Gas Turbine Spinning Reserve Operation to Support Frequency Drops in Small Grid

The use of gas turbines in relatively small grids is often connected with an additional requirement from the grid side. Such a requirement can be the increase of power production within seconds to support the stability of a grid. This topic was investigated thoroughly in 1985 for several types of power plants. In 1992 ABB received an order for a gas turbine power plant on the island of Puerto Rico where a fast loading response with 40% load increase within 3 seconds was required. Based on earlier investigations the order was accepted. The powerplant built a „Steam Enhanced Power (SEP) plant“, each consisting of three powertrains each with a gas turbine, a once through steam generator and an exhaust system with an SCR for emission control. This paper describes the control functions necessary to meet the requirements and the consequences for the operation of the plant. Results from the acceptance tests where the rapid loading from a standby mode at 60% load was simulated will be shown and discussed in detail.