Short circuit detection device and short circuit detection method for rotating electrical machine

Abstract

The invention is structured to include: a difference calculation unit (44) for calculating the difference between a measured value of a voltage or impedance of an excitation winding through which an AC excitation current flows and a value when the AC excitation current flows when the excitation winding is in a good state; and a short-circuit state analysis unit (45) for comparing the difference when the AC excitation current flows at a first frequency with a threshold value, and when the difference is smaller than the threshold value, estimating the short-circuit resistance (R) from the difference value based on data indicating the relationship between the short-circuit resistance (R) and the difference value at the first frequency, and when the difference is greater than the threshold value, causing an excitation power source (2) to cause an AC excitation current to flow through the excitation winding at a second frequency lower than the first frequency, and estimating the short-circuit resistance (R) from the difference value obtained using the AC excitation current at the second frequency based on data indicating the relationship between the short-circuit resistance (R) and the difference value at the second frequency.

Description

Technical Field

[0001] The present application relates to a short circuit detection device and a short circuit detection method for a rotating electrical machine. Background Art

[0002] There is disclosed a device or method for detecting the occurrence of a short circuit by calculating impedance based on the voltage and current when an AC excitation current is passed through an excitation winding in a rotating electrical machine such as a turbine generator (see, for example, Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-506686 (Paragraphs 0022 to 0034, Figure 1 Figure 4) Summary of the Invention

[0006] Technical issues to be solved by the invention

[0007] However, conventional impedance calculation methods have low accuracy and only determine whether a short circuit has occurred, making it difficult to quantitatively determine the short circuit state.

[0008] The present application discloses a technology for solving the above-mentioned technical problems, and aims to quantitatively evaluate a short-circuit state in a rotating electrical machine.

[0009] Technical solutions to solve technical problems

[0010] The short-circuit detection device disclosed in the present application is characterized by comprising: an excitation power supply for passing an AC excitation current at a predetermined frequency through an excitation winding provided in a rotating electrical machine; a difference calculation unit for calculating a difference between a measured value of a voltage or impedance of the excitation winding when the AC excitation current is flowing and a value when the AC excitation current is flowing in a good state; and a short-circuit state analysis unit for comparing the difference when the AC excitation current is flowing at a first frequency with a threshold value. If the difference is less than the threshold value, the short-circuit resistance is estimated from the difference based on data indicating a relationship between the short-circuit resistance and the difference at the first frequency, the short-circuit resistance being an indicator of the degree of short circuiting occurring between layers of the excitation winding. If the difference is greater than the threshold value, the excitation power supply is caused to pass the AC excitation current through the excitation winding at a second frequency lower than the first frequency, and the short-circuit resistance is estimated from the difference obtained using the AC excitation current at the second frequency based on data indicating a relationship between the short-circuit resistance and the difference at the second frequency.

[0011] In addition, the short-circuit detection method for a rotating electric machine disclosed in the present application is characterized in that it includes: an excitation step of causing an AC excitation current to flow through an excitation winding provided in the rotating electric machine at a predetermined frequency; a difference calculation step of calculating the difference between a measured value of a voltage or impedance of the excitation winding through which the AC excitation current flows and a value when the AC excitation current flows when the excitation winding is in a good state; and a short-circuit state analysis step of estimating a short-circuit resistance based on the difference, the short-circuit resistance being an indicator of the degree of short circuit generated between layers of the excitation winding, wherein in the short-circuit state analysis step, The difference when an AC excitation current flows at a first frequency is compared with a threshold value. When the difference is smaller than the threshold value, the short-circuit resistance is estimated from the difference based on data indicating the relationship between the short-circuit resistance and the difference at the first frequency. When the difference is greater than the threshold value, the excitation step is performed at a second frequency lower than the first frequency, and the short-circuit resistance is estimated from the difference obtained using the AC excitation current at the second frequency based on data indicating the relationship between the short-circuit resistance and the difference at the second frequency.

[0012] Effects of the Invention

[0013] According to the short-circuit detection device or the short-circuit detection method for a rotating electrical machine disclosed in the present application, since the short-circuit resistance is estimated based on the correlation with the frequency, quantitative evaluation of the short-circuit state is possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram showing the structure of the short-circuit detection device according to the first embodiment.

[0015] Figure 2 This is a schematic diagram modeling the state within the winding when an AC excitation current flows through the field winding of a two-pole rotating electrical machine in which a short circuit occurs at one pole.

