JPH0979004A - Zero speed detecting device of turning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out restart of a turning device smoothly even when a zero speed detecting signal output from a zero speed detecting device is into an off-condition when a steam turbine is stopped. SOLUTION: In a revolution speed detecting unit 29, revolution speed of a turbine rotor is detected on the basis of voltage according to a clearance between a revolution speed detecting gear 3 which is arranged by directly connecting to a turbine rotor and a distance sensor 11. In a zero speed detecting unit 13, it is judged whether or not detected revolution speed of the turbine rotor is in a zero speed revolution speed setting value and less, and the zero speed detecting signal is outputted to the turning device when zero speed error detection preventing function is not during operation. A reset circuit 30 for releasing the zero speed error detection preventing function is arranged between the revolution speed detecting unit 29 and the zero speed detecting unit 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zero speed detecting device for a turning device that rotates a steam turbine at a predetermined low speed.

[0002]

2. Description of the Related Art Generally, a steam turbine is often used as a prime mover for driving a large rotating machine such as a generator, a pump or a blower. If the turbine rotor of the steam turbine is stopped while the steam turbine is not operating, an unbalance occurs due to the weight of the turbine rotor itself. If the vehicle is operated while the imbalance is generated, the vibration is increased and the operation is often inconvenient.

In order to prevent such inconvenience, the steam turbine is equipped with a turning device. That is, while the steam turbine is not operating, the turbine rotor is forcibly rotated at a low rotational speed of about 3 to 10 rpm by a driving device such as a small electric motor to prevent the turbine rotor from being deformed to one side. There is.

FIG. 4 is a block diagram of a conventional turning device applied to a steam turbine. Turbine rotor 1
During normal operation, it is continuously rotated at the rated speed by the driving force of steam sent from the main stop valve (not shown). When the steam turbine drives the generator of the electric power system, the rated speed is 3000 rpm synchronized with the system frequency.
Or, most of them are 3600 rpm. Turbine rotor 1
A ring gear 2, a rotation speed detection gear 3, and a turbine load device 4 are fixed to the rotor 1, and rotate at the same rotation speed together with the turbine rotor 1.

In this case, the turning clutch closing signal a output from the turning closing control device 5 to the driving device 6 for connecting the turning clutch is OFF.
Therefore, the driving device 6 for connecting the turning clutch is in a non-operating state, and the turning clutch 8 having a role of connecting / disconnecting the turning motor 7 and the ring gear 2 is in a disengaged state. Therefore, during normal operation of the steam turbine, the turbine rotor 1, the rotation speed detection gear 3, the ring gear 2, and the turbine load device 4 all rotate at the same rotation speed, but the turning motor 7 does not rotate.
Disconnected from

As described above, since the turning clutch 8 is disengaged during the normal operation of the steam turbine, the turning clutch engagement detection signal b output from the position detector 9 to the turning closing control device 5 is in the OFF state. Has become. Further, the turning motor starting signal c output from the turning injection control device 5 to the turning motor 7 is OFF, and the turning motor 7 is stopped.

On the other hand, the zero speed detecting device 10 constantly monitors the rotation speed of the rotation speed detecting gear 3, and when the rotation speed drops from a high speed to a zero speed set rotation speed (about 1 to 5 rpm), the turbine rotor. It is determined that 1 has stopped.
Then, the zero speed detection signal d is output. During operation of the steam turbine, the rotational speed is the rated rotational speed, so the zero speed detection signal d output from the zero speed detection device 10 to the turning injection control device 5 is in the OFF state.

Here, a detailed view of the zero speed detecting device 10 is shown in FIG. The zero speed detection device 10 includes the rotation speed detection unit 2
9 and the zero speed detection unit 13. The rotation speed detection unit 29 is configured by a combination of the rotation speed detection gear 3, the distance sensor 11, and the distance sensor amplifier 12, and the rotation speed detection gear 3 and the distance sensor 11 that rotate with the rotation of the turbine rotor 1. The voltage signal detected based on the distance relationship is amplified by the distance sensor amplifier 12 to detect the rotation speed of the turbine rotor 1.

