Isolation switch mechanical defect detection method

Abstract

The invention provides a method for detecting mechanical defects of an isolating switch. The method comprises the following steps: acquiring a motor voltage signal and a current signal in a closing operation process of a diagnosed isolating switch; calculating motor output power according to the voltage signal and the current signal, and drawing a corresponding motor output power-time curve; and comparing and analyzing the motor output power-time curve and the normal state curve of the isolating switch of the same model as the diagnosis object, and judging whether the diagnosed isolating switch has mechanical defects or not and the defect type of the mechanical defects. According to the method, voltage and current of a power supply side of a motor in the action process of the disconnecting switch in an online operation state are detected, corresponding input power is calculated, loss generated in the transmission process of the power in the motor is subtracted on the basis, the output power of the motor is obtained, a corresponding motor output power-time curve is drawn, and the output power of the motor is calculated. And the mechanical state of the disconnecting switch is judged according to the motor output power curve in the action process of the disconnecting switch.

Description

Technical Field

[0001] The present invention relates to the field of power systems, and more specifically, to a method for detecting mechanical defects of an isolating switch. Background Art

[0002] High-voltage disconnectors are one of the important switchgear in the power system. They are driven by an electric operating mechanism to drive the transmission mechanism to complete the opening and closing of the main knife switch. Disconnectors are installed on both sides of the circuit breaker. They are mainly used to isolate voltage, switch circuits, and switch small currents. When switching the operation mode or shutting down the equipment for maintenance, the disconnector forms an obvious circuit disconnection point after the disconnector is opened, which can ensure the safe isolation of the power-off equipment and lines from the operating system. In order to ensure the personal safety of maintenance personnel and the safety of equipment, the electrical equipment needs to have sufficient dynamic thermal stability, mechanical strength and insulation strength. However, since most high-voltage disconnectors work in outdoor environments such as power plants and substations, the rotation and transmission mechanisms are exposed to harsh atmospheric environments for a long time, and are eroded by wind, frost, rain and snow. In addition, due to untimely operation and maintenance, various faults and defects are prone to occur.

[0003] The fault defects of high-voltage disconnectors are mainly reflected in four aspects, namely overheating of the conductive circuit, insulator breakage, improper operation, and rust and jamming, and the latter three are all mechanical defects. There are many methods for diagnosing insulator breakage failures, such as vibration acoustic flaw detection, stress detection, and infrared temperature measurement. In existing studies, the finite element method is used to derive the relationship between the stress strain and the load of the porcelain column insulator, and the disconnector is determined by stress detection. Due to the three-phase linkage structure of the high-voltage disconnector and the complex transmission mechanism between the master and slave poles, the electrical equipment has many types of mechanical failures, and the location of the fault point is difficult to determine. Summary of the invention

[0004] The present invention solves the defects in the existing research and provides a method for detecting mechanical defects of an isolating switch, comprising: Obtain the motor voltage signal and current signal during the closing operation of the diagnosed disconnector; Calculate the motor output power according to the voltage signal and the current signal, and draw a corresponding motor output power-time curve; The motor output power-time curve is compared and analyzed with the normal state curve of the same type of disconnector as the diagnosed object to determine whether the diagnosed disconnector has mechanical defects and the type of defects.

[0005] The present invention provides a method for detecting mechanical defects of an isolating switch, which detects the voltage and current on the power supply side of a motor during the operation of the isolating switch in an online operation state, calculates the corresponding input power, and on this basis, subtracts the loss caused by the power transmission inside the motor to obtain the output power of the motor, and then draws the corresponding motor output power-time curve, so as to judge the mechanical state of the isolating switch through the motor output power curve during the operation of the isolating switch. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 A flow chart of a method for detecting mechanical defects of an isolating switch provided by the present invention; Figure 2 It is a schematic diagram of the original waveform and sampling waveform of the measured voltage and current of the isolating switch; Figure 3 It is a schematic diagram comparing the motor output power-time curve when the isolating switch bearing is stuck and the normal state curve; Figure 4 It is a schematic diagram showing the comparison between the motor output power-time curve when the three phases are in different phases and the normal state curve; Figure 5 It is a schematic diagram showing the comparison between the motor output power-time curve when the operation is not in place and the normal state curve; Figure 6 The present invention is a schematic diagram of the overall process of the isolating switch mechanical defect detection method provided by the present invention. DETAILED DESCRIPTION

