A method and device for analyzing shaft voltage components of a static excitation generator

Abstract

The application discloses a kind of static excitation generator shaft voltage component analysis method and device, the method is applied to generator, the method includes: measuring the shaft voltage component parameter of generator under different measurement state;Whether the shaft voltage component parameter reaches dangerous value is detected;If yes, then output classification alarm.The device includes rotor body, one end of the rotor body is steam end large shaft, the other end of the rotor body is excitation end large shaft, steam end carbon brush is connected on the steam end large shaft, excitation end carbon brush is connected on the excitation end large shaft, shaft voltage suppressor is connected on the excitation end carbon brush, the steam end carbon brush and the shaft voltage suppressor are electrically connected with relay.The application adopts the above method, with the advantages of high measurement accuracy, sensitive and effective, high degree of automation, guide repair.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrical measurement and control, in particular to a static excitation generator shaft voltage component analysis method and device. BACKGROUND

[0002] Shaft voltage refers to the voltage induced on the generator shaft due to generator magnetic field asymmetry, generator shaft magnetization, electrostatic charging, etc. The existence of shaft voltage in large generators is difficult to avoid. When the shaft voltage is too high, it will cause many hazards, so each generator manufacturer has specified the allowable safety upper limit value. Each power plant needs to measure the shaft voltage of the generator during operation regularly. The traditional three-machine excitation system mainly exists two kinds of shaft voltage, electrostatic voltage (DC) and quasi-power frequency voltage (AC).

[0003] With the popularization of static excitation at the machine end, a new source of shaft voltage is added to the generator rotor, i.e. the so-called "trigger pulse coupling voltage" (300Hz) formed by the trigger pulse of the excitation regulator coupled to the rotating shaft. Its pulse width is only about 0.3ms. In extremely adverse conditions, the peak value of this pulse voltage can reach 150-200 volts, far exceeding the oil film breakdown threshold. If it cannot be detected in time, it will seriously threaten the safe operation of the unit.

[0004] The existing shaft voltage test method only tests the true rectified effective value (RMS) of the quasi-power frequency AC shaft voltage, but the "trigger pulse coupling voltage" has been ignored for a long time. This leads to inaccurate analysis of shaft voltage, low sensitivity, and the measured results cannot accurately reflect the problems existing in the motor.

[0005] Therefore, how to improve the accuracy of shaft voltage detection is a technical problem to be solved by those skilled in the art. SUMMARY

[0006] In order to solve the above technical problems, the present application provides a static excitation generator shaft voltage component analysis method, applied to a generator, the method comprising:

[0007] Measuring the shaft voltage component parameters of the generator under different measurement states;

[0008] Detecting whether the shaft voltage component parameters reach a dangerous value;

[0009] If so, output a classification alarm.

[0010] Preferably, the shaft voltage component parameters of the generator under different measurement states are measured, specifically:

[0011] Measuring the electrostatic suspension potential of the generator under the state of relay closing or breaking, to obtain a DC component U0;

[0012] Or, measure the trigger pulse coupling voltage of the generator in the state of the closing or breaking of the relay and the input or exit of the shaft voltage suppressor, to obtain a 6 times frequency pulse component U6;

[0013] Or, measure the true rectified effective value (RMS is Root Mean Square) of the generator in the state of the closing or breaking of the relay and the input of the shaft voltage suppressor, to obtain a power frequency-like alternating current component U1.

[0014] Preferably, it is detected whether the shaft voltage component parameter reaches a dangerous value; if so, a classified alarm is output, specifically:

[0015] When the relay is closed, it is detected that U0 is greater than X0, and a first type of alarm is output.

[0016] When the relay is broken, it is detected that U0 is less than Y0, and a second type of alarm is output.

[0017] When it is detected that U6 is greater than X6, a third type of alarm is output.

[0018] When it is detected that U1 is greater than X1, a fourth type of alarm is output.

[0019] Correspondingly, the application also provides a shaft voltage component analysis device for a static excitation generator, characterized in that the device comprises a rotor body, one end of the rotor body is a steam end large shaft, the other end of the rotor body is an excitation end large shaft, a steam end carbon brush is connected to the steam end large shaft, an excitation end carbon brush is connected to the excitation end large shaft, a shaft voltage suppressor is connected to the excitation end carbon brush, and a relay is electrically connected between the steam end carbon brush and the shaft voltage suppressor.

