Hydrogenerator rotor winding turn-to-turn short circuit on-line detection signal processing method

Abstract

The invention discloses a hydro-generator rotor winding turn-to-turn short circuit on-line detection signal processing method, which relates to the technical field of synchronous generator fault diagnosis and comprises the following steps of: A, acquiring an induced voltage of a measuring coil; b, preprocessing the acquired induced voltage; c, determining a corresponding relation between the pulse voltage and the magnetic pole in a rotation period by using the phase discrimination signal; d, extracting the extreme value of the pulse voltage waveform corresponding to each magnetic pole; e, the fundamental wave amplitude A1 of the current waveform and the fundamental wave amplitude A0 of the historical waveform when the turn-to-turn short circuit does not occur are obtained through Fourier transform, and the current induced voltage pulse extreme value array is multiplied by A0 / A1; f, if the absolute value of a certain extreme value in the adjusted current extreme value array is smaller than the absolute value of the numerical value corresponding to the historical extreme value array, and the difference between the absolute value of the historical extreme value and the absolute value of the current extreme value exceeds a set threshold value, it is judged that the turn-to-turn short circuit fault occurs in the magnetic pole winding corresponding to the extreme value. The method is good in anti-interference performance and high in diagnosis sensitivity.

Description

Technical Field

[0001] The present invention relates to the technical field of synchronous generator fault diagnosis, and in particular to an online detection signal processing method for inter-turn short circuit of the rotor winding of a hydro-generator. Background Art

[0002] Due to reasons such as moisture and dirt, the rotor winding of a hydro-generator is prone to inter-turn short circuit faults. There is a lack of effective online detection methods for the inter-turn short circuit faults of the rotor winding of hydro-generators. On the one hand, it is because of the lack of means for detecting the magnetic field of hydro-generators. On the other hand, it is because the inter-turn short circuit of the rotor winding has similar characteristics to the pole non-circularity fault, and the pole non-circularity of hydro-generators is extremely common. Therefore, the diagnosis is prone to interference and misjudgment.

[0003] To address the problem of the lack of means for detecting the magnetic field of hydro-generators, a patent application in the prior art, "A Diagnostic Method and System for Magnetic Field Asymmetry Faults of Synchronous Generators" (202310998923.X), first proposed winding coils on the positioning ribs and ring plates on the back of the generator stator core as magnetic field detection sensors for the generator, making it possible to measure the magnetic field of hydro-generators. This method can detect the magnetic field asymmetry faults of hydro-generators, but it cannot further distinguish the fault types. Therefore, on the basis of this technical solution, it is necessary to further develop a new signal processing algorithm so that it can diagnose the inter-turn short circuit faults of the rotor winding of hydro-generators. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an online detection signal processing method for inter-turn short circuit of the rotor winding of a hydro-generator, which can solve the deficiencies of the prior art and provide a technical means with good anti-interference performance, sensitive and reliable diagnosis for the online diagnosis of inter-turn short circuit of the rotor winding of a hydro-generator based on the magnetic field.

[0005] To solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0006] An online detection signal processing method for inter-turn short circuit of the rotor winding of a hydro-generator includes the following steps: A. Install a measuring coil on the stator of the hydro-generator to obtain the induced voltage of the measuring coil; B. Preprocess the obtained induced voltage; C. The numbers of the generator poles are successively 1 to N, where N is the total number of generator poles; use the phase discrimination signal to determine the correspondence between each pulse voltage and the poles within one rotation period; D. Extract the extreme values of the pulse voltage waveforms corresponding to each magnetic pole; for the positive pulse voltage waveform, take the maximum value; for the negative pulse voltage waveform, take the minimum value; record the maximum or minimum values of the pulse voltage waveforms corresponding to each magnetic pole in sequence according to the magnetic pole number. E. Perform Fourier transforms on the current waveform and the historical waveform of the induced voltage signal within one rotation period respectively, to obtain the fundamental wave amplitude A1 of the current waveform and the fundamental wave amplitude A0 of the historical waveform when there is no turn-to-turn short circuit. Multiply the current induced voltage pulse extreme value array by A0 / A1 to obtain the adjusted current extreme value array. F. Compare the values of the adjusted current extreme value array and the historical extreme value array corresponding to each magnetic pole number respectively. If the absolute value of an extreme value in the adjusted current extreme value array is less than the absolute value of the corresponding value in the historical extreme value array, and the difference between the absolute value of the historical extreme value and the absolute value of this current extreme value exceeds the set threshold, then it is determined that the turn-to-turn short circuit fault has occurred in the magnetic pole winding corresponding to this current extreme value.

