The requirement for reactive power is primarily driven by the interaction of real power flows on the transmission system with the complex impedances of the various elements that make up the network together with the demand at the lower voltage system interfaces. National Grid is required to maintain the real and reactive power balances between sources of generation and points of demand. Unlike system frequency, which is consistent across the network, voltages experienced at points across the system form a 'voltage profile', which is uniquely related to the prevailing real and reactive power supply and demand. Without the appropriate injections of reactive power at correct locations, the voltage profile of the transmission system will exceed statutory planning and operational limits. Further details are in the Introduction to Reactive document below.
What Services do we procure?
National Grid controls Reactive Power through two Balancing Services:
General Information