Method of effecting fast turbine valving for improvement of power system stability

[5. The method of claim 1 in which one quarter of the turbine's control valves

• are rapidly closed by valve actuator oil dumping.] 6. In a steam-electric installation incorporating [a U.S. type] an alternating current type generator driven by a compound type steam turbine incorporating control valves ahead of the high pressure turbine, and intercept valves ahead of the turbine or turbines that receive steam from the discharge of the high pressure turbine, which installation also includes a reheater, and also a once-through boiler, one or more power operated valves that are arranged so that when opened they provide a path by which steam can by-pass from a point ahead of the turbine to the flash tank of said boiler, [and from thence to the condenser,] which valves are subject to the control [ofa-- of a control system which [causes] is operative under load conditions to cause them to open when the pressure ahead of the valves exceeds a preset value which is less than that pressure that will cause discharge of steam through the turbine's high pressure safety valves, and are also so controlled as to close when pressure falls to a preset value that exceeds the normal operating pressure of the turbine, the generator of which installation [is part of] makes connection to a power system which includes a plurality of prime mover driven generators, which generators are interconnected by a plurality of alternating current transmission circuits, the method of employing fast turbine valving as a way to avoid development of system instability [as a consequence of stability endangering events of a type adapted to cause the generator of the said installation to experience a sudden at least momentary reduction of load,] which comprises the steps of,
• 1. providing within the turbine and steam generator control system, for response to a fast valving initiation signal input by bringing into effect preprogrammed jointly effected processes, of
• a. at least partial intercept valve closure effected fast enough to have a favorable effect on generator rotor first swing stability, and control valve repositioning plus intercept valve reopening so effected as to cause turbine driving power subsequent to generator rotor first forward swing to hold below a preset value that is less than the driving power that applied prior to the event that brought about development of the signal,
• b. runback of rate of steam production within the steam generator to a value that will cause termination of whatever discharge of steam through said steam by-pass valves may take place with provision so that said runback is effected rapidly enough and is otherwise so executed to avoid overheating of the reheater.
• 2. providing in a preprogrammed manner so that [a fast valving signal is generated and transmitted as an input to the turbine and steam generator control system on the occurrence of certain types of events that endanger preservation of system stability.]
• a. a fast valving signal is generated on the occurrence of system stability endangering events of a type that cause the said generator to experience a sudden at least momentary reduction of load,
• b. the said fast valving signal is made available as an input to that portion of the turbine's control system that is adapted to bring into
• effect the said preprogrammed processes.

[10. The method of claim 6 in which one quarter of the turbine's control valves are rapidly

• closed by valve actuator oil dumping.] 11. In a steam-electric installation which [is part of] incorporates an alternating current type generator driven by a compound type steam turbine incorporating control valves ahead of the high pressure turbine, and intercept valves ahead of the turbine or turbines that receive steam from the discharge of the high pressure turbine, the generator of which installation makes connection to a power system which includes a plurality of prime mover driven generators, which generators are interconnected by a plurality of alternating current transmission circuits, the method of employing fast turbine valving as a way to avoid development of system instability [as a consequence of stability endangering events of a type adapted to cause the generator of the said installation to experience a sudden at least momentary reduction of load,] which comprises the steps of,
• 1. providing within the turbine's control system for response to a fast valving signal input by bringing into effect preprogrammed processes of,
• a. at least partial closure of the turbine's intercept valves,
• b. partial intercept valve reopening, to the extent of at least 25 percent [brought to completion] on a flow basis, effected within 1/2 second [of termination of closure, and] after the peak of the generator rotor first forward swing, with termination of fast opening occurring when the valves are still only part way open, followed by more slowly effected full opening executed in a manner adapted to cause turbine driving power to hold below a preset value that is less than the driving power of the turbine at the instant of receipt of the said fast valving signal input,
• 2. providing in a preprogrammed manner so that [a fast valving signal is generated and transmitted as an input to the turbine and steam generator control system on the occurrence of certain types of events that endanger preservation of system stability.] a. a fast valving signal is generated on the occurrence of system stability endangering events of a type that cause the said generator to experience a sudden at least momentary reduction of load,
• b. the said fast valving signal is made available as an input to that portion of the turbine's control system that is adapted to bring into
• effect the said preprogrammed processes. 12. The process of
• claim 11, in which intercept valves in step (1), are fully closed. 13. The process of claim 11 in which intercept valve reopening is initiated within
• 0.1 second of completion of the closing process. 14. The process of claim 11 in which partial intercept valve reopening carried out in step (2) is effected with oil supplied from accumulators, and is terminated by operation of valves of cam operated type, with cam position determined by
• valve stroke. 15. The process of claim 11 in which fast partial intercept valve reopening, carried out in step 2, is effected by the transfer to the cylinder of each of the valve actuators, of a predetermined quantity of
• oil contained within a second cylinder. 16. The process of claim 11 in which control valves are repositioned in a manner adapted to bring into effect a preset sustained degree of partial closure, with provision so that said process of partial closure is accomplished rapidly enough, and to an extent sufficient, to prevent an increase in steam pressure ahead of the turbine's intercept valves that would suffice to cause discharge of steam through safety valves located ahead of said intercept valves.

