JP2014235091A - Residual life diagnostic system and residual life diagnostic method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate residual life of a rotary electrical machine in which mica is fixed by resin with high accuracy.SOLUTION: A residual life diagnostic system 26 has: a voltage measurement system 22; a partial discharge charge amount detector 23; a computer 24; an operation part 30; and an evaluation part 31. The voltage measurement system 22 measures applied voltage for every certain period, the partial discharge charge amount detector 23 measures a partial discharge charge amount of a stator coil corresponding to the applied voltage measured by a voltage measurement part. The computer 24 associates an applied electric field with the partial discharge charge amount from the applied voltage measured by the voltage measurement part and the partial discharge charge amount measured by a partial discharge charge amount measurement part. The operation part 30 calculates relation between the partial discharge charge amount acquired by the measurement part and the applied voltage. The evaluation part 31 estimates insulation breakdown intensity residual ratio of a rotary electrical machine based on a calculation result of the operation part 30 and the applied electric field in the set predetermined partial discharge charge amount, and estimates residual life of the rotary electrical machine based on its estimation result.

Description

  The present invention relates to an insulation diagnosis technique for a rotating electrical machine, and more particularly to a technique effective for diagnosis of insulation in a stator coil in which a mica layer such as an induction motor or a generator is fixed with a resin.

  In an insulation system for a stator coil of a rotating electrical machine, it is known to estimate the remaining insulation life by monitoring the secular change of the absolute value of the characteristic represented by the maximum partial discharge charge amount and the dielectric loss tangent, for example. Here, the maximum partial discharge charge amount is a value of the partial discharge charge amount generated at a frequency of about once per cycle of the applied voltage at a normal voltage.

  As an estimation technique of this type of remaining insulation life, a method for monitoring insulation of an electric machine during operation is shown, and the maximum discharge charge amount, total charge amount, average discharge current, and discharge generation phase-charge amount- There is one that evaluates an abnormality in an insulator by using an occurrence frequency characteristic or the like (see, for example, Patent Document 1).

JP 2000-206213 A

  With the diversification of insulation systems, in the stator coil insulation system in which mica is fixed with resin, when defects develop, the mica obstructs the direction of progress, and the direction of progress may not always match the direction of the electric field. . For this reason, it is difficult to correlate the maximum partial discharge charge amount, which is one of the diagnostic indicators of the above-described estimation technique of the remaining insulation life, and the degree of progress of deterioration, and it is difficult to accurately evaluate the state of deterioration. There's a problem.

  An object of the present invention is to provide a technique capable of accurately estimating the remaining life in a rotating electrical machine in which mica is fixed with a resin.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  That is, a typical outline is applied to a remaining life diagnosis system and a remaining life diagnosis method, and has the following characteristics.

  The remaining life diagnosis system includes a measurement unit, a calculation unit, and an evaluation unit. A measurement part acquires the relationship of the partial discharge charge amount with respect to the applied voltage applied to the stator coil of the rotary electric machine. The calculation unit calculates the relationship between the partial discharge charge amount acquired by the measurement unit and the applied voltage. The evaluation unit determines the dielectric breakdown of the rotating electrical machine based on the calculation result of the calculation unit and the applied electric field or applied voltage, the dielectric characteristic (Δ2), or the combination of the applied electric field and the dielectric characteristic at a predetermined partial discharge charge amount set in advance. The residual strength rate is estimated, and the remaining life of the rotating electrical machine is estimated based on the estimation result.

  The remaining life diagnosis method includes a measuring unit that performs electrical measurement on a stator coil of a rotating electrical machine, an arithmetic unit that performs arithmetic processing on a measurement result obtained by the measuring unit, and a calculation result obtained by the arithmetic unit. The remaining life of the stator coil is diagnosed by a remaining life diagnosis system having an evaluation unit for evaluation.

  This remaining life diagnosis method includes the following steps.

  In the measurement unit, the applied voltage applied to the stator coil of the rotating electrical machine and the partial discharge charge amount with respect to the applied voltage are measured, and the applied electric field and the partial discharge charge amount are associated with each other based on the measurement result.

  In the calculation unit, the relationship between the partial discharge charge amount acquired by the measurement unit and the applied electric field is calculated.

  The evaluation unit estimates the dielectric breakdown strength remaining rate of the rotating electrical machine based on the calculation result of the calculation unit and the generated electric field, dielectric characteristics, or a combination of the generated electric field and dielectric characteristics of a predetermined partial discharge charge amount. This is a step of estimating the remaining life of the rotating electrical machine based on the estimation result.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  The remaining life of the rotating electrical machine can be estimated with high accuracy.

It is explanatory drawing which shows an example of a structure of a rotary electric machine. It is sectional drawing of the slot in the rotary electric machine of FIG. 5 is a flowchart illustrating an example of acquisition processing of partial discharge charge amount characteristics with respect to an applied voltage according to the first embodiment. 1 is a block diagram illustrating an example of a configuration in a remaining life diagnosis system according to Embodiment 1. FIG. It is a flowchart which shows the specific example of a diagnosis in the remaining life diagnostic system of FIG. It is a schematic diagram which shows an example of the result at the time of using the differential value with respect to the applied electric field of the partial discharge charge amount made into the natural logarithm display for the calculation method. It is a schematic diagram which shows an example of the measurement result at the time of using the differential value with respect to the applied electric field of partial discharge charge amount. It is a schematic diagram which shows an example of the main insulating layer after thermal deterioration and after mechanical deterioration. It is a flowchart which shows an example of the evaluation process by the deterioration level evaluation part provided in the remaining life diagnostic system of FIG. It is a flowchart which shows an example of the residual rate estimation process by the dielectric breakdown strength residual rate estimation part provided in the remaining life diagnosis system of FIG. It is explanatory drawing which shows the relationship between the electric field generated of the partial discharge charge amount of the stator coil evaluated as a dangerous level, and dielectric strength remaining rate. It is explanatory drawing which shows the relationship between the electric field of a stator coil evaluated as a monitoring level or a warning level, and dielectric breakdown strength residual rate. It is explanatory drawing which shows the relationship between the difference of the stator coil evaluated with the monitoring level or the warning level, and dielectric breakdown strength residual rate. It is explanatory drawing which shows an example of the estimation of the remaining life by the remaining life estimation part provided in the remaining life diagnosis system of FIG. 10 is a flowchart illustrating an example of acquisition processing of partial discharge charge amount characteristics with respect to an applied voltage according to the second embodiment. It is a flowchart which shows an example of the residual rate estimation process by this Embodiment 3. It is explanatory drawing which shows the relationship between the partial discharge charge amount of a stator coil evaluated as a dangerous level, and dielectric strength remaining rate. It is explanatory drawing which shows the relationship between the partial discharge charge amount of a stator coil evaluated as a monitoring level or a warning level, and dielectric strength remaining rate. It is a block diagram which shows an example of a structure of the remaining life diagnosis system by Embodiment 4. FIG. 20 is a flowchart illustrating an example of acquisition processing of partial discharge charge amount characteristics with respect to applied voltage by the remaining life diagnosis system of FIG. 19. FIG. FIG. 20 is an explanatory diagram showing an example of estimation of a dielectric loss tangent increase start electric field according to the sixth embodiment.