[0016] In Figure 3 Figure 3A and Figure 3B Graphs showing the relationship between short-circuit resistance and each pole voltage and the relationship between short-circuit resistance and the voltage difference between the two poles as analysis results when an AC excitation current is passed through the field winding at a first frequency in a modeled rotating electrical machine.

[0017] In Figure 4 Figure 4A and Figure 4B Graphs showing the relationship between short-circuit resistance and each pole voltage and the relationship between short-circuit resistance and the voltage difference between the two poles as analysis results when an AC excitation current is passed through the field winding at a second frequency in a modeled rotating electrical machine.

[0018] In Figure 5 Figure 5Aand Figure 5B This graph shows the relationship between the short-circuit resistance and the voltage difference between the two poles, which is the analytical result when an AC excitation current flows through the excitation winding at a first frequency in a modeled rotating electrical machine, normalized by the maximum voltage difference and displayed in the form of a graph with normal coordinates and a double logarithmic coordinate system.

[0019] In Figure 6 Figure 6A and Figure 6B This graph shows the relationship between the short-circuit resistance and the voltage difference between the two poles, which is the analytical result when an AC excitation current flows through the excitation winding at a second frequency in a modeled rotating electrical machine, normalized by the maximum voltage difference and displayed in the form of a graph with normal coordinates and a double logarithmic coordinate system.

[0020] Figure 7 This figure shows the correlation between the normalized voltage difference and the estimated short-circuit resistance using a mathematical formula obtained by simplifying the modeled rotating electrical machine according to the situations classified according to the degree of influence of impedance and reactance in the short-circuit detection device and the short-circuit detection method for the rotating electrical machine according to the first embodiment.

[0021] Figure 8 This is a flowchart for explaining the operation of the short-circuit detection device and the short-circuit detection method for a rotating electrical machine according to the first embodiment.

[0022] Figure 9 This is a block diagram showing a hardware configuration of a control unit of the short-circuit detection device according to the first embodiment or for executing the short-circuit detection method for a rotating electrical machine.

[0023] Reference numerals

[0024] 1: Short-circuit detection device; 2: Excitation power supply; 3: Measuring unit; 4: Control unit; 41: Frequency setting unit; 42: Measurement value calculation unit; 43: Data holding unit; 44: Difference calculation unit; 45: Short-circuit status analysis unit; 9: Rotor; 9c: Iron core; 9p1: 1st pole; 9p2: 2nd pole; 9s: Slot; R: Short-circuit resistance. DETAILED DESCRIPTION

[0025] Implementation method 1.

[0026] Figures 1 to 8 1 is a diagram for explaining a short-circuit detection device and a short-circuit detection method for a rotating electrical machine according to a first embodiment. Figure 1 This is a schematic diagram showing the structure of a short-circuit detection device together with the rotor of a rotating electrical machine to be evaluated. Figure 2 This is a schematic diagram modeling the state inside the winding when an AC excitation current flows through the excitation winding of the rotor of a two-pole rotating electrical machine in which one pole is short-circuited.

[0027] In addition, FIG3 is a graph showing the Figure 2 The analytical results when the AC excitation current flows through the excitation winding at the first frequency of 6000 Hz in the model, that is, the relationship between the short-circuit resistance and the voltage of each pole ( Figure 3A ) and the relationship between the short-circuit resistance and the voltage difference between the two poles ( Figure 3B ) of the figure, Figure 4 is also in Figure 2 3 when the AC excitation current flows through the excitation winding at the second frequency of 60 Hz in the model, Figure 4A This is a graph showing the relationship between short-circuit resistance and voltage at each electrode. Figure 4B This is a graph showing the relationship between short-circuit resistance and the voltage difference between the two electrodes.

[0028] Then, Figure 5 shows the maximum voltage difference. Figure 3B The relationship between the short-circuit resistance and the voltage difference between the two electrodes is normalized and shown in the form of a normal coordinate curve diagram ( Figure 5A ) and a graph in the form of a double logarithmic coordinate graph ( Figure 5B ), Figure 6 shows the maximum voltage difference Figure 4B The relationship between the short-circuit resistance and the voltage difference between the two electrodes is normalized and shown in the form of a normal coordinate curve diagram ( Figure 6A ) and a graph in the form of a double logarithmic coordinate graph ( Figure 6B ).and then, Figure 7 To show the simplified mathematical formula corresponding to the three cases divided according to the degree of influence of impedance and reactance, Figure 5B and Figure 6B The graph of the correlation between the normalized voltage difference and the estimated short-circuit resistance is shown in FIG. Figure 8 This is a flowchart for explaining the operation of the short-circuit detection device and the short-circuit detection method for a rotating electrical machine.

