Dynamic response characteristics of heavy duty gas turbines and combined cycle systems in frequency regulating duty

Privatization of the electric utility industry in the United Kingdom has resulted in plans for numerous installations of both simple cycle and combined cycle gas turbine power plants manufactured by the author´s company and its business associates. Several of these power plants are now in service, or are currently entering service. At almost the same time, the National Grid Company has been formulating a Code containing requirements for power plants interconnecting with the National Grid. Many of these requirements relate to the dynamic response capability of the connected equipment. This paper discusses four of these requirements and the associated dynamic characteristics of the gas and steam turbine prime movers when operating in a combined cycle configuration, producing steam from gas turbine exhaust heat for additional power production in a steam turbine. The four requirements to be discussed include: load pickup capability; off-frequency operating limits; off frequency power generating capability; and a recommended method for combining system frequency correction and megawatt output demands.