[0007] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In addition, the technical features in the various embodiments or single embodiments provided by the present invention can be arbitrarily combined with each other to form a feasible technical solution. This combination is not subject to the constraints of the sequence of steps and / or the structural composition mode, but must be based on the ability of ordinary technicians in this field to achieve. When the combination of technical solutions is contradictory or cannot be achieved, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0008] Typical mechanical defects that occur frequently in disconnectors include transmission jam, inadequate opening and closing, and three-phase out of phase. The following describes mechanical defects such as transmission jam, inadequate opening and closing, and three-phase out of phase. Among them: (1) Transmission jam: High-voltage disconnectors work outdoors, and the surfaces of their metal parts are in direct contact with the air, which is prone to chemical reactions such as oxidation, which in turn causes the material to rust. At the same time, harmful solid particles and gas components in the atmosphere react chemically with water to generate electrolyte solutions that adhere to the surface of metal parts, which also accelerates electrochemical corrosion. In addition to external environmental factors, the disconnector structure itself has mechanical parts such as rotating bearings and shaft pins. When the sealing design is unreasonable, external factors such as dust and rainwater enter the gap of the rotating shaft, and long-term accumulation will also cause internal corrosion of the mechanical parts. Rust is a common problem of high-voltage disconnectors, and the rust problem usually causes different degrees of transmission mechanism jamming, which reduces the mechanical strength of the components and makes the disconnector difficult to operate. In severe cases, it will cause damage and deformation of parts, and a sharp increase in operating torque and other adverse effects. (2) Inadequate opening and closing: Two travel limit switches are installed in the electric operating mechanism of the high-voltage disconnector, which cut off the power supply of the drive motor at the end of the opening and closing operations, respectively, to control the start and stop actions of the opening and closing operations. When the contact touches the limit position block, the closed contact is disconnected or the open contact is closed, thereby changing the state of the control circuit. If the position of the limit block is offset, the limit block does not contact the contact when the closing operation is about to end, and the limit switch cannot be cut off, causing the drive motor to continue to rotate, resulting in an over-closing fault; or because the limit nut is loose, the screw length changes, causing the position of the limit switch to change, and the motor stops running before the upper rotating arm of the operating insulator passes the "dead point", which leads to the disconnector not opening and closing.

[0009] (3) Three-phase synchronization: Three-phase linkage is an important mechanical motion feature of high-voltage disconnectors. For high-voltage disconnectors, three-phase synchronization refers to the larger value of the minimum contact distances of the other two phases when one of the three phases reaches the just-closed position first during the opening and closing operation. After the high-voltage disconnector is disassembled and packed and shipped out of the factory, it needs to be installed and debugged on site. If the debugging is not appropriate, the mechanical dimensions of the cross-link, inter-phase link, and master-slave crank arm may differ from the standard state, which may cause leading or lagging three-phase synchronization faults.

[0010] For the detection of mechanical defects of disconnectors, some scholars have proposed that the mechanical state of disconnectors can be determined by detecting the torque or strain of the operating lever during the operation of the disconnector. It is proposed to install a torque sensor at the handle of the manual operating mechanism of the disconnector, and to determine whether the disconnector is in a normal state by detecting the operating torque during the manual operation of the disconnector. This method is simple to operate, and there is no need to destroy the original structure when installing the detection device. However, some models of disconnectors require a large torque when operated manually, and it is difficult to ensure that the hand-cranking speed is consistent during the measurement process. The test repeatability is poor, resulting in a large number of burrs on the detection curve, which seriously interferes with the state judgment and lacks accuracy.