[0029] use Figure 1 The structure of the short-circuit detection device 1 according to the first embodiment will be described. Before describing the short-circuit detection device 1 in detail, the rotor 9 of a turbine generator, which is a rotating electrical machine to be evaluated for short circuits, will be described. The rotor 9 includes a shaft 9a, an iron core 9c rotatably supported about the shaft 9a, and a plurality of slots 9s provided on the outer circumference of the iron core 9c (in the figure, some of the slots from the first slot 9s-1 to the 24th slot 9s-24 are designated with individual reference numerals).

[0030] While there are no limitations on the number of slots or poles, for simplicity of explanation, this first embodiment uses a 24-slot, two-pole rotor 9 as an example. The odd-numbered slot groups of the slots 9s, from the first slot 9s-1 to the 23rd slot 9s-23, are arranged counterclockwise over a quarter of a circumference. The even-numbered slot groups, from the second slot 9s-2 to the 24th slot 9s-24, are arranged clockwise over a quarter of a circumference, facing the odd-numbered slot groups.

[0031] Furthermore, a series-connected field winding is wound and housed in each slot 9s, from the 1st slot 9s-1 to the 24th slot 9s-24. Consequently, the core 9c is divided into a first pole 9p1 (left side in the figure) comprising the 1st slot 9s-1 to the 11th slot 9s-11 and the 2nd slot 9s-2 to the 12th slot 9s-12, and a second pole 9p2 (right side in the figure) comprising the 13th slot 9s-13 to the 23rd slot 9s-23 and the 14th slot 9s-14 to the 24th slot 9s-24.

[0032] The short-circuit detection device 1 of the first embodiment includes an excitation power supply 2 for flowing an AC excitation current through the field winding of a rotating electrical machine; a measuring unit 3 for detecting a signal indicating the current flowing through the field winding and a signal indicating the voltage between the terminals; and a control unit 4 for setting test conditions and analyzing short-circuit conditions. The excitation power supply 2 is connected to both ends of the field winding wound around slots 9s (the first slot 9s-1 portion and the 24th slot 9s-24 portion). While the measuring unit 3 is shown connected to both ends of the field winding of the first pole 9p1 (the first slot 9s-1 portion and the 12th slot 9s-12 portion), when detecting a short circuit, it is also connected sequentially to the remaining poles (the second pole 9p2).

[0033] The control unit 4 includes a frequency setting unit 41 for setting the excitation frequency of the excitation power supply 2; a measured value calculation unit 42 for calculating measured values ​​of the impedance and voltage of the excitation winding in units of poles based on the signal detected by the measurement unit 3; and a difference calculation unit 44 for calculating the difference between the measured values. It also includes a short-circuit state analysis unit 45 for quantitatively evaluating the short-circuit resistance based on a correlation selected from the data stored in the data storage unit 43 based on the calculated difference and the excitation frequency. Furthermore, although it will be described later that the short-circuit state analysis unit 45 instructs the frequency setting unit 41 to set the frequency based on the analysis results, it can also be interpreted that the frequency setting unit 41 is included in the short-circuit state analysis unit 45. The details of the calculation content will be explained together with the description of the operation.

[0034] Here, the above-mentioned rotating motor is as follows Figure 2As shown in the model, it is assumed that the excitation winding of the first pole 9p1 is not short-circuited (hereinafter referred to as the "intact pole"), while the excitation winding of the second pole 9p2 (the portion of slot 9s-13) is short-circuited (hereinafter referred to as the "short-circuited pole"). The excitation winding of each slot 9s is wound with multiple turns, such as the first turn 9st-1 to the nth turn 9st-n in the first slot 9s-1. The state is then shown where a short-circuit site Psc, where a short circuit occurs between turns, exists within the excitation winding of the 13th slot 9s-13 of the short-circuited pole (second pole 9p2).

[0035] In this state, when an AC excitation current is passed through the field winding using an excitation power supply, the excitation current from the excitation power supply flows through the remaining turns of the field winding, excluding the turns where the short-circuit point Psc occurs. Excitation flux flows through the leakage flux path within the iron core 9c and at the ends of the field winding. The excitation flux also intersects with the short-circuit circuit (short-circuit point Psc), generating a large short-circuit current in the short-circuit circuit and generating a counter-magnetic flux that cancels the excitation flux. Because the voltage at the short-circuited pole is reduced compared to the intact pole by the amount of excitation flux canceled by the counter-magnetic flux, prior art documents and other publications disclose methods for detecting the presence of a short circuit by detecting the difference in voltage or impedance between the two poles.

