Patent Application
20220146593
The present invention relates to a short-circuit detection device and a short-circuit detection method for detecting a short circuit of a field winding of a rotating electric machine.
As a device configured to detect a short circuit of a field winding of a turbine generator being an example of a rotating electric machine, there has been proposed a device configured to detect a change of a field magnetic flux caused by the short circuit of the field winding by means of a magnetic flux detector, for example, a search coil, configured to detect a magnetic flux generated in an air gap between a rotor and a stator (see, for example, Patent Literature 1). Here, in contrast to a sound magnetic pole which is, of two magnetic poles of the rotor, one magnetic pole in which no short circuit has occurred, a short-circuit magnetic pole which is the other magnetic pole in which a short circuit has occurred is reduced in field magnetic flux amount due to reduction of the number of turns of the field winding. The device described in Patent Literature 1 is configured to use such a characteristic to detect this reduction in field magnetic flux amount, to thereby detect the occurrence of the short circuit.
[PTL 1] JP 58-005682 A
In this case, in the search coil aiming to detect the reduction in magnetic flux caused by the short circuit of the field winding, a main magnetic flux interlinks in addition to the field magnetic flux generated in a rotor slot. The main magnetic flux is caused by an interaction between the field magnetic flux and an armature reaction magnetic flux. The field magnetic flux generated in the rotor slot is a leakage magnetic flux flowing between adjacent rotor slots. Such a magnetic flux is hereinafter referred to as “rotor slot leakage magnetic flux.”
Accordingly, the magnetic flux reduction amount caused by the short circuit of the field winding is a magnetic flux amount corresponding to one short-circuit turn at most. In contrast, the rotor slot leakage magnetic flux caused by the remaining turns of the field winding is several times thereof corresponding to the number of turns for one slot, and further, the main magnetic flux is several hundred times thereof corresponding to the number of turns obtained by summing up the numbers of turns for several tens of slots. That is, a short-circuit signal and a noise signal which is several ten times to several hundred times of the short-circuit signal are superimposed on a search coil voltage signal. Accordingly, an accuracy of detecting the short circuit of the field winding may be degraded depending on a condition of the rotating electric machine.
The present invention has been made to solve the above-mentioned problems, and has an object to provide a short-circuit detection device and a short-circuit detection method with which a short circuit of a field winding can be detected with high accuracy.
According to one embodiment of the present invention, there is provided a short-circuit detection device including: a signal acquisition unit configured to acquire, from a magnetic flux detector configured to detect a magnetic flux generated in an air gap between a rotor and a stator of a rotating electric machine, a detection signal corresponding to the magnetic flux; a signal processing unit configured to subject the detection signal acquired by the signal acquisition unit to filtering of removing at least one component of odd-order components included in the detection signal, to thereby generate a filtered signal being the detection signal subjected to the filtering; and a short-circuit detection unit configured to detect a short circuit of a field winding of the rotating electric machine through use of the filtered signal generated by the signal processing unit.
According to one embodiment of the present invention, there is provided a short-circuit detection method including: a signal acquisition step of acquiring, from a magnetic flux detector configured to detect a magnetic flux generated in an air gap between a rotor and a stator of a rotating electric machine, a detection signal corresponding to the magnetic flux; a signal processing step of subjecting the detection signal acquired in the signal acquisition step to filtering of removing at least one component of odd-order components included in the detection signal, to thereby generate a filtered signal being the detection signal subjected to the filtering; and a short-circuit detection step of detecting a short circuit of a field winding of the rotating electric machine through use of the filtered signal generated in the signal processing step.
According to the present invention, it is possible to provide the short-circuit detection device and the short-circuit detection method with which the short circuit of the field winding can be detected with high accuracy.
Now, a short-circuit detection device and a short-circuit detection method according to each of preferred embodiments of the present invention are described with reference to the accompanying drawings. In the illustration of the drawings, the same components are denoted by the same reference symbols, and the overlapping description thereof is herein omitted.
First, the configuration of the turbine generator is described. As illustrated in
The field winding 13 is subjected to DC excitation from an external power supply so that the rotor core 11 is magnetized into two poles. In this manner, in the rotor core 11, two magnetic poles 14 are formed. In
In a stator core 21 of the stator 20, a plurality of stator slots 22 are formed. A multi-phase winding 23 is wound in the plurality of stator slots 22. The multi-phase winding 23 is subjected to AC excitation so that a rotation magnetic field is caused in the air gap 30. The turbine generator illustrated in
Now, with reference to
As illustrated in
Referring back to the description of
A short-circuit detection device 100 is connected to the search coil 24. The short-circuit detection device 100 includes a signal acquisition unit 101, a signal processing unit 102, and a short-circuit detection unit 103. The signal acquisition unit 101 is configured to acquire the search coil voltage signal from the search coil 24 as a detection signal. The signal processing unit 102 is configured to subject the detection signal acquired by the signal acquisition unit 101 to high-frequency filtering to be described later, to thereby generate and output a filtered signal. The short-circuit detection unit 103 is configured to calculate a waveform of a difference between the filtered signal output by the signal processing unit 102 and the filtered signal in a sound state stored in advance, and detect the short circuit of the field winding 13 from the calculated waveform of the difference.