FIG. 6 is a characteristic diagram for explaining the detection principle. FIG. 6A is a characteristic diagram showing the voltage characteristics of the gap x between the rotation speed detection gear 3 and the distance sensor 11 and the distance sensor detection voltage v. x1 is a gap between the tooth tip of the rotation speed detection gear 3 and the tip of the distance sensor 11 (minimum gap between the rotation speed detection gear 3 and the distance sensor 11), and v1 is the detection voltage of the distance sensor 11 at that time. Is. Also,
v2 is a rotation speed pulse detection threshold voltage, and v3 is a saturation detection voltage of the distance sensor 11.

FIG. 6B is a characteristic diagram showing the voltage characteristic of the distance sensor output voltage V detected by the distance sensor 11 and the time t as the rotation speed detection gear 3 rotates. When the rotation speed detection gear 3 rotates, the distance sensor 1
The distance between 1 and the rotation speed detection gear 3 changes within a fixed time by a rotation speed proportional to the rotation speed. Therefore, the voltage of the distance sensor output signal V of the distance sensor amplifier 12 has a pulsed output voltage waveform corresponding to the rotation speed, as shown in the distance sensor output voltage characteristic of FIG.

The distance sensor output signal V from the distance sensor amplifier 12 is input to the pulse / rotation speed converter 14 of the zero speed detecting section 13 via the distance sensor output signal line 26. In addition, the rotation speed detection unit 29 and the zero speed detection unit 13
Are connected by a power supply line 27 of the distance sensor amplifier 12 and a common ground line 28 of the distance sensor amplifier 12.
Distance sensor output signal V from the distance sensor amplifier 12
Is converted into a normalized rotation speed signal by a pulse / rotation speed converter 14 provided inside the zero speed detection unit 13. This is because the number of teeth of the rotation speed detection gear 3 is set in advance inside the pulse / rotation speed converter 14,
Count the number of pulses per second in (b), multiply by 60,
When it is divided by the number of teeth of the rotation speed detection gear 3, the value becomes the rotation speed signal (rpm).

In the rotation speed alarm setting device 16, this pulse /
The rotation speed signal from the rotation speed converter 14 is compared with the zero speed rotation speed signal preset in the zero speed rotation speed setting device 15, and the rotation speed signal from the pulse / rotation speed converter 14 is zero. Logical value "1" only when the speed is lower than the speed signal
The signal is output to the AND operation circuit 17a.

On the other hand, the zero speed erroneous detection preventing function of the zero speed detecting device 10 is configured as follows. The rate of change of the rotational speed signal from the pulse / rotational speed converter 14 per unit time is monitored by the rotational speed change rate alarm setter 18, and if the rate of change of the rotational speed exceeds a certain level, a logical value "1" is output. The signal is output to the OR operation circuit 19a. Similarly, the amplifier output voltage upper / lower limit alarm setter 20 monitors whether the distance sensor output signal V is within a preset specified range value, and when it exceeds the specified value, a signal of logic "1" is output. Is output to the OR operation circuit 19a. A case where the distance sensor output signal V deviates from the preset specified range value is when the distance sensor 11 is disconnected or when the cable is removed. Similarly, the supply voltage from the zero speed detection unit power supply 21 is monitored by the power failure alarm setter 22, and when the supply voltage falls below a specified range, a signal of logical value "1" is given to the OR operation circuit 19a. Output to.

