JPH0217683B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a vibration monitoring device that measures and monitors the shaft vibration of high-speed rotating machines such as steam turbines and generators. This invention relates to a turbine vibration monitoring device that prevents trips and the like from occurring.

[Technical background of the invention]

The most important thing in the operation of high-speed rotating machinery such as steam turbines used in power generation plants is:
The aim is to suppress the shaft vibration to an appropriate level under all operating conditions.

By the way, signs of excessive shaft vibration often appear when the turbine is started or when the load changes, and vibration is one of the many general operational monitoring items that requires particularly strict monitoring.

In addition, as nuclear power plants continue to increase in capacity and play an important role as base load in Japan, there is a strong demand for improved reliability of rotating machinery such as turbines and generators, which are the main equipment of nuclear power plants. It has come to be. Therefore, measurement of vibration, which is an indicator of the reliability of rotating machinery, is extremely important, and the vibration meter used therein must also be highly reliable. Similarly, a vibration monitoring device that uses a vibration meter as a sensor must also be highly reliable.For example, if a malfunction of the vibration meter causes an emergency stop of the steam turbine,
It is inevitable that this will cause difficulties in social life, and sufficient care must be taken when configuring the vibration monitoring device.

From this point of view, steam turbine generators used in thermal power plants and nuclear power plants are constantly monitored for shaft vibration of the turbine rotor and generator rotor, and an alarm is issued when the vibration amplitude value exceeds a certain value. An automatic alarm system that notifies the operator of the abnormality by emitting an alarm, or when the vibration amplitude increases further and exceeds a set value, automatically trips the steam turbine by rapidly closing the inlet steam stop valve. An automatic trip device is installed for safety reasons.

FIG. 1 is a diagram showing general vibration measurement points of a turbine generator, and the high pressure turbine rotor 1, the low pressure turbine rotor 2, and the generator rotor 3 are
It is flange-coupled as a single shaft system, and is supported by bearings 5 at the front and rear journal parts 4 of each rotor body.

By the way, a vibration meter 6 is usually attached to the bearing 5 as shown in FIG. That is, the outer cylinder 9 of the vibration meter 6 is fixed to a bearing stand 8 installed on a foundation stand 7. A spring 10 is placed inside the outer cylinder 9.
A detection rod 11 is provided concentrically within the bearing 5, and the tip of the detection rod 11 is pressed against the journal portion 4, and a detector 12 is attached to the base end of the detection rod 11. ing.

Thus, when the journal section 4 vibrates, the vibration is transmitted to the detector 12 by the detection rod 11 that is in contact with it. In the contact-type vibrometer 6 as described above, the detector 12 is usually composed of a velocity meter or an accelerometer, so the absolute vibration of the journal section 4 can be detected as velocity or acceleration via the detection rod 11. Can be done. Therefore, the output from the vibrometer 6 is integrated by an integrator 13 and converted into a displacement signal. The model of the vibration meter 6 is the bearing stand 8.
There is also a non-contact type that uses a displacement meter that can directly detect changes in the relative displacement between the shaft and the journal section 4. By the way, the displacement signal is rectified by the rectifier 14 and is input to the comparison/judgment device 15 after being changed into a vibration amplitude change which is the absolute value of the displacement.

The comparison/judgment device 15 has a built-in arithmetic circuit that compares the amplitude signal with a predetermined vibration limit value, that is, an alarm value or a stop value, and when the vibration amplitude of the journal section 4 exceeds the alarm value, the alarm device is activated. 1
An alarm signal is output to the trip device 6, and when the vibration increases further and exceeds the stop value, a stop signal is output to the trip device 17. Therefore, the alarm device 16 or the trip device 17 issues an alarm depending on the output of the comparison/judgment device 15 to inform the operator of the abnormality or trip the turbine generator.

The comparison/judgment device 15 is provided corresponding to the vibration meter 6 mounted on each bearing 5, and the output signal of each comparison/judgment device 15 is transmitted to a common alarm device 16 and a trip, respectively, as shown in FIG. Device 17
One vibration monitoring device is configured.

