JPS5879451A - Monitoring device for shaft voltage - Google Patents

Abstract

PURPOSE:To discriminate the presence or absence of a malfunction of a shaft grounding device by continuously monitoring the DC and AC components of a shaft voltage. CONSTITUTION:A shaft grounding device which is made of a current collecting brush 3a and a grounding line 8 is mounted on one end of a rotational shaft 1. A current collecting brush 3b is mounted in the same size as the shaft grounding device at the other end of the shaft 1, and an electric signal obtained thereby is transmitted via a cable 7 to a monitoring device 15. The device 15 passes the signal through a low pass filter 11, produces only the DC component, passes the same signal through a high pass filter 12, produces the AC component, thereby isolating the DC signal and the AC signal, and inputs them to monitoring instrument 20, which continuously monitors the DC and AC components of the shaft voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION (C) Technical Field of the Invention The present invention relates to a shaft voltage monitoring device for a rotating machine.

(J) Prior Art In turbine generators and other types of rotating machinery, shaft voltage may be generated due to electrical or mechanical causes.
25 When the value becomes excessive, a shaft current is induced in the control device that is directly or indirectly driven by the rotating shaft and in the bearing that supports the rotating shaft.

There is a risk of electrical discharge and associated electrolytic corrosion.

Conventionally, to prevent such shaft voltage generation.

A widely used method is to release the voltage generated in the rotating shaft to the ground using a shaft grounding device. A current collector brush 3 is attached to the stationary S of the rotating machine so that this shaft grounding device comes into contact with the rotating shaft of the zero-rotation machine shown in FIG.

With this current collecting brush 3, the rotating shaft l and the stationary part are brought to the same potential, and then connected to a grounding point 3 to the earth 30 via a grounding line provided in the stationary part. Although FIG. 1 also shows a conventional shaft grounding device, an electrical insulating material 6 is interposed between the current collecting brush 3 and the stationary part 1 when the current collecting brush 3 is attached to the stationary part.

For this reason, a grounding line t is provided that directly connects the current collecting brush 3 to the grounding point j. Therefore, the voltage generated on the rotating shaft is transferred from the current collector brush 3 to the grounding wire tI (grounding wire in Figure 2).
and escapes to the earth 30.

On the other hand, the shaft voltage itself has conventionally been measured using temporary wiring at the site using a portable DC voltmeter as part of regular site patrols approximately every week.Q) Problems with the conventional technology mentioned above Conventional shaft grounding devices such as
The disadvantage is that it is extremely difficult to determine whether the grounding function is being maintained normally. In other words, the degree of wear on the current collector brush J is determined by periodic dimensional measurements and visual inspection, but this only estimates the grounding function as an indirect measure of the amount of wear, and is not sufficient for the purpose of monitoring Ie performance. In addition, K must go to the location to actually install the current collecting brush 3 in order to make a determination, which has the drawback of placing a large burden on the operator.

Furthermore, the shaft voltage monitoring method as described above has the following problems. Figure 3 shows the results of a long-term continuous recording test regarding the DC component shaft voltage of a large steam turbine, which is a typical rotating machine. As can be seen from Figure 3, the axial voltage is normally small and relatively stable, but under some circumstances it suddenly takes a turn for the worse, causing not only an increase in the value of P, but also an increase in its transformation and width. shows a tendency to increase with
This means that not only the DC component but also the AC component is increasing as the shaft voltage. Discharge phenomena in minute gaps occur both under DC voltage and AC voltage, and there is a lower limit voltage for generation. Taking these things into consideration, it is insufficient to monitor the DC component alone when shaft voltage is being monitored, and it is necessary to monitor the AC component as well. Furthermore, as shown in Figure 3, if the situation suddenly changes, intermittent monitoring is hardly profitable, and continuous monitoring is necessary.

←) Purpose of invention The present invention has been made in consideration of such circumstances.

The purpose of the present invention is to provide a shaft voltage monitoring device that can intermittently monitor the direct current and alternating current components of the shaft voltage, determine whether or not there is an abnormality in the shaft grounding device based on the indicated value, and prompt the operator to take corrective action. It is said that

<S> Structure of the Invention In order to achieve this object, the present invention provides a plurality of current collecting brushes in contact with a rotating shaft of a rotating machine, and a grounding wire for grounding at least one of the current collecting brushes.

