JPH0363643B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an overspeed prevention device provided to prevent overspeed at the time of negative shutoff in steam turbine power generation equipment.

[Conventional technology]

Conventionally, a hydraulic rotation speed control system as shown in FIG. 3 has been known as a rotation speed control system for a steam turbine. That is, in FIG. 3, reference numeral 10
indicates a boiler, and the steam generated in this boiler 10 is passed through a main servo 12 for a control valve to a steam turbine 1.
4 and drives the generator 16. The rotation speed of the steam turbine 14 is detected by a rotation speed detector 18, and the detected value is compared with a set value set by a rotation speed setting value 20. The rotational speed deviation obtained as a result is calculated by the auxiliary driven piston 22, the pilot valve auxiliary servo 24, and the control valve driven piston 26.
The signal is amplified by the control valve main servo 12 and is configured to operate the main servo 12 for feedback control. That is, the steam turbine 14 is controlled so that the steam flow rate is adjusted depending on the rotational speed deviation.

Therefore, in such a state, if the steam turbine 14 performs negative shutoff, the steam turbine 1
The number of revolutions at No. 4 increases, but strict control is required so that the number of revolutions at this time stays within an allowable value. However, in the conventional rotation speed control system described above, the control valve main servo 12 is operated in the closing direction so that the rotation speed reaches the rotation speed set value 20, but this is not detected after the rotation speed has actually increased. The operation is delayed because the command is generated. For this reason, it is possible that the increase in the number of rotations does not fall within the permissible value.

From this point of view, in the conventional rotation speed control system, an overspeed prevention device is also used. That is, this overspeed prevention device includes an overspeed prevention solenoid valve 28.
and a solenoid valve operation circuit 30, the generator 16
A power detector 36 is connected to the output lines of the generator 16 through an instrument transformer 32 and a current transformer 34, respectively, and the output (active power) signal of the generator 16 detected by the power detector 36 is connected to the solenoid valve operating circuit. 30 to open the overspeed prevention solenoid valve 28 for, for example, one second when the output of the generator 16 suddenly decreases as in the case of load cutoff. In this case, the overspeed prevention solenoid valve 28 is connected to the auxiliary driven piston 2 of the rotation speed control system.
It is installed in a branched hydraulic circuit on the output side of No. 2, and is normally kept in a closed state. Therefore, as described above, when the overspeed prevention solenoid valve 28 is opened, the oil pressure on the outlet side of the driven piston 22 suddenly decreases, and as a result, the control valve main servo 12 is suddenly closed. In this way, when the electric power suddenly decreases during load shedding, the overspeed prevention solenoid valve 28 is instantly opened for a set time by the solenoid valve operation circuit 30, so that the rotation speed control system 18, 20, 22 The control valve main servo 12 is closed without waiting for the command, and the increase in rotational speed is suppressed.

However, the rotational speed control system in the conventional turbine generator configured as described above has the following problems. For example, FIG. 4 shows a schematic diagram of a system including the turbine generator 16 described above. Turbine generator 16 is connected to bus bar 40,
The circuit is configured to supply power to the load 42 via the circuit breaker 44. Further, reference numeral 48 indicates a power source connected to a system 50 different from the bus 40 via a circuit breaker 52, and the bus 40 and the circuit breakers 54, 5
6 and a transformer 58 in parallel. Furthermore, this power source 48 is connected via circuit breakers 66 and 68 and a transformer 70 to a load 62 that is connected via a circuit breaker 64 in another system 60 . In this case, as a general operation, generator 1
6 to the load 62. On the other hand, load 42
, power is supplied from the generator 16 and the power source 48, that is, the power flow of the transformer 58 is transferred from the power source 48 to the load 4.
2. Therefore, if the power supply 48 is tripped, the generator 16 will bear the load 62 in addition to the load 42. On this occasion,
If there is sufficient output in the operating state of the generator 16, the output of the generator 16 is increased by the governor operation of the driving steam turbine (not shown) of the generator 16. On the other hand, if the grids 40 and 60 are different consumers, power transmission from the generator 16 to the grid 60 is not permitted. Therefore, in order to prevent such reverse power flow (power flow from the system 40 to 50, 60), a reverse power relay or an overcurrent relay (not shown) is provided at the set point of the circuit breaker 54 or 56, In the event of reverse power flow, the circuit breaker 54 or 56 is tripped by the operation of these relays, so that the bus 40 is operated independently.

Here, if we consider the operation of the overspeed prevention device, when the power supply 48 trips, the generator 16
When the output of the generator 16 increases and a relay or the like subsequently operates and trips the circuit breaker 54 or 56, the generator 16
output will drop sharply. That is, from the perspective of the overspeed prevention device, since the output suddenly decreases from a high state, the overspeed prevention solenoid valve 28 becomes open, and the control valve main servo 12 closes. In this state, since there is a load 42, there is no overspeed, and there is no need for the overspeed prevention device to operate. In this case, closing the control valve main servo 12 will cause unnecessary disturbance to the power system, unnecessarily disturbing the power balance of the bus 40, which has become an independent system, and in some cases, the bus There is a drawback that it causes all 40 trains to stop.

