Corona shields for thyristor valves at ultra-high voltages

UHVDC operating levels present a particular challenge for the insulation of thyristor valves. AREVA T&D's R&D teams have carried out electric field stress studies to determine the best profile for the corona shields, built a test object and subjected it to DC and switching impulse tests that validated the theoretical model. The end result after the next phase of development will be a new design of corona shield, suitable for DC applications up to 800 kV.