Rule-based determination of plant operating state to avoid governor valve instabilities on a 500 MW turbogenerator

Power stations are required to adjust their output continually in response to the demands of the National Grid. This requires, in particular, accurate control of the fuel flow to the boiler and of the governor valve which regulates the steam flow to the turbine. Control of these parameters is generally considered together and referred to as Load Control. Work has been carried out by the CEGB into improved methods of load control in order to achieve more rapid and predictable load changes and improved control near to plant constraints. This enables both power stations and the Grid System to be operated more efficiently and with less damage to the paint. In particular, a major project has been undertaken on a 500 MW coal-fired unit at West Burton Power Station. The paper considers the implementation of a rule-based technique to achieve improved control of the governor valves. This enables an operating region, where discontinuous governor valve movement occurs, to be avoided and thus achieves: better control of the generated output; and much reduced wear of the valve mechanism which is both expensive to repair and can only be serviced during periods of extended plant shut-down