[Problem that the invention seeks to solve]

Therefore, the present invention provides a turbine overspeed prevention device that detects a rapid decrease in active power and closes the steam turbine control valve for a predetermined period of time to prevent the steam turbine from overspeeding. By delaying the reaction speed when the active power increases, it prevents the turbine control valve from closing in response to rapid changes in power.
An object of the present invention is to provide a turbine overspeed prevention device that can prevent unnecessary disturbances from being applied to a power system.

[Means for solving problems]

Therefore, in the present invention, the turbine overspeed control is configured to detect a rapid decrease in the active power output from the turbine generator and close the control valve of the turbine for a predetermined period of time to prevent the turbine from overspeeding. The prevention device is equipped with a power detector that detects the active power of the generator and an overspeed prevention solenoid valve installed in the hydraulic circuit that opens and closes the turbine regulator valve to delay the response speed when the active power increases rapidly. The present invention is characterized in that a circuit is provided for controlling the overspeed prevention electromagnetic valve so as to prevent the overspeed prevention solenoid valve from being closed.

In the above-mentioned turbine overspeed prevention device, the control circuit for the overspeed prevention solenoid valve is composed of a high gain amplifier, an integrator, a polarity inverting amplifier, a comparator, and an auxiliary relay. It is preferable that the time constant of the integrator be set large to delay the reaction speed of the comparator when the active power increases rapidly.

In this case, the characteristics of the integrator with respect to rapid increases and decreases in the active power detected by the power detector can be variably set by the constant voltage setting values of positive polarity and negative polarity provided on the input side of the integrator.

[Effect]

According to the present invention, the turbine is configured to prevent overspeeding of the turbine by detecting a rapid decrease in active power, which is the output of the turbine generator, and closing the control valve of the turbine for a predetermined period of time. The prevention device can delay the response speed of the control circuit that closes the accelerator valve in the event of a rapid increase in active power, and prevents the adjustment valve from closing in response to rapid changes in active power. This makes it possible to prevent disturbances in the power system and maintain stable power balance at low cost.

〔Example〕

Next, embodiments of the turbine overspeed prevention device according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows the main circuit configuration of the overspeed prevention device of the present invention, in which the rotation speed control system is based on the detection signal of the power detector 36 that detects the output (active power) of the generator 16 shown in FIG. This figure shows a control circuit for controlling an overspeed prevention solenoid valve 28 provided in a branch path of the output side hydraulic circuit of the driven piston 22. For convenience of explanation, the same reference numerals are given to the same components as those in the circuit shown in FIG. (-) polarity. However, in the circuit of this embodiment, a high gain amplifier 80, an integrator 82, a high gain amplifier 80, an integrator 82, A polarity inverting amplifier 84, a comparator 86, and an auxiliary relay 88 are connected and arranged in this order.

Now, assuming that there is no change in the output (active power) of the generator 16, the output of the polarity inverting amplifier 84 will have the same value and opposite polarity as the output of the power detector 36. In other words, since the amplifier 80 theoretically has an infinite gain, the power detector 36 and the polarity inverting amplifier 8
High gain amplifier 80 so that the output values of 4 are equal
provides a signal to an integrator 82. Therefore, the integrator 82 changes its output (same as the output of the polarity inverting amplifier 84) until the input becomes 0V, so that it finally becomes the same value as the output of the power detector 36 (opposite polarity). Therefore, when there is no change in the output of the generator 16, the input signal of the comparator 86,
(The output signal of the power detector 36 and the output signal of the polarity inverting amplifier 84) have the same value and opposite polarity, and the comparator 86 does not generate any output signal.

However, the comparator 86 is configured such that the output signal of the polarity inverting amplifier 84 is larger than the output signal of the power detector 36, and the difference between the absolute value of the signal and the absolute value of the signal is set in the comparator 86 in advance.
The output signal is configured to generate an output signal when a predetermined positive value set point is exceeded. This relationship is shown by the following equation, and the specific operating characteristics are shown in FIG.

| Signal | - | Signal | > Setting value ...( ₁ ) As shown in FIG.
The output I of the polarity inverting amplifier 84 becomes 0V, but since the output of the polarity inverting amplifier 84 is discharged according to the time constant of the integrator 82, the above equation (1) holds true for a predetermined time τ, and during this time the output signal of the comparator 86 Based on this, the overspeed prevention solenoid valve 28 is opened via the auxiliary relay 88, and the control valve main servo 12 is closed as described above, thereby realizing a series of operations for overspeed prevention. The operating time of the overspeed prevention solenoid valve 28 at this time is determined by the time constant of the integrator 82.
It is determined by the magnitude of the constant voltage set by the constant voltage circuit 90.