[0020] Preferably, the structure of the shaft voltage suppressor is a capacitor device connected in parallel between the excitation end large shaft and the ground net.

[0021] Preferably, the device is externally connected with a measurement and control unit, an acquisition unit and an analysis unit.

[0022] The measurement and control unit is used to control the relay and the shaft voltage suppressor to switch different measurement states.

[0023] The acquisition unit comprises a digital oscilloscope and is used to acquire shaft voltage component parameters in different measurement states of the device.

[0024] The analysis unit is used to detect whether the shaft voltage component parameter reaches a dangerous value, and output a classified alarm according to the detection result.

[0025] Therefore, the application adopts the above method and device, and has the following beneficial effects compared with the prior art:

[0026] The three main sources of shaft voltage are analyzed and measured separately for three components: DC component, sixth harmonic pulse component, and power frequency-like AC component. This results in more accurate measurements and a more sensitive reflection of existing generator safety issues. The measurement and control unit, acquisition unit, and analysis unit can all be implemented using commercially available general-purpose components and software, resulting in low cost and ease of implementation. The testing process is designed to be automated. The analysis unit accurately identifies the sources of harmful shaft voltage, and the detection results can guide maintenance work, accurately pinpointing the fault source of harmful shaft voltage and helping technicians quickly resolve safety issues.

[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the principle of a static excitation generator shaft voltage component analysis device according to the present invention;

[0029] Figure 2 This is a schematic diagram of typical waveforms of U6 and U1 measured by a digital oscilloscope in this invention;

[0030] Figure 3 This is a schematic flowchart of the method of the present invention;

[0031] Figure 4 This is a schematic diagram of the external part of the device of the present invention.

[0032] The attached diagram shows: 1. Rotor body; 2. Steam end main shaft; 3. Steam end carbon brush; 4. Excitation end main shaft; 5. Excitation end carbon brush; 6. Shaft voltage suppressor; 7. Digital oscilloscope; C1-C4, relays. Detailed Implementation

[0033] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0034] This application provides a method for analyzing the shaft voltage components of a static excitation generator, applicable to generators, such as... Figure 3 As shown, it includes:

[0035] S101 measures the shaft voltage component parameters of the generator under different measurement conditions.

[0036] The shaft voltage component parameters of the generator in different measurement states are measured, i.e., the shaft voltage component parameters are obtained according to different measurement states of the rotor of the generator, including a direct current component U0, a 6-fold frequency pulse component U6 and a power frequency-like alternating current component U1.

[0037] In order to improve the accuracy of the measurement results, in some embodiments of the present application, the shaft voltage component parameters of the generator in different measurement states are measured, specifically:

[0038] The electrostatic suspension potential of the generator in the state of the relay being closed or broken is measured, to obtain the direct current component U0;

[0039] Or, the trigger pulse coupling voltage of the generator in the state of the relay being closed or broken and the shaft voltage suppressor being put in or taken out is measured, to obtain the 6-fold frequency pulse component U6;

[0040] Or, the true rectified effective value of the generator in the state of the relay being closed or broken and the shaft voltage suppressor being put in is measured, to obtain the power frequency-like alternating current component U1.

[0041] S102, whether the shaft voltage component parameter reaches a dangerous value is detected;

[0042] If yes, a classified alarm is output;

[0043] If no, no classified alarm is output.

[0044] Based on the shaft voltage component parameters, i.e., the direct current component U0, the 6-fold frequency pulse component U6 and the power frequency-like alternating current component U1, whether the three kinds of shaft voltage component parameters reach a dangerous value is respectively detected, different classified alarms are output according to the detection results, the source of the "harmful shaft voltage" is quickly found out, and the staff is guided for maintenance.

[0045] In order to accurately judge the source of the "harmful shaft voltage" and guide the maintenance, in some embodiments of the present application, whether the shaft voltage component parameter reaches a dangerous value is detected; if yes, a classified alarm is output, specifically:

[0046] When the relay is closed, U0 is detected to be greater than X0, and a first classified alarm is output;

[0047] When the relay is broken, U0 is detected to be less than Y0, and a second classified alarm is output.

