JP4877115B2 - Partial discharge position identification device for rotating electrical machines - Google Patents

Description

  The present invention relates to an apparatus for measuring an electromagnetic wave based on partial discharge generated during operation of a rotating electrical machine.

  A high voltage is generated or applied to a stator winding of a rotating electric machine such as a generator or an electric motor during operation, and an electrical stress is applied to an insulating layer of the stator winding. If this is over a long period of time, the insulating material will be deteriorated, such as cracking or peeling, and the intensity of partial discharge generated from the stator winding will be large and the amount will increase. By measuring the intensity and amount of the partial discharge, the deterioration state of the insulation is grasped. As a measuring method, means for detecting an electromagnetic wave based on partial discharge with an antenna and measuring and analyzing the signal has been applied from the feature that it can be easily attached to a rotating electrical machine.

  In a conventional partial discharge measuring device for a rotating electrical machine, an electromagnetic wave based on a partial discharge generated from a stator winding is detected by an antenna, and a discharge band is calculated by detecting a component in the microwave band of the discharge electromagnetic wave. . Abnormality determination is performed by the abnormality determination circuit based on this discharge charge amount. (For example, refer to Patent Document 1).

JP-A-4-313074 (Claim 1)

  In the prior art, it is possible to detect electromagnetic waves based on partial discharge from the stator slot of the rotating electrical machine and from outside the stator slot. However, since these are mixed, the source of partial discharge is in the stator slot. It was difficult to identify whether it was out of the stator slot. For this reason, the insulation deterioration is evaluated from the electromagnetic wave intensity without considering the place where the partial discharge occurs. Electromagnetic waves based on the partial discharge generated in the stator slot propagate in the air between the stator core in the stator slot and the stator winding, and therefore exclude some frequency bands. Attenuation increases. Therefore, in the above-described evaluation of insulation deterioration, there is a problem that only low accuracy evaluation can be obtained.

  The present invention has been made to solve the above-described problems, and detects electromagnetic waves based on partial discharges from the stator slot and from outside the stator slot, and the generation source of the partial discharge is within the stator slot. Or whether it is out of the stator slot.

  In the partial discharge position specifying device for a rotating electrical machine according to the present invention, an electromagnetic wave based on the partial discharge of the rotating electrical machine is detected and frequency analysis is performed. By comparing the intensity of the electromagnetic wave within the frequency band determined by the dimensions of the stator slot with the intensity of the electromagnetic wave outside this frequency band, it is determined whether the detected electromagnetic wave source is inside the stator slot or outside the stator slot To do.

  Since the present invention enables the frequency analysis of electromagnetic waves based on partial discharge to identify whether the generated partial discharge is inside or outside the stator slot, it is possible to evaluate the insulation deterioration obtained from the detected electromagnetic wave intensity. Accuracy can be improved.

Embodiment 1 FIG.
FIG. 1 is an end cross-sectional view of a rotating electrical machine and a block diagram of a partial discharge position specifying device according to Embodiment 1 for carrying out the present invention. The rotating electrical machine takes a generator as an example. FIG. 2 is a schematic diagram of the stator slot and the electromagnetic wave propagating in the stator slot in the first embodiment for carrying out the present invention. FIG. 3 shows the frequency spectrum of the electromagnetic wave in the first embodiment for carrying out the present invention. FIG. 4 is a relationship diagram of the intensity of the electromagnetic wave in the first embodiment for carrying out the present invention.

  In FIG. 1, reference numeral 1 denotes a stator of a rotating electrical machine. The stator 1 has a stator core 2 and a stator winding 3. A portion of the stator winding 3 that protrudes outside the stator core 2 is a stator winding end 4. Reference numeral 5 denotes a rotor, and reference numeral 6 denotes a frame of the rotating electrical machine.

  Opposing to the end of the stator core 2, a horn antenna 10 having a directivity and a directivity in a microwave band is disposed on the inner wall of the frame 6. One or a plurality of horn antennas 10 can be provided, and in order to detect all electromagnetic waves radiated from the stator winding 3, the opening of the horn antenna 10, the end of the stator core 2, and the horn antenna Although it is affected by the distance, three are often attached at intervals of 120 degrees in the circumferential direction. However, it is not always necessary to detect all electromagnetic waves radiated from the stator winding 3. The horn antenna 10 is attached via a bushing 13 that passes through a central portion of a metal lid 12 that closes an opening of a small case 11 attached to the frame 6.