The logical sum operation circuit 19a outputs a logical value "0" when all the three input logical signals have a logical value "0", and any one of the three input logical signals is logical. When the value is "1", the logical value "1" is output. Once the output signal of the logical sum operation circuit 19a becomes the logical value "1", the signal of the logical value "1" is changed to the logical value while the output of the rotation speed alarm setting device 16 is the logical value "1" through the logical product operation circuit 19a. By returning to the input side of the sum operation circuit 19a, each output signal of the rotation speed change rate alarm setter 18, the amplifier output voltage upper / lower limit alarm setter 20, and the power failure alarm setter 22 returns to the logical value "1". Also keeps the output signal of the logical sum operation circuit 19a at the logical value "1".

When the output signal of the OR operation circuit 19a has the logical value "1", the logical NOT operation circuit 23 inputs the signal of the logical value "0" to the AND operation circuit 17a. At this time, even if the output signal of the rotation speed alarm setting device 16 is the logical value "1", the output signal of the AND operation circuit 17a remains the logical value "0". That is, the zero speed detection signal d is not output.

When the output signal of the OR operation circuit 19a has the logical value "0", the logical NOT operation circuit 23 inputs the signal of the logical value "1" to the AND operation circuit 17a. Further, when the output signal of the rotation speed alarm setting device 16 has a logical value “0”, that is, when the rotation of the rotation speed detecting gear 3 has a value larger than the zero speed setting rotation speed, the logical sum is obtained. The hold circuit of the arithmetic circuit 19a is disconnected.

Therefore, in this state, if the three output signals of the rotation speed change rate alarm setter 18, the amplifier output voltage upper / lower limit alarm setter 20, and the power failure alarm setter 22 have returned to the logical value "0", The output signal of the logical sum operation circuit 19a returns to the logical value "0". From this, the rotation speed alarm setter 16
When the output signal of is a logical value "1", the AND operation circuit 1
The output signal of 7a becomes a logical value "1". That is, the zero speed detection signal d is output.

As described above, in the conventional zero speed detecting device, when the rate of change of the rotational speed is high, when the amplifier output signal is out of the specified range, and when the power supply of the zero speed detecting device is cut off, the zero speed detecting device is operated. Since the reliability cannot be guaranteed, a zero speed erroneous detection prevention function is provided to prevent the zero speed detection signal from being output on the safety side.

Next, the turning injection control device 5 controls the turning clutch connecting drive device 6 after confirming that the turbine rotor 1 has stopped using the zero speed detection signal d as described above. The structure is such that the turning clutch 8 can be safely engaged. An operation logic configuration diagram of the turning injection control device 5 will be described with reference to FIG.

First, when the steam turbine is in normal operation, the automatic turning mode signal e has a logical value "1", but the steam turbine enters from a fully closed main stop valve (not shown). Since the steam is rotating at the rated speed, the two signals of the zero speed detection signal d and the turbine main block valve fully closed signal f naturally have the logical value "0". Therefore, the output signal of the logical product arithmetic circuit 17c becomes the logical value "0", and one input signal of the logical product arithmetic circuit 17d has the logical value "0", so the output signal of the logical product arithmetic circuit 17d becomes the logical value "0". It remains "0" and the turning clutch engagement logic 24 does not operate. Here, the turning clutch connecting logic 24 is an operation logic for connecting the turning clutch 8 by using the turning clutch connecting drive device 6 between the ring gear 2 and the turning motor 7 of FIG.

Next, when the main shutoff valve is fully closed to stop the steam turbine, the turbine main shutoff valve fully closed signal f becomes a logical value "1", but the turbine rotor 1 continues to rotate for a while due to inertia. Therefore, the zero speed detection signal d does not immediately become the logical value "0". In this state, the rotation speed of the turbine rotor 1 is gradually decreasing. When the rotational speed of the turbine rotor 1 gradually decreases and falls below the zero speed set rotational speed, the zero speed detection signal d becomes the logical value “1” for the first time. As a result, the output signal of the logical product arithmetic circuit 17c becomes the logical value "1", and this signal is held and becomes the logical value "1" while the automatic product turning mode signal e is ON by the logical product arithmetic circuit 17e. Therefore, since both input signals of the logical product arithmetic circuit 17d become the logical value "1", the output signal of the logical product arithmetic circuit 17d becomes the logical value "1", and the turning clutch connecting logic 24 operates to connect the turning clutch 8. Let Turning clutch 8
When is connected, the position detector 9 operates, and the turning clutch connection detection signal b becomes a logical value "1" and is input to the turning closing control device 5.