  In the following embodiments, when it is necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant to each other. There are some or all of the modifications, details, supplementary explanations, and the like.

  Further, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), especially when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and may be more or less than the specific number.

  Further, in the following embodiments, the constituent elements (including element steps and the like) are not necessarily indispensable unless otherwise specified and apparently essential in principle. Needless to say.

  Similarly, in the following embodiments, when referring to the shape, positional relationship, etc. of components, etc., the shape of the component is substantially the case unless it is clearly specified and the case where it is clearly not apparent in principle. And the like are included. The same applies to the above numerical values and ranges.

  In all the drawings for explaining the embodiments, the same members are denoted by the same reference symbols in principle, and the repeated explanation thereof is omitted. In order to make the drawings easy to understand, even a plan view may be hatched.

(Embodiment 1)
<Summary of invention>
The first outline is a remaining life diagnosis system having a measurement unit (voltage measurement system 22, partial discharge charge detector 23, computer 24), a calculation unit (calculation unit 30), and an evaluation unit (evaluation unit 31). .

  A measurement part acquires the relationship of the partial discharge charge amount with respect to the applied voltage applied to the stator coil of the rotary electric machine. The calculation unit calculates the relationship between the partial discharge charge amount acquired by the measurement unit and the applied voltage.

  The evaluation unit is based on the calculation result of the calculation unit and the applied electric field, dielectric characteristic (Δ2), or a combination of the applied electric field and the dielectric characteristic at a predetermined partial discharge charge amount set in advance, or the dielectric breakdown strength remaining rate of the rotating electrical machine And the remaining life of the rotating electrical machine is estimated based on the estimation result.

  The second outline is a remaining life diagnosis method using a remaining life diagnosis system (remaining life diagnosis system 26). The remaining life diagnosis system includes a measurement unit (voltage measurement system 22, partial discharge charge amount detector 23, computer 24) that performs electrical measurement on a stator coil of a rotating electrical machine, and an arithmetic unit that performs processing on the measurement results obtained by the measurement unit. Unit (arithmetic unit 30) and an evaluation unit for evaluating the stator coil from the calculation result by the calculation unit.

  This remaining life diagnosis method includes the following steps.

  In the measurement unit, the applied voltage applied to the stator coil of the rotating electrical machine and the partial discharge charge amount with respect to the applied voltage are measured, and the applied electric field and the partial discharge charge amount are associated from the measurement result.

  In the calculation unit, the relationship between the partial discharge charge amount acquired by the measurement unit and the applied electric field is calculated.

  The evaluation unit estimates the dielectric breakdown strength remaining rate of the rotating electrical machine based on the calculation result of the calculation unit and the generated electric field, dielectric characteristics, or a combination of the generated electric field and dielectric characteristics of a predetermined partial discharge charge amount. Based on the estimation result, the remaining life of the rotating electrical machine is estimated.

  Hereinafter, the embodiment will be described in detail based on the above-described outline.

  First, the structure of the rotating electrical machine 1 will be briefly described.

  FIG. 1 is an explanatory diagram illustrating an example of a configuration of a rotating electrical machine.

  As shown in FIG. 1, the rotating electrical machine 1 is generally composed of a rotor 2 and a stator 3. As shown in FIG. 2, the stator 3 includes a stator core 4, an iron core slot 5, and a stator coil 6.

  The stator coil 6 includes an upper coil 6a and a bottom coil 6b. The stator coil 6 is provided with a wedge 7 for fixing the stator coil 6 to the iron core slot 5. An insulating member spacer 8 is provided between the upper coil 6a and the bottom coil 6b to secure a space. The stator coil 6 is electrically connected outside the stator core 4.

  The stator coil 6 is composed of a wire solidifying coil 9. The strand fixing coil 9 has a configuration in which several strands 9a subjected to strand insulation 10 are aligned, the strands 9a are bundled, and an insulation stuffing 11 is applied to integrate them. A main insulating layer 12 in which mica tape with a glass cloth or the like as a backing material is wound a predetermined number of times is formed around the wire fixing coil 9.

  The stator coil 6 is obtained by, for example, impregnating the main insulating layer 12 with a thermosetting resin such as an epoxy resin in an impregnation tank, and then heat-curing the thermosetting resin, or using a heat such as an epoxy resin in advance. There is one obtained by hot pressing a semi-cured prepreg mica tape containing a curable resin. By the processing steps represented by the above, the stator coil 6 including the main insulating layer 12 having a good insulation characteristic with few defects represented by voids can be obtained.

  The main insulating layer 12 is desired to be completely filled with the mica tape layer and the thermosetting resin. However, the generator coil has some defects such as voids and peeling. When a voltage equal to or higher than the partial discharge start voltage is applied to an insulating layer having voids or peeling inside, partial discharge occurs at a minute defect such as a void or peeling.

  In addition to the micro defects existing from the beginning in the insulating layer, micro defects are newly formed mainly by thermal and mechanical stresses. It is known that when a thermal / mechanical / electrical / other stress is applied due to a long-term operation, the stress develops and the breakdown voltage and mechanical strength decrease.

  FIG. 3 is a flowchart showing an example of the process of acquiring the partial discharge charge amount characteristic with respect to the applied voltage according to the first embodiment.

