A rotor AC impedance testing device and method based on damped oscillation

Abstract

The present invention discloses a rotor AC impedance testing device and method based on damped oscillation. The device includes: a charging module for charging a standard capacitor bank in a test preparation state so that the voltage across the standard capacitor bank reaches a preset voltage value; the standard capacitor bank for storing energy in the test preparation state and discharging to the generator rotor in the test state to trigger a damped oscillation process; a switching module for switching between the test preparation state and the test state; and a result determination module for collecting and recording the waveform of the damped oscillation process and determining test result data based on the oscillation frequency corresponding to the waveform and the capacitance value of the standard capacitor bank, thereby reducing the power supply capacity and weight of the device, and improving the automation level and test accuracy of the generator rotor AC impedance test since it does not involve manual voltage regulation and does not set current sensors.

Description

Technical Field

[0001] This application relates to the technical field of power plants, and more specifically, to a rotor AC impedance testing device and method based on damped oscillation. Background Art

[0002] Performing an AC impedance test on the generator rotor coil is a routine test item in power plants. Its purpose is to timely detect the turn-to-turn short circuit fault of the rotor coil by analyzing the changes in AC impedance and active power loss under a certain voltage.

[0003] The traditional test method usually is to apply a power frequency AC voltage (0 - 220V) to both ends of the generator rotor coil through slip rings using a common manual autotransformer in the laboratory, and at the same time measure the current flowing through the generator rotor coil and its active power (active power loss), based on which the AC impedance of the coil can be calculated.

[0004] Since the AC impedance value is generally small (5 - 8Ω), the current value flowing through the coil during the test is large (above 40A), exceeding the range of a general ammeter head, and needs to be converted through a current transformer. Correspondingly, the capacity of the test power supply is also required to be large (above 10KVA), and the volume and weight of the autotransformer (above 20kg) are also large.

[0005] Because there are accumulations of measurement errors in each link such as current transformers and low power factor wattmeters, the repeatability accuracy of the traditional test method is poor.

[0006] In addition, due to the fact that the autotransformer generally can only be adjusted manually, the automation level of the entire set of test instruments has been difficult to improve for a long time.

[0007] Based on the above situation, there is an urgent need for a generator rotor coil AC impedance testing device with a small power supply capacity, light weight, high automation level, and high test accuracy to solve the above problems. Summary of the Invention

[0008] The present invention discloses a rotor AC impedance testing device based on damped oscillation, which is used to solve the technical problems in the prior art that due to using an autotransformer for rotor AC impedance testing, the test power supply has a large capacity and weight, low automation level, and poor test accuracy. The device includes:

[0009] A charging module, used to charge a standard capacitor bank in the test preparation state so that the voltage across the standard capacitor bank reaches a preset voltage value;

[0010] The standard capacitor bank is used to store energy in the test preparation state and discharge to the generator rotor in the test state to trigger a damped oscillation process;

[0011] A switching module that enables the device to enter the test preparation state based on a test preparation instruction sent by a user, and enables the device to enter the test state when preset test conditions are met;

[0012] A result determination module for collecting and recording the waveform of the damped oscillation process, and determining test result data based on the oscillation frequency corresponding to the waveform and the capacitance value of the standard capacitor bank;

[0013] Wherein, the preset test conditions are detecting a test instruction sent by the user or the voltage across both ends reaching the preset voltage value.

[0014] In some embodiments of the present application, the result determination module includes:

[0015] An oscilloscope, the first end and the second end of which are respectively connected to two slip rings of the generator rotor, for collecting and recording the waveform of the damped oscillation process;

[0016] A waveform recognition module for recognizing the waveform based on preset graphic recognition software and determining the oscillation frequency;

[0017] A calculation module for determining the test result data according to the oscillation frequency and the capacitance value;

[0018] Wherein, the test result data includes the AC impedance, quality factor, and active power loss of the generator rotor.

[0019] In some embodiments of the present application, the switching module is a relay, including:

[0020] A coil that is energized when receiving the test preparation instruction and de-energized when the preset test conditions are met;

[0021] A discharge switch group including a first switch and a second switch connected in parallel. The first switch and the second switch are simultaneously opened when the coil is energized and simultaneously closed when the coil is de-energized;

[0022] A charging switch that is closed when the coil is energized and opened when the coil is de-energized;

[0023] Wherein, the first switch is connected in series between the first slip ring of the generator rotor and the first end of the standard capacitor bank, the second switch is connected in series between the second slip ring of the generator rotor and the second end of the standard capacitor bank, the charging switch is connected in series between the first end of the standard capacitor bank and the first end of the charging module, and the common connection point of the second end of the standard capacitor bank and the second end of the charging module is grounded.