[0011] Other researchers pointed out that since there is a proportional relationship between the torsional strain of the output shaft of the disconnector operating mechanism and the output torque, the mechanical state of the disconnector can also be reflected by measuring the strain of the output shaft during operation. However, due to the high sensitivity of strain gauges, the strain detection results are affected by many factors such as the location of the strain gauge and external signal interference, and are not suitable for long-term online use.

[0012] In addition, some researchers have proposed that the mechanical fault of the disconnector can be diagnosed by detecting the mechanical vibration signal at a certain position of the operating mechanism of the disconnector. The single-channel vibration signal at a certain point of the B-phase beam of the disconnector is analyzed, and the feature of the vibration signal is extracted by empirical mode decomposition. Then, the sample is trained by the support vector machine algorithm. This method can accurately diagnose the mechanical state of the disconnector and is effective; based on the ReliefF algorithm, the multi-channel vibration signals collected at multiple positions of the disconnector are fused, and the BP neural network algorithm is used to diagnose the fault of the disconnector, which can accurately identify the fault location and type of the disconnector; some scholars took the GW4-126 disconnector as the research object, installed high-precision vibration sensors on the disconnector contacts, detected the vibration signals during mechanical movement, and extracted the features of the vibration data to obtain non-stationary signals that can effectively identify the mechanical state of the disconnector.

[0013] Comprehensive analysis of the above research results shows that most of the current mechanical defect diagnosis methods related to high-voltage disconnectors use different characteristic state quantities as the basis for judgment, but lack accurate model demonstration.

[0014] Figure 1 A flow chart of a method for detecting mechanical defects of an isolating switch provided by the present invention, such as Figure 1 As shown, the method includes: Step S1, obtaining the motor voltage signal and current signal during the closing operation of the diagnosed isolating switch.

[0015] The method of obtaining the motor voltage signal and current signal during the closing operation of the diagnosed isolating switch includes: based on the two-wattmeter detection principle, using two voltage sensors to respectively detect the line voltage of the driving motor in the operating mechanism box; u ab and u bc is used for detection, and two current sensors are used to detect the input phase current of the motor a and b respectively. i a. i b.

[0016] It can be understood that the present invention adopts the two-meter method principle to detect the voltage and current on the power supply side of the motor during the operation of a certain GW4 type disconnector in an online operation state, calculates the corresponding input power, and subtracts the loss caused by the power transmission inside the motor on this basis to obtain the output power of the motor, and then draws the corresponding motor output power-time curve to judge the mechanical state of the disconnector through the motor output power curve during the operation of the disconnector.

[0017] Among them, the two-wattmeter method is a method commonly used to measure the power of three-phase motors, especially for three-phase systems with delta connection and star connection. Its principle is to calculate the total three-phase power in a three-phase system by measuring the readings of two single-phase wattmeters.

[0018] The wiring method of the two-meter method is: For the triangle connection (Delta), the instrument wiring method is: The current coils of the two single-phase wattmeters are connected in series between phase lines A and B, and B and C respectively, and the voltage coils of the two single-phase wattmeters are connected to phase lines A and C respectively.

[0019] For star connection (Y), the instrument wiring method is: connect the current coils of two single-phase power meters in series between phase lines A and B, B and C respectively, connect the voltage coils of two single-phase power meters to phase lines A and C respectively, and use the neutral line as a reference.

[0020] The present invention is based on the two-wattmeter detection principle and uses two voltage sensors to measure the line voltage of the driving motor in the operating mechanism box respectively. u ab and u bc is used for detection, and the two current sensors are used to detect the input phase current of the motor a and b respectively. i a. i b.

[0021] Step S2, calculating the motor output power according to the voltage signal and the current signal, and drawing a corresponding motor output power-time curve.

[0022] Among them, according to the line voltage of the motor u ab, u bc and motor a, b two-phase input current i a. i b. Calculate the motor input power and power loss. The power loss includes copper loss, iron loss, and mechanical loss. The motor output power = motor input power - power loss.

[0023] The voltage and current sensors are used to measure the voltage and current waveforms of the equipment under test, and the sampled data are obtained after sampling. The sampled data are calculated according to a certain time.T To segment, Figure 2 The original waveform and sampling waveform of the measured voltage and current of the isolating switch.

