General Electric Company

William G Gorman

Charles Michael Jones

William George Carberg

Michael James Molitor

A method and control system can implement a transient exhaust pressure protection logic to avoid a turbine exhaust vacuum trip due to a short duration turbine exhaust pressure transient that may be caused by a large reduction in turbine flow coupled with a transient increase in exhaust pressure, which specifically occurs during full load rejections. When full load rejection conditions are sensed by power load unbalance and confirmed by secondary indications, normal alarm settings and trip settings for turbine exhaust pressure are blocked for a delay period while transient operating limits are in place.

Method for operating steam turbine with transient elevated back pressure

To provide auxiliary steam, a low pressure valve is opened in a combined cycle system to divert low pressure steam from the heat recovery steam generator to a header for supplying steam to a second combined cycle's steam turbine seals, sparging devices and cooling steam for the steam turbine if the steam turbine and gas turbine lie on a common shaft with the generator. Cooling steam is supplied the gas turbine in the combined cycle system from the high pressure steam turbine. Spent gas turbine cooling steam may augment the low pressure steam supplied to the header by opening a high pressure valve whereby high and low pressure steam flows are combined. An attemperator is used to reduce the temperature of the combined steam in response to auxiliary steam flows above a predetermined flow and a steam header temperature above a predetermined temperature. The auxiliary steam may be used to start additional combined cycle units or to provide a host unit with steam turbine cooling and sealing steam during full-speed no-load operation after a load rejection.

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Malta, NY, United States of America

William G Gorman