The Circulation Calculation and Analysis of the UHV-HGIS System with the Three-Dimensional Magnetic Field Model

Large mount of power loss can be caused by circulation in UHV shells and grounding system due to its high voltage level and large capacity. Taking a certain UHV HGIS switch station as example, the circulation value is obtained and analyzed through building a 3-D finite model of the switch station and analyzing its coupled electromagnetic field. Results of finite analysis and field-circuit coupling method are applied to calculation of circulation and temperature rise in grounding wires. Calculation results show that: the maximum of the shell circulation is about 3500A with the rated current 6300A on the bus. Adoption of bi-layer grounding network can limit the circulation value in the main grounding network to 20A, while 700A in the sub-grounding network. But this method proves no affection on the short wire current. How the vertical grounding electrode deep acts on the circulation value in grounding network is analyzed as well. The results can acts as reference for the UHV HGIS manufacturers.

I. Introduction

The circulation is introduced by alternative electromagnetic field that caused by bus current in GIS/HGIS (Gas Insulated Switchgear/Hybrid Gas Insulated Switchgear). It usually flows among 3-phase shells linked by short wires or among shells, grounding wires and grounding network wires. Practice finds that the circulation, which usually cause power loss and heat problem when flowing trough GIS shells, has the same order of magnitude with that of the load current on the bus. This performance will speed up insulation aging or even damage the insulation and then decrease lifetime and safety of associated devices. Researches on GIS magnetic field and circulation on shells by finite elements method have been set about by foreign engineers [1]–[2]. But few of their analysis are focused on UHV grounding system, the model and calculating are not acute enough as well.