Techniques for the calculation of the transient torque of a steam turbine following step and ramp type displacements of throttle valves are developed. The objective is an improvement in steam turbine representation for digital and other studies of electric power systems under disturbed conditions, including transient stability. The turbine model used as a building block for the transient theory is a length of pipe, representing loop pipe or reheat boiler, followed by a multi-stage turbine. The theory of unsteady flow of compressible fluids is applied to the problem and this, together with throttle, nozzle and steam turbine equations, allows the transient torque to be calculated. A digital computer programme has been developed which could be used as a sub-routine in an overall transient stability programme. The dominant transient feature is a transport lag and not an exponential time delay, as is commonly assumed. Moreover this transport lag, being associated with the local sonic velocity rather than the steam particle velocity, has a value about one-tenth of the usually assumed exponential time lag in mass-flow. Methods are indicated for extending the transient response obtained for the above turbine model to multi-cylinder turbines. The conclusion to be drawn is that, for any fast turbine control or transient condition (on a time-scale of seconds rather than tens of seconds), the conventional assumption of an exponential time constant will be substantially in error. Such fast disturbances will almost certainly have their origins on the power system side. It is from the power system point of view that this paper is written.
Manual Tracking Performance in Patients with Cerebellar Incoordination: Effects of Mechanical Loading