Reliability centred maintenance strategy for high-voltage-networks

Due to the liberalisation of the European electricity market many companies concentrate more and more on reducing network operation costs by optimising or simply reducing maintenance activities. On the other hand a massive reduction of maintenance comes along with less reliable network components and hence less quality of supply for the customers. This paper presents a method to optimise the maintenance activities in high-voltage (HV)-distribution networks and therefore to save operational costs with a minimum loss of customers quality of supply. The customer´s energy not delivered in time, which is the highest aggregated reliability´ parameter recording the number of interruptions as well as their duration and the interrupted power, is dedicated to the network components which cause the supply interruptions. This dedication shows, which part of the energy not delivered in time of the whole network is caused by an individual component and so the importance of an individual component. This leads to a ranking of all network components and a classification into maintenance groups. For those groups which comprehend the less important components the maintenance effort is reduced significantly, while for the more important components the effort stays constant high or is even increased. Parameter studies assuming a much higher failure frequency for those components which are maintained less validate the proposed method. They show that reducing maintenance activities at the right, less important components does not decrease customer´s quality of supply significantly. Finally the paper presents practical experience gathered from the first two years of practising the presented method to several German 110-kV-distribution networks