JPS59170407A - Vibration monitoring device for steam turbine - Google Patents

Abstract

PURPOSE:To prevent a monitoring device from erroneously operating upon starting of a turbine at a high speed-up rate, by providing vibration and speed detectors to the turbine so that the limit values of vibration amplitude and amplitude changing rate are selected in accordance with the speed-up rate of the turbine to monitor vibrations. CONSTITUTION:A vibration amplitude abnormal detecting circuit 2 receives signals from a steam turbine vibration amplitude detector 1 and a vibration amplitude changing rate circuit 3. Meanwhile a signal from a turbine speed detector 7 is delivered to a switch 6 through a speed-up rate discriminating circuit. This switch 6 has a contact 6a for switching between amplitude limit value circuits 4a, 4b having different set values. Upon starting of the turbine when the discriminating circuit 5 switches the contact 6a in accordance with the speed-up rate of the turbine, the detecting circuit 2 determines whether vibration amplitudes and amplitude changing rates are within their stable ranges or not, and closes alarm issuing contacts 21a, 21b or a turbine stopping contact 22 if they are in a dangerours range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a vibration monitoring device for a steam turbine.

[Technical background of the invention and its problems]

FIG. 1 is a diagram showing an example of the tendency of vibration amplitude values during turbine startup. In the figure, the horizontal axis shows the rotation speed of the turbine, and the vertical axis shows the vibration amplitude value. Point b3 on the horizontal axis is the rated rotational speed of the turbine, and the rotational speed region between point b3 and point b2 is called the critical speed range, and generally ranges from 1200 rpm to 230 rpm.
This is the rotational speed range of Orpm. As can be seen from the figure,
As shown by curve A, the characteristics of the vibration amplitude value during turbine startup generally tend to increase rapidly at point bo, which enters the critical speed range.

Conventional vibration monitoring devices for steam turbines with such vibration amplitude value characteristics have a limit value curve as the vibration amplitude value for the vibration amplitude change rate, and when all vibration amplitude values exceeding this limit value curve are detected, an alarm output process is performed. , or performs turbine stop processing.

An example of a conventional vibration monitoring device is shown in FIG. In the figure, vibration amplitude value characteristic 1 detected by vibration amplitude detector 1
' is input to the vibration amplitude abnormality detection circuit 2, and at the same time,
A vibration amplitude change rate signal 3' input to the vibration amplitude change rate calculator 3 and calculated by the vibration amplitude change rate calculator 3 is also input to the vibration amplitude abnormality detection circuit 2. In addition, the vibration amplitude abnormality detection circuit 2 includes a signal from a limit value circuit 4 that includes a limit value for stopping the turbine that relates the vibration amplitude change rate and the vibration amplitude, and a limit value for issuing a large vibration alarm. 4' is also input to the vibration amplitude abnormality detection circuit 2. The vibration amplitude abnormality detection circuit 2 calculates the vibration amplitude signal 1' and the vibration amplitude change rate signal 3', and further calculates and compares the vibration amplitude signal 1' and the signal 4' of the limit value circuit 4 to detect the vibration amplitude that exceeds the signal 4' of the limit value circuit 4. If the value is determined to be fC, the alarm output contacts 21a and 21b
7: Output simultaneously. Further, if the vibration amplitude value is larger than the alarm value, a contact point 22 is output to stop the turbine. Special notification contact 21aFi is used for alarm,
When the rotational speed of the turbine is in the critical speed range, the contact point 21b is connected to an input to another turbine automatic start device (not shown), and the turbine is activated. It is used to reduce the speed of the motor to a safe speed. Further, the contact 22 for stopping the Kubin is used to protect the turbine, and although not shown, is input to a turbine stop circuit, so that when the contact 22 operates, the turbine is immediately stopped.

In order to simplify the explanation, Fig. 2 is explained using an example of one detector, but generally the number of circuits shown in Fig. 2 is equivalent to each bearing of a turbine generator. .

Further, a conventional vibration monitoring method will be explained in detail with reference to FIG.

FIG. 3 is a diagram showing a conventional vibration monitoring limit value curve as a typical example.

In the figure, the horizontal axis shows the vibration amplitude change rate, the vertical axis shows the vibration amplitude value, the curved line indicates the turbine stop limit value curve, and the curved line indicates the turbine vibration monitoring limit value curve.

Area A is a safe area, and if the vibration value of the turbine is within this area, it indicates that it is safe. Area B, which is surrounded by the curve opening and the curve mark, indicates that the vibration value is in an alarm state. Region C has a large vibration value, indicating that the turbine must be stopped immediately.

As can be seen from the curve shown in Figure 3, when monitoring vibration values, the limit value is set to the vibration amplitude value relative to the vibration amplitude change rate, and when the vibration amplitude change rate is small, for example, In this case, the vibration amplitude value reaches the alarm point when the vibration amplitude value reaches the value of α3 or more, and in the case of a2 where the vibration amplitude change rate is large, an alarm is output when the vibration amplitude value reaches the small value of α1 or more.

