Investigation of water treeing — electrical treeing transition in power cables

Water treeing is a phenomenon that is already known for more then 35 years and is one of the reasons for cable failures (polymeric cables) in the medium-voltage network. The final stage of water treeing is the formation of electrical trees on top of the water trees. Due to the fact that the moment of electrical tree initiation is crucial to determine the condition of the cable this paper will focus on the investigation of the moment of transition from water trees to electrical trees. The emphasis will be on the behaviour of the PDIV, PDEV and PD-level as function of time. It has been observed that after the moment of first initiation the PDIV decreased with 40% to 50% and the PD activity up to of hundreds of [pC] remained constant.