Application of time-limited ratings to underground cables to enable life extension of network assets

Abstract

Underground cables have thermal inertia that can be leveraged to tolerate loading beyond 100% of capacity for short periods of time. These short term overloads allow the calculation of time-limited ratings for cables that are routinely underutilized such as those in N-1 configurations. These ratings are often not considered as part of distribution network modelling and only sometimes applied by network operators. Recent advances in cable rating technology allow network operators to calculate time-limited ratings in real time to adapt to contingency situations on their network. This paper proposes a methodology for determining the benefits of using time-limited ratings on an 11kV ring network. A case study shows how increasing loadings can be mitigated by the use of time-limited ratings and how this affects the economics of operating and planning a power system, including for avoiding network reinforcement.