Improving Feeder Automation for Medium Voltage Distribution Networks

Abstract

Distribution Network Automation is being introduced by Distribution System Operators (DSOs) as part of the Smart Grid implementation. Present HV and MV networks are being extended and modified so that they will be able to meet the increase in electrical demand and the changes to the Power Generation Sector. Past analysis showed that during peak demand periods, many components of the MV network are operated close to their maximum capacity and with no redundancy. This means that in the short-term, significant parts of the network will be unable to meet the peak demand in case of a failure of one of the main components. Furthermore, significant parts of the network will be unable to meet the expected increase in demand in the long-term should load growth increases significantly. Although there have been many academic studies on designing automation schemes, they are often approached from a theoretical optimisation viewpoint. However, it is essential to approach this from an operations engineering perspective because a real network provides daily operational restrictions to a DSO, although these are not always visible from outside the DSO organisation. Nevertheless, this does have a direct impact on the quality of supply given to the DSO customers. The research objective is to obtain an optimisation method and determine the most appropriate MV substation locations, where automation technology can be installed, as a function of network operations restrictions. The research analysed a Maltese 11kV network, which is like DSO networks in UK. Hence what was achieved from this research is also adaptable to UK networks. Customer minutes lost and energy not supplied were achieved by considering MV restrictions that exist in networks substation location, substation access and switchgear operational restrictions. All these have been factored in the optimisation process to select the optimum locations where existing substations could be automated. The optimisation process included the actual automation cost for the existing switchgear in the selected substations. In addition, the maintenance cost required for 15 years was included. This 15-year time horizon is the expected lifetime of the switchgear automation. The research results show that it is not necessary to have all substations automated as 35% of the network will provide the optimum benefits. The case study results gave between 8% to 26% improvement as against those substations automated by the DSO and a cost savings of about 16%. The unused budget funds, which would have been spent on the remaining substations, will be utilised to improve the same network with switchgear replacement, new MV cables to interlink the feeders as well as replacing and upgrading old cables having lower ampacity.