Reactive power management at Transmission/Distribution interface

Abstract

National Grid, the UK Transmission System Operator (TSO) has metered frequent voltage rise excursions at 275–400 kV network since 2011–12, particularly during the minimum demand periods. This rise in system voltage is more severe in the areas with high penetration of underground cables. The steep decline in the reactive power demand in the last few years is the potential cause behind this voltage rise issue. Currently there is no responsibility of Distribution Network Operators (DNOs) to manage the reactive power exchanges at Transmission/Distribution interfaces i.e. at Grid Supply Points (GSPs), however soon to be implemented European Demand Connection Code (ENTSO-E) will make it obligatory for DNOs to limit these exchanges to 0MVar at GSPs during minimum demand periods for a loading below 25% of the peak MW demand at the GSPs. The enforcement of this code is helpful for the National Grid to maintain voltage levels within the statutory limits; on the however this will have a negative impact in the business case of DNOs, who will have to make costly investments for the installation of reactive power compensation equipment. This work proposes an Active Network Management (ANM) approach to limit the reactive power export to National Grid by using the Power Factor Control (PFC) of Distributed Generation (DG) and Demand Side Management (DSM) as control variables in a multi-period Optimal Power Flow (OPF) framework.