Patent Application
20110184672
The present application claims priority from Japanese Patent application serial no. 2010-013992, filed on Jan. 26, 2010, the content of which is hereby incorporated by reference into this application.
The present invention relates to an insulation diagnostic unit and algorithm for an electric machine that measure an electromagnetic wave deriving from partial discharge which occurs in an insulator of an electric machine, and that detect a premonitory phenomenon prior to occurrence of, especially, a breakdown, and to equipment including the diagnostic unit.
Electric machines including a motor and being closely involved in industries and daily life, and facilities for power generation, power transmission, and power transformation serving as power sources for the electric machines are pieces of infrastructural equipment that support modern society. If the electric machines fail, social activities are seriously affected. The electric machines are therefore requested to be highly reliable.
However, as long as the electric machines are industrially manufactured, deterioration in performance due to a defect occurring at a factory or due to long-term use is unavoidable. If part of the electric machine relevant to insulation is damaged, it would be a fatal damage. Therefore, a defect in the part should be discovered and coped with as early as possible.
As an effective approach to detection of an insulation defect in an electric machine, partial discharge is detected as a premonitory phenomenon of a breakdown. Further, as one of approaches to detection of the partial discharge, there is a method of measuring an electromagnetic wave generated during discharge. The method has the merit that since a signal is measured in a non-contact manner using an external antenna or sensor without the necessity of manipulating an electric machine that is an object, while the electric machine is in operation, the measurement can be readily achieved.
By the way, the antenna or sensor catches an environmental electromagnetic wave such as a communication wave or a broadcast wave. Therefore, a technology for separating and extracting an electromagnetic wave, which derives from partial discharge, from the environmental electromagnetic wave is requested. Proposals have been made in literatures concerning related arts in efforts to overcome the drawback.
In relation to a related art described in patent document 1 (JP-A-6-201754), a proposal has been made of a method of removing a frequency spectrum of an environmental electromagnetic wave that is granted permission to use in an area where an electric machine is disposed, and recognizing the remaining spectrum as an electromagnetic wave generated from the machine.
In patent document 2 (JP-A-2003-43094), a description is made of a method of measuring an electromagnetic wave received when partial discharge does not occur in an electric machine that is an object, storing a frequency spectrum of the electromagnetic wave as a spectrum of an environmental electromagnetic wave, comparing a frequency spectrum, which is observed when the electric machine is in operation, with the stored spectrum of the environmental electromagnetic wave, and thus sensing partial discharge.
In patent document 3 (JP-A-10-210647), a description is made of a method of detecting a frequency spectrum of an environmental electromagnetic wave, selecting a frequency band in which the frequency spectrum is seldom observed, and thus observing a spectrum due to partial discharge. In patent document 4 (JP-A-2006-329636), a description is made of a method of selecting a frequency band, in which a few environmental electromagnetic waves fall, using a sensor sensitive to a narrow frequency band, and thus observing the frequency band.
As mentioned above, many technologies have been proposed in relation to the fact that when partial discharge is detected as a premonitory phenomenon of a breakdown by measuring an electromagnetic wave, the electromagnetic wave should be separated or extracted from an environmental electromagnetic wave. The technologies have drawbacks.
For example, the method described in the patent document 1 does not take account of an environmental frequency that changes from one to another with a change of areas where the electric machine exists in a case where an electric machine is an onboard machine of mobility equipment that moves between the areas between which the environmental frequency that is granted permission to use differs from one to another.
In the method described in the patent document 2, a spectrum of an environmental electromagnetic wave has to be measured with the operation of an electric machine ceased. It is hard to adopt the method for the electric machine that has to be continuously operated. In particular, when the electric machine is an onboard machine of mobility equipment, the mobility equipment has to be moved to a place of initial measurement for the purpose of measurement. In addition, the mobility equipment cannot be used during the measurement. Besides, the insulation performance of the electric machine cannot be measured until the next measurement timing.
According to the methods described in the patent documents 3 and 4, measurement has to be performed when partial discharge from an electric machine does not occur or occurs to an unserious extent, and a spectrum of an environmental electromagnetic wave has to be then discriminated. It is hard to adopt the methods for the electric machine that has to be continuously operated.