[0007] Preferably, the installation position of the magnetic flux measurement coil is the positioning rib or ring plate on the back of the stator core of the hydro-generator.

[0008] Preferably, in step B, the obtained induced voltage is filtered to remove high-order harmonics, so as to obtain a smooth pulse voltage waveform with positive and negative alternations corresponding to the number of magnetic poles of the generator.

[0009] Preferably, it is assumed that the magnetic field generator generating the phase discrimination signal is attached to the large shaft in the same azimuth as the i-th magnetic pole of the rotor, 1≤i≤N. The fixed azimuth of the phase discrimination sensor lags behind the measurement coil by m magnetic poles in the rotor rotation direction. At the same time, the phase discrimination signal and the pulse voltage signal induced by the magnetic pole are collected. The phase discrimination signal appears only once in one rotation period of the generator. The pulse voltage signals induced by each magnetic pole appear N equally spaced, positive and negative alternating pulses in one rotation period. The induced voltage pulse coinciding with the phase discrimination signal pulse is the one induced by the k-th magnetic pole; when 1≤i+m≤N, k = i + m, when i + m > N, k = i + m - N.

[0010] Preferably, in step F, the set threshold is less than or equal to 5% of the average value of the absolute values of the historical extreme value array.

[0011] The beneficial effects brought by adopting the above technical solutions are as follows: The signal processing method for on-line detection of turn-to-turn short circuit in the rotor winding of the hydro-generator proposed by the present invention can specifically identify the turn-to-turn short circuit fault in the rotor winding without being interfered by rotor dynamic eccentricity and magnetic pole non-circularity. By converting the magnetic field extreme values, therefore, the judgment of the turn-to-turn short circuit fault in the rotor winding is not affected by the operating conditions of the unit. Description of the Drawings

[0012] Figure 1 It is the sampling diagram of the induced voltage of the measuring coil within a rotation period when the generator's no-load rotor winding is normal in a specific embodiment of the present invention; Figure 2 It is Figure 1 the image after filtering; Figure 3 It is the sampling diagram of the absolute value of the extreme value of the induced voltage of the measuring coil within a rotation period when the generator's no-load rotor winding is normal and after filtering in a specific embodiment of the present invention; Figure 4 It is the sampling diagram of the induced voltage of the measuring coil within a rotation period when there is an inter-turn short circuit in the 14th pole of the generator's no-load rotor in a specific embodiment of the present invention; Figure 5 It is Figure 4 the image after filtering; Figure 6 It is the sampling diagram of the absolute value of the extreme value of the induced voltage of the measuring coil within a rotation period when there is an inter-turn short circuit in the 14th pole of the generator's no-load rotor and after filtering in a specific embodiment of the present invention; Figure 7 It is the sampling diagram of the absolute value of the difference between the absolute values of the voltage pulses of each pole when the generator's no-load rotor winding is normal and when there is an inter-turn short circuit in the 14th pole in a specific embodiment of the present invention; Figure 8 It is the sampling diagram of the induced voltage of the measuring coil within a rotation period when there is an inter-turn short circuit in the 14th pole of the rotor under the condition of no-load and low excitation of the generator in a specific embodiment of the present invention; Figure 9 It is Figure 8 the image after filtering; Figure 10 It is the sampling diagram of the absolute value of the extreme value of the induced voltage of the measuring coil within a rotation period when there is an inter-turn short circuit in the 14th pole of the rotor under the condition of no-load and low excitation of the generator and after filtering in a specific embodiment of the present invention; Figure 11 It is the sampling diagram of the absolute value of the difference between the absolute values of the extreme values of the voltage pulses of each pole after reduction when the generator's no-load rotor winding is normal and when there is an inter-turn short circuit in the 14th pole in a specific embodiment of the present invention. Specific Embodiment

[0013] The on-line detection signal processing method for the inter-turn short circuit of the rotor winding of a hydro-generator provided by the present invention includes the following steps: A. Install a measuring coil on the positioning ribs or ring plates on the back of the stator core of the hydro-generator to obtain the induced voltage of the measuring coil.

[0014] B. Filter the obtained induced voltage to remove high-order harmonics, so as to obtain a smooth pulse voltage waveform with positive and negative alternation corresponding to the number of generator magnetic poles.