That is, if the vibration amplitude change rate is large, the alarm is likely to be issued even if the vibration value is small, and if the vibration amplitude change rate is small, the alarm is likely to be issued after the vibration amplitude value reaches a relatively large value.

Therefore, when the vibration amplitude value of the turbine tends to increase rapidly, the abnormal condition is quickly detected, an alarm is output, and at the same time necessary measures are taken, such as reducing the speed of the turbine or making an emergency stop of the turbine. It is intended to do so.

Further, as shown in FIG. 3, the limit value curve for performing full monitoring has no particular relation to the speed increase rate of the turbine, and is a fixed limit value curve.

On the other hand, the method of starting a turbine is to determine whether it is cold or warm up based on the turbine condition, that is, the turbine metal temperature, and determine the no-pin speed increase rate. , 150rprn
A ramp rate of /min is used.

However, in the case of a variable pressure operation plant, the steam control valve is operated with the steam control valve almost fully open, so the turbine metal is not cooled by throttling the steam control valve as in conventional constant pressure plants. The metal temperature of the plant will stop at a higher metal temperature than that of conventional foot pressure plants. Therefore, when the turbine is restarted after a short shutdown time, the turbine metal temperature remains high, so there is a need to complete startup of the turbine in the shortest possible time and reduce thermal stress on the turbine. Therefore, 300 rpm/min was adopted as the speed increase rate of the turbine.

When 300 rpIv' is adopted as the turbine speed increase rate, the vibration amplitude increase rate during the turbine startup process becomes large.
Conventional turbine speed increase rate 100rprrV, 150r
The value is about twice that of pm/min.

The details will be explained using FIG. 4. FIG. 4 is a diagram showing vibration amplitude characteristics in the turbine startup process from the rotation speed of bo to the rotation speed of bl shown in FIG. 1, where the horizontal axis shows time and the vertical axis shows the vibration amplitude value.

Furthermore, for convenience of explanation, curve 2 and curve H in the figure are illustrated with characteristics assuming that the vibration amplitude value is the same value with respect to the rotational speed of the turbine. In the figure, curve 2 is turbine k 30
．． 0rpr] 1/min, curve E is turbine k 150r
The characteristics are shown when the respective speeds are increased in pm/min.

In the figure, the vibration amplitude value α. In the case of , the intersection with curve 2 is time eTt, the time 2 is the intersection of ho and e, 'r T3 time, and if the vibration amplitude value is α2, the intersection with curve 2 is time Tt.

Assuming that the intersection point with curve E is k at time T4, when the turbine is sped up at each speed increase rate, the time required to reach the rotation speed from the vibration amplitude value α0 to the vibration amplitude value α2 is as follows. .

Tt Tl"'t1 time'r4T3"'t2 time Further, the number of rotations from the vibration amplitude value α0 to α2 is
Then, the relationship between time 1 when increasing at L50 rprrv/min and time t1 when increasing at 300 rprrV/min is as shown in the following equation.

Therefore t, -2t! Therefore, when the voltage is increased by 150 rprrV, the total time is twice as long as when the voltage is increased by 30 orprrV.

Further, the rate of increase in vibration amplitude during that time can be calculated using the following formula.

Vibration amplitude change rate when increasing speed by 150 rpm; a0
8゜-month-h E1((r;1Zo) tz 2 tt 300 r Vibration amplitude increase rate when increasing speed at pm/min: a2,,-!!Unim1 Therefore, the same vibration amplitude change V( α2-α.) But 300
The vibration amplitude change rate when increasing speed at rpm 7 minutes is 150
The rate of change in vibration amplitude is twice that when the speed is increased at 7 minutes per rpm.

The above relationship will be explained with reference to FIG.

First, consider the case where the speed is increased at 150 rpm/min.
The vibration amplitude change rate from α0 to α2 is ao, and the vibration amplitude value at that time is α2, so the intersection point is X. This intersection X is within the safe area of area A. On the other hand, when increasing the speed at 300 rpm/min, the vibration amplitude change rate is twice ao (2go), so at the same vibration amplitude value α2, the intersection becomes Y and B
It will enter the area of alarm condition.

In other words, in conventional vibration monitoring methods, when the speed increase rate of the turbine is increased, it is affected by the increase in speed, resulting in erroneous detection.
The turbine will be fully automatic. Furthermore, it becomes a serious factor that impairs the start-up of the plant by causing the turbine to come to an emergency stop.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned drawbacks, and by providing a vibration amplitude increase rate corresponding to the speed increase rate of the turbine, and changing all of the above limit values according to the speed increase rate, the magnitude of the speed increase rate is influenced. The purpose of the present invention is to obtain a vibration monitoring device for a steam turbine that is free from vibrations.