  The measurement cable 14 connected to the horn antenna 10 passes through the bushing 13 described above and is connected to the electromagnetic wave acquisition means 21 of the partial discharge occurrence position specifying device 20. The partial discharge generation position specifying device 20 includes an electromagnetic wave acquiring means 21, a frequency analyzing means 22, and a discharge position specifying means 23. The discharge position specifying means 23 outputs external outputs of the out-slot discharge output 24 and the in-slot discharge output 25. Have. The out-slot discharge output 24 and the in-slot discharge output 25 may be logically distinguished. For example, the output signal is flagged and output as a signal that can be distinguished from one output. Also good.

  Next, the operation will be described. When the rotating electrical machine is operating, a voltage is generated or applied to the stator winding 3, and a partial discharge is generated from the stator winding 3. When a partial discharge occurs, a discharge electromagnetic wave is generated based on this partial discharge, propagates through the frame 6 and is detected by the horn antenna 10. This detected signal is transmitted through the measurement cable 14, acquired by the electromagnetic wave acquisition means 21 of the partial discharge occurrence position specifying device 20, subjected to analog / digital conversion, etc., passed to the frequency analysis means 22, and subjected to Fourier transform, etc. Frequency spectrum analysis is performed by this method. The result of the frequency analysis means 22 is passed to the discharge position specifying means 23, and the electromagnetic wave detected by the horn antenna 10 based on the result of the frequency spectrum analysis is either the electromagnetic wave based on the partial discharge outside the stator slot or the stator slot. If the electromagnetic wave is identified based on the partial discharge at and is identified as the electromagnetic wave based on the partial discharge outside the stator slot, the electromagnetic wave signal obtained by the electromagnetic wave obtaining means 21 is output as the out-slot discharge output 24, When the electromagnetic wave based on the partial discharge in the stator slot is specified, the electromagnetic wave signal acquired by the electromagnetic wave acquiring means 21 is output as the in-slot discharge output 25.

  FIG. 2 shows a part of the stator slot 7 that accommodates the stator winding 3 provided in the stator core 2, and schematically shows the propagating electromagnetic wave. The dimensions of the stator slot 7 are a stator slot depth 30 and a stator slot width 31. The stator core 2 has a plurality of stator slots 7. The stator slot depth 30 and the stator slot width 31, which are dimensions of the stator slots, are the same in any of the stator slots 7.

  The electromagnetic wave based on the partial discharge generated in the stator winding 3 inside the stator slot 7 hardly propagates through the stator core 2 and the stator winding 3, so that the stator is inside the stator slot 7. It propagates through the gap between the iron core 2 and the stator winding 3. Reference numeral 32 denotes an electromagnetic wave propagating from a gap in the direction of the stator slot depth 30, and 33 denotes an electromagnetic wave propagating from a gap in the direction of the stator slot width 31. These electromagnetic waves 32 and 33 easily propagate electromagnetic waves having a frequency derived from the dimensions of the stator slot depth 30 and the stator slot width 31, and when the electromagnetic waves in this frequency band are propagated outside the stator core 2. Is not so attenuated. Electromagnetic waves having frequencies other than those derived from the dimensions of the stator slot depth 30 or the stator slot width 31 are difficult to propagate in the stator slot 7 and are attenuated when propagated to the outside of the stator core 2. .

  Here, the frequency derived from the dimension of the stator slot depth 30 or the stator slot width 31 described above can be obtained as follows.

  The depth dimension of the stator slot is a value unique to each rotating electric machine, and can be known from actual measurements and design drawings. If this depth dimension is 200 mm, for example, it is expressed by the following relational expression.

L (stator slot depth: 200 mm) = λ (wavelength) / [2 · √ε _r (relative permittivity)]

Therefore, the frequency of the electromagnetic wave guided by the depth of the stator slot is determined as follows. Note that the electromagnetic wave velocity c≈3.0 × 10 ⁸ and ε _r ≈1.

f (frequency) = c (electromagnetic wave velocity) / λ
= C / (2 · √ε _r · L)
≒ 0.75GHz

  Similarly, the width dimension of the stator slot can be obtained by the same calculation. For example, when the width dimension is 50 mm, f (frequency) ≈5.0 GHz. Thus, the electromagnetic wave having the frequency determined in this way easily propagates in the stator slot 7.

