Application and modelling of quadrature boosters for the HV transmission system

Multiple quadrature boosters are used on the transmission network of the UK's National Grid Company plc (NGC) to improve the utilisation of its existing assets. The on-load tap changers installed on the quadrature boosters permit the system operator to adjust the power flow pattern as system conditions change. In operational timescales, the quadrature booster tap positions are optimised to eliminate or minimise any uplift in the total generation cost due to transmission thermal constraints. In planning the development of the transmission system, a frequent objective is to maximise the transfer capability of the existing network and thereby avoid unnecessary reinforcement. NGC has developed in-house software tools to automatically optimise the tap positions of interacting quadrature boosters. These tools are used to assess network capability under specific conditions stipulated by the security standards, and to estimate optimised future operational cost for specified periods, e.g., a year. This paper discusses these recent developments and some of their applications.