Further, the foregoing technologies cannot separate or discriminate a transient electromagnetic wave such as an illegal electromagnetic wave.
Accordingly, an object of the present invention is to provide an insulation diagnostic unit and algorithm for an electric machine capable of monitoring all the time a state of partial discharge which occurs in an electric machine to be continuously operated, or especially, in an electric machine that is an onboard machine of mobility equipment, and equipment including the diagnostic unit.
An insulation diagnostic unit for an electric machine in accordance with the present invention includes: a sensor disposed near an electric machine; an instrument that performs spectrum analysis on an output of the sensor; a load detection method for the electric machine; a data table in which an output of the load detection method and an output of the spectrum analysis instrument are recorded; a first routine that notes a spectrum relevant to a specific frequency, which is obtained by the spectrum analysis instrument, from among data items recorded in the data table, and obtains a correlation coefficient on the basis of plural data items concerning the magnitudes of the noted spectrum and plural data items of a load detected at the times of measurement of the plural data items; and a second routine that classifies the noted spectrum relevant to the specific frequency into a spectrum of an environmental electromagnetic wave or a spectrum of an electromagnetic wave due to partial discharge from the electric machine on the basis of the value of the correlation coefficient obtained by the first routine.
Preferably, a third routine that sequentially changes the spectrum relevant to the specific frequency, which is noted from among the data items recorded in the data table, and repeatedly executes the first routine and second routine is included in order to obtain frequency components of an electromagnetic wave due to partial discharge from the electric machine.
Preferably, the electric machine and the insulation diagnostic unit for the electric machine are mounted in mobility equipment.
Preferably, the electric machine and the insulation diagnostic unit for the electric machine are mounted in rotative equipment.
Preferably, when the value of the correlation coefficient obtained by the first routine is close to 1, the spectrum concerned is recognized as a spectrum of an electromagnetic wave due to partial discharge. When the value is close to 0, the spectrum concerned is recognized as a spectrum of an environmental electromagnetic wave.
Preferably, a detector that detects a position of mobility equipment and a memory in which electromagnetic-wave frequencies that are granted permission to use are stored in association with areas in which the position of the mobility equipment exists are further included. Based on an output of the detector that detects the position of the mobility equipment, the electromagnetic-wave frequency stored in the memory in association with the area where the position exists is excluded from an output of the spectrum analysis instrument, and the resultant data is recorded in the data table.
According to an insulation diagnostic algorithm for an electric machine in accordance with the present invention, data obtained by performing spectrum analysis on an electromagnetic wave measured around an electric machine, and a load on the electric machine are fetched. Plural data items of a specific spectrum out of data items resulting from the spectrum analysis are collated with the load on the electric machine. The specific spectrum whose magnitude varies along with a change in the load on the electric machine is recognized as frequency components of an electromagnetic wave due to partial discharge from the electric machine, and a spectrum whose magnitude is independent of the change in the load is recognized as frequency components of an environmental electromagnetic wave.
Preferably, pieces of information on electromagnetic-wave frequencies that are granted permission to use are preserved in association with areas. When the electric machine exists in any of the areas, the electromagnetic-wave frequency that is granted permission to use in the area is excluded from the data resulting from the spectrum analysis. The plural data items of the specific spectrum are then collated with the load on the electric machine.
Equipment including an insulation diagnostic unit for an electric machine in accordance with the present invention includes an electric machine, and an insulation diagnostic unit for an electric machine including: a sensor disposed near the electric machine; an instrument that performs spectrum analysis on an output of the sensor; a load detection method for the electric machine; a data table in which an output of the load detection method and an output of the spectrum analysis instrument are recorded; a first routine that notes a spectrum relevant to a specific frequency, which is obtained by the spectrum analysis instrument, from among data items recorded in the data table, and obtains a correlation coefficient on the basis of plural data items concerning the magnitudes of the spectrum, and plural data items of a load; and a second routine that classifies the noted spectrum relevant to the specific frequency into a spectrum of an environmental electromagnetic wave or a spectrum of an electromagnetic wave due to partial discharge from the electric machine according to the value of the correlation coefficient obtained by the first routine.
Preferably, the equipment is mobility equipment.
