JPS6050461A - Method of non-destructive insulation test - Google Patents

Abstract

PURPOSE:To enable easy and positive detection of insulation defect caused by contamination etc., by changing gas-pressure and kind of gas inside a pressure vessel and gas resistance of atmosphere of a machine or an instrument to be tested. CONSTITUTION:A specimen 10 is placed in a pressure vessel 20 and pressure inside the vessel 20 is available for change by a vacuum pump 22. As an example, when an apparent insulation resistance is tested by admitting helium into the vessel 20 as a gas the initial spark voltage of which being lower than air and lowering the inside gas pressure under a constant applied voltage, the value of opparent insulation resistance by starting of discharge drops abruptly and further, changes of insulating distance as well as kind of gas invite obvious difference of gas pressure under which the insulating resistance drops drastically. Consequently, by lowering gas resistance of atmosphere by means of changing gas pressure and kind of gas of atmosphere, easy and positive detection of insulation defect caused by contamination, etc. susceptible to overlooking can be available.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a non-destructive insulation testing method for diagnosing the quality of the insulation performance of electrical equipment, and in particular, to a non-destructive insulation testing method for diagnosing the quality of the insulation performance of electrical equipment. The present invention relates to a method for testing a P-wire to be destroyed, in which the insulation resistance of a device under test is measured by changing the type of gas.

[Prior art]

Conventional insulation tests of this type include the following.

FIG. 1 shows a sample 10 used as a model for insulation testing of coils and the like. In the figure, / is the conductor, C is the insulator of the conductor l, and 3 & is the electrode attached to the length of Ll, leaving an insulation distance of 1 on each end for the length of 1 of the insulator.

FIG. 1 shows a schematic diagram of a conventional test device.

In FIG. 2, reference numeral 10 is the sample shown in FIG. 1, and a power source E and an insulation resistance measuring device A are connected in series between the conductor 1 and the electrode 3 of this sample IO. And power supply EK
Therefore, voltage is applied.

The insulation resistance is measured by measuring the leakage current using an insulation resistance measuring device AK. Note 1: Normally, a megohmmeter is used for simplicity. Further, the electrical equivalent circuit of FIG. 1 is shown in FIG. 3.

In Figure 3, R' and A are the power supply and insulation resistance measuring device, respectively, RV is the volume resistance of the insulator 20, and Rs is the electrode 3.
The surface resistance of the portion corresponding to the length lj (see Fig. 1) of the terminal end to the conductor l, and RA are also the same as those of the electrode 3.
The length of the insulator from the conductor l to the conductor l is 1.2 (see Figure 1)
is the gas resistance of the atmosphere in the area corresponding to . These 3
The two resistors Rv+Rs+RA are connected in parallel to the power source E and the insulation resistance measuring device A, respectively.

From the circuit shown in FIG. 3, the overall resistance value R of the sample obtained by the test method shown in FIG. 1 can be expressed as follows. Normally, when the surface condition of the device under test is good, when measuring the S green resistance in a low temperature atmosphere, the volume resistance Rv, the surface resistance R8, and the gas resistance RA of the atmosphere are measured.
Since both have a large insulation resistance value, the overall insulation resistance value R in equation (1) naturally becomes large. However, if the surface of the device under test is contaminated with hygroscopic resistance dust, the surface resistance R8 becomes small, and even if the volume resistance Rv and the gas resistance RA of the measurement atmosphere are large, the overall equation (1) The insulation resistance value R shows almost the same value as the surface resistance Rs.

In addition, 1. For example, if a defective part that becomes a discharge path occurs in an insulator, its volume resistance Rv decreases and its surface resistance Rv decreases.
s, even if the gas resistance RA of the atmosphere is large, the overall insulation resistance value R shows almost the same value as the volume resistance Rv.

As described above, with the conventional test method, in the case of a circuit as shown in FIG. 3, it was possible to detect dirt on the surface of the insulator or an insulation defect in the defective part of the PR material. However, as shown in Fig. 1, for example, contamination dust adheres to only the length of the IJ shown by 2 out of 12 lengths of the green material -i, and the surface resistance is reduced. J- indicated by b
In some cases, the bottom part is healthy and has a large surface resistance.

