In the restructuring of the privatised electricity supply industry in England and Wales, the management of the quality of supply was allocated to National Grid Company pie (NGC) in its Transmission licence through a mechanism called Ancillary Services. NGC was bound by an economic purchase obligation to procure and despatch technical services for controlling voltage, frequency and transmission constraints which also included reserve and grid recovery services or Black Start. The structure and strategy behind a portfolio of contracts enables NGC as the Grid Operator to despatch and utilise these services to facilitate reliable and economic system operation within prescribed supply quality standards. This paper addresses some of the key measures taken to identify the system requirements for frequency control services and technical/contractual mechanisms put in place for establishing the capability of generating plant to provide these services. The paper also discusses the frequency control strategy in England and Wales, the role of the Grid Code and monitoring systems in facilitating service delivery, as well as frequency control measures under abnormal operating conditions.
