Real-time thermal rating and active control improved distribution network utilisation

This paper describes work carried out in the UK as part of a collaborative project including Parsons Brinckerhoff, Durham University, Scottish Power Energy Networks (SPEN), ALSTOM Grid and Imass, part-sponsored by the UK Government´s Technology Strategy Board (TSB) which aims to explore the potential to exploit the dynamic thermal capability of distribution system equipment. Application of continuously changing (rather than seasonal) ratings, which can be updated in real-time, could enable generators to enhance their energy export, defer network reinforcement and also allow increased access to distribution networks for weather dependant forms of generation, such as wind. The aim of the project is to evaluate the extra thermal capacity available in the critical network components, overhead lines, transformers and cables when the thermal limits are varied many times a day according to the prevailing environmental conditions. This technique is known as Dynamic Thermal Rating (DTR). In 2009 prototype protection relays were installed of SPEN´s network to gather electrical and environmental data locally for an overhead line, transformer and underground cable. The protection relays can also calculate the dynamic thermal rating of the local component. The paper includes an analysis of the field data gathered from site which is used to verify the accuracy and benefits of the real time thermal ratings.