[0036] However, the voltage difference or impedance difference caused by a short circuit includes not only a resistance component but also a reactance component. For example, at relatively high excitation frequencies, fluctuations in the reactance component dominate in regions with low resistance, while fluctuations in the resistance component dominate in regions with relatively high short-circuit resistance. In other words, the difference (voltage difference, impedance difference) between the intact and short-circuited poles caused by a short circuit depends on the excitation frequency and the short-circuit resistance at the time of the short circuit, and is not necessarily clearly expressed. In other words, when any of these conditions differ, different differences occur even under the same short-circuit conditions, leading to problems with short-circuit detection accuracy, such as false detections based on values ​​significantly different from the threshold.

[0037] On the other hand, the inventors of the present application have discovered that the way a voltage difference (or impedance difference) appears with respect to a short-circuit resistance varies depending on the excitation frequency. Specifically, at high frequencies, quantification is difficult due to the need for separation from the reactance component as described above. However, even high-resistance short circuits can be detected, enabling complete short circuit detection. Meanwhile, at low frequencies, even if a short circuit occurs, the voltage difference is small, potentially allowing for the possibility of missing a high-resistance short circuit. However, the influence of the reactance component is minimal, and the short-circuit resistance and voltage difference are inversely proportional, making quantification easy.

[0038] In other words, it was discovered that by switching the excitation frequency for measurement, the short-circuit resistance, an indicator of the degree of short circuiting between turns (or layers) of the field winding, can be quantitatively evaluated with high precision, regardless of its magnitude. Therefore, according to the short-circuit detection device 1 or the short-circuit detection method for a rotating electrical machine of the first embodiment, a function for calculating the short-circuit resistance based on a voltage difference (or impedance difference) is switched in accordance with the excitation frequency, thereby quantitatively estimating the short-circuit resistance. Since the short-circuit resistance can be quantitatively estimated, it is possible to monitor the temporal changes in the short-circuit state and to determine the usable period until a problem such as heat generation occurs.

[0039] Regarding this feature, Figure 2 This article describes the relationship between the voltage at each pole, or the voltage difference, and the short-circuit resistance when AC excitation current flows through the field winding of the model shown. Using the short-circuit resistance as a parameter, the voltage at each pole is analytically calculated for eight conditions with varying short-circuit resistance.

[0040] Due to the dependence of the reactance component in the excitation winding circuit on the excitation frequency, at frequencies of 6000Hz and 60Hz, the voltages of the poles on the vertical axis ( Figure 3A and Figure 4A ) and voltage difference ( Figure 3B and Figure 4B Furthermore, to be precise, the reactance component is affected by both the skin depth within the core 9c and the magnetic resistance of the leakage flux through the non-magnetic material portion including the air region, so it is not completely proportional to the excitation frequency.

[0041] In any case, since the absolute values ​​of the voltage and voltage difference on the vertical axis vary depending on the excitation frequency, it is known that simply comparing with the threshold value may result in false detection depending on the measured excitation frequency. Furthermore, in order to study the voltage difference in detail, the relative value of the voltage difference at the analysis point under the condition of minimum short-circuit resistance is re-plotted. Figure 3B 、 Figure 4B 5 and 6 showing the relationship between the short-circuit resistance and the voltage difference.

[0042] In Figures 5 and 6, only Figure 3B 、 Figure 4B The voltage difference in the image is converted to a relative value and redrawn in normal coordinates. Figure 5A and Figure 6A By comparison, the difference in the properties of the interpolation function Ei obtained by interpolating the 8 analytical points Pa is not clear. However, when the two points are plotted in double logarithmic coordinates, Figure 5A and Figure 6A And get Figure 5B and Figure 6B When compared, it can be seen that the relationship between short-circuit resistance and voltage difference is different at 6000 Hz and 60 Hz.

[0043] exist Figure 5B With the 6000 Hz AC excitation current shown, a large short-circuit current flows through the low-resistance region RdL of the short-circuit circuit. As the impedance of the excitation winding circuit becomes dominated by the reactance component rather than the resistance component, the voltage difference remains approximately constant and large regardless of the magnitude of the short-circuit resistance. In contrast, in the region Rcr, where the resistance is higher than region RdL, the resistance component is not negligible, and only a small amount of short-circuit current flows. Consequently, the voltage difference becomes more dependent on the short-circuit resistance, decreasing as the short-circuit resistance increases.