[Embodiments of the invention]

The invention will be explained below with reference to the drawings. , FIG. 5 is a block diagram showing an embodiment of the present invention, and the same parts as those of the conventional device shown in FIG. 2 are given the same reference numerals, and the explanation thereof will be omitted.

In the figure, 7 is a turbine speed detector, 7' is its speed signal, 5 is a speed increase rate determination circuit, 5' is its output signal, 6 is a limit value switch, 6a is its switching contact, 4a, 4b are These are respective vibration amplitude limit value circuits corresponding to the speed increase rate of the turbine.

As is clear from the above description, the present invention provides a conventional turbine vibration monitoring device with a speed increase rate determination circuit 5 that determines the entire turbine speed increase rate, a switch 6 that switches a limit value based on the determination result, and a turbine speed increase rate. limit value circuits 4a, 4
The speed signal 7' of the turbine speed detector 7 is input to the speed increase rate determination circuit 5, the speed increase rate determination circuit 5 determines the speed increase rate of the turbine, and the turbine vibration to be used at that time is Determine the amplitude limit value curve. The output 5' of the speed increase rate determination circuit 5 is inputted to the switching device 6, and the vibration amplitude limit value is provided to a limit value circuit 4a corresponding to the speed increase rate.

One of the vibration amplitude limit value curves 4b is selected by the contact 6a of the switch 6 and inputted to the vibration amplitude abnormality detection circuit 2.

Based on this vibration amplitude limit value, monitoring similar to the conventional turbine vibration monitoring shown in FIG. 2 is performed.

In the embodiment shown in FIG. 5 of the present invention, two limiting circuits 4a and 4b are shown, but it is possible to use two or more limiting circuits. Not even.

Furthermore, in the above embodiment, the rotational speed of the turbine is used to calculate the speed increase rate of the turbine, but the speed increase rate of the turbine is determined as the turbine startup schedule based on the turbine mismatch immediately before the turbine startup. Therefore, instead of the turbine rotational speed, a turbine start schedule calculation function may be added, and the turbine speed increase rate based on the turbine start schedule calculation result may be input to the speed increase rate determination circuit 5.

Furthermore, it is also possible to provide a separate device with a turbine schedule calculation function, functionally link that device with the device of the present invention, and send an analog value or contact signal that determines the turbine speed increase rate, which is a calculation result of the separate device, to the device. A similar effect can be achieved by manual effort.

Further, the same effect can be achieved even if the operator inputs the turbine speed increase rate into the present device using a separate device or a push button switch installed in the present device that completely determines the turbine speed increase rate.

〔Effect of the invention〕

Conventional vibration monitoring devices functioned well at relatively low turbine speed-up rates, but with the adoption of variable voltage plants and the recent move toward full-scale mid-range operation of thermal power plants, the plant start-up time has decreased. A high speed increase rate will be adopted for the purpose of shortening the engine speed, etc., and monitoring using conventional vibration monitoring equipment has serious defects that can hinder plant startup, such as erroneous detection and tripping of the turbine.

By adopting the present invention, this defect can not only be eliminated, but also an appropriate limit value can be set in accordance with the rotational increase rate, so strict monitoring of turbine vibration can be realized1.

[Brief explanation of drawings]

Figure 1 is a curve diagram showing an example of the characteristics of vibration amplitude values during the startup process of a turbine, Figure 2 is a block diagram showing an example of a conventional vibration monitoring device, and Figure 3 is an example of vibration amplitude limit values. FIG. 4 is a curve diagram showing an example of the characteristics of vibration amplitude values, and FIG. 5 is a block diagram showing an embodiment of the present invention. l... Vibration amplitude detector 2... Vibration amplitude abnormality detection circuit 3... Vibration amplitude change rate circuit 4a, 4b... Limit value circuit 5... Acceleration rate determination circuit 6... Switching device substitute Person Patent Attorney Kensuke Chika (and 1 other person) 1st cause her bt bz b3 □ Rotating ridge 2nd figure

Claims (1)

[Claims] In a steam turbine vibration monitoring device that uses both the vibration amplitude value and the vibration amplitude change rate to determine abnormalities in the vibration of the steam turbine, a device for obtaining the speed increase rate of the steam turbine and the output of this device are input. a circuit for determining a speed increase rate of the steam turbine; and a plurality of limit value circuits each incorporating a vibration limit value determined by both a vibration amplitude value and a vibration amplitude change rate according to a speed increase rate of the steam turbine. and a selection circuit for selecting all of the vibration limit values of this circuit, detects the speed increase rate of the steam turbine, selects all of the vibration limit values corresponding to this speed increase rate, and uses the vibration limit values to select all of the vibration limit values of the steam turbine. A steam turbine vibration monitoring device whose entire feature is to determine vibration abnormalities.