MV cable lifetime improvement analysis through transformer tap changes

Cable life depends mainly on the thermal stress, which relates to the current applied on the cable. Voltage changes in medium voltage (MV) cables due to transformer tap changes will also change the current flowing through the cable, which will change the cable temperature. In order to extend the cable life, this paper aims to simulate and analyse the potential thermal lifetime improvement of cables through long-term tap changes within the statutory levels. Firstly, the IEC standard (60287) method for rating and modelling cables is applied to evaluate the cable temperature under different voltages and relative currents. Different cable configurations will also be considered in simulations as temperature is dependent on the cable dimensions. Then, typical thermal lifetime analytical expressions will be used to evaluate the long-term influence of voltage changes. Lastly, the obtained thermal lifetime assessments under different transformer tap changes and different cable configurations will provide a potential understanding of cable lifetime changes through implementation of permitted regulatory voltage changes.