Vibration monitoring equipment in such turbines is
The main purpose is to protect the turbine generator from vibrations caused by internal factors of the turbine generator itself, such as unbalanced vibration of the rotor, rubbing, oil whip, and steam whirl, and to improve safety. ing. However, the vibration meter 6
Since it is an absolute vibration meter installed as shown in the figure, it can be used not only when the journal section 4 vibrates, but also when the journal part 4 vibrates.
Even if the entire body including the bearing stand 8 vibrates, the vibration will be sensed. Although such a phenomenon does not occur unless a considerable external force is applied,
There are cases such as earthquakes that cannot be ignored.

By the way, the bearing stand 8 is generally fixed to the foundation stand 7, as shown in FIG.
is installed on a mat 18, and the mat 18 is further placed on the ground 19. Therefore, when an earthquake occurs, the vibration is transmitted from the ground 19 to the mat 18, and furthermore, the bearing stand 8 and the journal section 4 are vibrated via the foundation stand 7.

When this vibration system consisting of the turbine/generator and the turbine foundation is modeled, as shown in Fig. 5, it corresponds to the total mass of the high-pressure turbine rotor 1, low-pressure turbine rotor 2, and generator rotor 3 in Fig. 1. It can be replaced with a general spring mass system consisting of a mass 20, a spring 21 corresponding to the rigidity of the turbine/generator base 7, and a damper 22 representing a damping term. Assuming that the mass corresponding to the total mass of the rotor is M, the spring constant of the spring 21 is K, and the damping coefficient of the damper 22 is D, the turbine for the external force x ₁ =A ₀ sinωt applied to the mat 18. The response of the generator is the input amplitude A ₀
When expressed as a ratio of response amplitude A ₂ to A 2 , it becomes as shown below.

Here, η=ω ₀ /ω ω ₀ : Natural frequency of the foundation system including the turbine generator If the damping is small, if the frequency component of the seismic wave and the natural frequency of the foundation system match,
That is, when η=1, the vibration of the turbine generator placed on the foundation becomes large. Although the excitation force varies depending on the vibration characteristics of the base 7, it may reach about 2 to 5 times the excitation force at the mat 18. In addition, the vibration meter 6 is designed to sense the vibration displacement even if the entire bearing pedestal 8 vibrates, so even if an external force such as an earthquake acts on the foundation pedestal, the amount of vibration displacement will reach the stopping value. When this point is reached, a stop signal is also issued to the trip device 17, causing the steam turbine to trip.

The relationship between vibration displacement and acceleration is expressed by the following equation.

δ=α×9800/(2πf) ² ………(2) Here, δ: Vibration displacement α: Acceleration f: Frequency As you can see from this equation, even if the acceleration is small, if the frequency is low, the displacement will be large. occurs.
For example, if the acceleration is 0.05G and the frequency is 5Hz, the displacement will be 0.5mm. As mentioned above, seismic waves are amplified by propagating through the foundation and input to the bearing pedestal 7, but for example, if the vibration response magnification is 2.
Therefore, when the mat 18 is vibrated by an earthquake motion of 0.025G, the bearing stand 7 is vibrated by 0.05G, and the displacement is amplified to 0.5mm. Therefore, if this exceeds the stop value, the comparator 15 outputs a stop signal and the steam turbine trips. Seismic waves include many frequencies, and as can be seen from equation (1), the amplitude response magnification differs depending on each frequency, so such a simple calculation is not sufficient, but the results of this study indicate that at least 0.025G This indicates the possibility that even a small earthquake could cause the steam turbine to trip and stop power transmission from the plant.

The above is a case in which the vibration meter 6 directly senses seismic waves or amplified seismic waves via the bearing pedestal 8 and leads to a trip.
The temporary large amplitude induced as a result of applying a forced external displacement between the bearing 5 and the rotary journal 4 may lead to a trip value.

Techniques have been established to deal with the former, but the latter phenomenon has been clarified through recent case analysis, and even if the former is completely addressed, carelessness due to earthquakes will still occur. This means that the possibility of a serious turbine trip remains. On the other hand, if the large-capacity turbines and generators responsible for the base load trip unnecessarily, the impact on the power system will be extremely large.
It develops into a wide-area power outage accident, causing social chaos.