Preferably, the equipment is rotative equipment.
Preferably, a detector that detects a position of mobility equipment, and a memory in which electromagnetic-wave frequencies that are granted permission to use are stored in association with areas in which the position of the mobility equipment exists are further included. Based on an output of the detector that detects the position of the mobility equipment, the electromagnetic-wave frequency stored in the memory in association with the area in which the position exists is excluded from the output of the spectrum analysis instrument, and the resultant data is recorded in the data table.
According to the present invention, an electromagnetic wave deriving from partial discharge from an electric machine can be separated or discriminated from an environmental electromagnetic wave without the necessity of ceasing operation of the electric machine. As a result, since information on the partial discharge occurring in the electric machine can always be grasped, a change in insulation performance of the electric machine can be recognized without a delay.
Referring to the drawings, an embodiment of the present invention will be described below.
As the electromagnetic-wave sensor 11, an electromagnetic-wave antenna, an electric field probe, or a magnetic field probe may be adopted. As the measuring instrument 12, a spectrum analyzer, a signal data logger having a frequency analyzing feature, or a filter may be adopted. If necessary, an amplifier or an analog-to-digital converter may be included in the measuring instrument.
An attached installation 2 is connected to the electric machine 1, and inputs or outputs electric energy from or to the electric machine 1 over a power cable 3. When the electric machine 1 is a motor or the like, the attached installation 2 is a power supply. When the electric machine 1 is a power generator or the like, the attached installation 2 is a load. In this specification, a power to be inputted or outputted to or from the electric machine 1 shall be called a load. Information on the load is fetched into the signal processor 13.
An electromagnetic-wave signal actually fetched into the signal processor 13 exhibits many spectra. For a better understanding of the principles of the present invention, a description will be made of a simple case where the electromagnetic-wave signal exhibits two spectra A and B. In
In the foregoing case, the level of the spectrum A remains nearly unchanged whether the load on the electric machine 1 is heavy or light. In contrast, as for the spectrum B, when the load on the electric machine 1 is light, the spectrum level is low. When the load is heavy, the spectrum level is high. At this time, the spectrum A may be recognized as a spectrum of an electromagnetic wave coming from an external environment, such as, a communication wave or a broadcast wave (that is, an environmental electromagnetic wave), while the spectrum B may be recognized as an electromagnetic wave deriving from partial discharge from the electric machine 1.
In addition, load information concerning the machine is fetched in the form of a digital value signal 101 into the signal processor 13. Further, location information 102 or azimuth information 103 concerning the electric machine or equipment including the electric machine is described as reference information.
In a memory 131 incorporated in the signal processor 13, a time of measurement, a load, a frequency, a level, and a location and azimuth information which are included if necessary are sequentially stored in association with one another. From among the data items stored in the memory 131, necessary data is extracted by an arithmetic block 132 at appropriate timing, and analyzed as a load characteristic of a spectrum level.
As one of analysis modes, there is a method of obtaining a correlation coefficient indicating a correlation of a spectrum level relevant to a frequency i to a load. Based on the relationship to a threshold determined in advance in consideration of an insulating material or an insulation system employed in the electric machine 1, a spectrum of an environmental electromagnetic wave or a spectrum of an electromagnetic wave due to partial discharge is recognized. The recognition will be described in conjunction with
In contrast, the spectrum B described in conjunction with
A load characteristic of a spectrum level of an electromagnetic wave due to partial discharge is diversified by an effect of an insulating material, an insulation system, temperature, or humidity.
Next, referring to
The two sets of spectrum data items 1 and 2 represent observed spectra a, b, c, etc., and j. Between the sets of spectrum data items, the spectra are observed at the same frequencies, that is, the same spectral positions. However, between the sets of spectrum data items, although the spectrum levels of some of the spectra are identical to those of counterparts, the spectrum levels of the others thereof are different from those of counterparts. More particularly, the spectra b, c, f, h, and j have the spectrum levels thereof varied depending on whether the load is heavy or light, while the spectra a, d, e, g, and i have the spectrum levels thereof held nearly constant irrespective of the load.