[0044] On the other hand, Figure 6B With the 60Hz AC excitation current shown, the excitation frequency is low, so regardless of the short-circuit resistance, the voltage difference remains inversely proportional to the short-circuit resistance Rdr throughout the entire region. This is because the impedance of the excitation winding circuit is dominated by the resistive component, rather than the reactive component.

[0045] When the short-circuit resistance is set to R and the relative value of the voltage difference is set to Z, the interpolation function Ei shared by Figures 5 and 6 can be expressed as Figure 7 The polynomial shown in (Equation (E1)). In addition, in Equation (E1), A n , Bn, C n , Dn is any real number.

[0046] Here, in the region Rdr where the resistance component is dominant at low frequencies, C n =0 and D n = -1, so Z can be expressed by the function (3) which is inversely proportional to the short-circuit resistance R. On the other hand, when A depends on the reactance at high frequencies n = 0. In this case, in the region RdL where the short-circuit resistance R is small, Z can be represented by function (1) which is a constant value, and in the region Rcr where the short-circuit resistance R is large, Z can be represented by function (2) in which the voltage difference decreases exponentially as the short-circuit resistance increases.

[0047] That is, formula (E1) can universally express the relationship between the voltage difference or impedance difference and the short-circuit resistance in the range of 60 to 6000 Hz where the influence of the reactance component and the resistance component changes. That is, by preparing the comparison data in advance as mathematical formula data or numerical data, the short-circuit resistance can be quantitatively estimated based on the voltage difference, impedance difference, etc. measured by switching the excitation frequency. Furthermore, by performing multi-point measurements at multiple excitation frequencies simultaneously, the estimation accuracy of the short-circuit resistance can be improved even for voltage differences and impedance differences with different absolute values. In addition, Z in formula (E1) is not limited to the voltage difference, and the short-circuit resistance can be similarly evaluated even if it is converted to an impedance difference.

[0048] Next, refer to Figure 8 The flowchart of the description explains the operation of the short-circuit detection device 1 constructed based on the above-mentioned insights, that is, the short-circuit detection method of the rotating electrical machine. First, based on the instruction from the short-circuit state analysis unit 45, the frequency setting unit 41 sets the excitation frequency to 6000 Hz as the frequency on the high-frequency side with high short-circuit sensitivity (first frequency). The excitation power supply 2 allows the AC excitation current to flow through the excitation winding at the set first frequency (step S10). Then, the measuring unit 3 detects a signal representing the current value at this time from the excitation power supply 2, and detects a signal representing the voltage value generated at each pole of the first pole 9p1 and the second pole 9p2 from the connected terminals (step S20). At this time, it can be as follows Figure 1 The measurement is shown for each pole, but it is also possible to measure both poles simultaneously.

[0049] The measured value calculation unit 42 calculates the impedance of each of the two electrodes using the current signal and the voltage signal output from the measuring unit 3, and the difference calculation unit 44 calculates the difference (step S30). Figure 2 As explained in [1], when only one pole (the short-circuited pole) is short-circuited, a voltage difference occurs between the poles, allowing the impedance difference to be calculated. However, in the case of high-frequency excitation, as described above, even if the short-circuit degree is small (the short-circuit resistance is large), a significant impedance difference (voltage difference) will appear. Therefore, even if the acquired signal contains some noise, short circuits can be detected without omission. However, when the short-circuit resistance is small, it is difficult to separate it from the reactance component, making it unsuitable for quantifying the short-circuit resistance. Therefore, the short-circuit state analysis unit 45 compares the calculated impedance difference (or voltage difference) with the threshold value (step S40).

[0050] Regarding the threshold, for example, Figure 5BIn this way, the difference value corresponding to the inflection point of the reactance component and the resistance component of the short-circuit circuit when the short-circuit resistance is plotted on the horizontal axis and the difference value is plotted on the vertical axis. Alternatively, the difference value can be set to the boundary between the region Rcr where the difference value clearly changes in accordance with the change in short-circuit resistance and the region where it is unclear. Furthermore, the difference value on the high-frequency side can be set to the upper limit of the short-circuit resistance, where the fluctuation of the measured value due to noise, etc. on the low-frequency side is small and the short-circuit resistance can be accurately estimated.

[0051] If the calculated difference is equal to or exceeds the threshold value set in this manner, the short-circuit resistance can be accurately estimated based on the measurement results using the high-frequency AC excitation current. On the other hand, if the difference is less than the threshold value, the estimation based on the measurement value using the low-frequency excitation current is appropriate.