A circuit that separates an electric signal between an ungrounded brush and a grounded brush in the current collecting brush into a DC signal and an AC signal, and a monitoring instrument that monitors the DC signal and AC signal separated by the separation circuit. This constitutes an axial voltage monitoring device comprising:

(6) Embodiments of the Invention The embodiments of the present invention will be explained below with reference to the drawings.

Figure D shows the first embodiment of the present invention, 0 rotation axis/-g
A shaft grounding device consisting of a current collecting brush ja and a grounding wire j is attached to sK. In addition, a current collector brush 3b is attached to the rotating shaft/other 11iK with the same dimensions as the shaft grounding device, and an electric signal generated by this is transmitted to the monitoring device tr via a cable.

Monitoring device /3 passes this signal through a low pass filter //
The signal is passed through the filter to take out only the DC component, and the same signal is passed through a high-pass filter 12, which also extracts the AC component, thereby separating it into a DC signal and an AC signal, and inputting the signals to the monitoring instrument I, respectively. The visual instrument is the detection end 16 of the DC signal.
The voltage between the AC signal detection terminal /7 and the ground terminal it, which is the terminal of the ground wire t connected to the ground J#t, is monitored.

Figures 3 to 7 show examples of such monitoring instruments, and Figure S shows the DC signal at the DC signal terminal L being monitored by a DC voltmeter, and the AC signal terminal being monitored by a DC voltmeter. The configuration is such that the alternating current signals are monitored by an alternating current voltmeter. Figure 6 shows the AC/D○ converter 13 in the bypass filter saw.
Connect the AC signal to DC signal. 23 is a scanner which switches the detection end /6 and 170 input signals at appropriate time intervals and inputs them to the DC voltmeter. Figure 7 shows the dot type DO voltage h with built-in 6 and 1 scanners.
This dot type DO shows an example using i-recorder 8.
The voltage recorder J may be a continuous pen writing type voltage recorder, and the voltage recorders Mj [¥1 and the voltmeters ν and n in Fig. It is also possible to provide only a monitoring function that issues a food report only when a certain value is reached.

With this configuration, it is possible to continuously monitor the DC and AC components of the shaft voltage. In the monitoring instrument of 4IK Fig. 6, the number of voltmeters can be reduced. Furthermore, if voltmeter 2/1 is used as an alarm setting device, monitoring can be made more easily.

FIG. 1 shows a first embodiment of the invention. Regarding one current collecting brush ja, jbK, both have the same configuration for monitoring shaft voltage. In other words, the signal of the current collecting brush Ja (Jb) is transmitted through cable 7! p-pass filter //IL(//1)), high/(J・Fik I/
The output number i of these filters is input to the monitoring instrument. And the current collecting brush 3a (, yb
) between the ground eta, (tb) and the switch /ea(/
tb) is interposed.

Therefore, it is possible to arbitrarily switch between the shaft grounding function and the shaft voltage monitoring function at both ends of the rotating shaft l.

Because of this, in this embodiment, when an abnormal shaft voltage is measured for shaft voltage monitoring, the switch /la or /11) of that system is closed and grounded to the earth 30. It is possible to prevent abnormal axle load E+,
It is possible to instruct operators on specific processing methods when ordering abnormal shaft voltage. Furthermore, it is possible that the abnormal shaft voltage is caused by an abnormality in the current collecting brush, and a work instruction to inspect the current collecting brush can be given.

FIG. 7 shows a third embodiment of the present invention in which each system at both ends of the 0-rotation axis l is one system.

That is, at one end of the rotating shaft there is a current collector brush j a + j
.

and switch /4'a, /4IO, respectively.
Rhopan filter //at//C1 bypass filter /2a, /-〇, are connected and these outputs are connected to the monitoring instrument m
is input. 1 at the other end of the IF11 rotation axis! electric brush 3
b, J (1 is in contact, switches /Qb, /da d, low-pass filter //'b, // d, bypass filter saw 1), /2 (1 are connected, these outputs are monitored Input to the instrument.

With such a configuration, in this embodiment, it is possible to ascertain the contact status of each $lightning brush. That is, one of the current collecting brushes 3a *Jc of the rotating shaft / is placed at the same position KN with respect to the axial direction of the rotating shaft l, and should exhibit one equipotential.

