Corona Effects on AC Circuits on an Indonesian 500 kV Hybrid Overhead Line

Converting an AC circuit of an existing multi circuit overhead line (OHL) to DC is a promising solution to increase the OHL’s transmission capacity. This is called a "hybrid OHL". Because of the small distances, electromagnetic coupling occurs between the AC and DC circuits. This influences conductor surface gradients, which in return affects corona effects such as audible noise (AN). In this contribution, a case study regarding a fictive Indonesian hybrid OHL is used to present AC surface gradient calculations under DC influence. Furthermore, results from laboratory experiments are presented. The aim of the experiments was to explore the AN behavior of AC lines under DC influence. Additionally, the performance of noise reducing surface treatments under hybrid conditions has been investigated. The gathered results show that an AC line’s corona behavior worsens substantially under DC influence. Surface treatments, however, seem to retain their noise reducing effects even under hybrid influences.