Performance of Composite Outdoor Insulator Under Superimposed Direct and Switching Impulse Voltages

High Voltage Direct Current (HVDC) systems are increasingly being adopted around the world to integrate renewable resources, increase power transfer, and allow flexible grid operation. HVDC overhead lines play a critical role in this, focus is needed on research of composite outdoor insulators failure. In case pole ground fault bipolar scheme, healthy experiences slow transient overvoltage similar Switching Impulse (SI) superimposed operational DC voltage. However, there no standard test for such voltage superimposition. This paper investigates performance insulator stressed with superimposition under dry rain conditions. To determine direct influence flashover voltage, results have been compared SI only case. Four different conductivities used program because these can be exposed acid conductive types, typical industrialized environments. Both vertical horizontal orientations studied. It was possible conclude that, most cases, pre-energization has negative impact performance. The conductivity leads lower values, orientation outperforms configuration. Under conditions, voltages were all larger than switching surge. Thus, fault, failure risk appears low. further higher polluted