In FIG. 7, when the operation of the turning clutch engagement logic 24 is completed, the turning clutch engagement operation completion signal g becomes a logical value "1" and the turning clutch engagement detection signal b becomes a logical value "1".
The output of the AND operation circuit 17f becomes the logical value "1". This signal is the turning motor activation signal c, whereby the turning motor 7 starts to rotate, and the turbine rotor 1 enters the turning operation state. When the turbine rotor 1 is in the turning operation state, the rotation speed increases and the zero speed signal d becomes the logical value "0", but the logical sum operation circuit 1
The signal is held by 9b and turning continues.

Here, the automatic turning mode signal e is set to OF
When F (logical value "0") is set, the turning motor 7 is stopped, the steam turbine is stopped, and the zero speed signal d is turned ON (logical value "1") again. Further, the AND operation circuit 17c releases the hold of the OR operation circuit 19b. Then, the automatic turning mode signal e is turned on again.
If N (logical value “1”) is set, the zero speed signal d has the logical value “1”, so that the turning operation is started again.

Thus, normal operation of the steam turbine,
When the turning operation and the turning stop operation are repeated, no inconvenience occurs even if the zero speed detecting device of the conventional turning device is used.

[0025]

However, if the zero speed detecting device is turned off or the distance sensor 11 is removed for the purpose of periodic inspection or the like while the steam turbine is stopped,
The amplifier output voltage upper / lower limit alarm setter 20 and the power failure alarm setter 22 operate to set the zero speed detection signal output d to a logical value "0".

In this state, the steam turbine is stopped, but in this state, the zero speed detection device is restored even if the zero speed detection device is turned on again or the distance sensor 11 is reconnected. Because of the zero speed error detection prevention function of 10, the zero speed detection signal output d is a logical value "0".
It remains. In order to cancel this, once, a rotation speed higher than the zero speed set rotation speed is input to the zero speed detection device 10, and the rotation speed may be gradually reduced to the zero speed set rotation speed or less.

Therefore, in this state, the only way to reset the zero speed detection signal output d to the logical value "1" is to turn the turbine rotor 1 up once in the turning operation and then gradually lower it to stop it. Absent.

However, in the operation logic of the turning-on control device 5 shown in FIG. 7, the turning clutch engagement logic 24 is never activated when the 42 zero speed detection signal d has the logical value "0". Therefore, in the turning operation, the rotation of the turbine rotor 1 cannot be increased once and then gradually decreased to be stopped. As described above, when the zero speed detection device is turned off or the distance sensor 11 is removed for the purpose of periodic inspection, the turning operation control device 5 cannot be used to perform the turning operation again, and the turbine is started. It will not be possible.

Conventionally, in order to deal with such a problem, the output of the zero speed detecting device is intentionally output by the human hand by using a temporary jumper wire 25 as shown in FIG. Zero speed detection signal d
Was set to the logical value "1" and the turning device was started.
However, this method may cause forgetting to remove the short-circuit cable due to a human error.

An object of the present invention is to provide a turning device capable of smoothly restarting the turning device even if the zero speed detection signal output is turned off due to maintenance of the zero speed detection device when the steam turbine is stopped. To get the zero speed detection device of the device.

[0031]

According to a first aspect of the present invention, the rotational speed of the turbine rotor is detected based on the voltage corresponding to the gap between the rotational speed detecting gear directly connected to the turbine rotor and the distance sensor. The turning device detects if the rotation speed of the turbine rotor detected by the rotation speed detection unit and the rotation speed detection unit is less than or equal to the zero speed rotation speed set value, and the zero speed false detection prevention function is not operating. And a zero speed detecting section for outputting the zero speed detecting signal, and a reset circuit provided between the rotation speed detecting section and the zero speed detecting section for canceling the zero speed false detection preventing function.

