Condition based replacement of medium voltage cables saves millions-case study Botkyrka

The method for diagnosis of water trees in XLPE cables based upon measurements of dielectric losses and capacitance as function of frequency has been verified. Based upon diagnostic measurements in 1996 a replacement strategy was decided upon for the Vattenfall 24 kV network of Botkyrka and the most severely degraded cables were replaced. This work reports on the measurements made in 1996 and selective repeated measurements in 2002. The development of the ageing is analysed. The failure statistics are reported and the effectiveness of the diagnostic method is proved. The costs savings using a replacement strategy based upon diagnostic measurements is presented.