[0024] Calculation interval T Not too small, nor too large: T The minimum value is half of the power frequency cycle, that is, 0.01s; when T If the value is too large, such as 0.1s, the corresponding active power data during the disconnector operation period is 70~80, and the data volume is relatively small. Under normal circumstances, the relationship between the calculation cycle T and the power supply frequency cycle cycle is: 1 / 2cycle≤T≤2cycle. When calculating, it is recommended to set the calculation interval time length T to the power supply frequency cycle 0.02s.

[0025] The three-phase average power of the motor is calculated based on the three-phase balance principle. In a discrete system, the instantaneous average power is calculated by measuring the sampled values ​​of voltage and current within a cycle. Assume that within a cycle there is N The instantaneous average power can be calculated using the following formula.

[0026] Calculate the instantaneous power of phase A: ; Calculate the instantaneous power of phase B: ; Calculate the instantaneous power of phase C: ; in, ; ; In the formula, , , They represent the line voltage of phases A and B, the line voltage of phases B and C, and the line voltage of phases A and C at the nth sampling point in the calculation cycle, respectively. , , They represent the A-phase current, B-phase current and C-phase current of the n-th sampling point respectively. , , They respectively represent the instantaneous power of phase A, phase B and phase C at the nth sampling point in the calculation period.

[0027] The average power Pavg during the calculation period is: ; = ; Among them, the average power Pavg within the cycle is the motor input power within the calculation cycle.

[0028] After calculating the motor input power within the calculation cycle, the motor output power is obtained by subtracting the loss power from the motor input power. Among them, the motor loss mainly includes copper loss, iron loss, and mechanical loss. The copper loss is mainly caused by the motor winding resistance, which is proportional to the square of the current.

[0029] Copper loss can be expressed as: ; Among them, i=1,2,3, respectively represents phase A, phase B and phase C, represents the copper loss of the i-th phase, represents the phase current of the i-th phase, represents the resistance of the i-th phase winding.

[0030] Iron loss mainly consists of hysteresis loss and eddy current loss, which is related to the operating frequency and magnetic flux density of the motor. Iron loss is usually provided on the motor nameplate. Mechanical loss includes wind friction loss and bearing friction loss, etc. Mechanical loss is usually also determined by experiment.

[0031] According to the calculated motor input power and power loss, the motor output power within the calculation period is obtained, and the motor output power-time curve is drawn.

[0032] Step S3, comparing and analyzing the motor output power-time curve with the normal state curve of the same type of disconnector as the diagnosed object, to determine whether the diagnosed disconnector has mechanical defects and the defect type.

[0033] Among them, mechanical defects include mechanical defects such as bearing jam, three-phase out of sync and improper operation. Compare and analyze the motor output power-time curve with the normal state curve of the same model of the diagnostic object disconnector to determine whether the diagnosed disconnector has mechanical defects and the defect type, including: obtaining the motor output power-time curve within the calculation period; extracting the first characteristic quantity, the second characteristic quantity and the third characteristic quantity of the motor output power-time curve respectively; respectively comparing the first characteristic quantity, the second characteristic quantity and the third characteristic quantity with the first characteristic quantity, the second characteristic quantity and the third characteristic quantity of the motor output power-time curve in the normal state, and judging whether the diagnosed disconnector has mechanical defects such as bearing jam, three-phase out of sync and improper operation according to the comparison results.

[0034] The first characteristic quantity is the average output power within the calculation period, the second characteristic quantity is the closing operation time corresponding to the first mutation point of the power curve, and the third characteristic quantity is the closing end time.