According to a second aspect of the present invention, in the first aspect, the reset circuit sets the power source line of the distance sensor amplifier for amplifying the voltage detected by the distance sensor and the distance sensor output signal output by the distance sensor amplifier to zero speed. The distance sensor output signal line for transmitting to the detection unit and the distance sensor output signal line and the common ground line of the distance sensor amplifier are alternately turned on / off to generate a simulated signal of the rotation speed detection signal. It was done like this.

According to a third aspect of the present invention, in the second aspect of the present invention, a plurality of distance sensors of the rotation speed detecting section are provided, and a distance for amplifying the voltage detected by the distance sensor is provided corresponding to each distance sensor. A power supply line for the sensor amplifier, a distance sensor output signal line for transmitting the distance sensor output signal output from the distance sensor amplifier to the zero speed detecting section, and a common ground line for the distance sensor amplifier are provided, and the reset circuits are respectively provided. This is provided between the power supply line of the distance sensor amplifier and the distance sensor output signal line, and between each distance sensor output signal line and the common ground line of the distance sensor amplifier.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the reset circuit outputs the power supply line of the distance sensor amplifier for amplifying the voltage detected by the distance sensor and the distance sensor output signal output from the distance sensor amplifier. The distance sensor output signal line for transmission to the zero speed detection unit is turned on / off to generate a simulated signal of the rotation speed detection signal.

[0035]

Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing the first embodiment of the present invention. The zero speed detection device 10 according to the first embodiment is provided with a reset circuit 30 for canceling the zero speed erroneous detection prevention function between the rotation speed detection unit 29 and the zero speed detection unit 13. is there.

This reset circuit 30 is used in the distance sensor 1
Between the power supply line 27 of the distance sensor amplifier for amplifying the voltage detected in 1 and the distance sensor output signal line 26 for transmitting the distance sensor output signal output from the distance sensor amplifier 12 to the zero speed detection unit, The distance sensor output signal line 26 and the common ground line 28 of the distance sensor amplifier 12 are alternately turned on / off to generate a simulated signal of the rotation speed detection signal V. The reset circuit 3
0 is one rotation speed detection gear 2 for one rotation speed detection gear 3
9 of the distance sensor 11 and the distance sensor amplifier 12
The one for the set is shown.

As shown in FIG. 1, between the distance sensor output signal line 26 and the power supply line 27 of the distance sensor amplifier 12,
Distance sensor output signal line 26 and distance sensor amplifier 12
The manual operation contact 31 of the reset circuit 30 is provided between the common ground line 28 and the common ground line 28 so that the distance sensor output signal line 26 is alternately contacted with the power line 27 and the common ground line 28 by the manual operation of the operator. It was done. As a result, the potential of the distance sensor output signal line 26 of the zero speed detection unit 13 is changed into a pulse wave shape, and the rotation speed detection unit 29 simulates that the rotation speed signal is input to prevent erroneous detection of zero speed. It resets the function.

First, the manual operation contact 31 is manually turned on.
N, the distance sensor output signal line 26 to the cable 32
And the distance sensor amplifier 12 through the manually operated contact 31.
Connected to the power supply line 27. Then, pass the cable 33 with resistor from the power supply line 27 of the distance sensor amplifier 12,
A current flows into the distance sensor output signal line 26. If the resistance value of the cable with resistor 33 is properly set, the potential of the distance sensor output signal line 26 becomes a value higher than the pulse detection threshold voltage v2 of FIG.