Therefore, the potential of current collector pushers ja and Ja is ′! When a difference of kj11 occurs, it can be seen that there is an abnormality in either the Ja or Jo current collecting brush. To determine which current collector brush is abnormal, operate each switch a or /.
This can be determined by closing 4'O and observing the change. j That is, when one switch operation 1 is closed, the system is connected to the ground point 3, so
The voltage becomes zero, but if the current collector brush 3a is abnormal and does not make good contact with the rotating shaft l, the voltage of the current collector brush 3C will not reach zep. Therefore, it can be determined that the current collecting brush Ja is abnormal.

As described above, in this embodiment, not only can the precision be improved by single measurement of the shaft voltage at both ends of the rotating shaft, but also the contact status of the current collector brush in mg can be determined by operating the switch. In other words, inspection can be performed at rapid intervals without directly approaching the rotating machine. This is extremely important in cases where access to the site is not easy, such as the 1% atom cataviso.

(7) Modifications of the invention The above is an example of application to a single-axis rotating machine.

If the rotating machine has a multi-shaft system such as a large steam turbine, it is sufficient to configure each shaft as in the above embodiment. Monitoring instruments can be provided for each shaft, but the same (You can monitor it with a monitoring instrument.)

(J) Effects of the Invention As described above, the present invention brings a plurality of current collecting brushes into contact with the rotating shaft of a rotating machine, at least one of them is grounded, and a current collecting brush that is not grounded and a current collecting brush that is grounded are separated. Since the DC and AC components of the electrical signal during the period are separated and monitored, continuous monitoring of the shaft voltage is possible, and the occurrence of abnormal voltage can be immediately notified to the operator.

Furthermore, it provides a means of dealing with abnormal voltages, and at the same time, it is also possible to remotely check the contact status of the current collector brush.

The burden on the operator can be reduced. As a result, safe operation of the rotating machinery can be ensured, so it can last for a long time.

[Brief explanation of the drawing]

1 shows a conventional shaft grounding device, FIG. 3 shows continuous shaft voltage recording in a large steam turbine, and FIG. 7 shows a shaft voltage monitoring device according to the first embodiment of the present invention. 5, 7 and 7 are examples of monitoring instruments, FIG. 3 is a shaft voltage monitoring device which is an embodiment of the λth embodiment of the present invention, and FIG. 2 is a third embodiment of the present invention. This is a certain 1t1ilc pressure monitoring device. C... Rotating shaft, C... Stationary part, 3... Current collector brush,
q...Grounding wire, 6...Insulator, t...Grounding wire,
//...Low pass filter, /:l...Bypass filter, /3...AO/DC! ·converter,/
K...switch, /j...monitoring device, J-...monitoring instrument, 2/...DO voltmeter, 〃...AOl [pressure gauge,
And...the pressure recorder, 30...the earth. a (Jli 1 agent Inomata Wei City 4 figs. 5 car 60 170

Claims (1)

[Claims] /0 A plurality of current collecting brushes in contact with a rotating shaft of a rotating machine;
A grounding wire that grounds at least one of the current collecting brushes, a circuit that separates an electric signal between an ungrounded brush and a grounded brush among the current collecting brushes into a DC signal and an AC signal, and this separation circuit. A shaft voltage monitoring device comprising a monitoring instrument that monitors a DC signal and an AC signal separated by. 17 Claim 7. In a currently manufactured device. An axial voltage monitoring device comprising a switch that connects any current collecting brush of the current collecting flage to the grounding wire. 3. Percentage range In the apparatus according to claim 1. A current collecting brush is brought into contact with each 101-second point of the rotating shaft, and an electric signal from each of these current collecting brushes is taken out.5Also a shaft voltage monitoring device. 1. Any one of claims 1 to 3 Kt
! The shaft voltage monitoring device according to claim 1, wherein the monitoring instrument is a voltmeter. 1.% Allowance The shaft voltage monitoring device according to any one of claims 1 to 3, wherein the monitoring instrument is a voltmeter. 6. The shaft voltage monitoring device according to any one of claims 1 to 3, wherein the monitoring instrument is an alarm setting device.