Therefore, there has been a need for a turbine vibration monitoring system that can accurately deal with shaft vibration phenomena that occur even during an earthquake.

[Purpose of the invention]

In view of these points, the present invention provides a turbine vibration monitoring device that prevents unnecessary turbine trips due to the occurrence of earthquakes and can minimize the chances of turbine trips. The purpose is to obtain.

[Summary of the invention]

The present invention includes a vibration detection device that continuously detects vibrations of a rotating shaft, and a vibration signal detected by the vibration detection device is compared with a predetermined vibration limit value, and when the vibration signal exceeds the vibration limit value, A device for detecting an earthquake in a turbine vibration monitoring system that has a comparison judgment device that outputs a trip signal to automatically stop the unit in case of an earthquake, and an automatic trip device that inputs the trip signal and automatically stops the unit. is provided, and the comparison judgment device is configured to switch the vibration limit value from the vibration limit value for normal operation to a higher earthquake vibration limit value based on the earthquake signal output from the earthquake detection device when an earthquake occurs. This is characterized by the provision of a switching means, which prevents unnecessary turbine trips from occurring in the event of an earthquake.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 6 to 15. In the drawings, the same parts as those of the conventional device are designated by the same reference numerals, and detailed explanation thereof will be omitted.

FIG. 6 is a schematic system diagram of the turbine vibration monitoring device of the present invention, in which each comparison/judgment device 15 receives not only the signal from the vibration meter 6 but also the earthquake signal output from the earthquake detection device 23 installed separately. is also input, and the vibration limit value of the comparison/judgment device 15 is switched from the vibration limit value for normal operation to the earthquake vibration limit value in response to the earthquake signal.

That is, FIG. 7 is a diagram showing an example of the configuration of a general normal vibration limit value used in a comparison judgment device, and is used to notify an operator of the occurrence of an abnormal condition for a certain level of vibration amplitude value. an alarm value 24, a trip value 25 which outputs a trip signal to the automatic trip device 17 to signal that the amplitude has reached an amplitude value at which the unit should be stopped due to the progress of an abnormality; It consists of a backup trip value 26 for dealing with malfunctions in which no output occurs. Therefore, when the vibration amplitude value becomes large and exceeds the trip value 25, or reaches the backup trip value, a unit trip signal is outputted via the timer 27, as shown in FIG. 8a or FIG. 8b. The unit is then tripped.

On the other hand, in the present invention, as shown in FIG. killed,
Only the higher backup trip values 26 remain. Therefore, even if an earthquake occurs, the automatic trip device 17 will not operate if the vibration amplitude is less than the backup trip value, thereby preventing unnecessary turbine trips from occurring.

In addition, as shown in Fig. 10a and b, both the large vibration trip value 25 and the backup trip value 26 are killed by the earthquake signal, and a vibration limit value is set for the seismic trip value 28 at a higher level. A similar effect can be obtained even if the switching is performed.

Which of the above methods to adopt should be determined depending on how the backup trip value 26 is set.
If it is set at a level slightly higher than that as a simple backup of 5, as shown in Figure 10a, an earthquake trip value of 28 determined from the strength limit of the upper turbine generator bearing is set. Should. On the other hand, backup trip value 2
6 is set based on the bearing strength limit from the beginning, it is sufficient to simply eliminate the vibration large trip value 25, which is the normal operation limit value, as shown in FIG. 9a.

Incidentally, the above-described switching of the limit values may be performed using the earthquake signal from the earthquake detection device 27 as described above, but as shown in FIGS. The limit value may be switched when both the vibration signal and the large vibration signal from the vibration meter 6 are output. Although any value lower than the large vibration trip value 25 can be selected as the large vibration signal in this case, it is most practical to use the large vibration alarm value 24, which is the normal operation limit value. As soon as the vibration falls below the alarm value or the earthquake subsides, the limit value for normal operation will be automatically returned.
It becomes possible to prevent malfunction of the earthquake detection device.

