220kV变电站主变110kV侧接地方式分析

220 kV变电站主变中性点接地方式直接影响到主变的安全稳定运行,当220 kV变电站的110 kV侧发生单相接地故障时,有可能造成主变遭受冲击而损坏。因此列举出了220 kV变电站中可能出现的主变中性点接地方式,分析了110 kV侧发生单相接地故障时,主变中性点接地方式对流入主变短路电流的影响,并计算了相应的短路电流,提出单相接地故障对主变的冲击最严重。可以通过改变主变中性点的接地方式来保护主变,最后提出了具体的保护措施,并给出唐山供电公司的一个应用实例。

Analysis of Grounding Modes of 110 kV Side of Transformer in 220 kV Substation

The grounding modes of main transformer in 220 kV transformer station will influence the stability of main transformers significantly. Short circuit current may do harm to transformer when a single-phase grounding fault occurs in the 110 kV side of 220 kV Transformer Substation.Main transformers in 220 kV transformer station are three-winding transformer commonly,their winding structures are usually Y/y/d connected with the neutrals grounded modes.This paper presents the possible grounding modes of 220 kV transformer substation,and analyses the influence of grounding modes of 220 kV Transformer Substation on the short circuit current that feeds into transformer when a single phase grounding occurs in the 110 kV side of 220 kV transformer substation,the method for computing the short circuit current is also provided.The single-phase grounding is the worst fault that does harm to transformer,and transformer could be protected by selecting suitable grounding modes.The main transformer neutral grounding via little reactance will enlarge the zero sequence equivalent reactance of electric power system,meanwhile,single phase shorts circuit current will remarkably reduce and the shorts circuit currents that feed into the winding of transformer will reduce too,this method could protect main transformers in 220kV transformer substation effectively.At the end,an actual case of Tangshan electric power company was presented.