As a hardware configuration of the short-circuit detection device 100 according to the first embodiment, for example, a configuration illustrated in
As illustrated in
Next, with reference to
A view in the upper stage of
The three-phase short-circuit condition is a condition in which a voltage generated between the terminals of the multi-phase winding 23 is zero, and a rated current flows through the multi-phase winding 23. As can be understood from
The iron loss condition is a condition in which a current flowing through the multi-phase winding 23 is zero, and a rated voltage is generated between the terminals of the multi-phase winding 23. As can be understood from
The rated load condition is a condition in which a rated voltage is generated between the terminals of the multi-phase winding 23, and a rated current flows through the multi-phase winding 23. As can be understood from
As can be understood from
Next, with reference to
As can be understood from
Next, with reference to
As illustrated in
In Step S12, the search coil voltage signal acquired in Step S11 is subjected to low-frequency filtering of cutting low frequencies caused by the armature reaction magnetic fluxes. Subsequently, the search coil voltage signal subjected to the low-frequency filtering is output as a filtered signal. As a filter for performing the low-frequency filtering, a low-frequency filter designed so as to cut the low frequencies caused by the armature reaction magnetic fluxes is used. After that, the processing proceeds to Step S13.
In Step S13, a short-circuit detection signal is generated by subtracting the filtered signal in the sound state from the filtered signal output in Step S12, and this short-circuit detection signal is output. After that, the processing proceeds to Step S14.
In Step S14, the occurrence of the short circuit and the position of the rotor slot 12 at which the short circuit has occurred are detected based on the feature of a peak or the like appearing in the short-circuit detection signal output in Step S13. After that, the processing is ended.
Next, with reference to
Further, as a condition of the low-frequency filtering to be performed on the search coil voltage signal, there is adopted a condition in which components of the rotor slot leakage magnetic fluxes included in the search coil voltage signal are sufficiently cut. Specifically, as the condition of the low-frequency filtering, there is adopted a condition in which a 24th order component and components having lower orders of the search coil voltage signal are cut. The number “24” given as a specific numerical example of the order of the filter is a numerical value selected for convenience so that rotor slot order components included in the search coil voltage signal can be sufficiently cut.
The search coil voltage signal mainly includes components caused by the armature reaction magnetic fluxes, and the rotor slot order components which are components caused by the rotor slot leakage magnetic fluxes. The components caused by armature reaction magnetic fluxes include a first-order component. The rotor slot order components are also called orders of space harmonics of the rotor slots 12. The rotor slot order components include a 47th order component and a 49th order component. The above-mentioned condition is determined in consideration of such points. The numbers “47” and “49” exemplified as specific numerical values are values uniquely determined by the specification of the rotor 10. The n-th order (n=1, 2, . . . ) herein is a component which varies “n” times in the horizontal axis of
In the case (I) illustrated in
The results illustrated in
Next, with reference to
As illustrated in
In Step S22, the signal processing unit 102 subjects the search coil voltage signal acquired in Step S21 to high-frequency filtering of removing at least one of main odd-order components of the rotor slot order components included in the search coil voltage signal. Subsequently, the signal processing unit 102 generates and outputs a filtered signal being the search coil voltage signal subjected to the high-frequency filtering. As a filter for performing the high-frequency filtering, a high-frequency filter designed so as to remove at least one of the main odd-order components of the rotor slot order components is used. After that, the processing proceeds to Step S23.
In Step S23, the signal processing unit 102 generates a short-circuit detection signal by subtracting the filtered signal in the sound state from the filtered signal output in Step S22, and outputs the short-circuit detection signal. After that, the processing proceeds to Step S24.
In Step S24, the short-circuit detection unit 103 detects the occurrence of the short circuit and the position of the rotor slot 12 at which the short circuit has occurred based on the feature of a peak or the like appearing in the short-circuit detection signal output in Step S23. After that, the processing is ended. As described above, the short-circuit detection unit 103 uses the filtered signal generated by the signal processing unit 102 to detect the short circuit of the field winding 13 of the turbine generator.
