Ancillary Services for Transmission Systems by Tap Stagger Operation in Distribution Networks

With the integration of intermittent renewable generation, transmission voltage problems have become more dynamic. The deployment and tuning of numbers of VAr compensators at various locations may not be cost-effective. This webinar will introduce an alternative method, which utilises the distribution network assets, such as a large number of parallel transformers, to provide reactive power absorption services for transmission systems. The operation of parallel transformers in safe and small different tap positions, with staggered taps, can provide a means of absorbing reactive power. The aggregated VAr absorption from many pairs of parallel transformers could be used to provide voltage support to the upstream transmission network. This webinar will discuss both the economic and dynamic impacts of the proposed method. For the economic analysis, the associated costs of applying the tap staggering technique are investigated from the perspective of transmission system operators. In addition, the dynamic impacts of tap staggering on transmission voltages are compared with the switching of shunt reactors. The outcomes from this research could potentially lead to a new reactive power ancillary service involving distribution networks, which may be treated as a smart grid tool to enhance the transmission system VAr management in the future.