The earthquake detection device 23 may use a seismograph to output an earthquake signal when an earthquake has a certain amplitude or more, or it may use a seismometer to output an earthquake signal when an earthquake with a certain intensity occurs. You may also do so. Further, these earthquake detection devices 23 may be installed on the mat 18 of the turbine generator foundation 7 as shown in FIG. 13, or on the foundation 7 as shown in FIG. If it is installed on the mat 18 as shown in Figure 13, it is possible to make settings related to the intensity of the earthquake that occurs, but if it is installed on the foundation 7 as shown in Figure 14, the vibration response magnification can be adjusted. It is necessary to take the settings into consideration. However, in the latter case, there is an advantage that the set value can be related to the strength of the bearing 5.

In addition, although the above embodiments have been shown to be equipped with an earthquake detection device consisting of a seismometer, etc., in the event of an earthquake, a vibration meter of a plurality of bearings arranged in the axial direction of the turbine/generator shaft system is used. Since large vibrations occur at the same time even if the bearings are far apart, the vibration meter installed in each bearing indicates that when the vibrations of two bearings reach the large vibration alarm value as shown in Figure 15a, or As shown in FIG. 15b, a signal may be output when the vibrations of the three bearings reach a large vibration alarm value, thereby detecting the occurrence of an earthquake, and the output signal may be used as an earthquake signal.

By the way, as mentioned above, the vibration limit value for normal operation in the comparison judgment device is based on the unbalanced vibration of the rotor system,
The purpose is to protect steam turbines and generators from increased vibration caused by internal factors such as rubbing, oil whip, and steam whirl, and to detect as early as possible an upward trend from normal vibration levels. Normally, the strength is set to be slightly lower than the strength limit of the bearings that support the rotor system. In other words, the risk of large vibrations generally lies in the contact between rotating parts and stationary parts, and the tendency for this to diverge due to the thermal bending phenomenon of the rotor that occurs as a result of local heating of the rotor. The vibration limit value is set as low as possible.

On the other hand, the response of the rotor system during an earthquake corresponds to the case where the vibration system is given forced external displacement from its stable position as shown in Figure 5, but the vibration characteristics of the turbine/generator shaft system due to normal design are similar to those shown in Figure 5. It has been clarified that the rotor system, bearing, and bearing stand move as one, with extremely high rigidity. In such a case, the vibration meter should take measures to prevent the seismic motion from being detected by the vibration meter, but if the seismic motion appears as a relative vibration between the rotor and the bearing, the vibration system shown in Figure 5 may be Natural frequency is 8~
This is a case that is relatively close to the predominant frequency of earthquakes, which is said to be 10 Hz, and at this time the rotor, although temporarily,
It has a waveform in which the seismic wave and the frequency corresponding to the natural frequency are superimposed, and it causes large vibrations that exceed the vibration large trip value for normal operation. Examples of this can be seen in large-capacity steam turbines/generators with four-pole machines, and because the rated rotational speed is 1500 or 1800 rpm, they often have a natural frequency around 12 to 15 Hz. As a result, it becomes highly susceptible to the effects of earthquakes.

However, although the amplitude of large vibrations caused by an earthquake can be as large as the bearing gap, the frequency is the frequency of the seismic wave or the natural frequency of the system, so the rated rotation frequency It has the characteristic of being sufficiently lower than Therefore, even if rubbing occurs due to this vibration, since there is no rotational synchronous component, it will not lead to local heating of the rotor and will not lead to bending. The large vibrations excited by seismic waves will converge once the seismic motion converges, and there is little risk of developing into a divergent vibration phenomenon, and it can be said to have extremely stable properties. Therefore, in this case, the limit for safe operation is given by the strength of the bearing that supports the rotor system, and it is sufficient to monitor the vibration limit value set based on this strength. That is, there is no need to apply the vibration limit value for normal operation, which is set to a low value as described above, to large vibrations caused by seismic waves.

For this reason, even if the vibration limit value is switched to the vibration limit value for earthquakes in response to the occurrence of an earthquake as in the present invention, there is no problem in terms of safety. can be prevented from tripping, and unnecessary turbine trips can be eliminated.