[0052] Therefore, if the difference is less than the threshold value ("No" in step S40), the difference in impedance under the 6000 Hz AC excitation current is applied to the above-mentioned function (2) to estimate the short-circuit resistance (step S50). Alternatively, it is also possible to estimate how much short-circuit resistance has occurred in the short-circuit pole by comparing it with analytical data or measurement data previously stored in a data table or the like as the relationship between the short-circuit resistance and the difference. Then, based on the estimated value, the calculation of the usage period or the fault determination is performed (step S100), and the short-circuit status such as the estimated value is displayed on a display unit (not shown) (step S200), and the process ends.

[0053] On the other hand, if the difference is greater than the threshold ("YES" in step S40), the short-circuit state analysis unit 45 instructs the frequency setting unit 41 to set a low frequency of 60 Hz as the low-frequency side frequency (second frequency) to perform a quantitative assessment in the high-resistance region. The excitation power supply 2 switches the excitation frequency to the set second frequency, allowing AC excitation current to flow through the excitation winding (step S60). Then, similar to steps S20-S30, the current value at the second frequency and the voltage values ​​generated at the first pole 9p1 and the second pole 9p2 are detected (step S70). Based on the detected values, the impedance of each pole is calculated (step S80).

[0054] At the second frequency, since only one pole (the short-circuited pole) is short-circuited, a voltage difference is generated between the poles, and the impedance difference can be calculated. Furthermore, at the second frequency, the short-circuit resistance is inversely proportional to the impedance difference or voltage difference, so by applying the obtained difference to function (3), the short-circuit resistance can be accurately and quantitatively evaluated (step S90). At the second frequency, it is also possible to estimate how much short-circuit resistance has occurred in the short-circuited pole by comparing it with the analytical data or measurement data that has been previously stored in a data table as the relationship between the short-circuit resistance and the difference. Then, based on the estimated value, calculation or fault judgment during use is performed (step S100), and the short-circuit condition such as the estimated value is displayed on the display unit (not shown) (step S200) and the process ends.

[0055] The above operation description illustrates an example in which, based on a model in which one electrode is intact and the other is short-circuited, the measurement unit 3 calculates a measured value, such as a voltage or impedance, for each of the intact and short-circuited electrodes, and the difference calculation unit 44 estimates the short-circuit resistance based on the difference between the calculated measured values. However, this is not limiting. For example, measurement data or analysis data from the initial operation state may be stored in the data storage unit 43, and the difference calculation unit 44 may estimate the short-circuit resistance of each electrode based on the difference between the stored data and the measured values.

[0056] As described above, the short-circuit detection device 1 or the short-circuit detection method for a rotating electrical machine according to Embodiment 1 can quantitatively estimate short-circuit resistance. This makes it possible to select the timing for scheduled maintenance or perform priority maintenance, thereby enabling stable operation of the rotating electrical machine. This method is particularly effective in applications where continuous abnormality monitoring is required, where a stoppage of a rotating electrical machine due to a fault could significantly adversely affect power infrastructure, and where maintenance frequency is limited in remote areas or when a large number of rotating electrical machines are used.

[0057] In the short-circuit detection device 1 of the first embodiment, when the portion that performs calculation or control (eg, the control unit 4) is indicated as hardware 10, as an example, Figure 9 As shown, the hardware 10 includes a processor 101 and a storage device 102. The storage device 102 is similar to the data holding unit 43 and includes a volatile storage device such as a random access memory (not shown) and a non-volatile auxiliary storage device such as a flash memory. Alternatively, an auxiliary storage device such as a hard disk may be provided instead of the flash memory. The processor 101 executes a program input from the storage device 102. In this case, the program is input from the auxiliary storage device to the processor 101 via the volatile storage device. In addition, the processor 101 can output data such as calculation results to the volatile storage device of the storage device 102, or can store data in the auxiliary storage device via the volatile storage device.

[0058] In addition, this application describes various illustrative embodiments and examples, but the combination of various features, forms, and functions described in the embodiments is not limited to the contents described as embodiments, and can be applied alone or in various combinations. Therefore, within the technical scope disclosed in this specification, countless unillustrated variations are envisioned. For example, this includes the case where at least one component is deformed, added, or omitted, and also includes the case where at least one component is extracted and the combination is changed.