[0035] Correspondingly, the first characteristic quantity, the second characteristic quantity and the third characteristic quantity are respectively compared with the first characteristic quantity, the second characteristic quantity and the third characteristic quantity of the motor output power-time curve in a normal state, and it is judged whether the diagnosed disconnector has mechanical defects such as bearing jamming, three-phase out of phase and improper operation according to the comparison result, including: If the difference between the output power average value of the diagnosed isolating switch within the calculation cycle and the output power value under normal conditions exceeds the set range, it is determined that the diagnosed isolating switch has a bearing jamming mechanical defect; If the closing operation time corresponding to the first mutation point of the power curve of the diagnosed disconnector is earlier than the closing operation time corresponding to the first mutation point under normal state by a first set time, it is determined that the diagnosed disconnector has a three-phase out-of-phase mechanical defect; If the closing completion time of the diagnosed disconnector is earlier than the closing completion time under normal conditions by a second set time, it is determined that the diagnosed disconnector has a mechanical defect of improper operation.

[0036] The following is a detailed introduction to the detection of different types of mechanical defects: Detection of bearing jam: After the disconnector is put into operation for a long time, the sealing sleeve of the bearing seat gradually ages, and the erosion of dust, water vapor, harmful gases, etc. causes the grease to be lost and solidified, resulting in a significant increase in the movement resistance torque and a bearing jam fault. In order to conduct a simulation test of the bearing jam defect, a clamp is fixedly installed on the A-phase active pole slot steel of the test object GW4-126 type disconnector to clamp the A-phase active pole porcelain bottle flange, and the severity of the bearing jam is simulated by adjusting the fastening nut on the clamp. Adjust the power supply voltage of the operating mechanism box to 380V, and use the above-mentioned power detection method to detect the motor output power during the closing operation of the disconnector in the state of bearing jam, and draw the corresponding motor output power-time curve for comparison with the normal state, see. Figure 3 .

[0037] It is observed that at the initial stage of closing the disconnector, the motor output power curve in the state of bearing jamming is basically the same as that in the normal state. When the closing operation is about 1s, the power value gradually increases. This is because during the closing operation, the bearing components do not rotate at a uniform speed, and the speed increases first and then decreases. When the speed is low, the bearing friction is static friction, which brings a small resistance torque, and the power required to be output by the operating mechanism is correspondingly small. During the translational operation stage of the disconnector (when the contact fingers are not in contact), the power curve in the state of bearing jamming has periodic fluctuations. This is because when a clamp is used to clamp the bottom flange of the A-phase rotating insulator to simulate the bearing jam defect, when the flange and the clamp rotate relative to each other, the friction resistance torque between the clamp and the flange is ideally constant, so the relative motion is theoretically a gentle relative sliding process. However, during the actual operation, periodic relative sliding occurs between the flange and the clamp, which leads to large fluctuations in the motor output power curve. At the same time, due to Figure 3 It can be clearly seen that the motor output power value when the bearing is stuck is much higher than that in the normal state. Through calculation, it is found that the average motor output power is 26.48W in the normal state, and the average motor output power is 49.95W when the bearing is stuck, which is 88.63% higher than the normal state. This can be used as one of the bases for judging the mechanical state of the disconnector.

[0038] Therefore, when detecting the bearing jamming defect of the isolating switch, the first characteristic quantity of the motor output power-time curve of the diagnosed isolating switch, that is, the mean motor output power, can be extracted, and the mean motor output power of the diagnosed isolating switch can be compared with the mean motor output power of the isolating switch in the normal state. If the proportion of the mean motor output power of the diagnosed isolating switch exceeding the mean motor output power of the isolating switch in the normal state is greater than the set threshold, it is determined that the diagnosed isolating switch has a bearing jamming defect.

[0039] For the defect detection of three-phase out-of-phase: debugging operation is required after the on-site installation or power outage maintenance of the disconnector. If the debugging is improper, the disconnector will have the hidden danger of three-phase out-of-phase failure. For the GW4 type disconnector, the adjustable parts are waist-shaped grooves (also called oblong holes, 35mm long) located at the ends of the linkage crank arm and the driven crank arm for fixing bolts. By moving the position of the bolt (diameter 15mm) in the waist-shaped hole, the center distance of the crank arm length can be adjusted to achieve the actual adjustment of the crank arm length. The joints of the interphase connecting rod and the cross connecting rod are connected to the crank arm with nuts and screws. By rotating the connecting rod, the thread engagement depth is changed to achieve the adjustment of the connecting rod length.