In other words, considering the case of a large-capacity nuclear turbine, which is currently a quadrupole unit, the trip value, which is the limit value for normal operation, is set at 25/100 mm, but if this is determined from the bearing strength limit, it is 35/100 mm. It is possible to tolerate an amplitude value of at least 100% or more, making it possible to avoid trips due to earthquakes with sufficient margin. In addition, even if the vibration develops into divergent vibration during an earthquake, the seismic vibration limit value will automatically return to the normal operation limit value around the time the earthquake converges, as mentioned above. Therefore, the automatic trip device is activated at that point, preventing further increase in vibration, and there is no risk of damaging the main body of the device.

〔Effect of the invention〕

As explained above, in the present invention, when an earthquake occurs, the earthquake signal is used to change the vibration limit value of the comparison judgment device in the turbine vibration monitoring device from the vibration limit value for normal operation to a higher earthquake vibration limit value. Since the switch is made to switch, it is possible to prevent accidental tripping even when shaft vibration increases due to seismic motion, and to continue operation close to the design limit in terms of strength of the equipment. Therefore, the turbine generator will not trip due to even the slightest earthquake, significantly improving operational durability, providing a more stable power supply, and preventing disruptions caused by large power outages. can be prevented.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the shaft system of the turbine, Figure 2 is an explanatory diagram of the mounting structure of the vibration meter of the vibration monitoring device on the bearing,
Figure 3 is a schematic system diagram of a conventional turbine vibration monitoring device, Figure 4 is a vertical cross-sectional view of the bearing section of the turbine generator including the foundation, and Figure 5 is a model of the vibration system of the device in Figure 4. FIG. 6 is a schematic system diagram of the vibration monitoring device of the present invention, FIG. 7 is an explanatory diagram of vibration limit values of the turbine vibration monitoring device, and FIG. 8 a and b
9A, 10A, 11A and 1 are block diagrams showing the concept of conventional vibration monitoring, respectively.
2a is an explanatory diagram of the operation of the present invention, FIGS. 9b, 10b, 11b, and 12b are block diagrams showing the concept of vibration monitoring of the present invention, and FIGS. FIG. 14 is an explanatory diagram of the installation state of the earthquake detection device, and FIGS. 15a and 15b are block diagrams showing the concept when using the vibration meter itself as earthquake detection means. 1... High pressure turbine rotor, 2... Low pressure turbine rotor, 3... Generator rotor, 5... Bearing, 6
... Vibration meter, 7 ... Foundation stand, 8 ... Bearing stand, 15
... Comparison and judgment device, 16 ... Alarm device, 17 ...
Trip device, 23...Earthquake detection device.

Claims (1)

[Claims] 1. A vibration detection device that continuously detects vibrations of a rotating shaft, and a vibration signal detected by the vibration detection device is compared with a predetermined vibration limit value, and the vibration signal is determined to be within the vibration limit value. A turbine vibration monitoring system that has a comparison judgment device that outputs a trip signal to automatically stop the unit when the value exceeds a value, and an automatic trip device that inputs that trip signal and automatically stops the unit, is designed to detect earthquakes. In addition to providing a detection device, the comparison judgment device is provided with:
The present invention is characterized by providing a switching means for switching the vibration limit value from a vibration limit value for normal operation to a higher earthquake vibration limit value in response to an earthquake signal output from an earthquake detection device when an earthquake occurs. , turbine vibration monitoring equipment. 2. The turbine vibration monitoring device according to claim 1, wherein the earthquake detection device is a seismometer or a seismometer placed on the turbine foundation ground or the turbine foundation. 3. The switching from the vibration limit value for normal operation to the seismic vibration limit value is performed when both the large vibration signal from the vibration detection device and the earthquake signal from the earthquake detection device are output. A turbine vibration monitoring device according to claim 1. 4. Claim No. 4, characterized in that the earthquake detection device consists of vibration meters each mounted on a plurality of bearings of a turbine generator, and uses large vibration signals from the plurality of vibration meters as an earthquake signal. The turbine vibration monitoring device according to item 1.