JPS6119945B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for diagnosing insulation of electrical equipment.

Electrical equipment, especially rotating electrical equipment such as large generators and motors, is affected by emergency shutdowns in many ways.
High reliability has been required for a long time. For this reason, although these devices are designed with sufficient safety factors in mind, voltage is constantly applied to their insulated coils during operation, and they are also exposed to mechanical vibration and thermal stress. , deterioration progresses over time.

In order to ensure the reliability of electrical equipment during operation, quality control during manufacturing is important, but it is also necessary to accurately understand aging deterioration during operation and estimate the operating life. However, there is currently no method or device for easily and accurately determining insulation deterioration.
At present, the following methods are used alone or in combination for insulation diagnosis.

(1) Method using insulation resistance or polarization index Usually, a voltage of 500V or 1000V is applied to the sample, and the absolute value of insulation resistance after 1 minute, or the absolute value of insulation resistance after 1 minute and 10
Insulation diagnosis is performed based on the ratio of insulation resistance (polarization index) after 30 minutes.

(2) Method using partial discharge measurement The number of partial discharge pulses generated by voltage application and the amount of generated charge are measured using the broadband method or the tuning method, and the changes over time in the maximum amount of charge and the number of discharge pulses, as well as the pulse distribution due to voltage polarity, are investigated. Perform insulation diagnosis based on differences, etc.

(3) Alternating current test method This method determines the partial discharge inception voltage, void content, etc. from changes in the rate of increase in leakage current when alternating current voltage is applied to the sample, and performs insulation diagnosis based on these values. There are commercially available measuring devices.

(4) Method using withstand voltage test A constant DC or AC voltage is applied to the sample, and insulation diagnosis is performed based on the withstand voltage results.

However, although method (1) has the great advantage of being simple to measure and requiring only a small amount of equipment, there is a risk that the measured value will be greatly affected by the sample shape, surface condition, etc. be. Furthermore, since the insulation resistance value changes depending on the capacity of the equipment, etc., it is not preferable to use the absolute value of the insulation resistance to determine insulation deterioration. On the other hand, the polarization index is the insulation resistance 1 minute value.
Since it is a ratio of 10-minute values, there are fewer problems like those described with absolute insulation resistance values, but it has the disadvantage that the measurement time is longer than that for insulation resistance. In addition, as shown in Figure 1, there is little change over time in the polarization index of the model coil that has been subjected to forced aging through repeated heating and moisture absorption. There is no direct relationship between this and the time it takes for the sample to cause dielectric breakdown after applying a voltage for 10 minutes. In other words, the polarization index can only determine whether or not the sample has absorbed moisture, and it is difficult to determine whether the insulation has deteriorated over time.

Method (2) has been attracting attention as electronic computers have become more general-purpose in recent years, but it requires large-scale equipment for measurement, noise removal during measurement and measurement operations are complicated, and A major drawback is that real-time data processing is difficult at the location where the test electrical equipment is being used.

Like method (2), method (3) also has the disadvantage of requiring large-scale equipment for measurement, but if a commercially available automatic calculation device is used, the measurement can be completed in a short time. impact can be minimized. However, many commercially available devices are expensive and susceptible to external noise.

Method (4) is fundamentally different from methods (1), (2), and (3) described so far. Since this method directly measures withstand voltage characteristics, it is possible to obtain the most accurate information, but its biggest drawback is that the influence of voltage history remains.

SUMMARY OF THE INVENTION An object of the present invention is to provide an insulation diagnosis method and apparatus that can perform an inexpensive, simple, and accurate insulation diagnosis.

An embodiment of the present invention will be described below with reference to FIG. This insulation diagnostic device measures the first insulation resistance Rd immediately after the equipment under test has stopped operating or has been forcibly heated and cooled to near room temperature, and the first insulation resistance Rd after the equipment under test has stopped operating for a certain period of time or has been forced to absorb moisture for a certain period of time. an insulation resistance measuring device 11 for measuring the insulation resistance Rw of No. 2; and a memory device 12 for storing the measured value.
and the relative value of the first insulation resistance Rd and the second insulation resistance Rw input from the memory device 12.
A calculation device 13 that calculates Rw/Rd, and a calculation device 1
The display device 14 receives the output of No. 3 and displays the Rw/Rd value. The display device 14 is provided with an alarm device (not shown) that issues an alarm when the Rw/Rd value exceeds a certain value.