[0015] C. The numbers of each magnetic pole of the generator are successively 1 to N, where N is the total number of magnetic poles of the generator; it is assumed that the magnetic field generator generating the phase discrimination signal is attached to the large shaft in the same azimuth as the i-th magnetic pole of the rotor, 1 ≤ i ≤ N. The fixed azimuth of the phase discrimination sensor lags behind the measurement coil by m magnetic poles in the rotor rotation direction. At the same time, collect the phase discrimination signal and the pulse voltage signal induced by the magnetic poles. The phase discrimination signal appears only once in one rotation period of the generator. The pulse voltage signals induced by each magnetic pole appear N equally spaced, positive and negative alternating pulses in one rotation period. The induced voltage pulse that coincides with the phase discrimination signal pulse is the one induced by the k-th magnetic pole; when 1 ≤ i + m ≤ N, k = i + m, and when i + m > N, k = i + m - N.

[0016] D. Extract the extreme values of the pulse voltage waveforms corresponding to each magnetic pole; for the positive pulse voltage waveform, take the maximum value; for the negative pulse voltage waveform, take the minimum value; record the maximum or minimum values of the pulse voltage waveforms corresponding to each magnetic pole in sequence according to the magnetic pole numbers.

[0017] E. Perform Fourier transforms on the current waveform and the historical waveform when there is no turn-to-turn short circuit of the induced voltage signal in one rotation period respectively, to obtain the fundamental wave amplitude A1 of the current waveform and the fundamental wave amplitude A0 of the historical waveform when there is no turn-to-turn short circuit. Multiply the current induced voltage pulse extreme value array by A0 / A1 to obtain the adjusted current extreme value array.

[0018] F. Compare the corresponding values of the adjusted current extreme value array and the historical extreme value array when there is no turn-to-turn short circuit in sequence according to the magnetic pole numbers. If the absolute value of an extreme value in the adjusted current extreme value array is less than the absolute value of the corresponding value in the historical extreme value array, and the difference between the absolute value of the historical extreme value and the absolute value of this current extreme value exceeds the set threshold, it is determined that the turn-to-turn short circuit fault has occurred in the magnetic pole winding corresponding to this current extreme value.

[0019] Taking a hydro-generator in a hydropower plant as an example, the rated capacity of this generator is 777.8 MVA, the rated voltage is 18 kV, the rated power factor is 0.9, the rotor has a total of 20 pairs of poles, and the rated speed is 150 r / min. Three turns of measurement coils are wound on the ring plate on the back of the stator core of this generator.

[0020] When the generator is running under no-load condition, collect the induced voltage of the measurement coil. In one rotation period, the voltage waveform is as Figure 1 shown. It can be seen that there are a large number of high-order harmonics in the voltage waveform. Filter the voltage waveform to remove the high-order harmonics therein, and only retain the voltage pulses corresponding to the number of magnetic poles and arranged in positive and negative alternation, asFigure 2 as shown

[0021] From Figure 2 It can be seen that the voltage amplitudes induced by each magnetic pole on the measuring coil are not the same, and the amplitude sizes of each voltage pulse can reflect the strength of the magnetic field of the corresponding magnetic pole. Therefore, the maximum and minimum values of the voltage pulses induced by each magnetic pole are obtained, and the maximum and minimum values are arranged alternately according to the magnetic pole numbers. After taking the absolute value of them, as Figure 3 shown

[0022] To verify the effectiveness of the detection method, a 3-turn short-circuit fault of the rotor winding is simulated on the 14th magnetic pole, and the waveform of the coil-induced voltage collected is as Figure 4 shown, and the filtered waveform is as Figure 5 shown. Further, the extreme values of the pulse voltages corresponding to each magnetic pole in Figure 4 are obtained. After taking the absolute value of them, as Figure 6 shown

[0023] To perform fault diagnosis, we must set a fault judgment threshold. Observing that the average value of the historical extreme values is about 50 mV, 5% is taken as the fault judgment threshold, that is, 2.5 mV

[0024] Subtract Figure 3 the data of the extreme values of the voltage pulses of each magnetic pole in Figure 6 from the corresponding data of the extreme values of the voltage pulses in Figure 7 and take the absolute value, as Figure 3 shown. (Since Figure 6 and are in the same working state, and the fundamental wave amplitude A1 = A0 obtained after Fourier transform, so the reduction step can be omitted)

[0025] It can be seen that the deviation between the two increases significantly at the 14th magnetic pole, and the absolute value of the current extreme value is less than the absolute value of the historical extreme value, and the deviation exceeds the set threshold of 2.5 mV. It can be judged that there is an inter-turn short-circuit fault in the rotor winding of the 14th magnetic pole Figure 8 shown, and after filtering as Figure 9 shown. The extreme values of the pulse voltages corresponding to each magnetic pole, as Figure 10 shown

[0026] Respectively for Figure 2 the waveform and Figure 9The waveform is subjected to Fourier transform to obtain the fundamental wave amplitudes A1 = 50.17 mV and A0 = 28.06 mV respectively. Multiply the current coil induced voltage pulse extreme value array (table) by A0 / A1 to obtain the adjusted current extreme value array, as Figure 10 shown.