The spectra a, d, e, g, and i having the spectrum levels thereof held nearly constant irrespective of the load can be recognized as spectra of environmental electromagnetic waves independent of the electric machine 1. The spectrum data items 3 representing the spectra a, d, e, g, and i alone are obtained as data items representing environmental-electromagnetic wave spectra.
When the spectrum data 3 concerning an environmental electromagnetic wave alone is excluded from each of the spectrum data items 1 and 2, spectrum data 4 representing a spectrum deriving from partial discharge occurring when the load is heavy, and spectrum data 5 representing a spectrum deriving from partial discharge occurring when the load is light can be obtained. Between the spectrum data items 4 and 5, the spectral positions (frequencies) are identical to each other but the levels are different from each other.
Now, the environmental electromagnetic waves whose spectra are represented by the spectrum data items 3 include mainly a broadcast wave for television or the like and communication waves sent to or from portable cellular phones or various types of wireless devices. Specific frequencies are assigned to the environmental electromagnetic waves in advance. In contrast, the frequency of an electromagnetic wave due to partial discharge from an electric machine is determined with an electrostatic capacitance or an inductance dependent on the structure, dimensions, or material of the electric machine, and with the length of a cable serving as a radiation antenna or a structure around a route along which the cable is laid down.
Referring to
As a statistical technique of grasping the tendency as a numerical value, a well-known correlation coefficient is utilized. More particularly, when a correlation coefficient indicating the correlation between the load factor and spectrum level is obtained by taking the graph of
As the correlation coefficient, a Pearson product-moment correlation coefficient can be utilized. In principle, the coefficient has no unit, and takes on a real number ranging from −1 to 1. When the coefficient is close to 1, two random variables are said to have a positive correlation. When the coefficient is close to −1, the random variables are said to have a negative correlation. When the coefficient is close to 0, the correlation between the random variables is feeble. In the case shown in
The correlation coefficient is obtained as mentioned above. In order to decide based on the calculated coefficient whether a spectrum is recognized as a spectrum of an environmental electromagnetic wave or a spectrum of an electromagnetic wave due to partial discharge, one or two values should be designated as a threshold for the recognition based on the correlation coefficient. For example, there is a method in which: assuming that α denotes the threshold, if a spectrum level is equal to or larger than α, a spectrum having the spectrum level is recognized as the spectrum of an electromagnetic wave due to partial discharge; and if the spectrum level falls below α, the spectrum having the spectrum level is not recognized as the electromagnetic waves due to partial discharge. Another method is such that: thresholds are set to two values α and β (β<α); a spectrum whose spectrum level is equal to or larger than a is recognized as the spectrum of an electromagnetic wave due to partial discharge; a spectrum whose spectrum level falls below β is recognized as the spectrum of an environmental electromagnetic wave; and a spectrum whose spectrum level falls below a and is equal to or larger than β is recognized as neither the spectrum of the environmental electromagnetic wave due to partial discharge not the spectrum of the environmental electromagnetic wave. Herein, the thresholds α and β are pre-determined for each electric machine.
In the data acquisition routine, first, at step S100, an electromagnetic wave is acquired from the sensor 11 at regular intervals. At step S101, spectrum analysis is carried out. At step S103, data is recorded in the data table. At step S102, load information concerning the electric machine is acquired synchronously with acquisition of spectrum data. The series of pieces of processing is repeated until a termination command is issued.
At step S103, when a certain number of data items has been recorded in the data table, the recognition routine of the succeeding stage is activated. In the recognition routine, first, at step S104, data of a spectrum that is an object of recognition, for example, the i-th data is selected from among plural spectrum data items acquired as shown in
Thereafter, at step S105, a load characteristic is analyzed as shown in
At step S106, a correlation coefficient R is calculated by utilizing, for example, the Pearson product-moment correlation coefficient. At steps S107 to S110, whether the spectrum a expresses an environmental electromagnetic wave or an electromagnetic wave due to partial discharge is decided based on the obtained correlation coefficient R. For the discrimination, a criterial threshold α and a criterial threshold β (where β<α) are preserved in advance. The criterial thresholds α and β are designated for each electric machine, and are normally set to 0.7 and about 0.3 respectively.