  FIG. 3 shows a frequency spectrum obtained by spectrum analysis by the frequency analysis means 22 of the partial discharge generation position specifying device 20, where the horizontal axis indicates the frequency and the vertical axis indicates the detected electromagnetic wave signal intensity (electromagnetic wave intensity). When the frequency analysis means 22 performs spectrum analysis on the electromagnetic wave based on the partial discharge generated in the stator slot 7 described above, the frequency analysis result has a peak at a frequency determined by the stator slot depth 30 and the stator slot width 31. Is obtained. That is, it becomes like the graph of the frequency spectrum of the discharge electromagnetic wave in the stator slot shown by 51 in FIG. Further, when the spectrum analysis of the electromagnetic wave based on the partial discharge generated outside the stator slot 7 is performed, a frequency analysis result having no peak at a specific frequency is obtained, and the frequency spectrum of the discharge electromagnetic wave outside the stator slot indicated by 50 in FIG. It looks like the graph of

Here, a frequency outside the frequency region determined by the dimension of the stator slot is f ₁ , and a frequency determined by the dimension of the stator slot is f ₂ . In the above example, f ₂ = 0.75 GHz or f ₂ = 5.0 GHz. The electromagnetic wave intensities at frequencies f ₁ and f ₂ of the frequency spectrum 50 of the discharge electromagnetic wave outside the stator slot and the frequency spectrum 51 of the discharge electromagnetic wave inside the stator slot are a, b, c, and d, respectively.

FIG. 4 is a graph in which the intensity of the electromagnetic wave at the frequency f ₁ is plotted on the horizontal axis and the intensity of the electromagnetic wave at the frequency f ₂ is plotted on the vertical axis. As shown in FIG. 4, the discharge electromagnetic wave outside the stator slot is a straight line passing through the origin with an inclination of b / a, which is the ratio of the electromagnetic wave intensity at frequency f ₁ and the electromagnetic wave intensity at f ₂ in FIG. Plotted in the distribution 52 of the discharge electromagnetic wave outside the stator slot which is in the vicinity. Further, the discharge electromagnetic wave in the stator slot is a stator in the vicinity of a straight line passing through the origin with an inclination of d / c which is a ratio of the intensity of the electromagnetic wave at the frequency f ₁ and the intensity of the electromagnetic wave at f ₂ in FIG. Plotted in the distribution 53 of the discharge electromagnetic wave in the slot.

The reason is as follows. If the electromagnetic wave is based on a partial discharge generated outside the stator slot, the propagation path from the partial discharge occurrence point to the antenna is the air propagation at the end of the stator winding, so the intensity of each partial discharge generated randomly Are different from each other, the ratio of the intensity of the electromagnetic wave having the frequency f ₁ and the frequency f ₂ of the frequency spectrum 50 of the discharge electromagnetic wave generated outside the stator slot is substantially constant, and only the intensity depends on the intensity of the partial discharge. Because it changes. Similarly, if the electromagnetic wave based on the generated partial discharge in a stator slot, since the propagation path from the partial discharge generation point to the antenna is in air-gap in the stator slots propagation, the frequency f ₁ electromagnetic waves Since the intensity is attenuated and the intensity of the electromagnetic wave having the frequency f ₂ is not so attenuated, the frequency f ₁ of the frequency spectrum 51 of the discharge electromagnetic wave generated in the stator slot is different even if the intensity of each partial discharge generated randomly is different. This is because the ratio of the intensity of the electromagnetic wave having the frequency f ₂ is substantially constant, and only the intensity changes depending on the intensity of the partial discharge.

  In this way, by detecting electromagnetic waves based on partial discharge with a microwave antenna such as a horn antenna and performing frequency analysis on this, discharge electromagnetic waves generated inside the stator slot and discharge electromagnetic waves generated outside the stator slot Thus, it is possible to specify whether the partial discharge is generated in the stator slot or outside the stator slot. As a result, the inspection time required to identify the insulation deterioration location is shortened, leading to cost reduction. In addition, since the insulation deterioration inside and outside the stator slot can be evaluated separately, the determination accuracy of the insulation deterioration level of the entire rotating electrical machine can be improved.

Embodiment 2. FIG.
In the first embodiment, the frequency band of the electromagnetic wave detected by the horn antenna 10 is not particularly specified, but the horn antenna 10 can detect an electromagnetic wave in a band including a frequency determined by the depth of the stator slot. Also good.