[0059] Specifically, the excitation frequency is not limited to the above-mentioned combination of 60 Hz and 6000 Hz, but can be appropriately changed within the limited range of the diagnostic object device. For example, it is preferably a combination of the base frequency (60 Hz) and a frequency corresponding to n times (100 times in this example) thereof. Furthermore, it is not limited to two types, but can be three or more. In addition, although an example is shown in which the range of quantitative evaluation at each frequency is allocated in a selective manner according to whether the difference is greater than a threshold, it is not limited to this. For example, it can also be set to estimate the short-circuit resistance at each frequency of the two frequencies in an area close to the threshold, and change the weight according to the distance from the threshold. In addition, as a diagnostic object, the structure of the rotating electrical machine is not limited to two poles, nor is it limited to a generator. In addition, it is not limited to a rotor, and it can also be a stator as long as an excitation winding is wound thereon. Furthermore, the short-circuit resistance can also be estimated in units of slots instead of poles.

[0060] As described above, the short-circuit detection device 1 according to the embodiment is configured to include: an excitation power supply 2 for passing an AC excitation current through an excitation winding provided in a rotating electrical machine (e.g., a rotor 9) at a predetermined frequency; a difference calculation unit 44 for calculating the difference between a measured value of a voltage or impedance of the excitation winding through which the AC excitation current flows and a value when the AC excitation current flows when the excitation winding is in a good state; and a short-circuit state analysis unit 45 (including a frequency setting unit 41) for comparing the difference when the AC excitation current flows at a first frequency (6000 Hz) with a threshold value, and, if the difference is smaller than the threshold value, performing a short-circuit state analysis based on the difference between the short-circuit resistance R and the difference. Based on data indicating the relationship at a first frequency (e.g., function (2)), a short-circuit resistance R is estimated based on the difference, which is an indicator of the degree of short circuit generated between layers of the excitation winding. When the difference is greater than a threshold value, the excitation power supply 2 causes an AC excitation current to flow through the excitation winding at a second frequency (60 Hz) lower than the first frequency. Based on data indicating the relationship between the short-circuit resistance R and the difference at a second frequency (e.g., function (3)), the short-circuit resistance R is estimated based on the difference obtained using the AC excitation current at the second frequency. This makes it possible to quantitatively evaluate the short-circuit state in the rotating electrical machine over a wide range of short-circuit resistance values.

[0061] In this case, if the short-circuit state analysis unit 45 is configured to predict the usable period of the rotating electrical machine based on the estimated value of the short-circuit resistance R, it is possible to select the timing for regular maintenance or perform priority maintenance, thereby enabling stable operation of the rotating electrical machine. This is particularly effective in applications where continuous abnormality monitoring is required, such as where a stoppage of the rotating electrical machine due to a fault could significantly adversely affect power infrastructure, or in remote areas or applications where the frequency of maintenance is limited, for example.

[0062] Furthermore, if the short-circuit state analysis unit 45 diagnoses that a short circuit has occurred in the rotating electrical machine when the estimated value of the short-circuit resistance R is lower than the lower limit value, repair / maintenance can be performed and the rotating electrical machine can be used with confidence.

[0063] In addition, if the differential calculation unit 44 calculates the difference between the measured values ​​of the voltage or impedance of each interval (for example, the first pole 9p1 part and the second pole 9p2 part) obtained by dividing the excitation winding into multiple sections as the difference value, the short-circuit resistance can be easily estimated even when there is no past data or it is difficult to form analytical data.

[0064] Furthermore, as described above, the short-circuit detection method for a rotating electrical machine according to the embodiment includes: an excitation step (steps S10 and S60) of causing an AC excitation current to flow through an excitation winding provided in the rotating electrical machine (e.g., the rotor 9) at a predetermined frequency; a difference calculation step (steps S20 to S30, S70 to S80) of calculating a difference between a measured value of a voltage or impedance of the excitation winding through which the AC excitation current flows and a value when the AC excitation current flows when the excitation winding is in a good state; and a short-circuit state analysis step (steps S50 and S90) of estimating a short-circuit resistance R based on the difference, the short-circuit resistance R being an indicator of the degree of short circuit generated between layers of the excitation winding, wherein, in the short-circuit state analysis step, the short-circuit resistance R is estimated at a first frequency. The difference when an AC excitation current flows at a first frequency (6000 Hz) is compared with a threshold value (step S40). If the difference is less than the threshold value ("No"), the short-circuit resistance R is estimated from the difference based on data indicating the relationship between the short-circuit resistance R and the difference at the first frequency (step S50). If the difference is greater than the threshold value ("Yes"), the excitation step is performed at a second frequency (60 Hz) lower than the first frequency (step S60). Based on data at the second frequency indicating the relationship between the short-circuit resistance R and the difference, the short-circuit resistance R is estimated from the difference obtained using the AC excitation current at the second frequency (step S90). This makes it possible to quantitatively evaluate the short-circuit state in the rotating electrical machine over a wide range of short-circuit resistance values.

