JPH01191072A - Monitoring method for rotary electric machine - Google Patents

Abstract

PURPOSE:To promptly find out an unusual winding condition and an insulation deterioration by measuring a high frequency current based on an electric discharge as well as a load current, monitoring the correlative relation of these load current and discharge current, and constantly monitoring the discharge status at the time when the load is suddenly changed. CONSTITUTION:A sensor, e.g. a current transformer 4 is connected to the neutral point of a stator winding 2 for an electric power source machine 1 and the load current is taken out, which is converted to a digital signal by an A/D converter 5 then recorded on a recorder 6. Coupling capacitors 71, 72, 73 consisting of solid capacitors with superior high frequency characteristics are connected to each of U, V, W phases of power source lines 3 which are connected to the winding 2, and through these capacitors 71, 72, 73 the high frequency currents based on the discharge are taken out and supplied to a detector 8. The output from the detector 8 is supplied to a filter 10 through a changeover switch 9. The output passes through the filter 10 is supplied to a measuring instrument 12 for the partial discharge through a resistance attenuator 11, thereby the unusual winding and the insulation deterioration are promptly informed.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention is a method for monitoring a rotating electrical machine that monitors winding abnormalities, insulation deterioration, etc. of a high-voltage rotating electrical machine based on electrical signals during operation. Regarding the method.

(Prior Art) Conventionally, as a method for determining the insulation deterioration of a rotating electric machine, for example, for a stator, after stopping the operation of the rotating electric machine, a high voltage is applied to the windings, and various electrical characteristics (insulation resistance, An electrical method is used to estimate the degree of deterioration of the insulation in each part by measuring alternating current, dielectric loss angle, partial discharge, etc. A mechanical method is used in which the coil is removed and the mechanical damage to the insulation portion and the deterioration of the winding fixing force are determined by visual inspection or sound.

However, in order to determine deterioration using these methods, it is necessary not only to stop the operation of the rotating electric machine but also to disconnect the line, and in some cases, it is also necessary to perform operations such as removing the rotor. For this reason, performing deterioration determination using such a series of methods requires a great deal of time, effort, and expense, and has the drawback that it is difficult to conduct deterioration determination tests frequently. In addition, implementing such a method may require time for preparation, so it has the disadvantage that it cannot adequately deal with cases where deterioration progresses rapidly.

Conventionally, in order to eliminate such inconveniences, a coupling capacitor is permanently inserted on the line side of a rotating electrical machine, and the discharge that occurs during operation of the rotating electrical machine is measured and the discharge status is measured. Methods for constantly monitoring the
ectr, In5u,, Vol, El-14no
, 2. April, 1979).

However, when this method is used under a constant load or relatively slow load fluctuations, such as in a generator, it is difficult to monitor the condition where insulation deterioration has progressed to a certain point and discharge occurs frequently. However, in the case of motors that are used under rapid load fluctuations, such as those seen in synchronous motors for steel, the slight discharge that occurs due to sudden load fluctuations is often overlooked. Satisfactory Monitoring As described above, with the conventional method, when the motor is used under sudden load fluctuations such as a steel motor, it is easy to overlook discharge, and the result is not satisfactory.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for monitoring a rotating electrical machine that can reliably monitor winding abnormalities, insulation deterioration, etc. of a rotating electrical machine used under rapid load fluctuations.

According to this invention, a high frequency current based on discharge is detected from a power line of a rotating electrical machine via a coupling capacitor, and a load current is detected from a neutral point of a stator winding or a power line, The correlation between these load currents and high frequency currents is monitored.

(Function) As a result, the discharge status can be constantly monitored in response to the load current during sudden load changes, so it becomes possible to quickly identify winding abnormalities, insulation deterioration, etc. that accompany sudden load changes.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration for explaining the same embodiment. In the figure, reference numeral 1 denotes a rotating electrical machine to which the embodiment is applied, such as a steel motor, and the motor 1 has U, V, and W phase windings as stator windings 2. A power supply line 3 consisting of U1V1W phases is connected to this stator winding 2.