[0027] Subtract Figure 3 the voltage pulse extreme value data of each magnetic pole in Figure 10 from the corresponding voltage pulse extreme value data in Figure 11 as shown.

[0028] It can be seen that the deviation between the two increases significantly at the 14th magnetic pole, and the current value is less than the historical value, and the deviation exceeds the set threshold. It can be judged that there is an inter-turn short circuit fault in the rotor winding, which proves that the new signal processing method can effectively eliminate the influence of the generator operating conditions.

[0029] The above measured results prove that by using the signal processing algorithm proposed in the present invention to process the induced voltage of the detection coil wound on the positioning ribs or ring plates of the hydro-generator, the on-line detection of the inter-turn short circuit fault of the rotor winding can be realized, and the specific position of the faulty magnetic pole can be located.

[0030] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0031] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. An on-line detection signal processing method for inter-turn short circuit of the rotor winding of a hydro-generator, characterized in that It includes the following steps: A. Install a measuring coil on the stator of the hydro-generator to obtain the induced voltage of the measuring coil; B. Preprocess the obtained induced voltage; C. The numbers of the generator's respective magnetic poles are successively 1 to N, where N is the total number of magnetic poles of the generator; Use the phase discrimination signal to determine the correspondence between each pulse voltage and the magnetic pole within one rotation period; D. Extract the extreme values of the pulse voltage waveforms corresponding to each magnetic pole; for the positive pulse voltage waveform, take the maximum value; for the negative pulse voltage waveform, take the minimum value; Record the maximum or minimum values of the pulse voltage waveforms corresponding to each magnetic pole successively according to the magnetic pole numbers; E. Perform Fourier transforms on the current waveform and the historical waveform when there is no turn-to-turn short circuit of the induced voltage signal within one rotation period respectively, to obtain the fundamental wave amplitude A1 of the current waveform and the fundamental wave amplitude A0 of the historical waveform when there is no turn-to-turn short circuit. Multiply the current induced voltage pulse extreme value array by A0 / A1 to obtain the adjusted current extreme value array; F. Compare the values corresponding to the adjusted current extreme value array and the historical extreme value array when there is no turn-to-turn short circuit successively according to the magnetic pole numbers. If the absolute value of a certain extreme value in the adjusted current extreme value array is less than the absolute value of the corresponding value in the historical extreme value array, and the difference between the absolute value of the historical extreme value and the absolute value of this current extreme value exceeds the set threshold, it is determined that the turn-to-turn short circuit fault has occurred in the magnetic pole winding corresponding to this current extreme value.

2. The on-line detection signal processing method for the inter-turn short circuit of the rotor winding of a hydro-generator according to claim 1, characterized in that: The installation position of the magnetic flux measuring coil is the positioning rib or the ring plate on the back of the stator core of the hydro-generator.

3. The on-line detection signal processing method for the inter-turn short circuit of the rotor winding of a hydro-generator according to claim 1, characterized in that: In step B, filter the obtained induced voltage to filter out the high-order harmonics, so as to obtain a smooth pulse voltage waveform with positive and negative alternation corresponding to the number of magnetic poles of the generator.

4. The on-line detection signal processing method for the inter-turn short circuit of the rotor winding of a hydro-generator according to claim 1, characterized in that: In step C, assume that the magnetic field generator generating the phase discrimination signal is attached to the large shaft in the same azimuth as the i-th magnetic pole of the rotor, 1 ≤ i ≤ N. The fixed azimuth of the phase discrimination sensor lags behind the measuring coil by m magnetic poles in the rotor rotation direction. At the same time, collect the phase discrimination signal and the pulse voltage signal induced by the magnetic pole. The phase discrimination signal appears only once within one rotation period of the generator. The pulse voltage signals induced by each magnetic pole appear N equally spaced, positive and negative alternating pulses within one rotation period. The induced voltage pulse coinciding with the phase discrimination signal pulse is the one induced by the k-th magnetic pole; when 1 ≤ i + m ≤ N, k = i + m, when i + m > N, k = i + m - N.

5. The on-line detection signal processing method for the turn-to-turn short circuit of the rotor winding of a hydro-generator according to claim 1, characterized in that: In step F, the set threshold is less than or equal to 5% of the average value of the absolute values of the historical extreme value array.

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