Next, with reference to
Meanwhile, as can be understood from
Next, with reference to
Further, as the condition of the high-frequency filtering performed on the search coil voltage signal, there is adopted a condition in which odd-order components having orders higher than the 24th order included in the search coil voltage signal are cut. The number “24” given as a specific numerical example of the order of the filter is a numerical value selected for convenience so that at least one component of the rotor slot order components included in the search coil voltage signal can be sufficiently cut. This condition is determined in consideration of the fact that the search coil voltage signal includes components which are caused by the armature reaction magnetic fluxes, and have the first order, and includes the rotor slot order components having the 47th and 49th orders. When the odd-order components having orders higher than the 24th order of the search coil voltage signal are cut, the rotor slot order components, that is, the rotor slot harmonics, can be sufficiently removed.
As can be understood from
It is effective to apply the short-circuit detection processing in the first embodiment to, for example, a specification in which the number of turns of the field winding 13 wound around the rotor slots 12 is large, a specification in which the number of rotor slots 12 is large, or the like. Further, it is also effective to apply the short-circuit detection processing in the first embodiment to an operation condition of the turbine generator in which the main magnetic fluxes are generated, an operation condition of the turbine generator in which a field current becomes relatively smaller than a current flowing through the multi-phase winding 23, or the like. Still further, it is also effective to apply the short-circuit detection processing in the first embodiment to a case in which a short circuit occurs in the rotor slot 12 present in the vicinity of the direction in which the magnetic flux flows, a case in which the search coil 24 is arranged close to the rotor surface, a case in which high-frequency noise of a measuring device itself is large due to an ambient environment, or the like.
As described above, according to the first embodiment, the short-circuit detection device 100 includes the signal acquisition unit 101, the signal processing unit 102, and the short-circuit detection unit 103. The signal acquisition unit 101 is configured to acquire, from the search coil 24 being an example of the magnetic flux detector configured to detect the magnetic flux generated in the air gap between the rotor 10 and the stator 20 of the rotating electric machine, the search coil voltage signal being an example of the detection signal corresponding to the magnetic flux. Further, the signal processing unit 102 is configured to subject the detection signal acquired by the signal acquisition unit 101 to filtering of removing at least one component of the odd-order components of the rotor slot order components included in the detection signal, to thereby generate the filtered signal being the detection signal subjected to the filtering. Further, the short-circuit detection unit 103 is configured to detect the short circuit of the field winding 13 through use of the filtered signal generated by the signal processing unit 102. In this manner, the short circuit of the field winding 13 can be detected with high accuracy. Specifically, regardless of the specification of the rotor 10 of the rotating electric machine, the operation condition of the rotating electric machine, the position of the slot in which the short circuit has occurred, the arrangement position of the search coil, and the like, the short circuit of the field winding can be detected with high accuracy even under a condition in which the detection of the short circuit has been difficult so far because of large main magnetic fluxes and large rotor slot leakage magnetic fluxes generated by the remaining field winding.
The configuration of the short-circuit detection device according to the first embodiment described above may be modified as follows.
As illustrated in
In Step S32, the signal processing unit 102 subjects the search coil voltage signal acquired in Step S31 to frequency analysis. After that, the processing proceeds to Step S33.
As described above, with the search coil voltage signal acquired in Step S31 being subjected to frequency analysis, even when the specification, for example, the number of turns of the field winding 13 of the turbine generator, is unclear, the orders of the rotor slot order components can be estimated from the main components. Further, in order to prevent erroneous detection of the short circuit, at least one of the odd-order components being a filter order capable of sufficiently separating the even-order components can be selected as appropriate. Further, through the frequency analysis, it can be determined which order component of the rotor slot order components is to be cut in the next step even without being designated by the user each time.
In Step S33, the signal processing unit 102 subjects the search coil voltage signal acquired in Step S31 to high-frequency filtering of removing at least one of main odd-order components of the rotor slot order components. Subsequently, the signal processing unit 102 outputs the search coil voltage signal subjected to the high-frequency filtering as a filtered signal. After that, the processing proceeds to Step S34. In this manner, the signal processing unit 102 subjects the detection signal to frequency analysis, and performs the filtering of removing at least one component of odd-order components included in the detection signal subjected to the frequency analysis.
In Step S34, the signal processing unit 102 generates a short-circuit detection signal by subtracting the filtered signal in the sound state from the filtered signal output in Step S33, and outputs the short-circuit detection signal. After that, the processing proceeds to Step S35.
In Step S35, the short-circuit detection unit 103 detects the occurrence of the short circuit and the position of the rotor slot 12 at which the short circuit has occurred based on the feature of a peak or the like appearing in the short-circuit detection signal output in Step S34. After that, the processing is ended.