  The depth dimension of the stator slot varies depending on the size of the rotating electrical machine and the like, but falls within a certain range. Assuming that this range is, for example, a range of 150 to 300 mm, among the electromagnetic waves based on the partial discharge generated in the stator slot, the wavelength of the electromagnetic wave propagating through the stator slot and radiating out of the stator slot is Is determined by the dimension of the stator slot depth, which is a space for propagating, and falls within the following range according to the calculation method in the first embodiment.

    f (frequency) ≈ 0.5 to 1.0 GHz

At this time, for example, as in the example of the first embodiment, if the stator slot depth dimension is 200 mm, f ₂ = 0.75 GHz, and a value such as f ₁ = 0.5 GHz is set. In the frequency spectrum analysis result of the discharge, the intensity of the electromagnetic wave at f ₁ = 0.5 GHz is plotted on the horizontal axis and the intensity of the electromagnetic wave at f ₂ = 0.75 GHz is plotted on the vertical axis as shown in the graph shown in FIG. Then, the discharge occurrence position is specified based on the distribution. In the graph of the example and FIG. _4, <but has a _{f 2, f 1> f 1} f 2 become may define a _{f 1,} for example it may be _f 1 = 1.0 GHz.

  Thus, the above-mentioned frequency range of 0.5 GHz to 1.0 GHz is set as a band including a frequency determined by the depth of the stator slot, and the horn antenna detects an electromagnetic wave in a band including the frequency determined by the depth of the stator slot. By making it possible, it is possible to specify the position where the discharge occurs, and the frequency range to be detected can be narrowed, so that an inexpensive antenna can be applied, leading to cost reduction.

Embodiment 3 FIG.
Although the second embodiment is characterized in that the frequency band of the horn antenna 10 can be detected including a frequency band determined by the depth of the stator slot, the horn antenna 10 includes a frequency band determined by the width of the stator slot. It may be possible to detect electromagnetic waves in the band

  The width of the stator slot varies depending on the size of the rotating electrical machine and the like, but falls within a certain range. Assuming that this range is, for example, a range of 20 to 100 mm, among the electromagnetic waves based on the partial discharge generated in the stator slot, the wavelength of the electromagnetic wave propagating in the stator slot and radiating out of the stator slot is This is determined by the dimension of the stator slot width, which is a space for propagating, and is as follows according to the method obtained in the first embodiment.

    f (frequency) ≈ 1.5 to 7.5 GHz

At this time, for example, as in the example of the first embodiment, if the stator slot width dimension is 50 mm, f ₂ = 5.0 GHz, and a value such as f ₁ = 7.0 GHz is set, and each discharge In the frequency spectrum analysis result of the above, the intensity of the electromagnetic wave at f ₁ = 7.0 GHz is plotted on the horizontal axis, and the intensity of the electromagnetic wave at f ₂ = 5.0 GHz is plotted on the vertical axis as shown in the graph shown in FIG. The discharge generation position is specified based on the distribution. In the above example, f ₁ > f ₂ and f ₁ <f _{2 in} the graph of FIG. 4, but f ₁ may be any value that is within the frequency range and different from f ₂ .

  Thus, the above-mentioned frequency range of 1.5 GHz to 7.5 GHz is set as a band including a frequency determined by the width of the stator slot, and the horn antenna can detect an electromagnetic wave in a band including the frequency determined by the width of the stator slot. By doing so, it becomes possible to specify the position where the discharge occurs, and the frequency range to be detected can be narrowed, so that an inexpensive antenna can be applied, leading to cost reduction. In addition, the detection accuracy can be improved by using together with an antenna that detects an electromagnetic wave in a band including a frequency determined by the depth of the stator slot applied in the second embodiment.

Embodiment 4 FIG.
The second embodiment is characterized in that the frequency band of the horn antenna 10 can be detected including the frequency determined by the depth of the stator slot. In the third embodiment, the frequency band of the horn antenna 10 is determined as the width of the stator slot. In the fourth embodiment, the frequency band of the horn antenna 10 is divided into a band including a frequency determined by the depth of the stator slot and a band including a frequency determined by the width. You may enable it to detect both. That is, the stator slot depth dimension is 150 mm to 300 mm from the second embodiment, the corresponding frequency range is 0.5 GHz to 1.0 GHz, and the stator slot width dimension is 20 mm to 100 mm from the third embodiment. If the corresponding frequency range is 1.5 GHz to 7.5 GHz, the frequency band of the horn antenna 10 in the fourth embodiment is 0.5 GHz to 7.5 GHz.