[0024] In some embodiments of the present application, the standard capacitor bank includes a plurality of capacitors connected in parallel. The first end of each capacitor is connected to the first end of the standard capacitor bank, and the second end of each capacitor is connected to the second end of the standard capacitor bank.

[0025] In some embodiments of the present application, the charging module is a constant voltage source or a constant current source.

[0026] In some embodiments of the present application, the capacity of the charging module is 500 VA.

[0027] In some embodiments of the present application, an automatic trigger button and an automatic waveform recording button are provided on the oscilloscope.

[0028] Correspondingly, the present invention also provides a method for testing the AC impedance of a rotor based on damped oscillation. The method is applied to the device as described above, and the method includes:

[0029] When detecting a test preparation instruction sent by the user, based on the switching module, the device is made to enter the test preparation state, so that the charging module charges the standard capacitor bank until a preparation completion prompt message is sent when the voltage across the two ends of the standard capacitor bank reaches a preset voltage value;

[0030] When preset test conditions are met, based on the switching module, the device is made to enter the test state, disconnecting the connection between the charging module and the standard capacitor bank and causing the standard capacitor bank to discharge to the generator rotor to trigger a damped oscillation process;

[0031] Based on the result determination module, the waveform of the damped oscillation process is collected and recorded, and the result determination module determines the test result data according to the oscillation frequency corresponding to the waveform and the capacitance value of the standard capacitor bank;

[0032] Wherein, the preset test conditions are detecting a test instruction sent by the user or the voltage across the two ends reaching the preset voltage value.

[0033] In some embodiments of the present application, after the waveform of the damped oscillation process is collected and recorded based on the result determination module, the method further includes:

[0034] Making the result determination module identify the waveform based on preset graphic recognition software and determine the oscillation frequency.

[0035] In some embodiments of the present application, the test result data includes the AC impedance, quality factor, and active power loss of the generator rotor.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1) The overall weight is light and easy to carry. The constant voltage / constant current source can be used as the charging module, and the relay can be used as the switching module. The total weight of the standard capacitor bank + constant voltage / constant current source + relay can be less than one-fifth of the device (autotransformer + measurement and control display box) in the prior art.

[0038] 2) It is easy to achieve automatic measurement. Since it does not involve an autotransformer that requires manual voltage regulation, it can be set for automatic testing according to external conditions such as specified voltage steps, specified time intervals, or specified rotational speeds, greatly reducing the labor intensity of operators.

[0039] 3) The measurement accuracy is high. Manual voltage regulation, mutual inductor conversion and other error sources are excluded. Only the capacitance value of the standard capacitor affects the test accuracy, and it can be regularly calibrated, which is very simple.

[0040] 4) The capacity of the test power supply is greatly reduced. It drops from about 10 KVA to 500 VA (0.5 KVA), which is about one-twentieth of the original. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0042] Figure 1 FIG. shows a schematic structural diagram of a rotor AC impedance test device based on damped oscillation proposed in an embodiment of the present invention;

[0043] Figure 2 FIG. shows a schematic structural diagram of a rotor AC impedance test device based on damped oscillation proposed in another embodiment of the present invention;

[0044] Figure 3 FIG. shows a schematic flow diagram of a rotor AC impedance test method based on damped oscillation proposed in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0046] The embodiments of the present application provide a rotor AC impedance test device based on damped oscillation, as Figure 1 shown, including:

[0047] A charging module 10, configured to charge a standard capacitor bank 20 in a test preparation state so that the voltage across the standard capacitor bank 20 reaches a preset voltage value;

[0048] The standard capacitor bank 20 is configured to store energy in a test preparation state and discharge to the generator rotor in a test state to trigger a damped oscillation process;

[0049] A switching module 30, which makes the device enter the test preparation state based on a test preparation instruction sent by the user, and makes the device enter the test state when preset test conditions are met;

[0050] A result determination module 40, configured to collect and record the waveform of the damped oscillation process, and determine test result data based on the oscillation frequency corresponding to the waveform and the capacitance value of the standard capacitor bank 20.

[0051] In this embodiment, when receiving a test preparation instruction sent by the user, the switching module 30 powers on and operates to make the device enter the test preparation state; when preset test conditions are met, the switching module 30 powers off and returns to make the device enter the test state, where the preset test conditions are detecting a test instruction sent by the user or the voltage across the standard capacitor bank 20 reaching the preset voltage value.

