Turbine control system with early valve actuation under unbalanced conditions

Claim 2

In a turbine-generator control system having a plurality of steam valves with means to position said valves to control the turbine, and further having fast closing triggers arranged to reduce steam flow through selected valves rapidly in response to actuating signals, the combination of: first control means providing a first signal responsive to a first value of mismatch between a first pair of normally matched signals representing turbine-generator-operating conditions, when said first valUe exceeds a first selected threshold value, second control means providing a second signal responsive to a time rate of change of said first value of mismatch which exceeds a second selected threshold value, and first logical AND means providing an actuating signal to a first one of said fast closing triggers when both of said first and second signals are applied to said AND means.

Claim 3

The combination according to claim 1, wherein said first pair of turbine-generator-operating conditions are steam pressure and generator terminal current.

Claim 4

The combination according to claim 1, wherein said first pair of turbine-generator-operating conditions are steam pressure and generator real load.

Claim 5

The combination according to claim 1, wherein said second control means includes a discriminator circuit having a transfer function Ts/1+Ts with means for adjusting the time constant T.

Claim 6

The combination according to claim 1, wherein said first and second control means each including a voltage comparator arranged to compare said mismatch signal with said threshold value and having additional means to adjust said threshold value to determine the degree of mismatch at which said first or second signal is supplied from the first or second control means respectively.

Claim 7

The combination according to claim 1 further including latching means operated by said first AND means to maintain said actuating signal, and also including reset means operated by said first control means when said first value falls below said threshold value and arranged to unlatch the latching means and thereby terminate the actuating signal.

Claim 8

The combination according to claim 1 and further including: third control means providing a third signal responsive to a second value of mismatch between a second pair of normally matched signals representing turbine-generator-operating conditions when said second value exceeds a third selected threshold value, fourth control means providing a forth signal responsive to a time rate of change of said second value of mismatch which exceeds a forth selected threshold value, and second logical AND means providing an output to a second one of said fast closing triggers when both of said third and forth signals are applied thereto.

Claim 9

The combination according to claim 7, wherein said first pair of turbine-generator-operating conditions are steam pressure and generator terminal current and wherein said second pair of operating conditions are steam pressure and generator real load.

Claim 10

The combination according to claim 7, further including means connected to provide an additional output from said second logical AND means to said first fast closing trigger, whereby said first trigger is actuated by an output from either the first or the second logical AND means while said second trigger is actuated by an output from said second logical AND means.

Claim 11

In a turbine-generator control system having a plurality of steam turbine valves with means to position said valves to control the turbine and further having fast closing triggers arranged to reduce steam flow through selected valves rapidly in response to actuating signals, the combination of: a first relay logic circuit responsive to a pair of normally matched signals representative of steam pressure and generator current and providing a first output signal when the mismatch and time rate of change of mismatch both exceed selected threshold values, a second relay logic circuit responsive to a pair of normally matched signals representative of steam pressure and generator real load and providing a second output signal when the mismatch and time rate of change of mismatch both exceed selected threshold values, a first trigger logic circuit responsive to said first relay logic circuit and arranged to effect one type of turbine valve actuation to control overspeed, and a second trigger logic circuit responsive to either or both of said first and second relay logic circuits and arranged to effect another type of turbine valve actuation to aid system stability.

Claim 12

In a turbine-generator control system having a plurality of steam turbine valves with means to position said valves to control the turbine and further having fast closing triggers arranged to reduce steam flow through selected valves rapidly in response to actuating signals, the combination of: a first relay logic circuit responsive to a pair of normally matched signals representative of steam pressure and generator current and providing a first output signal when the mismatch and time rate of change of mismatch both exceed selected threshold values, a second relay logic circuit responsive to a pair of normally matched signals representative of steam pressure and generator real load and providing a second output signal when the mismatch and time rate of change of mismatch both exceed selected threshold values, a first trigger logic circuit responsive to said first relay logic circuit and arranged to effect one type of turbine valve actuation to control overspeed, and a second trigger logic circuit responsive to either or both of said first and second relay logic circuits and arranged to effect another type of turbine valve actuation to aid system stability.