The configuration of the short-circuit detection device according to the first embodiment described above may be modified as follows. In a third embodiment of the present invention, the rotation of the rotor 10 is used to detect the short-circuit slot through use of the detection signal of the short-circuit magnetic pole in which the short circuit of the field winding 13 has occurred and the detection signal of the sound magnetic pole in which no short circuit of the field winding 13 has occurred.
A first modification example of the present invention is as follows. That is, the signal acquisition unit 101 of the short-circuit detection device 100 uses the rotation of the rotor 10 to acquire, from the search coil 24, each of the detection signal of the sound magnetic pole and the detection signal of the short-circuit magnetic pole. Subsequently, the signal processing unit 102 subjects each of those two detection signals to high-frequency filtering, to thereby output two filtered signals. The short-circuit detection unit 103 compares the two filtered signals with each other, to thereby detect the short circuit of the field winding 13. In this manner, the signal processing unit 102 generates a delay signal obtained by delaying a current filtered signal by a phase of 180 degrees in an electrical angle. Further, the short-circuit detection unit 103 compares the current filtered signal and the delay signal with each other, to thereby detect the short circuit of the field winding 13.
A second modification example of the present invention is as follows. That is, the signal acquisition unit 101 of the short-circuit detection device 100 acquires, from the search coil 24, a current detection signal and a past detection signal which is continuous or non-continuous from the current detection signal. The signal processing unit 102 outputs a current filtered signal and a past filtered signal obtained by subjecting the current detection signal and the past detection signal to high-frequency filtering, respectively. The short-circuit detection unit 103 compares the two filtered signals with each other, to thereby detect the short circuit of the field winding 13. In this manner, the short-circuit detection unit 103 compares a current filtered signal with a past filtered signal which is continuous or non-continuous from the current filtered signal, to thereby detect the short circuit of the field winding 13.
A third modification example of the present invention is as follows. That is, in the two-pole rotating electric machine, two search coils 24 are fixed and mounted at positions of the air gap 30 opposed to each other by 180 degrees. The signal acquisition unit 101 of the short-circuit detection device 100 acquires two detection signals from the two search coils 24, respectively. The signal processing unit 102 subjects each of the two detection signals to high-frequency filtering, to thereby output two filtered signals. The short-circuit detection unit 103 compares the two filtered signals with each other, to thereby detect the short circuit of the field winding 13. In this manner, the signal acquisition unit 101 acquires the detection signal from each of the plurality of search coils 24 arranged at positions different from each other by a phase of 180 degrees or more in an electrical angle. Further, the short-circuit detection unit 103 compares filtered signals corresponding to respective detection signals generated by the signal processing unit 102 with each other, to thereby detect the short circuit of the field winding 13.
The configuration of the short-circuit detection device according to the first embodiment described above may be modified as follows. In a fourth embodiment of the present invention, when the field winding 13 is short-circuited with a contact resistance being zero, as in the above-mentioned electromagnetic analysis, a magnetic flux corresponding to one turn is reduced. When the contact resistance is not zero, the magnetic flux reduction amount is less than that corresponding to one turn. Moreover, the magnetic flux reduction amount is different even with the same short-circuit condition between a rated load state and an intermediate load state of the field current.
As in those examples, when a threshold value having a certain value is provided, the short-circuit detection may become difficult. The signal subjected to the above-mentioned filtering has a good SN ratio, and regardless of the magnitude of the absolute value thereof, the short-circuit detection signal is clear. Accordingly, any of the signal subjected to the filtering by the signal processing unit 102 or the short-circuit detection signal generated by the signal processing unit 102 is subjected to signal amplification. As described above, the signal processing unit 102 is configured to amplify the filtered signal. In this manner, the short circuit of the field winding 13 can be easily determined based on the SN ratio or the count number of the short-circuit detection signal. When at least one component of even-order components caused by the short circuit of the field winding 13 is amplified, the change caused by the short circuit can be emphasized with respect to the odd-order components.
The first to fourth embodiments have been described as examples of the present invention, but the present invention is not limited to the configurations of the first to fourth embodiments. Within the scope not deviating from the gist of the present invention, the configurations of the first to fourth embodiments can be combined as appropriate, or can be modified partially or omitted partially.
10 rotor, 11 rotor core, 12 rotor slot, 13 field winding, 14 magnetic pole, 20 stator, 21 stator core, 22 stator slot, 23 multi-phase winding, 24 search coil, 30 air gap, 41 magnetic pole center direction, 42 inter-pole center direction, 100 short-circuit detection device, 101 signal acquisition unit, 102 signal processing unit, 103 short-circuit detection unit, 200 processor, 300 storage device
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/015984 | 4/12/2019 | WO | 00 |