[0052] In the test preparation state, the charging module 10 charges the standard capacitor bank 20, and completes the test preparation when the voltage across the standard capacitor bank 20 reaches the preset voltage value; in the test state, the charging module 10 stops charging the standard capacitor bank 20, and at the same time makes the standard capacitor bank 20 discharge to the generator rotor to trigger a damped oscillation process. At this time, the result determination module 40 collects and records the waveform of the damped oscillation process, and determines test result data based on the oscillation frequency corresponding to the waveform and the capacitance value of the standard capacitor bank 20.

[0053] From basic circuit knowledge, it can be known that the above oscillation frequency f is only related to the inductance value L and the capacitance value C. The relationship formula is: 2πfL = 1 / 2πfC. Since π is a mathematical constant, when the capacitance value C of the standard capacitor bank is known, as long as the oscillation frequency f is obtained from the waveform, the AC reactance value X can be calculated. L = 1 / 2πfC. The generator rotor coil has two main physical parameters, the DC resistance value r and the inductive reactance value X L , X L is related to the power supply frequency: that is, X L = 2πfL. The AC impedance value Z to be measured = In engineering, because the inductive reactance value X L is much larger than the DC resistance value r, it can be considered that: the AC impedance Z ≈ X L = 1 / 2πfC.

[0054] In some embodiments of the present application, to reliably determine the test result data, the result determination module 40 includes:

[0055] An oscilloscope, the first end and the second end of which are respectively connected to two slip rings of the generator rotor, for collecting and recording the waveform during the damped oscillation process;

[0056] A waveform recognition module, for recognizing the waveform based on a preset graphic recognition software and determining the oscillation frequency;

[0057] A calculation module, for determining the test result data according to the oscillation frequency and the capacitance value.

[0058] In this embodiment, two slip rings are provided on the generator rotor, the first end and the second end of the oscilloscope are respectively connected to these two slip rings, the waveform during the damped oscillation process is collected and recorded, and a preset graphic recognition software is set in the waveform recognition module, which can recognize the waveform and determine the oscillation frequency, and the calculation module determines the test result data according to the oscillation frequency and the capacitance value.

[0059] The test result data includes the AC impedance, quality factor, and active power loss of the generator rotor, where the AC impedance Z = 1 / 2πfC, f is the oscillation frequency, and C is the capacitance value; the quality factor ωL / R can be approximately obtained by counting the waveform of the damped oscillation; the active power loss can be determined according to the AC impedance Z and the preset voltage value.

[0060] In some embodiments of the present application, to improve the device integration and reduce the device volume, the waveform recognition module and the calculation module are integrated in the oscilloscope, so that the oscillation frequency can be directly recognized based on the oscilloscope and the test result data can be further determined.

[0061] In some embodiments of the present application, to reliably perform state switching on the device, as Figure 2 shown, the switching module 30 is a relay, including:

[0062] A coil C1, which is energized when receiving a test preparation instruction and de-energized when meeting a preset test condition;

[0063] A discharge switch group, including a first switch S11 and a second switch S12 connected in parallel. The first switch S11 and the second switch S12 are simultaneously opened when the coil C1 is energized and simultaneously closed when the coil C1 is de-energized;

[0064] A charging switch S2, which is closed when the coil C1 is energized and opened when the coil C1 is de-energized;

[0065] Among them, the first switch S11 is connected in series between the first slip ring 51 of the generator rotor and the first end of the standard capacitor bank 20, the second switch S12 is connected in series between the second slip ring 52 of the generator rotor and the second end of the standard capacitor bank 20, the charging switch S2 is connected in series between the first end of the standard capacitor bank 20 and the first end of the charging module 10, and the common connection point of the second end of the standard capacitor bank 20 and the second end of the charging module 10 is grounded.

[0066] In order to improve the compatibility and flexibility of the device, in some embodiments of the present application, such as Figure 2 As shown, the standard capacitor bank 20 includes a plurality of capacitors connected in parallel. The first end of each capacitor is connected to the first end of the standard capacitor bank 20, and the second end of each capacitor is connected to the second end of the standard capacitor bank 20.

[0067] In this embodiment, the capacitance value of the standard capacitor bank 20 can be adjusted by increasing or decreasing the capacitors. By setting an appropriate capacitance value, the oscillation frequency can be adjusted to around 50 Hz, which is convenient for comparing with the test results of traditional power frequency power supplies. For example, through simple calculation, it is known that for a rotor coil of 0.017 mH in a certain factory, matching a 625 μF standard capacitor can make the oscillation frequency fall around 50 Hz.