Next, the effect will be explained. Since this insulation diagnostic device has the above combination, it is possible to obtain the Rw/Rd value easily and inexpensively, and how the Rw/Rd value is related to dielectric breakdown is as follows.
This will be explained with reference to FIG. Figure 3 shows a motorlet sample corresponding to a 1/8 core model of an actual motor, which was forcibly degraded using a test procedure (described later) based on the American standard IEEE Std.275, and the insulation resistance shown in Figure 1 was measured using an insulation resistance measuring device The changes over time of Rd and the second insulation resistance Rw are measured and stored in the memory device 12, and the relative value Rw/Rd between the two is automatically calculated by the calculation device 13, and this is displayed on the display device 14. , the relative value Rw/Rd is plotted on a logarithmic graph against the heating aging time.

The test procedure described above involves testing the sample at 200°C and 250°C.
Vibration of 2G is applied to each of the three temperature levels of ℃ for one day. Next, a voltage of 2E + 1kV (E is the rated voltage) is applied for 10 minutes to perform a withstand voltage test, and then the insulation resistance is measured at a measurement voltage of 500V and a measurement time of 1 minute. This is the first insulation resistance Rd. Next, the sample is kept at 45°C and 100% relative humidity for 2 days. Next, a voltage of 2E + 1 kV was applied for 10 minutes to perform a withstand voltage test, and then the insulation resistance was measured in the same manner as above. This is the second insulation resistance Rw. more than 1
Repeat this as a cycle.

Curve A in Fig. 3 shows the changes over time of motorette samples heat-aged at 200°C, curve B at 220°C, and curve C at 250°C. This is the twisting aging time when the sample suffers dielectric breakdown during the withstand voltage test during the test procedure. As is clear from Figure 3
When the Rw/Rd value decreased from 10 ^-3 to 10 ^-4 , the sample suffered dielectric breakdown at the withstand voltage test voltage in all cases, indicating that the Rw/Rd value is related to dielectric breakdown.

Therefore, by measuring the Rw/Rd value, information related to dielectric breakdown can be obtained easily and inexpensively, and can be used to improve the reliability of equipment.
In actual equipment, during periodic inspections and repairs,
The Rw/Rd value can be measured economically and used as an indicator of insulation deterioration.

Furthermore, the activation energy obtained as a result of an Arrhenius plot of the bending time on the logarithmic graph of the Rw/Rd value obtained by this device is almost equal to the activation energy obtained from the heat resistance life curve of the motoret test. Therefore, short-term life evaluation tests using Rw/Rd values are also possible.

Note that the present invention is not limited to the embodiments described above and shown in the drawings; for example, the display device 14 may not be provided with an alarm device, or the above device may be assembled into another insulation diagnostic device. It goes without saying that the present invention may be modified in various ways without changing the gist thereof, such as that the present invention may be modified.

As explained above, according to the present invention, an insulation resistance measuring device, a memory device, and an Rw/Rd calculation device can be used.
By combining the Rw/Rd display device, it is possible to obtain information related to insulation breakdown at low cost and easily, and the insulation diagnosis method and its equipment contribute to improving the reliability of electrical equipment during operation. can get.

[Brief explanation of the drawing]

Fig. 1 is a curve diagram showing the change over time in the polarization index obtained with a conventional insulation diagnostic device, Fig. 2 is a block diagram showing an embodiment of the insulation diagnostic device of the present invention, and Fig. 3 is a curve diagram showing changes over time in the polarization index obtained with a conventional insulation diagnostic device. FIG. 2 is a curve diagram showing a change over time in the Rw/Rd value obtained with the apparatus shown in FIG. 2. FIG. 11...Insulation resistance measuring device, 12...Memory device, 13...Arithmetic device, 14...Display device.

Claims (1)

[Scope of Claims] 1. The first insulation resistance Rd immediately after the equipment under test has stopped operating or has been forcibly heated and cooled to near room temperature, and the first insulation resistance Rd after the equipment under test has stopped operating for a certain period of time or has been forced to absorb moisture for a certain period of time. 2. An insulation diagnostic method comprising: measuring the insulation resistance Rw of No. 2 with an insulation resistance measuring device, calculating Rw/Rd from the measured value with a calculation device, and displaying the result on a display device. 2 The first insulation resistance Rd immediately after the equipment under test has stopped operating or has been forcibly heated and cooled to near room temperature; and after the equipment under test has stopped operating for a certain period of time, the second insulation resistance Rw after forced moisture absorption for a certain period of time. an insulation resistance measuring device for measuring the measured values; a memory device for storing the measured values; and a relative value of the first insulation resistance Rd and the second insulation resistance Rw inputted from the memory device.
An insulation diagnostic device comprising: an arithmetic device that calculates Rw/Rd; and a display device that receives the output of the arithmetic device and displays the Rw/Rd value. 3. The insulation diagnostic device according to claim 2, wherein the display device is provided with an alarm device that issues an alarm when the Rw/Rd value exceeds a certain value.