This paper describes the development work leading to the design and testing work of a new corona shield for AREVA's 800 kV Ultra High Voltage Direct Current (UHVDC) thyristor valve. The design of the corona shields required an extensive electrostatic field investigation using numerical analysis, particularly the Boundary Element Method (BEM), an enhancement of the well known Finite Element analysis to calculate electrical stress. Some results from the laboratory tests are presented in the paper together with an assessment of the initial BEM analysis. The paper concludes by considering how the electrical clearances identified in the tests influence the design, and hence achieve an economically viable corona shield design for +/-800 kV UHVDC convertor stations.