In a nuclear steam electric installation which incorporates an alternating current type generator that is driven by a compound type steam turbine in which steam received from a nuclear steam supply source passes through control valves into a high pressure turbine and is discharged as a mixture of steam and water into one or more moisture separators in which the bulk of the water is separated out and discharges into a drain system, and from there returns eventually to the nuclear steam supply source, and in which demoisturized steam is discharged from the moisture separator or separators into one or more reheaters from which it passes into one or more low pressure turbines, which it enters through intercept valves, which installation includes one or more by-pass valves that are arranged to open and discharge high pressure steam to the condenser when steam pressure ahead of the valves exceeds a preset value, and close when pressure falls below said preset value, the generator of which installation makes connection to a power system which includes a plurality of alternating current transmission circuits, the method of employing fast valving as a way to avoid development of system instability which comprises the steps of

• 1. providing within the turbine and steam generator control system, for response to a fast valving initiation signal input by bringing into effect preprogrammed jointly effected processes of, at least partial intercept valve closure effected fast enough to have a favorable effect on generator rotor first swing stability, and control valve repositioning plus intercept valve reopening so effected as to cause turbine driving power subsequent to generator rotor first forward swing to hold below a preset value that is less than the driving power that applied prior to the event that brought about development of the signal,
• 2. providing in a preprogrammed manner so that
• a. a fast valving signal is generated on the occurrence of system stability endangering events of a type that cause the said generator to experience a sudden at least momentary reduction of load,
• b. the said fast valving signal is made available as an input to that portion of the turbine's control system that is adapted to bring into effect the said preprogrammed processes.

In a steam-electric installation which incorporates an alternating current type generator driven by a compound type steam turbine incorporating control valves ahead of the high pressure turbine, and intercept valves ahead of the turbine or turbines that receive steam from the discharge of the high pressure turbine, which installation also incorporates a fossil fuel type steam generator equipped with a reheater, and also one or more power operated relief valves located ahead of the high pressure turbine, which are so controlled as to open and discharge steam when pressure ahead of the valve or valves exceeds a preset value that is less than that at which the turbine's high pressure safety valves are set to open, and to reclose when pressure falls below a preset value which exceeds normal operating pressure ahead of the turbine, the generator of which installation makes connection to a power system which includes a plurality of prime mover driven generators, which generators are interconnected by a plurality of alternating current transmission circuits, the method of employing fast valving as a way to avoid development of system instability, which comprises the steps of,

• 1. providing the turbine and steam generator control system with a plurality of fast valving signal input channels, each of which, when it receives a signal, will bring into effect a different pair of preprogrammed jointly effected processes of
• a. intercept valve closure effected fast enough to have a favorable effect on generator rotor first swing stability, and control valve repositioning plus intercept valve reopening so effected as to cause turbine driving power subsequent to generator rotor first forward swing to hold below a preset value that is less than the driving power that applied prior to the event that brought about development of the signal,
• b. runback of rate of steam production within the steam generator to a value that will cause termination of whatever discharge of steam through said power operated relief valves that may at first take place, with provision so that said runback is effected rapidly enough and is otherwise so executed to avoid overheating of the reheater,
• 2. providing in a preprogrammed manner so that
• a. a fast valving signal is generated on the occurrence of system stability endangering events of a type that cause the said generator to experience a sudden at least momentary reduction of load,
• b. the said fast valving signal is selectively made available to one of the said plurality of fast valving signal input channels, in such manner that the pair of preprogrammed processes that will be activated will depend in a preprogrammed way on the nature of the stability endangering event.