Grounding system circulation calculation of ultra-high voltage switching substation

For the phenomena of UHV system high voltage and large capacity, circulating current in the shell and grounding network is relatively large. Under steady-state operation, shell will product a large loss of circulating current. Combined with the 1100 kV HGIS substations, according to the basic principles of electromagnetic transformers, GIS / HGIS shell equivalent circuit model is created and model parameters are determined. The π-type equivalent is used to show grounding element and the use of numerical methods for the electrical grounding system parameters. Analysis showed that circulating current of the main mesh is controlled to less than 20A and circulating current of the sub-mesh is controlled to less than 700A by using double level grounding network. However, the short-wire current is large. Further analysis, there is effect that application of deep vertical grounding electrode and short-wire reduce the circulating current of grounding network, and the best design have been given. Finally, the circulating current value and temperature rise of each part will be given.

I. Introduction

In the ultra-high voltage substations, due to the phenomenon of electromagnetic induction, induced current will appear in the GIS / HGIS shell. Circulation mainly exist in the circuits of three-phase shell short-wire, ground-wire and grounding network. Operation shows that shell circulation values and the bus current is basically the same order of magnitude [1]–[4]. At the same time of produced loss of circulation, heat loss will accelerate the aging of the insulation. Therefore, it is necessary to accurately calculate the GIS / HGIS shell circulation and grounding network circulation, and to in-depth study the limiting measures of the grounding system.