-connected side of the transformer may be grounded by adding Z-type grounding transformer and neutral resistor. With the characteristics of double busbars being in parallel in 35kV system of Nanjing road substation, some problems about the arrangement, capacity selecting and operation of Z-type grounding transformer are discussed. By analyzing and comparing several schemes for transformer differential protection in grounded-neutral system via low resistance,a new transformer differential protection scheme suited for the grounded-neutral system via low resistance is put forward.