[0048] This relay is a single relay C1, when the relay C1 is closed and U0 is greater than X0, the first classified alarm is output, and the first classified alarm indicates that there is a problem of poor contact between the large shaft and the carbon brush at the steam end.

[0049] When the relay C1 is broken and U0 is less than Y0, the second classified alarm is output, and the second classified alarm indicates that the water content of the steam turbine oil is too high.

[0050] In order to accurately determine the harmful shaft voltage source and guide the maintenance, in some embodiments of the application, it is detected whether the shaft voltage component parameter reaches a dangerous value; if yes, a classified alarm is output, specifically:

[0051] When it is detected that U6 is greater than X6, a third classified alarm is output.

[0052] When it is detected that U6 is greater than X6, a third classified alarm is output, and the third classified alarm indicates that the parameter adjustment of the shaft voltage suppressor capacitor-resistor circuit is poor.

[0053] In order to accurately determine the harmful shaft voltage source and guide the maintenance, in some embodiments of the application, it is detected whether the shaft voltage component parameter reaches a dangerous value; if yes, a classified alarm is output, specifically:

[0054] When it is detected that U1 is greater than X1, a fourth classified alarm is output.

[0055] When it is detected that U1 is greater than X1, X1 is a standard parameter raised by the generator manufacturer, a fourth classified alarm is output, and the fourth classified alarm indicates that there is an oil film oscillation or an uneven air gap peripheral adjustment problem.

[0056] The above three shaft voltage component measurements are separate measurements, and the measurement and control unit switches among the above three measurement states.

[0057] By applying the above technical scheme, a shaft voltage component analysis method of a static excitation generator, the method comprises: measuring shaft voltage component parameters of the generator in different measurement states; detecting whether the shaft voltage component parameter reaches a dangerous value; if yes, a classified alarm is output; based on the three shaft voltage component parameters, including a direct current component U0, a 6 times frequency pulse component U6 and a class power frequency alternating current component U1, it is detected whether the above three shaft voltage component parameters reach a dangerous value, and when any one shaft voltage reaches a dangerous value, a classified alarm is output. The staff solves the corresponding safety problem according to the alarm category. The automation level and measurement accuracy of the shaft voltage analysis of the static excitation generator are improved, various shaft voltage components are analyzed, and different safety problems corresponding to different shaft voltage components are found in time.

[0058] In order to further illustrate the technical idea of the application, the technical scheme of the application will be described in combination with a specific application scenario.

[0059] The shaft voltage component analysis method comprises:

[0060] Measuring shaft voltage component parameters of the generator in different measurement states;

[0061] Detecting whether the shaft voltage component parameter reaches a dangerous value;

[0062] If yes, output a classification alarm.

[0063] If no, do not output a classification alarm.

[0064] In order to improve the accuracy of the measurement results, in some embodiments of the present application, the shaft voltage component parameters of the generator in different measurement states are measured, specifically:

[0065] The measurement and control unit controls the disconnection of relay C1, the closure of relay C2, the disconnection of relays C3 and C4, and the collection unit collects the electrostatic suspension potential, and the digital oscilloscope measures the direct current voltage component U0 (electrostatic voltage).

[0066] The measurement and control unit controls the input or exit of the shaft voltage suppressor, controls the closure of C1, the disconnection of C2 and C3, and the closure of C4, and the collection unit collects the trigger pulse coupling voltage, and the digital oscilloscope measures the pulse voltage mode (peak height + pulse width) to obtain the 6 times frequency pulse component U6 (trigger pulse coupling voltage).

[0067] The measurement and control unit controls the input of the shaft voltage suppressor, controls the closure of C1, the disconnection of C2 and C3, and the closure of C4, and the digital oscilloscope measures and collects the true rectified effective value (RMS) to obtain the similar power frequency alternating current component U1.