A sensor is installed at the neutral point of the stator winding 2 of the electric motor 1.
For example, connect current transformer 4 to take out the load current, and transfer it to A
The signal is converted into a digital signal by the /D converter 5 and recorded on the recorder 6.

On the other hand, each USV of the power supply line 3 connected to the stator winding 2
, and the W phase are connected to coupling capacitors 71, 72, and 73 made of solid capacitors with excellent high frequency characteristics, and a high frequency current based on discharge is taken out through these capacitors 71 to 73 and applied to the detector 8. Then, the output from this detector 8 is applied to a filter 10 via a changeover switch 9. This filter 10 removes noise from a power source, broadcast waves, electromagnetic induction, and the like. Then, the output that has passed through the filter 10 is given to a partial discharge measuring device 12 via a resistance attenuator 11. Here, partial discharge measuring device 1
The waveform of the measurement result No. 2 is observed by an oscilloscope 13 and the signal is analyzed by a spectrum analyzer 14. Further, the output from the partial discharge measuring device 12 is given to the recorder 6 and recorded together with the above-mentioned load current.

When this monitoring method was applied to a steel synchronous motor (900KW-11KV) that had been in use for a long time, the results shown in Figure 2 were obtained. 4200K W-IIK V)
When applied to this method, the results shown in Figure 3 were obtained.

This result shows that in a synchronous motor that has been in use for a long time, large load fluctuations may occur due to, for example, steel ingots being caught in the motor, as shown in Figure 2 (
It was observed that when the load current changed significantly as shown in (a), corona pulses due to discharge frequently occurred as shown in (b) of the same figure. In contrast, with a newly manufactured synchronous motor for steel, even if the load current is cut off as shown in Figure 3 (a), corona pulses due to discharge are hardly generated as shown in Figure 3 (b). .

Therefore, when we removed the rotor and inspected the motor in detail as shown in Figures 1 and 2, where corona pulses frequently occur with load fluctuations, we found signs of deterioration and damage caused by electrical discharge in the insulators that make up the stator windings. It was seen. This suggests that when the amount of discharge increases as the load changes, the winding fixing force decreases and sometimes the deterioration of the winding insulation is accelerated.If the motor continues to operate in this state, The winding insulator may be damaged by electric discharge, worn out by vibration of the winding, etc., and this may cause dielectric breakdown.

Therefore, according to this monitoring method, the high frequency current based on discharge is measured together with the load current, and the correlation between these load currents and the amount of discharge is monitored. It is now possible to know in advance the deterioration of winding insulation and winding insulation, and it is also now possible to constantly monitor the deterioration state of winding fixing force, which conventionally could only be known visually.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be implemented with appropriate modifications without changing the gist.

For example, in the above embodiment, the load current is detected from the neutral point of the stator winding 2, but it may be detected from the power supply line 3 side.

[Effects of the Invention] According to the present invention, the high frequency current accompanying discharge is detected from the power supply line of the rotating electric machine via the coupling capacitor, and the load current is detected from the neutral point of the stator winding or the power supply line. Since the correlation between these load currents and high-frequency currents is monitored, it is now possible to constantly monitor the discharge status during sudden load changes, and to detect winding abnormalities that occur with sudden load changes. This means that insulation deterioration can be quickly detected.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram for explaining an embodiment of the present invention, and FIGS. 2 and 3 are measurement waveform diagrams for explaining the embodiment. DESCRIPTION OF SYMBOLS 1... Rotating electric machine, 2... Stator winding, 3... Power supply line, 4... Current transformer, 6... Recorder, 71-73.
...Coupling capacitor, 12...Partial discharge measuring device. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] The method includes a first step of measuring a load current from a rotating electric machine, and a second step of measuring a high-frequency current based on discharge from a power line of the rotating electric machine, and a high-frequency current measured from these first and second steps. A method for monitoring a rotating electrical machine, comprising monitoring winding abnormalities and insulation deterioration of the rotating electrical machine from a correlation between a load current and a high-frequency current.