The circuit at this time is as shown in Figure 5. In Figure S, R8a' * R8b are the insulators 2 and 2a, respectively.
.

This is the surface resistance of the part marked b, and the other parts are given the same reference numerals as in FIG. Therefore, the insulation resistance value R at this time
′ becomes . At this time, the volume resistance Rv of the insulator, the gas resistance RA of the atmosphere, and the surface resistance R of the ub part of the green material
If 8b is sufficiently large, even if the surface resistance Rsa of the λa portion of the insulator is very small, the overall insulation resistance value W will be a large value, which may cause errors when performing actual equipment maintenance, etc. judgment may be made. Also, as shown in Figure 6, there may be defects such as holes in the insulator! Even if this occurs, an atmosphere with high insulation resistance may fill the area around the defect. The equivalent circuit at this time is as shown in FIG. In FIG. 7, R8 represents the surface resistance of the defective portion 50, and RA connected in series with R8 represents the gas resistance of the atmosphere within the defective portion S. Other parts are given the same reference numerals as in FIG. The insulation resistance value R1 at this time is expressed as follows. Then, when the volume resistance and surface resistance Rv, Rs of the insulator 20 and the gas resistance RA of the atmosphere are large, and the surface resistance Rsr of the defective part is also sufficiently large, the measured insulation resistance value R'' shows a large value, In this case as well, defects will be overlooked.The conventional testing methods have the above-mentioned drawbacks.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the conventional test method as described above, and by placing the device under test in a pressure vessel and changing the gas pressure and type of gas in the pressure vessel, It is an object of the present invention to provide a destructive termination testing method that allows accurate identification of insulation defects by changing the gas resistance of the atmosphere of the equipment under test.

[Embodiments of the invention]

An embodiment of the present invention will be described below.

Fig. g shows the actual test equipment. In the figure, 10 is a sample, E is a power source for applying a voltage between the conductor of the sample IO and the electrode 30, and A) an insulation resistance measuring device for measuring the leakage current of the sample IO. This is the same as the conventional test method shown in Figure 1. SO is a pressure vessel in which the sample IO is placed.

U/ is a pressure gauge that indicates the pressure inside the pressure vessel 20, and -1 is a vacuum pump 1.23 for changing the pressure inside the pressure vessel SO.
is a valve installed in the pipe connecting the pressure vessel -〇 and the vacuum pump Yuko. Therefore, as an experiment, first, samples IO shown in FIG. 1 with an insulation distance of 1 millimeter and a sample IO with an insulation distance of 1 mm were prepared. Then, put this into the pressure vessel 20.

The apparent insulation resistance was measured in air and in helium gas, a gas with a lower minimum spark voltage than air, when the gas pressure was lowered under a constant applied voltage, and the characteristics of each gas pressure and insulation resistance were measured. I looked at it. The results are shown in FIG. In the figure, the vertical axis shows the insulation resistance as the terminal resistance index (logtoR), and the horizontal axis shows the gas pressure l111Hf. Curve A/
, A4', H/, and Hg indicate their respective characteristics. A/ is for the insulation distance in the air of 1 mm, Al' is for the insulation distance in the air of 1 mm, and H/ is for the insulation distance in the air of 1 mm. The insulation distance in helium gas is 1 mm, and the H41 has an insulation distance of 1 mm in helium gas. What we learned from Figure 9 is that the apparent P-edge resistance value rapidly decreases when discharge starts, and that insulation resistance rapidly decreases when the insulation distance corresponding to the interelectrode distance and the type of gas differ. The difference is that the gas pressure at which the drop begins is clearly different. Also, if the insulation distance is short, the gas pressure that starts the discharge is high.

This phenomenon supports the fact of Paschen's law that the spark generation voltage is directly proportional to the product of the atmospheric pressure and the gap length.

