Investigation on propensity difference of water tree occurrences in polymeric insulating materials

In case of medium voltage cables, the main cause of the insulation breakdown is water treeing by referring to the report of national power utility of Malaysia, Tenaga Nasional Berhad (TNB). The inconsistent and unreliable nature brings out the importance of research towards water tree detection of polymeric insulating cable. Early detection of water tree in underground polymeric cable is important in order to increase the cable efficiency by reducing the timeframe of the cable failure. From the previous research of water tree detection, the types of needle that have been used are metal and nickel. It was found that the usage of these needles has some weaknesses which lead to inefficiency of water tree detection. Corrosion, losses and corona discharge are some of the significant problems faced by using those materials. In addition to that, it was found that the time was taken longer using the previous method of water tree detection. Thus, in order to reduce the time of water tree detection and preventing the material´s physical failures, an improved method is proposed. Also, this paper presents the propensity difference of water tree detection in two different insulating materials namely cross-linked polyethylene (XLPE) and low-density polyethylene (LDPE). With the data and research being studied carefully, the water tree detection will be much easier to detect. The effect of ageing time in water tree detection was also discussed in this paper.