Next, the manual operation contact 31 is manually turned on in the reverse direction to connect the distance sensor output signal line 26 to the cable 3
2 and manually operated contact point 31 through distance sensor amplifier 1
2 to the common ground line 28. Then pass the cable 34 with resistor from the distance sensor output signal line 26,
A current starts to flow in the common ground line 28 of the distance sensor amplifier 12. If the resistance value of the cable 34 with a resistor is appropriately set, the potential of the distance sensor output signal line 26 will be as shown in FIG.
Is lower than the pulse detection threshold voltage v2.

The manually operated contact 31 is in a neutral position where it is not connected to the power supply line 26 or the common ground line 28 by the spring when no force is manually applied.

When the manual operation contact 31 is manually moved alternately, the potential of the distance sensor output signal line 26 changes in a pulsed manner with the pulse detection threshold voltage v2 as a boundary, so that the turbine rotor 1 operates at a low speed. A simulated signal equivalent to that of rotating is input to the zero speed detection unit 13.

Therefore, once a rotational speed higher than the zero speed set rotational speed is simulated, and then the speed at which the manually operated contact 31 is moved is gradually slowed down, the input rotational speed will decrease. When the state is reached and the input becomes equal to or lower than the input corresponding to the zero speed set rotation speed, the zero speed detection signal d is turned on and the reset is completed.

Next, a second embodiment of the present invention is shown in FIG. The second embodiment is different from the first embodiment shown in FIG.
A pair of distance sensors 11a and 11b and a pair of distance sensor amplifiers 12a and 12b are provided, whereas a reset circuit 31 is provided.

That is, two distance sensors 11 of the rotation speed detecting section 29 are provided, and the manual operation contacts 31a, 3 of the reset circuit 31 are provided corresponding to the respective distance sensors 11a11b.
1b, the manually operated contact 31a, the power supply line 27a of the distance sensor amplifier 12a, and the distance sensor output signal line 2
6a and between the distance sensor output signal line 26a and the common ground line 28a of the distance sensor amplifier 12a, while the manually operated contact 31b is connected to the power supply line 27b of the distance sensor amplifier 12b and the distance sensor output. Signal line 26
b, and between the distance sensor output signal line 26b and the common ground line 28b of the distance sensor amplifier 12b. That is, the two manually operated contacts, that is, the manually operated contact 31a and the manually operated contact 31b, are connected to the contact connecting rod 35.
The two sets of distance sensors 11 are made compatible with each other by operating simultaneously.

FIG. 3 is a block diagram showing a third embodiment of the present invention. This third embodiment is shown in FIG.
In contrast to the first embodiment shown in FIG. 3, the manual operation contact 31 of the reset circuit 30 is connected only between the distance sensor output signal line 26 and the power supply line 27 of the distance sensor amplifier 12 to turn on and off. It was done.

The reset circuit 30 includes a distance sensor amplifier 12 for amplifying the voltage detected by the distance sensor 11.
Is provided between the power supply line 27 and the distance sensor output signal line 26 for transmitting the distance sensor output signal V output from the distance sensor amplifier 12 to the zero speed detection unit 13. Then, the manual operation contact 31 is turned on / off between the distance sensor output signal line 26 and the power supply line 27 to generate a simulated signal of the rotation speed detection signal.

This is to carefully set the resistance value of the cable with resistance 33 and to open (turn off) the manually operated contact 31.
When the turbine rotor 1 is stopped and the voltage is lower than the pulse detection threshold voltage v2 of FIG.
The operation is the same as that of the first embodiment or the second embodiment,
The structure of the manually operated contact 31 is simpler and a commercially available product can be used.

[0048]

As described above, according to the present invention, even if the power is turned off or the distance sensor is removed for the periodic inspection of the turning device, the turning device can be smoothly operated again. You can That is, it is not necessary for an engineer of the manufacturing company of the turning injection control device to witness to make a hypothetical jumper wire and activate the turning injection control device.

As described above, even when the steam turbine is turned after the regular inspection of the steam turbine, it can be started only by operating the operator of the turning device according to the procedure manual. Further, since it is not necessary for the engineer of the manufacturing company of the turning injection control device to be present, it is possible to save labor costs.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a turning device of a steam turbine.