[0068] In order to accurately judge the "harmful shaft voltage source" and guide the maintenance, in some embodiments of the present application, whether the shaft voltage component parameters reach the dangerous value is detected; if yes, a classification alarm is output, specifically:

[0069] The electrostatic voltage is caused by the "dry" steam washing the turbine rotor blades, and the static charge is suspended on the insulating lubricating oil film in the entire rotor shaft system operating state, resulting in continuous accumulation of static charge. Because the lubricating oil film contains a certain amount of moisture, its insulation performance is limited, so the electrostatic voltage does not always continuously rise, but is a dynamic balance process composed of "washing accumulation" and "oil film discharge" mechanisms. By continuously measuring the electrostatic voltage U0, the change trend of the dynamic balance point can be monitored.

[0070] When relay C1 is closed and U0 is greater than X0, a first type of alarm is output, indicating that there is a problem of poor contact between the large shaft and the carbon brush at the steam end.

[0071] When relay C1 is disconnected and U0 is less than Y0, a second type of alarm is output, indicating that the water content of the turbine oil is too high.

[0072] X0 and Y0 are values set after comprehensive consideration of the entire generator set device, and are not fixed values, but will be relatively changed due to different specific conditions.

[0073] The trigger pulse coupling voltage U6 is formed by the trigger pulse of the excitation regulator coupled to the shaft. The shaft voltage suppressor at the excitation end is used to suppress the trigger pulse coupling voltage U6 caused by static excitation, and its RC snubber device is connected between the main shaft at the excitation end and the grounding grid.

[0074] When the analysis unit detects that U6 is greater than X6, it outputs a third type of alarm, which indicates that the parameters of the shaft voltage suppressor RC circuit are not properly adjusted.

[0075] X6 is a value set after comprehensively considering the condition of all generator set components. It is not a fixed value and will be changed relatively depending on the specific situation.

[0076] Additionally, the 6th harmonic pulse component U6 is the "common-mode voltage" coupled from the excitation regulator trigger pulse to the main shaft. Measured using a digital oscilloscope in pulse voltage mode (peak height + pulse width), the trigger pulse coupling voltage U6 is obtained. Inconsistent amplitude levels in U6 trigger an alarm, indicating a malfunction in the excitation regulator trigger pulse circuit. Continuously measuring the trend of U6 changes allows for load monitoring of faults related to the excitation regulator and trigger pulse circuit.

[0077] The power frequency AC voltage U1 is a component of shaft voltage, generated by the movement of a metal conductor cutting magnetic lines of force, but it has a different frequency and irregular waveform than the 50Hz power frequency AC voltage.

[0078] When the analysis unit detects that U1 is greater than X1, where X1 is a standard parameter set by the generator manufacturer, X1 = 10 volts when the generator power is below 300 MW, and X1 = 20 volts when the generator power is above 600 MW. A fourth type of alarm is output, indicating the presence of oil film oscillation or uneven adjustment around the air gap.

[0079] like Figure 2 As shown, the digital oscilloscope recorded typical waveforms of U1 and U6. The horizontal axial time is 20ms (equal to one cycle of power frequency AC). The lower continuous voltage U1 is not a standard sine wave, and its frequency is not 50Hz. According to the basic principle of electromagnetic induction, this parameter corresponds to the surge rate of the generator shaft system suspended on the oil film. A pulse voltage U6 (6th harmonic pulse component) with a frequency of 300Hz is superimposed on U1. Its reference potential is not consistent with the ground potential (zero potential), exhibiting obvious floating potential characteristics.

[0080] This application also proposes a device for analyzing the shaft voltage components of a static excitation generator, such as... Figure 1 As shown,

[0081] The device comprises a rotor body, one end of the rotor body is a steam end large shaft, the other end of the rotor body is an excitation end large shaft, a steam end carbon brush is connected to the steam end large shaft, an excitation end carbon brush is connected to the excitation end large shaft, an axle voltage suppressor is connected to the excitation end carbon brush, and the steam end carbon brush and the axle voltage suppressor are connected by a relay.

[0082] In order to accurately determine the source of harmful shaft voltage and guide maintenance, in some embodiments of the present application, the structure of the axle voltage suppressor is a resistance-capacitance device connected between the excitation end large shaft and the grounding net. The normal axle voltage suppressor is a resistance-capacitance absorption device connected between the positive and negative poles of the excitation bus, and the axle voltage suppressor of the present application is a resistance-capacitance absorption device connected between the excitation end large shaft (through the carbon brush) and the grounding net. The axle voltage suppressor with such a structure has better suppression effect on the common-mode voltage U6.