  In the measurement flowchart shown in FIG. 3, after an AC voltage, which is an applied voltage, is applied to the measurement target (Step S101), the AC voltage is boosted (Step S102), and the partial discharge charge amount is measured (Step S103). These processes are repeated (step S104), and the partial discharge charge amount characteristic with respect to the applied voltage is acquired after reaching the voltage of the measurement end condition (step S105).

  FIG. 4 is a block diagram showing an example of a configuration in the remaining life diagnosis system according to the first embodiment.

  As shown in FIG. 4, the remaining life diagnosis system 26 includes a voltage measurement system 22, a partial discharge charge amount detector 23, a computer 24, a display unit 25, a connection terminal 29, a calculation unit 30, and an evaluation unit 31.

  The voltage measurement system 22 measures an applied voltage that is a voltage applied to the stator coil 6 of FIG. The partial discharge charge amount detector 23 acquires the partial discharge charge amount of the partial discharge generated from the main insulating layer 12 of FIG.

  A high voltage power source 21 is connected to the connection terminal 29, the voltage measurement system 22, and the partial discharge charge amount detector 23. The connection terminal 29 is a terminal for applying an AC voltage supplied from the high voltage power supply 21 to the stator coil 6 of the rotating electrical machine 1 of FIG.

  The computer 24 acquires applied voltage and partial discharge charge amount characteristics. The display unit 25 displays the evaluation result of the evaluation unit 31 and the like. The calculation unit 30 performs calculation processing on the characteristics acquired by the computer 24. The evaluation unit 31 evaluates insulation deterioration based on the calculation result by the calculation unit 30.

  The evaluation unit 31 includes a deterioration level evaluation unit 33, a dielectric breakdown strength remaining rate estimation unit 34, and a remaining life estimation unit 35. The deterioration level evaluation unit 33 evaluates the deterioration level based on the calculation result obtained by the calculation unit 30.

  The dielectric breakdown strength residual rate estimation unit 34 estimates the dielectric breakdown strength residual rate based on the degradation level evaluation by the degradation level evaluation unit 33. Here, the dielectric breakdown strength remaining rate refers to the ratio of the dielectric breakdown strength over time (after deterioration) to the dielectric breakdown strength of the new stator coil 6 at the beginning of manufacture. The remaining life estimation unit 35 estimates the remaining life based on the dielectric breakdown strength remaining rate by the dielectric breakdown strength remaining rate estimation unit 34.

  In FIG. 4, the computer 24, the calculation unit 30, and the evaluation unit 31 have different hardware configurations. However, for example, the computer 24 may have the functions of the calculation unit 30 and the evaluation unit 31.

  Next, a specific diagnosis example in the remaining life diagnosis system 26 will be described.

  FIG. 5 is a flowchart showing a specific diagnosis example in the remaining life diagnosis system of FIG.

  First, when the remaining life diagnosis is started and the high voltage power supply 21 is operated, the AC voltage is gradually increased. The AC voltage of the high voltage power supply 21 is applied to the stator coil 6 of the rotating electrical machine 1 of FIG. Note that the stator coil 6 to be measured can be in the state of one stator coil 6 extracted from the rotating electrical machine 1.

  The voltage measurement system 22 measures the applied voltage level applied to the stator coil 6 for each certain voltage level, and the partial discharge charge amount detector 23 measures the partial discharge charge amount for each certain applied voltage level.

  When this is repeated and the voltage measurement system 22 and the partial discharge charge amount detector 23 acquire the applied voltage and the partial discharge charge amount up to a predetermined voltage (step S201), the acquired applied voltage and the partial discharge charge amount are: The data is output to the computer 24.

  The computer 24 associates the received applied voltage with the partial discharge charge amount, and acquires the partial discharge charge amount characteristic with respect to the applied voltage. Although the evaluation may be performed using the acquired applied voltage as it is, if the applied voltage acquired by the computer 24 is divided by the thickness of the insulating layer of the sample to be an applied electric field, the insulating layer thicknesses differ as normalized values. Therefore, the description will be made using this applied electric field-partial discharge charge amount characteristic.

  In general, a partial discharge charge amount using, for example, detection of current or electromagnetic wave is known. As an example, the configuration described in FIG. 4 of JP-A-3-99286 can be cited. The calculation unit 30 performs calculation processing on the partial discharge charge amount characteristics with respect to the applied electric field obtained by the above method (step S202).

  Thereafter, based on the calculation result obtained by the calculation unit 30, the deterioration level evaluation unit 33 of the evaluation unit 31 evaluates the deterioration level (step S203). Then, the dielectric breakdown strength remaining rate estimating unit 34 estimates the dielectric breakdown strength remaining rate based on the evaluation of the degradation level obtained by the degradation level evaluating unit 33 (step S204).

  Subsequently, the remaining life estimation unit 35 estimates the remaining life based on the estimation result of the dielectric breakdown strength remaining rate obtained by the deterioration level evaluation unit 33 (step S205). This estimation result is displayed on the display unit 25, for example.

  In the present embodiment, measurement is performed while increasing the AC voltage from about 0 V / mm to a preset voltage level, but in addition, the AC voltage is reduced from the preset voltage level. Diagnosis may be made based on measurement or data measured by combining pressure increase and pressure decrease.

  FIG. 6 is a schematic diagram illustrating an example of a result in the case where the differential value with respect to the applied electric field of the partial discharge charge amount displayed in the natural logarithm is used for the calculation method in the calculation unit 30. FIG. 7 is a schematic diagram illustrating an example of an actual measurement result when a differential value of the partial discharge charge amount with respect to the applied electric field is used.

  FIG. 6A shows the calculation result of thermal degradation, and FIG. 6B shows the calculation result of mechanical degradation. FIG. 7A shows an actual measurement result of thermal degradation, and FIG. 7B shows an actual measurement result of mechanical degradation.

  In FIG. 6A, when the applied electric field is increased from about 0 V / mm to a predetermined electric field, the differential value rapidly increases with a significant difference from the background level, and then rapidly decreases. An electric field region (hereinafter referred to as a first peak 27) and an electric field region in which the differential value is substantially constant at the background level. Here, the background level is a region where the partial discharge charge amount does not increase from the value at which the applied voltage can be regarded as 0 kV with respect to the increase of the applied voltage, and changes almost constant.