[0068] In order to ensure the reliability of the device, in some embodiments of the present application, the charging module 10 is a constant voltage source or a constant current source.

[0069] In this embodiment, since the charging module 10 is a constant voltage source or a constant current source, compared with an autotransformer, the volume and weight are reduced.

[0070] In order to ensure the reliability of the device, in some embodiments of the present application, the capacity of the charging module 10 is 500 VA.

[0071] In this embodiment, the capacity of the charging module 10 is 500 VA, which greatly reduces the test power supply capacity compared with about 10 KVA in the prior art.

[0072] In order to improve the automation level of the device, in some embodiments of the present application, an automatic trigger button and an automatic waveform recording button are provided on the oscilloscope.

[0073] In this embodiment, the device can be made to enter the test state to start testing when a test instruction sent by the user is detected. Before making the device enter the test state, it can also be set to "automatic trigger" by pressing or clicking the automatic trigger button, and set to "automatic waveform recording" by pressing or clicking the automatic waveform recording button. Since the automatic trigger and automatic waveform recording functions are enabled, it is not necessary for the user to send a test instruction. When the voltage at both ends of the standard capacitor bank reaches the preset voltage value, the device automatically enters the test state, improving the automation and reliability of the device.

[0074] By applying the above technical solution, the rotor AC impedance testing device based on damped oscillation includes: a charging module for charging a standard capacitor bank in a test preparation state so that the voltage across the standard capacitor bank reaches a preset voltage value; a standard capacitor bank for storing energy in a test preparation state and discharging to the generator rotor in a test state to trigger a damped oscillation process; a switching module for making the device enter the test preparation state based on a test preparation instruction sent by a user and making the device enter a test state when preset test conditions are met; and a result determination module for collecting and recording the waveform of the damped oscillation process and determining test result data based on the oscillation frequency corresponding to the waveform and the capacitance value of the standard capacitor bank. The preset test conditions are detecting a test instruction sent by the user or the voltage across both ends reaching the preset voltage value, so that the power supply capacity and weight of the device can be reduced, and since manual voltage regulation is not involved and no current sensor is provided, the automation level and test accuracy of the generator rotor AC impedance test are improved.

[0075] To further elaborate on the technical idea of the present invention, the technical solution of the present invention will be described in combination with a specific application scenario.

[0076] As Figure 2 shown, the generator rotor core 70 and the rotor coil 60 are assembled together, which is equivalent to an electromagnetic coil. The rotor coil 60 is led out to two slip rings (the first slip ring 51 and the second slip ring 52), and the waveform sampled by the oscilloscope in the result determination module 40 is also the voltage wave between the two slip rings.

[0077] "Test preparation" starts. The relay is powered on and operates, disconnecting the first switch S11 and the second switch S12, cutting off the electrical connection between the standard capacitor bank 20 and the rotor coil 60. At the same time, the charging switch S2 is closed to connect the charging module 10 (constant voltage / constant current source), and the standard capacitor bank 20 is charged with a preset safe current. The voltage across the standard capacitor bank 20 will continue to rise until it reaches the preset voltage value, and then "preparation completed" is reported.

[0078] Before the test starts, turn on the oscilloscope and set the relevant menus to "auto trigger", "auto recording waveform", etc. The device can automatically enter the test state to start the test. The relay is powered off and returns, disconnecting the charging switch S2, cutting off the charging circuit. At the same time, the first switch S11 and the second switch S12 are closed, enabling the standard capacitor bank 20 to discharge to the generator rotor coil 60, and a damped oscillation for testing is excited between the inductance of the generator rotor and the capacitance of the standard capacitor bank.

[0079] The result determination module 40 collects and records the waveform of the damped oscillation process, identifies the waveform based on preset pattern recognition software and determines the oscillation frequency, and then determines the test result data according to the oscillation frequency and the capacitance value of the standard capacitor bank 20.

[0080] Since the capacitance value of the standard capacitor bank does not change easily, one calibration can be used multiple times, and the oscilloscope can automatically measure and display the frequency of the damped oscillation. Even manual calculation of the AC impedance value is very simple and convenient.

