Operation Analysis of Neutral Point on Medium Voltage Side of 220 kV Transformer with Small Reactance Grounding

The operation of the Beijing power grid is divided into zones, and the grounding method used at the hub station has a significant impact on the overall operation of the electrical grid. In the K zone, the A substation adopts the operating mode of grounding the medium-voltage side neutral point of the 220 kV transformer through a small reactance. This article analyzes the neutral point grounding situation of the main transformer in this zone and the equivalent network of the A substation. It also calculates the short-circuit capacity of the A substation and the single-phase short-circuit current when different main transformers are operated in parallel. The calculation shows that grounding the neutral point through a small reactance can reduce the single-phase short-circuit current and meet the requirements for equipment thermal stability. The article also proposes the operational and switching requirements when the neutral point small reactance is put into operation.