[0083] In order to accurately determine the source of harmful shaft voltage and guide maintenance, in some embodiments of the present application, the device is externally connected with a measurement and control unit, a collection unit and an analysis unit, as shown in Figure 4

[0084] The measurement and control unit is used to control the relay and the axle voltage suppressor to switch different measurement states.

[0085] The collection unit comprises a digital oscilloscope and is used to collect shaft voltage component parameters in different measurement states of the device, as shown in Figure 2

[0086] The analysis unit is used to detect whether the shaft voltage component parameters reach a dangerous value and output a classified alarm according to the detection result.

[0087] In order to control the research and development cost, the measurement and control unit, the collection unit and the analysis unit all use general devices and general software that can be purchased on the market. All professional technicians in this industry can easily understand and reproduce them, and therefore, no further description is given here.

[0088] The axle voltage component analysis method and device are used to continuously detect the shaft voltage of the generator with static excitation of the generator end transformer and provide a basis for condition-based maintenance.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit them. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents, and these modifications or replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.​​

Claims

1. A static excitation generator shaft voltage component analysis device, characterized by, The device includes: The rotor body has a steam end main shaft at one end and an exciter end main shaft at the other end; a steam end carbon brush is connected to the steam end main shaft and an exciter end carbon brush is connected to the exciter end main shaft. A shaft voltage suppressor is connected to the excitation end carbon brush, and its structure consists of a resistive and capacitive component bridging the excitation end shaft and the grounding grid. The relay is electrically connected to the steam-end carbon brush and the shaft voltage suppressor; The relays include relay C1, relay C2, relay C3, and relay C4; One end of relay C1 is connected to the carbon brush at the steam end, and the other end is connected to relay C2 and ground; One end of relay C2 is connected to relay C1 and ground, and the other end is connected to relay C3 and relay C4; One end of relay C3 is connected to relays C2 and C4, and the other end is connected to the shaft voltage suppressor; One end of relay C4 is connected to relays C2 and C3, and the other end is connected to the excitation end carbon brush and shaft voltage suppressor; The external unit includes a measurement and control unit, an acquisition unit, and an analysis unit. The measurement and control unit is used to control the closing or opening of the relay and the activation or deactivation of the shaft voltage suppressor, switching between different measurement states. The acquisition unit includes a digital oscilloscope for acquiring shaft voltage component parameters under different measurement states. The analysis unit is used to detect whether the shaft voltage component parameters have reached dangerous values ​​and output classified alarms based on the detection results.

2. A method of analyzing a shaft voltage component of a static excitation generator, characterized by applying the static excitation generator shaft voltage component analysis device according to claim 1 to a generator. The method includes: The shaft voltage component parameters of the generator under different measurement conditions are measured, specifically: When measuring the DC component U0, relay C1 is closed or opened, relay C2 is closed, and relays C3 and C4 are opened respectively to collect the electrostatic floating potential. When measuring the 6th harmonic pulse component U6, control relay C1 to close, relays C2 and C3 to open, and relay C4 to close, and switch the shaft voltage suppressor to be in or out of the state, and collect the trigger pulse coupling voltage; When measuring the AC component U1 of the power frequency, control relay C1 to close, relays C2 and C3 to open, and relay C4 to close, while keeping the shaft voltage suppressor engaged, to collect the actual rectified effective value; Detect whether the axis voltage component parameter has reached a dangerous value; If so, output a category alarm, specifically: When relay C1 is closed and U0 is greater than X0, a first-type alarm is output, indicating poor contact between the main shaft and the carbon brush at the steam end. When relay C1 is disconnected and U0 is less than Y0, a second type of alarm is output, indicating that the turbine oil has too high water content; When U6 is greater than X6, a third type of alarm is output, indicating that the parameters of the shaft voltage suppressor RC circuit are not properly adjusted; When U1 is greater than X1, a fourth type of alarm is output, indicating that there is oil film oscillation or uneven adjustment around the air gap. X1 = 10 volts when the generator power is below 300 MW and X1 = 20 volts when the generator power is above 600 MW.

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