  There are two types of electromagnetic waves based on the partial discharge radiated from the stator slot, the frequency determined by the stator slot depth and the frequency determined by the stator slot width. Due to individual differences. For this reason, depending on the rotating electrical machine, an electromagnetic wave having a frequency determined by the stator slot depth is hardly detected, and an electromagnetic wave having a frequency determined by the stator slot width is detected, or vice versa, a frequency determined by the stator slot depth. Some electromagnetic waves with a frequency determined by the stator slot width are hardly detected.

  For this reason, by detecting the discharge electromagnetic wave in the range that combines the two frequency regions, the frequency determined by the depth of the stator slot and the frequency determined by the width of the stator slot, it is more reliably radiated from within the stator slot. Discharge electromagnetic waves can be detected and the intensity of the electromagnetic waves can be evaluated.

Embodiment 5 FIG.
In the first to fourth embodiments, the horn antenna 10 is applied to the antenna. However, as shown in FIG. 5, flat antennas 26 and 27 may be applied to the antenna. Since the flat antenna has a narrower frequency band that can be measured compared to the horn antenna, the flat antenna 26 can detect electromagnetic waves in a narrow band centered on the frequency f ₂ determined from the dimensions of the stator slot depth 30 or the stator slot width 31. Then, the flat plate antenna 27 capable of detecting an electromagnetic wave in a narrow band centered on the band f ₁ other than the frequency band determined from the dimension of the stator slot depth 30 or the stator slot width 31 is applied. Furthermore, when acquiring with the electromagnetic wave acquisition means 21, the electromagnetic waves in the peripheral frequency band are cut with a band pass filter or the like so that only the narrow frequency band that can be detected with the flat plate antenna 26 or 27 can be acquired. The intensity of electromagnetic waves is obtained by digital conversion. The acquired electromagnetic wave intensity is passed to the discharge position specifying means 23. As for the electromagnetic wave acquisition, a method of acquiring an electromagnetic wave and performing frequency analysis similarly to the first embodiment can be applied.

This is shown in FIG. The frequency spectrum 50 of the discharge electromagnetic wave outside the stator slot and the frequency spectrum 51 of the discharge electromagnetic wave inside the stator slot cannot be measured as shown by the dotted line in FIG. It is possible to measure between f _{2a and} f _{2b in a} narrow band sandwiched by f ₂ . Further, the electromagnetic wave detected by the flat plate antenna 27 can be measured between a narrow band f _1a -f _1b across the frequency f ₁ . When the discharge electromagnetic wave outside the stator slot is detected, the intensity of the electromagnetic wave that can be obtained by the flat antenna 27 is a which is the highest value in the frequency f _1a -f _1b , and the intensity of the electromagnetic wave that can be obtained by the flat antenna 26 is It becomes b which is the highest value in the frequency f _2a -f _2b . Further, when the discharge electromagnetic wave in the stator slot is detected, the intensity of the electromagnetic wave that can be obtained by the flat antenna 27 is c, which is the highest value in the frequency f _1a -f _1b , and the electromagnetic wave that can be obtained by the flat antenna 26. The intensity is d which is the highest value in the frequency f _2a -f _2b . These acquired electromagnetic wave intensities a to c may be different from the electromagnetic wave intensity at the frequency f ₁ or f ₂ , but because the frequency band is narrow and there is no peak in the target frequency band. There is no particular problem. Further, since the intensity d of the acquired electromagnetic wave has a peak at the frequency f ₂ determined by the size of the stator slot, it may be considered to be almost the same as the intensity of the electromagnetic wave at f ₂ .

Here, the intensities of electromagnetic waves a, b, c, and d at frequencies f ₁ outside the frequency region determined by the size of the stator slot and at frequency f ₂ inside the size region of the stator slot, f ₁ When the axis, f ₂ , is plotted as the vertical axis, it is almost the same as FIG. 4 shown in the first embodiment.