In the case of this experiment, even though the volume resistivity and the surface resistance of the bath insulation do not change due to the atmospheric gas pressure, the gas resistance of the atmosphere changes between the electrode distance, that is, the insulation distance. occurs, which causes a discharge current to flow and the apparent insulation resistance to change. What about the appearance when the discharge starts? If the edge resistance value is r, the gas pressure of the atmosphere at that time is p, the insulation distance is 1, and the relationship depending on the type of gas in the atmosphere is k, then rcx - kX p X 1 ... (can be expressed as gl) As shown in Figure 7, in a sample with low insulation resistance contaminants attached, the insulation distance becomes short.Therefore, the apparent insulation resistance value r becomes small. Since discharge starts at a higher gas pressure than a sample without contaminants, it is possible to clearly distinguish whether there is contamination or not.In addition, regarding the differences depending on the type of gas,
The product pxJ- of the gas pressure p in the atmosphere at the minimum spark voltage of helium gas and the length of the gap, that is, the insulation distance J, is considerably larger than that of air, and the gas pressure at which discharge starts at a constant applied voltage is higher for helium gas. It can be seen that the air is larger than that of the air. This can be understood from the fact that the value of k in equation (da) is smaller for helium than for air, and this means that when this experiment is actually applied to coil edge tests, etc. In this experiment, we used an ultra-edge resistance meter and a 5o
Although an OV megohmmeter was used, after the measurement, the sample was examined for deterioration due to discharge, and no damage was observed, and it was found to be a simple, safe, and reliable insulation testing method.

When applying this test method to an actual insulation test of a coil, etc., first check the gas pressure and insulation resistance characteristics of an unused coil, or the gas pressure and insulation resistance of a healthy sample of the coil. By examining the characteristics of the coil and comparing them with the characteristics of the coil to be actually tested, it is possible to easily, safely and reliably determine whether the insulation performance is good or bad. i.e. the IP of the coil to be tested for insulation
Green Low Resistance If the rapidly decreasing gas pressure is higher than that of the unused one or the healthy sample, it indicates that the insulation distance is short or there is a defect in the ground P edge. , it is possible to grasp the defective state according to the usage situation of each coil.

In the above embodiment, helium gas, which has a smaller D-hole voltage than air, was used, but argon gas, nitrogen gas, etc., which are inert gases, may also be used. Furthermore, the applicable equipment is not limited to coils, but can also be applied to insulation tests of components such as printed circuit boards that are composed of electrical circuits and insulating parts.

〔Effect of the invention〕

As described above, according to the present invention, when measuring insulation resistance, by changing the gas pressure and type of gas in the atmosphere of the equipment under test to lower the gas resistance of the atmosphere, it is possible to reduce the gas resistance of the atmosphere, which would otherwise be overlooked even with conventional measurements. Insulation defects due to contamination, etc. can now be detected easily, safely, and accurately.

[Brief explanation of drawings]

Figure 1 is an f11 diagram of a sample for measuring P-line resistance, Figure 1 is a schematic diagram of a conventional test device, Figure 3 is an electrical equivalent circuit diagram of Figure 1, and Figure 1 is a diagram of a contaminated sample. A perspective view, FIG. S is an electrical equivalent circuit diagram of the sample shown in FIG. Fig. 9 is a schematic diagram of a test device according to an embodiment of the present invention, and Fig. 9 is a diagram showing the characteristics of gas pressure and insulation resistance. E...power supply, A...insulation resistance measuring device, IO...sample, -
〇...Pressure vessel, U/...Pressure gauge 1.22...Vacuum pump +23...Pulp 0 In the drawings, the same reference numerals indicate the same - or equivalent parts. Agent Masu Oiwa Figure 1 Figure 2 Figure 3 Atsushi Figure 4 Figure 5

Claims (1)

[Claims] (1) In a non-destructive insulation test method for diagnosing the quality of the insulation performance of an electrical regulator, the iron equipment to be tested is placed in a pressure vessel,
The pressure of the air in the pressure vessel is reduced, or the air in the pressure passenger vessel is changed to a gas having a minimum spark voltage lower than the minimum spark voltage, and the pressure is reduced to obtain the MAR of the destructive test equipment. A non-destructive insulation test method to measure resistance. ((2) The non-destructive insulation testing method according to claim 7, wherein the gas having a lower minimum spark voltage than air is nitrogen gas. (3) The gas having a lower minimum spark voltage than air is an inert gas. A non-destructive green test method according to claim 7. (A non-destructive insulation testing method according to claim 3, wherein the inert gas is helium gas. (,t) Inertness 4. The non-destructive insulation testing method according to claim 3, wherein the gas is argon gas.