Electric Field Grading by Functionally Graded Materials (FGM) for HVDC Gas Insulated Power Apparatus

Functionally graded materials (FGM) have been investigated as innovative field grading and control techniques for gas insulated power apparatus such as gas insulated switchgears (GIS) and gas insulated transmission lines (GIL). We have so far verified that FGM with the spatial permittivity distribution can control the electric field distribution around GIS spacers under AC and impulse voltage stresses. In this paper, we proposed the new application of FGM for HVDC power apparatus (DC-FGM) and investigated the technical feasibility of the electric field control by DC-FGM. The calculation results revealed that DC-FGM with the spatial conductivity distribution in the spacer bulk can control the electric field distribution around the spacer in consideration of the temperature distribution under DC voltage stress.