  When the applied electric field E1 at which the differential value of the first peak 27 is maximum is compared with the preset value E for the applied electric field, the applied electric field E1 is lower than the set value E. By adding arithmetic processing in this way, evaluation independent of the measurer becomes possible.

  The tendency obtained by the measurement method and the calculation process shown in FIG. 6A is the same tendency as the example of the actual measurement result when the thermal deterioration shown in FIG. 7A is given. As shown in the schematic diagram of FIG. 8 (a), the mica tape forming the main insulating layer 12 is peeled and voided in the creeping direction. It shows a tendency that the degree of occurrence of the occurrence of the is increased. For this reason, mechanical strength decreases due to thermal deterioration, and the insulating layer is likely to crack due to vibration, electromagnetic force, centrifugal force, and the like.

  In the example of FIG. 7A, this means that defects such as cracks are easily formed in the penetration direction of the insulating layer, and it is considered necessary to take measures such as shortening the diagnosis period. Therefore, for example, it can be evaluated as a warning level which is the second level.

  In FIG. 6B, when the applied electric field is increased from about 0 V / mm to a predetermined electric field, the second peak 28 of the differential value appears in the electric field region higher than the first peak 27 of the differential value. The differential value has two peaks with respect to the applied electric field. When two peaks are detected in this way, it can be estimated that mechanical deterioration is added.

  The tendency obtained by the measurement method and the calculation process shown in FIG. 6B is the same as the example of the actual measurement result when the mechanical deterioration shown in FIG. 7B is given. This tendency is due to the fact that, as shown in the schematic diagram of FIG. 8B, the microcracks that progress in the penetration direction of the insulating layer and the defects such as peeling and voids through the cracks are combined and progress. .

  The defect that develops in the penetration direction of the insulating layer is a fatal defect for the insulating layer, and is likely to cause a significant decrease in the insulating performance represented by the breakdown voltage, for example, at the first level. It can be evaluated as a danger level. Thereby, evaluation independent of the measurer becomes possible.

  When the applied electric field E1 at which the differential value of the first peak 27 is maximum is larger than the set value and the second peak 28 does not exist, the deterioration due to heat and mechanical force applied to the insulating layer is small and there is a problem at present. It shows no. For this reason, it is considered that periodic diagnosis should be continued, and for example, it can be evaluated as a monitoring level that is the third level.

  Based on the above evaluation, the deterioration level evaluation part 33 performs an evaluation process.

  FIG. 9 is a flowchart showing an example of evaluation processing by the deterioration level evaluation unit 33 provided in the remaining life diagnosis system 26 of FIG.

  First, the deterioration level evaluation unit 33 determines whether or not the first peak 27 and the second peak 28 in FIG. 6 are detected based on the partial discharge charge amount with respect to the applied electric field by the calculation unit 30 (step S301). Is determined (step S302).

  When both the first peak 27 and the second peak 28 are detected in the process of step S302, it is determined that the risk level requires a detailed diagnosis (step S303).

  In the process of step S302, when only the first peak 27 is detected, the applied electric field E1 shown in FIG. 6 at which the differential value of the first peak 27 is maximum is equal to or lower than a preset set value E. It is determined whether or not (step S304).

  When the applied electric field E1 is smaller than the set value E, it is determined as a warning level that requires countermeasures such as shortening of the diagnosis period (step S305). It is determined that there is no monitoring level at which periodic monitoring is continued (step S306).

  FIG. 10 is a flowchart showing an example of a remaining rate estimation process by the dielectric breakdown strength remaining rate estimation unit 34 provided in the remaining life diagnosis system 26 of FIG.

  The dielectric breakdown strength residual rate estimation unit 34 estimates the dielectric breakdown strength residual rate based on the basic data accumulated in advance after the degradation level evaluation unit 33 evaluates the degradation level.

  When the determination (step S401) of the deterioration level evaluation unit 33 determines that the level is a danger level (step S402), the dielectric breakdown strength remaining rate estimation unit 34 calculates the generated electric field Eim of the predetermined partial discharge charge amount and the dielectric breakdown strength residual rate. From the relationship, the dielectric breakdown strength remaining rate is estimated (step S403).

  FIG. 11 is an explanatory diagram showing the relationship between the generated electric field Eim of the partial discharge charge amount of the stator coil evaluated as the dangerous level and the dielectric breakdown strength remaining rate. If the generated electric field Eim of the partial discharge charge amount is used as an evaluation index, it is known that there is a correlation with the dielectric breakdown strength remaining rate as shown in FIG. As the generated electric field Eim, an applied electric field E1 that maximizes the differential value of the first peak 27 may be used.

  Further, the electric field that determines the generated electric field Eim is the electric field that is detected to the second level 28 of the calculation result and that has been reduced to the background level, that is, the applied electric field E4 shown in FIGS. 6B and 7B. Also, the electric field is low.

  On the other hand, when the deterioration level evaluation unit 33 determines that the warning level or the monitoring level is set (step S402), the dielectric breakdown strength remaining rate estimation unit 34 determines the relationship between the electric field Eit and the dielectric property Δ2 and the dielectric breakdown strength remaining rate. From this, the dielectric breakdown strength remaining rate is estimated (step S404).

  FIG. 12 is an explanatory diagram showing the relationship between the electric field Eit of the stator coil evaluated as the monitoring level or the warning level and the dielectric breakdown strength remaining rate. FIG. 13 is an explanatory diagram showing the relationship between Δ2 of the stator coil evaluated as the monitoring level or the warning level and the dielectric breakdown strength remaining rate.

  The electric field Eit is an electric field in which a predetermined partial discharge charge amount is generated, and Δ2 is a difference between a dielectric loss tangent when a voltage of 2 kV is applied to the stator coil 6 and a dielectric loss tangent when a rated voltage is applied. It is.

  Assuming that the evaluation level is the warning level or the monitoring level and the electric field Eit at which the partial discharge charge amount is generated is used as an evaluation index, it is known that there is a correlation with the dielectric breakdown strength remaining rate as shown in FIG. Further, when Δ2 which is the difference between the dielectric loss tangent when 2 kV is applied and the dielectric loss tangent of the rated voltage is used as an evaluation index, it is known that there is a correlation with the dielectric breakdown strength remaining rate as shown in FIG.