[0081] An embodiment of the present application also proposes a method for testing the AC impedance of a rotor based on damped oscillation, which is applied to the device as described above. As Figure 3 shown, the method includes the following steps:

[0082] Step S101, when detecting a test preparation instruction sent by the user, based on the switching module, the device enters the test preparation state, so that the charging module charges the standard capacitor bank until a preparation completion prompt message is sent when the voltage across the standard capacitor bank reaches a preset voltage value;

[0083] Step S102, when meeting the preset test conditions, based on the switching module, the device enters the test state, disconnects the connection between the charging module and the standard capacitor bank, and makes the standard capacitor bank discharge to the generator rotor to trigger a damped oscillation process;

[0084] Step S103, based on the result determination module, collect and record the waveform of the damped oscillation process, and make the result determination module determine the test result data according to the oscillation frequency corresponding to the waveform and the capacitance value of the standard capacitor bank;

[0085] Wherein, the preset test condition is detecting a test instruction sent by the user or the voltage across the two ends reaching the preset voltage value.

[0086] In order to reliably determine the oscillation frequency, in some embodiments of the present application, after collecting and recording the waveform of the damped oscillation process based on the result determination module, the method further includes:

[0087] Making the result determination module identify the waveform based on preset graphic recognition software and determine the oscillation frequency.

[0088] In order to reliably determine the test result data, in some embodiments of the present application, the test result data includes the AC impedance, quality factor, and active power loss of the generator rotor.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A rotor AC impedance test device based on damped oscillation, characterized in that, The device includes: A charging module that is a constant voltage source or a constant current source, which is used to charge a standard capacitor bank in a test preparation state so that the voltage across the standard capacitor bank reaches a preset voltage value. Among them, the capacity of the charging module is 500VA; The standard capacitor bank includes a plurality of capacitors connected in parallel. The first end of each capacitor is connected to the first end of the standard capacitor bank, and the second end of each capacitor is connected to the second end of the standard capacitor bank; the standard capacitor bank is used to store energy in the test preparation state and discharge to the generator rotor in the test state to trigger a damped oscillation process; A switching module that makes the device enter the test preparation state based on a test preparation instruction sent by the user, and makes the device enter the test state when preset test conditions are met. Among them, the switching module is a relay, and the relay includes a coil, a discharge switch group and a charging switch; The coil is energized when receiving the test preparation instruction and de-energized when the preset test conditions are met; The discharge switch group includes a first switch and a second switch connected in parallel. The first switch and the second switch are both opened simultaneously when the coil is energized and both closed simultaneously when the coil is de-energized; The charging switch is closed when the coil is energized and opened when the coil is de-energized; Among them, the first switch is connected in series between the first slip ring of the generator rotor and the first end of the standard capacitor bank, the second switch is connected in series between the second slip ring of the generator rotor and the second end of the standard capacitor bank, the charging switch is connected in series between the first end of the standard capacitor bank and the first end of the charging module, and the common connection point of the second end of the standard capacitor bank and the second end of the charging module is grounded; The relay is used to make the device enter the test preparation state based on a test preparation instruction sent by the user, and make the device enter the test state when the preset test conditions are met. Among them, the preset test conditions are detecting a test instruction sent by the user or the voltage across the two ends reaching the preset voltage value; A result determination module that is used to collect and record the waveform of the damped oscillation process, and determine test result data based on the oscillation frequency corresponding to the waveform and the capacitance value of the standard capacitor bank. Among them, the result determination module includes an oscilloscope, a waveform recognition module and a calculation module; The oscilloscope is provided with an auto-trigger button and an auto-recording button. The first end and the second end of the oscilloscope are respectively connected to the two slip rings of the generator rotor, and are used to collect and record the waveform of the damped oscillation process; The waveform recognition module is used to recognize the waveform based on preset graphic recognition software and determine the oscillation frequency; The calculation module is used to determine the test result data according to the oscillation frequency and the capacitance value; Among them, the test result data includes the AC impedance, quality factor, and active power loss of the generator rotor.

2. A rotor AC impedance testing method based on damped oscillation, characterized in that, The method is applied to the device as described in claim 1, and the method includes: When a test preparation instruction sent by the user is detected, based on the switching module, the device enters a test preparation state, so that the charging module charges the standard capacitor bank until a prompt message of preparation completion is sent when the voltage across the standard capacitor bank reaches a preset voltage value; When preset test conditions are met, based on the switching module, the device enters a test state to disconnect the charging module from the standard capacitor bank and make the standard capacitor bank discharge to the generator rotor to trigger a damped oscillation process; Based on the result determination module, the waveform of the damped oscillation process is collected and recorded, the result determination module identifies the waveform based on preset pattern recognition software and determines the oscillation frequency, and the result determination module determines test result data according to the oscillation frequency corresponding to the waveform and the capacitance value of the standard capacitor bank, and the test result data includes the AC impedance, quality factor, and active power loss of the generator rotor; Among them, the preset test conditions are detecting a test instruction sent by the user or the voltage across the two ends reaching the preset voltage value.

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