For the foregoing decision or recognition, first, at step S107, the correlation coefficient R is compared with the criterial threshold α predesignated for each electric machine. If the correlation coefficient R is larger than the threshold α, the electromagnetic-wave spectrum is recognized as a spectrum of an electromagnetic wave deriving from partial discharge (step S109). If the correlation coefficient R is smaller than the threshold α, the correlation coefficient R is compared with the other predesignated criterial threshold β at step S108. If the correlation coefficient R is smaller than the threshold β, the electromagnetic-wave spectrum is recognized as a spectrum of an environmental electromagnetic wave (step S110). Depending on spectrum data, neither the spectrum of an electromagnetic wave due to partial discharge nor the spectrum of an environmental electromagnetic wave may be recognized.
Finally, after recognition of one spectrum a is completed, the spectrum to be recognized next is dealt with at step S111, and the recognition routine is repeated. For example, the spectrum b shown in
As mentioned above, for each spectrum, the spectrum is recognized as a spectrum of an environmental electromagnetic wave or a spectrum of an electromagnetic wave due to partial discharge. Therefore, finally, the spectra are, as shown in
According to the technique described in
In a case shown in
As a spectrum whose level varies along with the passage of time, there is a spectrum SP3 whose level does not correlate with the change in the load. The spectrum SP3 is a spectrum of an illegal electromagnetic wave originating from mobility equipment or an electromagnetic wave generated from a machine which is different from the electric machine serving as an object and is operated nearby.
In the embodiment of the present invention shown in
Incidentally, transient electromagnetic waves include, for example, a radio wave from an aircraft flying over, a radio wave from a train running nearby, and a radio wave from a patrol car. The radio waves are legal electromagnetic waves whose use in a particular area is permitted. A method of discriminating the radio waves will be described in relation with another embodiment of the present invention. Briefly, through discrimination based on information on the location of an electric machine, a decision can be made that the radio waves are not electromagnetic waves due to partial discharge from the electric machine.
Next, a discussion will be made of an effect of the position of mobility equipment on a result of assessment by the unit in accordance with the present invention in a case where the unit in accordance with the present invention is used while being mounted in the mobility equipment.
In a use state shown in
In the embodiment of the present invention shown in
Next, a discussion will be made of how the position of rotative equipment affects a result of assessment made by the insulation diagnostic unit in accordance with the present invention in a case where the insulation diagnostic unit is used while being mounted in the rotative equipment.
In a use state shown in
In the case shown in
In the embodiment of the present invention shown in
The mobility equipment 21 is provided with a global positioning system (GPS) antenna 31, and thus receives signals from GPS satellites 32. A positional information detector 33 acquires information on the location of the mobility equipment 21. The mobility equipment 21 has an area-by-area electromagnetic-wave frequency table 34. In the table, electromagnetic-wave frequencies whose use is permitted are recorded in association with areas.
On receipt of the information from the positional information detector 33 and the information retrieved from the area-by-area electromagnetic-wave frequency table 34, an environmental electromagnetic wave extraction routine 35 acquires information B on a spectrum of an environmental electromagnetic wave propagated in an area where the mobility equipment exists. The information B is fetched into the signal processor 13. The signal processor 13 obtains, as described in conjunction with
An example of the mobility equipment described in the present embodiment is a train that runs a long distance of several hundreds of kilometers at a high velocity without a stop. Even when the train runs over areas in which different frequencies of electromagnetic waves are permitted to be used, an environmental electromagnetic wave permitted in an area where the train exists can be accurately grasped. This is effective in reducing a possibility that an electromagnetic wave deriving from partial discharge from an electric machine such as a mounted motor or converter may be missed. Another example of the mobility equipment is an automobile that runs on an expressway and uses electric power as a drive source. An environmental electromagnetic wave permitted to be used in an area where the automobile exists, and an electromagnetic wave due to partial discharge occurring in an electric machine mounted in the automobile can be properly separated or discriminated from each other.
In a square indicating the signal processor 13 in
According to the present invention, a state of deterioration of an electric machine can be continuously measured. Especially when the electric machine is mounted in mobility equipment, a situation of partial discharge can be grasped. Therefore, the present invention can be applied to diverse electric machines.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-013992 | Jan 2010 | JP | national |
