HVDC Monopolar and Bipolar Cage Studies on the Corona Performance of Conductor Bundles

This paper reports on the use of test cages for obtaining the corona performance characteristics of conductor bundles under monopolar and bipolar dc excitation. A large nuimber of conductor bundles were tested under positive and negative monopolar dc as well as bipolar dc conditions in the outdoor test cages of IREQ. Radio interference (RI), audible noise (AN) and corona loss (CL) were investigated under fair weather and artificial rain. Empirical equations were derived for these three parameters: RI, AN and CL, as functions of the bundle geometry and conductor surface voltage gradient. Based on a comparison between cage and line test results, conclusions are drawn on the practical validity of cage tests for dc corona.