  As the electric field Eit, an applied electric field E1 that maximizes the differential value of the first peak 27 may be used. Furthermore, the electric field that determines the electric field Eit is lower than the electric field that has detected the first peak 27 and decreased to the background level, that is, the electric field E3 shown in FIGS. 6A and 7A. Use a low electric field.

  The dielectric breakdown strength remaining rate estimation unit 34 accumulates the relationship between the evaluation index shown in FIGS. 11 to 13 and the dielectric breakdown strength residual rate as basic data in advance, and performs insulation based on the evaluation index actually measured in the diagnosis target. The fracture strength remaining rate is estimated (step S405).

  Specifically, when the deterioration level evaluation unit 33 evaluates the risk level, the dielectric strength remaining rate is estimated from the relationship between the evaluation index and the dielectric strength remaining rate shown in FIG. Further, when the deterioration level evaluation unit 33 evaluates the warning level or the monitoring level, the dielectric strength remaining rate is estimated from the relationship between the evaluation index and the dielectric strength remaining rate shown in FIGS.

  When estimating the dielectric breakdown strength residual rate, an evaluation method is used that evaluates each of a plurality of evaluation indexes, uses the lowest estimated value, or combines multiple evaluation indexes by multivariate analysis such as regression analysis. May be estimated.

  Note that the estimated value can be diagnosed with high reliability in consideration of variations such as individual differences when statistical processing such as a 95% confidence interval is performed. Moreover, if the lower limit value is used for evaluation among the results of the statistical processing, it is possible to evaluate the device under the strictest conditions, which is effective for preventing accidents.

  Subsequently, the remaining life estimation unit 35 estimates the remaining life in the stator coil 6 (step S406).

  Here, the remaining life estimation technique by the remaining life estimation unit 35 will be described.

  FIG. 14 is an explanatory diagram showing an example of remaining life estimation by the remaining life estimation unit provided in the remaining life diagnosis system of FIG.

  The remaining life estimation unit 35 estimates the remaining life based on the dielectric breakdown strength remaining rate estimated as described above. In FIG. 14, the horizontal axis represents the number of years, and the vertical axis represents the dielectric breakdown strength remaining rate. The 95% reliability lower limit value of the dielectric breakdown strength remaining rate estimated as described above is plotted against the graph of FIG.

  Then, the 95% confidence lower limit value of the estimated dielectric strength remaining rate is connected to the initial value of 100%, the line is extrapolated, and the intersection of the preset life management value with the dielectric strength remaining rate and the current value The difference in years is evaluated as the remaining life. If the initial value is evaluated based on the lower limit of 95% with respect to the dielectric breakdown strength of 100%, it is possible to evaluate in consideration of variations at the time of manufacture.

  In addition, since the degree of deterioration may vary depending on the operating conditions before and after the diagnosis, it is possible to provide highly accurate diagnosis results by correcting the remaining life estimation line each time while managing trend data over time. can do.

  Based on the above, based on the differential value of the partial discharge charge amount with respect to the applied electric field expressed in natural logarithm, the phenomenon of deterioration due to the formation and development of minute defects that were difficult to appear in the absolute value of the characteristic represented by the maximum partial discharge charge amount. And can be estimated based on the basic data of the dielectric breakdown strength remaining rate and the evaluation index accumulated in advance for each deterioration phenomenon.

  And the insulation diagnostic technique which can estimate the insulation remaining life with high reliability based on the estimation result can be provided.

(Embodiment 2)
In the second embodiment, an insulation diagnosis technique for estimating a more accurate insulation remaining life will be described.

  FIG. 15 is a flowchart illustrating an example of acquisition processing of partial discharge charge amount characteristics with respect to an applied voltage according to the second embodiment.

  The configuration in the remaining life diagnosis system 26 is the same as that in FIG. 4 of the first embodiment. The voltage measurement system 22, the partial discharge charge amount detector 23, the computer 24, the display unit 25, the connection terminal 29, the calculation unit 30, And an evaluation unit 31.

  A difference from the first embodiment is a high-voltage power supply 21, which has a function of controlling a step-up speed or a step-down speed per second, for example, by a computer 24, for example. It is a point.

  First, the computer 24 supplies the measurement end voltage V, the step-up rate v per second, or the step-down rate v, the time interval Δt 1 at which the applied voltage is measured by the voltage measurement system 22, and the partial discharge charge amount detector 23. A time interval Δt2 for measuring the amount is set (step S601).

  Subsequently, the computer 24 outputs a control signal to the high voltage power source 21 to apply an AC voltage, which is an applied voltage, to the measurement target (step S602). Subsequently, the computer 24 outputs a control signal to the high voltage power source 21 to boost the AC voltage at the step-up speed v or step-down speed v set in the processing of step S601 (step S603), and measure the voltage. The applied voltage is measured by the system 22, and the partial discharge charge amount is measured by the partial discharge charge amount detector 23 (step S604).

  Here, the computer 24, the voltage measurement system 22, and the partial discharge charge amount detector 23 are connected by, for example, GPIB (General Purpose Interface Bus) and are in a synchronized state.

  The measurement interval of the applied voltage by the voltage measurement system 22 is every time interval Δt1 set in the process of step S601, and the interval of the partial discharge charge amount measurement by the partial discharge charge amount detector 23 is set in the process of step S601. Every time interval Δt2.

  As described above, the computer 24 automatically records the partial discharge charge amount characteristic with respect to the applied voltage by issuing a command synchronized with the voltage measurement system 22 and the partial discharge charge amount detector 23. The applied voltage measured by the voltage measurement system 22 and the partial discharge charge amount measured by the partial discharge charge amount detector 23 are stored in, for example, a memory included in the computer 24 (step S605).

  The frequency of occurrence of the partial discharge charge to be measured may be set arbitrarily. As an example, when the commercial frequency is 50 Hz, the frequency of occurrence is 50 pulses / second, and when the commercial frequency is 60 Hz, the signal having the frequency of occurrence of one or more times per one cycle of the applied voltage is 60 pulses / second. When it is acquired as the discharge charge amount, noise can be effectively removed.

  In addition, when the time intervals Δt1 and Δt2 are about 0.5 seconds and the measurement end voltage V is about 0.1 kV / second, it has been confirmed that the balance between the number of data and the evaluation accuracy can be appropriately maintained.

