Distribution network supports for reactive power management in transmission systems

To mitigate the excessive voltages in transmission systems with low demands, installing reactors or VAr compensators are often considered, which are expensive solutions. This paper presents a method to utilise the existing distribution network assets as an alternative solution to the problem. The operation of parallel transformers in small different tap positions, i.e. with staggered taps, can provide a means of absorbing reactive power. The aggregated reactive power absorption from many numbers of parallel transformers could be sufficient for the VAr support in the upstream transmission networks. A load flow model of a typical UK distribution network is studied considering the application of tap stagger at the primary substations. Results indicate the potential reactive power absorption through the use of the tap staggering technique is high. The deployment of this method in distribution networks may assist the transmission system operator in managing voltages when demand is low.