  Thus, by detecting electromagnetic waves based on partial discharge with two types of narrow-band flat antennas, it is possible to distinguish between discharge electromagnetic waves generated in the stator slot and discharge electromagnetic waves generated outside the stator slot, It is possible to specify whether the discharge generation position is inside the stator slot or outside the stator slot. As a result, the inspection time required to identify the insulation deterioration location is shortened, leading to cost reduction. In addition, detection by a narrowband antenna such as a flat plate antenna has an advantage that the influence of noise is less than that of a wideband antenna. Therefore, by using a flat plate antenna, it is possible to reduce the influence of noise, and it is possible to evaluate with higher accuracy. In addition, the electromagnetic wave acquisition unit can be configured with a simpler noise removal unit such as a band pass filter, which eliminates the need for the frequency analysis unit and leads to cost reduction. In addition, by using two different band antennas and separately evaluating the deterioration of the stator winding inside and outside the stator slot, the accuracy of determining the insulation deterioration level of the entire rotating electrical machine can be improved. In addition, since the flat antenna can be reduced in dimensions, such as the dimension in the thickness direction, the space of the antenna in the rotating electric machine can be suppressed to be small, and the installation property can be improved.

Embodiment 6 FIG.
In the first to fifth embodiments, the position of the antenna is not particularly specified, but the horn antenna 10 or the flat antennas 26 and 27 are placed at positions facing the stator slot 7 provided in the stator core 2. It can also be arranged.

  The antenna is disposed at a position opposite to the stator slot 7 to be detected by the electromagnetic wave, and the strength of the electromagnetic wave detected from the antenna is determined at the frequency determined by the size of the stator slot and the size of the stator slot. By comparing with the intensity of the electromagnetic wave at a frequency outside the frequency band determined by the above, it is possible to specify whether the discharge generation position is inside the stator slot or outside the stator slot.

  This makes it easier to detect electromagnetic waves based on the partial discharge generated in the stator slot of the stator winding, and improves the determination accuracy of the insulation deterioration level.

Embodiment 7 FIG.
In the sixth embodiment, the antenna is disposed at a position facing the stator slot 7, but may be disposed at a position facing the stator slot 7 of the high-voltage line. In a rotating electrical machine, the stator winding 3 is wound around a plurality of stator slots 7, of which a line connected to an external bus, that is, a line connected to a power source in the case of an electric motor, If there is, the line connected to the output section becomes a high-pressure line. The partial winding is likely to occur in the stator winding 3 of the high-voltage line, and the antenna is disposed at a position facing the stator slot 7 that houses the stator winding 3 of the high-voltage line.

  This makes it easier to detect electromagnetic waves based on the partial discharge generated in the stator slot of the stator winding, and improves the determination accuracy of the insulation deterioration level.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an end cross-sectional view of a rotating electrical machine and a block diagram of a partial discharge position specifying device showing Embodiment 1 of the present invention. It is a schematic diagram of the electromagnetic wave which propagates the stator slot and slot inside which shows Embodiment 1 of this invention. It is the frequency spectrum of the electromagnetic wave which shows Embodiment 1 of this invention. It is a related figure of the intensity of electromagnetic waves which shows Embodiment 1 of this invention. It is an end sectional view of a rotary electric machine and a block diagram of a partial discharge position specifying device showing Embodiment 5 of the present invention. It is the frequency spectrum of the electromagnetic wave which shows Embodiment 5 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stator 2 Stator iron core 3 Stator winding 7 Stator slot 10 Horn antenna 20 Partial discharge generation position specifying device 21 Frequency analysis means 23 Discharge position specifying means 24 Discharge output outside stator slots 25 Discharge output in stator slots 26 Flat antenna 27 Flat antenna 30 Stator slot depth 31 Stator slot width

Claims (1)

An antenna for detecting electromagnetic waves based on partial discharge generated from a stator winding wound around a stator slot of a stator core;
A frequency analysis means for frequency-analyzing the output of the antenna and outputting a signal intensity for each frequency;
Distinguishing between in-stator slot discharge and out-of-stator slot discharge is based on the ratio of the signal strength at the frequency derived from the dimensions of the stator slot and the signal intensity at a frequency other than the frequency derived from the dimensions of the stator slot. A discharge position specifying means ,
The rotating electrical machine part , wherein the frequency band targeted by the frequency analyzing means is a band including a peak frequency derived from a depth dimension of the stator slot and a peak frequency derived from a width dimension. Discharge location device.

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