  When the processing up to the measurement end voltage V is completed by repeating the processing of steps S603 to S605 (step S606), the calculation unit 30 performs calculation processing based on the relationship between the applied voltage and the partial discharge charge amount stored in the computer 24. The partial discharge charge amount characteristic with respect to the applied voltage is acquired (step S607).

  Note that the value of the applied voltage acquired as described in the first embodiment may be divided by the thickness of the insulating layer and evaluated as an applied electric field. Further, the partial discharge charge amount characteristic with respect to the applied electric field may be displayed on the display unit 25. Furthermore, the acquired data may be displayed on the display unit 25 as needed.

  The calculation unit 30 derives a differential value with respect to the applied electric field of the partial discharge charge amount expressed in natural logarithm. The differential value may be derived from an applied electric field having an arbitrary number of points and a partial discharge charge amount expressed in natural logarithm. As an example, the partial discharge charge amount logarithmically represented with the applied electric field can be accurately evaluated by deriving a differential value based on about 10 points of data.

  Thereafter, based on the obtained calculation result, the evaluation unit 31 evaluates the deterioration level based on the method described in FIG. 9, FIG. 10, FIG. The remaining rate and the remaining life are estimated and the result is displayed on the display unit 25. In this case as well, the computer 24 may be configured to have the functions of the calculation unit 30 and the evaluation unit 31.

  As described above, the data of the applied electric field and the partial discharge charge amount can be recorded in more detail, and a more reliable insulation diagnosis can be realized.

(Embodiment 3)
In the present third embodiment, an insulation diagnosis technique for estimating the residual dielectric breakdown strength rate by adding another evaluation index to the diagnosis techniques described in the first and second embodiments will be described.

  The degradation level evaluation unit 33 determines the degradation level according to the flowchart shown in FIG. 9 of the first embodiment, and then the dielectric strength remaining rate estimation unit 34 previously stores the relationship between the dielectric strength remaining rate and the evaluation index. From this, the dielectric breakdown strength is estimated.

  In addition, since the structure in the remaining life diagnosis system 26 is the same as that of FIG. 4 of the said Embodiment 1, description is abbreviate | omitted.

  FIG. 16 is a flowchart illustrating an example of the remaining rate estimation process according to the third embodiment. FIG. 17 is an explanatory diagram showing the relationship between the partial discharge charge amount Qim of the stator coil evaluated as the dangerous level and the dielectric breakdown strength remaining rate, and FIG. 18 shows the relationship of the stator coil evaluated as the monitoring level or the warning level. It is explanatory drawing which shows the relationship between the partial discharge charge amount Qit and dielectric breakdown strength residual rate.

  First, in the evaluation result by the deterioration level evaluation unit 33 (step S701), when it is determined that the level is a danger level (step S702), the dielectric breakdown strength remaining rate estimation unit 34 determines the evaluation index shown in FIG. 11 of the first embodiment. In combination with the partial discharge charge amount Qim generated in a predetermined electric field shown in FIG. 17, the dielectric breakdown strength remaining rate is estimated (step S703).

  It should be noted that the electric field that determines the partial discharge charge amount Qim is the electric field that has been detected to the background level by detecting the second peak 28 in FIG. 6 in the same manner as the partial discharge charge generation electric field Eim of the first embodiment. That is, the electric field is lower than the electric field E4 shown in FIGS. 6 (b) and 7 (b).

  On the other hand, when the deterioration level evaluation unit 33 evaluates the warning level or the monitoring level, in addition to the evaluation index shown in FIGS. 12 and 13, the partial discharge charge amount Qit generated in the predetermined electric field shown in FIG. In combination, the dielectric breakdown strength remaining rate is estimated (step S704).

  The electric field that determines the partial discharge charge amount Qit is an electric field that is lower than the electric field that has been detected to the background level and detected to the first peak 27 in FIG. 6, that is, FIG. 6 (a) and FIG. 7 (a). The electric field is lower than the electric field E3 shown in FIG.

  The relationship between the evaluation index and the dielectric breakdown strength remaining rate is accumulated as basic data in advance, and based on the evaluation index actually measured on the diagnosis target, the dielectric breakdown strength remaining rate estimation unit 34 is the diagram of the first embodiment. The residual dielectric breakdown strength rate is estimated by executing the processing shown in FIG. 10 (step S705). Thereafter, the remaining life estimation unit 35 estimates the remaining life in the stator coil 6 based on FIG. 14 of the first embodiment (step S706).

  As described above, a more accurate insulation diagnosis can be realized by combining a plurality of indexes.

(Embodiment 4)
In the fourth embodiment, a remaining life diagnosis system 26 that performs insulation diagnosis with higher accuracy by extracting a signal superior in diagnosis will be described.

  FIG. 19 is a block diagram showing an example of the configuration of the remaining life diagnosis system 26 according to the fourth embodiment.

  As shown in FIG. 19, the remaining life diagnosis system 26 includes the voltage measurement system 22, the partial discharge charge detector 23, the computer 24, the display unit 25, the connection terminal 29, the calculation unit 30, and the evaluation unit 31. In this configuration, the signal extraction unit 32 is newly provided in the same configuration as that of FIG.

  If the remaining life diagnosis is performed while a rotating electric machine such as another motor is operating, there is a possibility that an error may occur in measurement data due to the influence of noise of the motor. Therefore, the signal extraction unit 32 extracts a signal superior in diagnosis.

  FIG. 20 is a flowchart showing an example of acquisition processing of partial discharge charge amount characteristics with respect to applied voltage by the remaining life diagnosis system of FIG. In FIG. 20, the description is based on the data at the time of boosting, but it may be based on data at the time of step-down or a combination of data of step-up and step-down.

  Here, the processing of steps S801 to S807 in FIG. 20 is the same as the processing of steps S601 to S607 in FIG.

  In FIG. 20, when the acquisition of the partial discharge charge amount characteristic with respect to the applied voltage by the calculation unit 30 (step S807) ends, signal extraction by the signal extraction unit 32 is performed (step S808).

  As described in the first embodiment, the signal extraction unit 32 extracts a signal that is significant for diagnosis with respect to the differential value of the partial discharge charge amount expressed in natural logarithm with respect to the applied electric field. As an example of signal extraction, noise separation by applied voltage phase, threshold value of signal level is set in advance for differential value, or differential value exceeds preset level at multiple points If not, there is a technique such as processing as noise.