[0065] In the short-circuit state analysis step (step S100), if the usable period of the rotating electrical machine is predicted based on the estimated value of the short-circuit resistance R, the timing of periodic maintenance or priority maintenance can be selected, thereby enabling stable operation of the rotating electrical machine. This is particularly effective in applications where continuous abnormality monitoring is required, where a stoppage of the rotating electrical machine due to a fault could significantly adversely affect power infrastructure, and where maintenance frequency is limited in remote areas or applications with a large number of rotating electrical machines.

[0066] In the differential calculation step (steps S20 to S30, S70 to S80), if the difference between the measured values ​​of the voltage or impedance of each interval (for example, the first pole 9p1 part and the second pole 9p2 part) obtained by dividing the excitation winding into multiple sections is calculated as the difference value, the short-circuit resistance can be easily estimated even when there is no past data or it is difficult to form analytical data.

Claims

1. A short circuit detection device, characterized in that: have: an excitation power supply for passing an AC excitation current at a predetermined frequency through an excitation winding provided in the rotating electrical machine; a difference calculation unit that calculates a difference between a measured value of a voltage or impedance of the field winding through which the AC field current flows and a value when the AC field current flows through the field winding in a good state; and The short circuit state analysis unit performs the following tasks: comparing the difference when an AC excitation current flows at a first frequency with a threshold value, When the difference is smaller than the threshold value, the short-circuit resistance is estimated from the difference based on data indicating the relationship between the short-circuit resistance and the difference at the first frequency, the short-circuit resistance being an indicator of the degree of short circuit generated between layers of the field winding. When the difference is greater than the threshold value, the excitation power supply causes an AC excitation current to flow through the excitation winding at a second frequency lower than the first frequency, and based on data representing the relationship between the short-circuit resistance and the difference at the second frequency, the short-circuit resistance is estimated based on the difference obtained using the AC excitation current at the second frequency.

2. The short circuit detection device according to claim 1, characterized in that: The short-circuit state analyzing unit predicts a usable period of the rotating electric machine based on the estimated value of the short-circuit resistance.

3. The short circuit detection device according to claim 1 or 2, characterized in that: The short-circuit state analysis unit diagnoses that a short circuit has occurred in the rotating electrical machine when the estimated value of the short-circuit resistance is lower than a lower limit value.

4. The short circuit detection device according to any one of claims 1 to 3, characterized in that: The difference calculation unit calculates, as the difference value, a difference between measured values ​​of the voltage or the impedance in each section into which the field winding is divided into a plurality of sections.

5. A short circuit detection method for a rotating electrical machine, characterized in that: include: an excitation step of causing an AC excitation current to flow through an excitation winding provided in the rotating electrical machine at a predetermined frequency; A difference calculation step of calculating the difference between a measured value of a voltage or impedance of the field winding through which the AC excitation current flows and a value when the AC excitation current flows through the field winding in a good state; as well as a short-circuit state analysis step of estimating a short-circuit resistance based on the difference, the short-circuit resistance being an indicator of the degree of short circuit generated between layers of the field winding; Wherein, in the short-circuit state analysis step, the difference when the AC excitation current flows at a first frequency is compared with a threshold value, When the difference is smaller than the threshold, the short-circuit resistance is estimated from the difference based on data indicating the relationship between the short-circuit resistance and the difference at the first frequency, When the difference is greater than the threshold value, the excitation step is performed at a second frequency lower than the first frequency, and the short-circuit resistance is estimated based on the difference obtained using the AC excitation current at the second frequency based on data representing the relationship between the short-circuit resistance and the difference at the second frequency.

6. The short-circuit detection method of a rotating electrical machine according to claim 5, characterized in that: In the short-circuit state analysis step, a usable period of the rotating electrical machine is predicted based on the estimated value of the short-circuit resistance.

7. The short-circuit detection method of a rotating electrical machine according to claim 5 or 6, characterized in that: In the difference calculation step, a difference between measured values ​​of the voltage or the impedance in each section into which the field winding is divided into a plurality of sections is calculated as the difference value.

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