On the other hand, when increasing the output of the generator 10, the time constant of the integrator 82 is set to a large value at a predetermined time _t2 , as shown in FIG. In other words, even if the power increases at time _t2 , the polarity inverting amplifier 84
Since the output signal of has not yet reached the magnitude of the output signal of the power detector 36, even if the power decreases again at time _t3 , the left side of the equation (1) does not reach the set value,
The overspeed prevention solenoid valve 28 is not excited and is not operated to open. Such an operation can be realized by a constant voltage circuit 92 connected to the input side of the integrator 82. In addition, in the case of such an increase in power, the output signal of the high gain amplifier 80 is infinity with positive (10) polarity, which is actually the maximum value of the calculation level of the overspeed prevention device.
Vmax (for example, 10V). If the time constant of the integrator 82 for such an input signal is T _I and the voltage of the constant voltage circuit 92 is set to Vmax/10, the time for the integrator 82 to reach a constant value is 10
× _TI becomes. Therefore, in the case of power reduction, the integration characteristic of the integrator 82 changes depending on the set voltage of the constant voltage circuit 90.

〔Effect of the invention〕

As is clear from the embodiments described above, according to the present invention, the characteristics of the output signal of the polarity inverting amplifier 84 with respect to a sudden decrease in the output of the generator 16 detected by the power detector 36 (after times t ₁ and t ₃ ) can be freely set with the constant voltage circuit 90, and the characteristics (times t ₂ , t ₄
(after) can be freely set using the constant voltage circuit 92.

As described above, according to the present invention, when the output of the generator increases due to a trip in the power supply of another power system, this can be instantly sensed and the increase in power can be detected without operating the overspeed prevention solenoid valve. Therefore, it is possible to prevent the main servo for the control valve from being operated unnecessarily, and it is possible to prevent disturbances in the power system and maintain the power balance of the system at low cost.

Furthermore, the device of the present invention can also be used as a measure to improve transient stability through turbine high-speed valve control. Furthermore, the device of the present invention operates during the first wave of sudden power reduction even during power fluctuations after a grid ground fault, and can be effectively used as a circuit that does not need to operate during that cycle. can do.

Although the preferred embodiments of the present invention have been described above, it goes without saying that various design changes can be made without departing from the spirit of the present invention.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram showing an embodiment of the turbine overspeed prevention device according to the present invention, Fig. 2 is an operating characteristic diagram of the device shown in Fig. 1, and Fig. 3 is a diagram of the conventional steam turbine generator. FIG. 4 is a block circuit diagram of the rotation speed control system, and is a system explanatory diagram showing an example of connection between the turbine generator and other power systems. 10...Boiler, 12...Main servo for regulating valve,
14... Steam turbine, 16... Generator, 18...
...Rotation speed detector, 20...Rotation speed setting device, 22...
...Auxiliary driven piston, 24...Pilot valve auxiliary servo, 26...Adjustment valve driven piston, 28...
...Solenoid valve for overspeed prevention, 30...Solenoid valve operation circuit,
32...Instrument transformer, 34...Current transformer, 36...
... Power detector, 40 ... Bus bar, 42 ... Load, 4
4... Breaker, 48... Power supply, 50... Power system, 52... Breaker, 54, 56... Breaker, 5
8... Transformer, 60... Power system, 62... Load, 64... Breaker, 66, 68... Breaker, 7
0...Transformer, 80...High gain amplifier, 82...
...Integrator, 84...Polarity inversion amplifier, 86...Comparator, 88...Auxiliary relay.

Claims (1)

[Claims] 1. Turbine overspeed prevention configured to detect a rapid decrease in active power output from a turbine generator and close a turbine control valve for a predetermined period of time to prevent turbine overspeed. The device is equipped with a power detector that detects the active power of the generator and an overspeed prevention solenoid valve installed in the hydraulic circuit that opens and closes the turbine control valve, thereby delaying the response speed when the active power increases rapidly. A turbine overspeed prevention device, comprising: a circuit for controlling the overspeed prevention solenoid valve from being closed. 2. In the turbine overspeed prevention device according to claim 1, the control circuit for the overspeed prevention solenoid valve is composed of a high gain amplifier, an integrator, a polarity inversion amplifier, a comparator, and an auxiliary relay. However, when the active power detected by the power detector rapidly increases, the time constant of the integrator is set large to delay the response speed of the comparator. 3 In the turbine overspeed prevention device according to claim 2, the characteristics of the integrator with respect to rapid increases and decreases in active power detected by the power detector are determined by the positive polarity and negative polarity provided on the input side of the integrator. A turbine overspeed prevention device that is variably set by a constant voltage setting value.