  Note that noise removal and signal extraction can be performed more effectively by combining not only one but a plurality of noise removal and signal extraction. Then, based on the result of noise removal and signal extraction, the evaluation unit 31 performs a diagnosis and displays the result on the display unit 25. In this case as well, the computer 24 may be configured to have the functions of the calculation unit 30, the signal extraction unit 32, and the evaluation unit 31.

  In this manner, noise removal and signal extraction are performed by the signal extraction unit 32, and a highly reliable diagnosis result can be obtained by determining the deterioration level and estimating the remaining life based on a signal significant for diagnosis. it can.

(Embodiment 5)
In the fifth embodiment, as the calculation method of FIG. 6 by the calculation unit 30, an increase amount of the partial discharge charge amount with respect to a predetermined voltage increase or a decrease amount of the partial discharge charge amount with respect to a predetermined voltage decrease is used. Based on the result, the remaining insulation life is diagnosed.

  A voltage increase width used for arithmetic processing is set in advance, and an increase amount of the partial discharge charge amount with respect to the set electric field increase width is derived based on the relationship between the applied electric field and the partial discharge charge amount obtained in the first embodiment. Based on the result, insulation deterioration is diagnosed.

  Accordingly, the insulation remaining life is estimated by the method described in the first embodiment based on the result of classifying the deterioration level. Note that both the electric field and the partial discharge charge amount may be diagnosed at the time of step-down, that is, based on the combination of the decrease amount of the partial discharge charge amount with respect to the voltage decrease width and the step-up and step-down.

  As described above, it is possible to quantitatively diagnose insulation deterioration without depending on the measurer.

(Embodiment 6)
In the sixth embodiment, a technique for diagnosing using a dielectric loss tangent increasing electric field from the voltage characteristic of dielectric loss tangent as an alternative to generated electric fields Eim and Eit of a predetermined partial discharge charge amount as an evaluation index will be described.

  It is known that the dielectric loss tangent is more resistant to electrical noise than the partial discharge. Therefore, when the generated electric fields Eim and Eit are difficult to detect due to the occurrence of electrical noise in the vicinity, the dielectric loss tangent increase starting electric fields Etanδim and Etanδit are used as an alternative.

  The derivation of the increase starting point of the dielectric loss tangent is performed based on the dielectric loss tangent characteristic with respect to the applied electric field shown in FIG. For the derivation, a method of deriving from the intersection of approximate lines of the dielectric loss tangent characteristic on the low electric field side and the dielectric loss tangent characteristic on the high electric field side as shown in FIG. 21 may be used.

  Also for this evaluation index, as in the first embodiment, the relationship with the dielectric breakdown strength remaining rate is acquired in advance as basic data, and the generated electric field Eim or the generated electric field Eit is changed to the dielectric loss tangent increase starting electric fields Etanδim and Etanδit, respectively. Instead, diagnosis is performed by the same processing as in the first embodiment, and the remaining life is estimated.

  As described above, a highly accurate remaining life diagnosis can be provided even in an environment with a lot of electrical noise.

(Embodiment 7)
In the seventh embodiment, the degradation level is evaluated by pattern recognition using a fingerprint method or the like with respect to the applied electric field-partial discharge charge amount characteristic, or the differential value of the partial discharge charge amount expressed in natural logarithm with respect to the applied electric field. The remaining insulation life is obtained based on the result.

  Preliminary data for the monitoring level, warning level, and dangerous level applied electric field-partial discharge charge amount characteristics, or the pattern of the differential value for the applied electric field of the partial discharge charge amount displayed in the natural logarithm, respectively, are stored, and the measurement results The accumulated data is evaluated by pattern recognition such as fingerprint method.

  Based on the evaluation result, the remaining insulation life is estimated by the technique of the first embodiment. In addition, a highly reliable result can be obtained by evaluating both the applied electric field-partial discharge charge amount characteristics and the differential value of the partial discharge charge amount expressed in natural logarithm with respect to the applied electric field. You may evaluate using only one side.

  As described above, it is possible to provide an insulation diagnosis method capable of quantitatively evaluating the deterioration level without depending on the measurer.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  In addition, this invention is not limited to above-described embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described.

  Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. . In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 Rotating electrical machine 2 Rotor 3 Stator 4 Stator iron core 5 Iron core slot 6 Stator coil 6a Upper coil 6b Bottom coil 7 Wedge 8 Insulation member spacer 9 Stranding coil 9a Strand 10 Strand insulation 11 Insulation padding 12 Main insulation Layer 21 High voltage power supply 22 Voltage measurement system 23 Partial discharge charge detector 24 Computer 25 Display unit 26 Remaining life diagnosis system 27 First peak 28 Second peak 29 Connection terminal 30 Calculation unit 31 Evaluation unit 32 Signal extraction unit 33 Deterioration level evaluation unit 34 Dielectric strength remaining rate estimation unit 35 Remaining life estimation unit

Claims (15)