FIG. 5 is a block configuration diagram of a zero speed detection device of a conventional turning device.

FIG. 6 is an operation characteristic diagram of a zero speed detection device of a conventional turning device.

FIG. 7 is an operation logic configuration diagram of the turning injection control device.

FIG. 8 is an explanatory diagram of a method for resetting a post-zero-speed detection prevention function of a zero-speed detection device of a conventional turning device.

[Explanation of symbols]

 1 Turbine rotor 2 Ring gear 3 Rotation speed detection gear 4 Turbine load device 5 Turning input control device 6 Turning clutch coupling drive device 7 Turning motor 8 Turning clutch 9 Position detector 10 Zero speed detection device 11 Distance sensor 12 Distance sensor amplifier 13 Zero speed detection unit 14 Pulse / rotation speed converter 15 Zero speed rotation speed setting device 16 Rotation speed alarm setting device 17 AND operation circuit 18 Rotation speed change rate alarm setting device 19 OR operation circuit 20 Amplifier output voltage upper / lower limit alarm Setting device 21 Zero speed detection power supply 22 Power failure alarm setting device 23 Logical NOT operation circuit 24 Turning clutch coupling logic 25 Hypothetical jumper wire 26 Distance sensor output signal wire 27 Power supply wire 28 Common ground wire 29 Rotation speed detection part 30 Reset circuit 31 Manual operation Working contact 32 Cable 33, 34 Resistor cable

Claims (4)

[Claims] 1. When the rotation speed of the turbine rotor is detected to be equal to or lower than a predetermined zero speed rotation speed set value and the predetermined zero speed erroneous detection prevention function is not operating, the turbine rotor is set to a predetermined rotation speed. In a turning device that rotates at a low rotation speed, in a zero speed detection device of a turning device that outputs the zero speed detection signal as one of turning start conditions, the rotation speed of the turbine rotor is directly connected to the turbine rotor. The rotation speed detection unit that detects based on the voltage corresponding to the gap between the rotation speed detection gear and the distance sensor, and the rotation speed of the turbine rotor detected by the rotation speed detection unit is the zero speed rotation speed. If the zero speed error detection function is not operating, it is judged whether or not it is less than the set value, and the turning device receives the zero speed detection signal. A zero speed detecting section for outputting a signal, and a reset circuit provided between the rotational speed detecting section and the zero speed detecting section for canceling the zero speed erroneous detection prevention function. Zero speed detection device for turning device. 2. The reset circuit transmits a power supply line of a distance sensor amplifier for amplifying a voltage detected by the distance sensor and a distance sensor output signal output from the distance sensor amplifier to the zero speed detection unit. The distance sensor output signal line and the distance sensor output signal line and the common ground line of the distance sensor amplifier are alternately turned on and off to generate a simulated signal of the rotation speed detection signal. The zero speed detection device for a turning device according to claim 1, wherein 3. A power supply line of a distance sensor amplifier for amplifying a voltage detected by the distance sensor, wherein a plurality of the distance sensors of the rotation speed detection unit are provided, and the distance sensor is provided corresponding to each of the distance sensors. A distance sensor output signal line for transmitting a distance sensor output signal output by the distance sensor amplifier to the zero speed detection unit, and a common ground line of the distance sensor amplifier are provided, and the reset circuit is
The power supply line of each of the distance sensor amplifiers and the distance sensor output signal line, and between each of the distance sensor output signal lines and a common ground line of the distance sensor amplifiers are provided. The zero-speed detection device of the turning device according to 2. 4. The reset circuit transmits a power supply line of a distance sensor amplifier for amplifying a voltage detected by the distance sensor and a distance sensor output signal output from the distance sensor amplifier to the zero speed detecting unit. The zero speed detecting device of the turning device according to claim 1, wherein the distance sensor output signal line is turned on / off to generate a simulated signal of the rotation speed detection signal.