A measurement unit for acquiring a relationship of a partial discharge charge amount to an applied voltage applied to a stator coil of a rotating electrical machine;
A calculation unit for calculating the relationship between the partial discharge charge amount acquired by the measurement unit and the applied voltage;
Based on the calculation result by the calculation unit and the applied electric field or applied voltage, dielectric characteristics, or the combination of the applied electric field or applied voltage and the dielectric characteristics at a predetermined partial discharge charge amount, the dielectric strength of the rotating electrical machine remains. An evaluation unit that estimates the rate and estimates the remaining life of the rotating electrical machine based on the estimation result;
Having a remaining life diagnosis system. The remaining life diagnosis system according to claim 1,
The measuring unit is
A voltage measuring unit for measuring the applied voltage every certain period;
A partial discharge charge amount measurement unit for measuring a partial discharge charge amount of the stator coil corresponding to the applied voltage measured by the voltage measurement unit;
From the applied voltage measured by the voltage measurement unit and the partial discharge charge amount measured by the partial discharge charge amount measurement unit, a control unit associating the applied electric field or applied voltage with the partial discharge charge amount;
Have
The remaining life diagnosis system, wherein the calculation unit differentiates a partial discharge charge amount associated with the control unit. The remaining life diagnosis system according to claim 2,
The evaluation unit is
A deterioration level evaluation unit that determines an insulation deterioration level of the stator coil based on the differential value calculated by the calculation unit;
Based on the determination result of the deterioration level evaluation unit, a dielectric breakdown strength residual rate estimation unit that estimates the dielectric breakdown strength residual rate of the stator coil,
Based on the dielectric breakdown strength remaining rate estimated by the dielectric breakdown strength remaining rate estimation unit, a remaining life estimation unit that estimates the remaining life of the stator coil;
Having a remaining life diagnosis system. The remaining life diagnosis system according to claim 3,
The deterioration level evaluation unit determines whether there are two peak periods in which the differential value is greater than a threshold value in the differential value calculated by the calculation unit, and determines the two peak periods. If it is determined that the stator coil has a first deterioration level of the stator coil is large, and if the peak period is one, it is determined whether the applied electric field in the maximum differential value of the peak period is equal to or less than a set value. When the applied electric field is equal to or lower than a set value, it is determined as a second level that is a deterioration level smaller than the first level. When the applied electric field is larger than the set value, the deterioration level of the stator coil Is a third level in which there is no problem in the remaining life diagnosis system. The remaining life diagnosis system according to claim 4,
The dielectric breakdown strength remaining rate estimation unit determines the dielectric breakdown based on the relationship between the generated electric field or voltage of the partial discharge charge amount and the dielectric breakdown strength remaining rate when the deterioration level evaluation unit determines that the first level. A remaining life diagnosis system that estimates the residual strength rate. The remaining life diagnosis system according to claim 4,
The dielectric breakdown strength remaining rate estimation unit, when the degradation level evaluation unit determines that the second level or the third level, the set generation voltage or electric field of the partial discharge charge amount, or dielectric A remaining life diagnosis system that estimates the dielectric strength remaining rate from the relationship between any of the characteristics and the dielectric strength remaining rate. A measurement unit that performs electrical measurement in a stator coil of a rotating electrical machine, a calculation unit that performs arithmetic processing on a measurement result acquired by the measurement unit, and an evaluation unit that evaluates the stator coil from the calculation result by the calculation unit; , A remaining life diagnosis method by a remaining life diagnosis system comprising:
Measuring the applied voltage applied to the stator coil of the rotating electrical machine and the partial discharge charge amount with respect to the applied voltage in the measurement unit, and associating the applied electric field with the partial discharge charge amount from the measurement result;
In the calculation unit, a step of calculating the relationship between the partial discharge charge amount acquired by the measurement unit and the applied electric field;
In the evaluation unit, based on a calculation result of the calculation unit and a generated electric field, dielectric characteristics of a partial discharge charge amount set in advance, or a combination of the generated electric field and the dielectric characteristics, a dielectric breakdown strength residual rate of the rotating electrical machine Estimating the remaining life of the rotating electrical machine based on the estimation result;
A remaining life diagnosis method. The remaining life diagnosis method according to claim 7,
The step of acquiring the relationship of the partial discharge charge amount,
Measuring the applied voltage every certain period;
Measuring a partial discharge charge amount of the stator coil corresponding to the measured applied voltage;
Associating the applied electric field with the partial discharge charge based on the measured applied voltage and the partial discharge charge;
Have
The calculation step includes differentiating the associated partial discharge charge amount, the remaining life diagnosis method. The remaining life diagnosis method according to claim 8,
Estimating the remaining life of the rotating electrical machine,
Determining an insulation deterioration level of the stator coil based on a differential value calculated by the calculation unit;
Estimating a dielectric breakdown strength remaining rate of the stator coil based on the determination result of the insulation deterioration level;
Estimating the remaining life of the stator coil based on the estimated dielectric breakdown strength remaining rate;
A remaining life diagnosis method. The remaining life diagnosis method according to claim 9,
The step of determining the insulation deterioration level includes:
In the differential value calculated by the calculation unit, determining whether there are two peaks that are periods during which the differential value is greater than a threshold value;
When it is determined that the peak has two peaks, the first coil is determined to have a large deterioration level. When the peak is determined to be one, the applied electric field at the maximum differential value of the peak is When it is determined whether the applied electric field is equal to or less than a set value, it is determined that the applied electric field is greater than the set value. Determining a third level in which the deterioration level of the stator coil is not a problem;
A remaining life diagnosis method. The remaining life diagnosis method according to claim 10,
In the step of estimating the dielectric breakdown strength remaining rate, the dielectric breakdown strength is determined from the relationship between the set electric field or voltage generated for the partial discharge charge amount and the dielectric breakdown strength residual rate when it is determined to be the first level. A remaining life diagnosis method that estimates the remaining rate. The remaining life diagnosis method according to claim 10,
The step of estimating the dielectric breakdown strength remaining rate includes determining the generated electric field or generated voltage of the partial discharge charge amount, or the dielectric characteristics when it is determined that the second level or the third level. A remaining life diagnosis method that estimates the dielectric breakdown strength residual rate from the relationship between any of the above and the dielectric breakdown strength residual rate. The remaining life diagnosis method according to claim 10,
The step of estimating the dielectric breakdown strength remaining rate is performed by using the partial discharge charge amount generated in the set applied electric field in addition to the set generated electric field or generated voltage of the partial discharge charge amount. Estimating the remaining life diagnosis method. The remaining life diagnosis method according to claim 10,
The step of estimating the dielectric breakdown strength residual rate is a predetermined application of a generated electric field or generated voltage of the partial discharge charge amount set when it is determined as either the second level or the third level. A remaining life diagnosis method for estimating a residual strength of dielectric breakdown strength based on at least one of a partial discharge charge amount generated in an electric field or a dielectric property. The remaining life diagnosis method according to claim 10,
In the step of estimating the remaining life of the stator coil, the initial dielectric breakdown strength remaining rate is set to 100% or a lower limit value in consideration of manufacturing variations, and the estimated dielectric breakdown strength remaining rate is varied due to individual differences. When the extraordinary line connecting the estimated dielectric breakdown strength residual rate and the estimated dielectric breakdown strength residual rate is extrapolated, the intersection of the life management value with the dielectric breakdown strength residual rate and A remaining life diagnosis method that estimates the remaining life as a point that reaches the lifetime.

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