[0040] The fault simulation experiment takes the three-phase out-of-phase defect of phase A leading as an example for analysis. By adjusting the length of the cross-link rod of phase A of the test object to make it extend by 4mm, when the contact finger of phase A has been in contact, the contact fingers of phases B and C have not been in contact. The power detection method is used to detect the motor output power during the closing operation of the disconnector under the three-phase out-of-phase state, and the corresponding output power-time curve is drawn for comparison with the normal state, see Figure 4 During the closing operation of the three-phase out-of-phase state, because the contact fingers of phase A contact in advance, in order to overcome the resistance caused by the contact fingers cutting into the contact fingers, the operating mechanism box needs to output more power to provide the operating rod to rotate, then the closing operation time corresponding to the first mutation point of the power curve is reduced to 5.47s (5.57s in the normal state). At this time, the meshing behavior of the contact fingers changes. In order to overcome the friction torque during the meshing process, the operating mechanism needs to output more power, so the first typical peak value of the closing waveform curve increases significantly.

[0041] Based on this, when detecting the three-phase out-of-phase defects of the disconnected switch, the second characteristic quantity of the motor output power-time curve of the diagnosed disconnected switch is extracted, that is, the closing operation time corresponding to the first mutation point on the power curve, and the closing operation time corresponding to the first mutation point on the power curve of the diagnosed disconnected switch is compared with the closing operation time corresponding to the first mutation point on the power curve under the normal state of the disconnected switch. If the closing operation time of the diagnosed disconnected switch is earlier than the closing operation time under the normal state, it indicates that the diagnosed disconnected switch has a mechanical defect of three-phase out-of-phase.

[0042] For the defect detection of inadequate operation: When the high-voltage disconnector is in online operation, the limit switch in the operating mechanism box controls the stop of opening and closing. When the limit nut and the limit device in the box are improperly installed or loose, the disconnector will not operate properly or over-operate. Inadequate operation will cause unequal contact force between the contact and the left and right contact fingers, increase the overall contact resistance of the contact fingers, and easily cause overheating after long-term current operation. The defect simulation experiment adjusts the length of the limit nut to make it contact with the limit switch baffle in advance to simulate the defect of inadequate operation.

[0043] In the case of incomplete operation, the limit nut contacts the limit baffle in advance, causing the contact for closing and stopping the operation to be triggered early. Figure 5 When the disconnector is not properly operated, the disconnector stops closing at 7.27s, which is 0.1s earlier than the normal state. Except for the closing end stage, in other intervals, the output power curves of the incomplete operation and the normal state are basically overlapped. Therefore, by comparing the maximum closing operation time according to the power detection curve, it can be judged whether the disconnector under test has the defect of incomplete operation.

[0044] Therefore, when detecting the defect of improper operation of the diagnosed disconnecting switch, the third characteristic quantity of the motor output power-time curve of the diagnosed disconnecting switch is extracted, that is, the closing completion time. If the closing completion time of the diagnosed disconnecting switch is significantly earlier than the closing completion time of the disconnecting switch under normal conditions (the advance time exceeds the set threshold time), then it is determined that the diagnosed disconnecting switch has a mechanical defect of improper operation.

[0045] See also Figure 6 , is a schematic diagram of the overall process of a disconnector mechanical defect detection method provided by the present invention. First, a power detection device (including two voltage sensors and two current sensors) is used to detect the motor voltage and current signals during the closing operation of the disconnector to be diagnosed. The motor output power is obtained by calculation, and the corresponding motor output power-time curve is drawn to compare and analyze the detection curve with the normal state curve of the disconnector of the same model as the diagnosis object. According to the differences in characteristic quantities such as the typical peak or trough distribution position, number, amplitude and power mean of the curve, it is judged whether the disconnector to be detected has mechanical defects and the defect type. For example: if the closing operation end time is shorter than the normal state, it is judged that there is an inadequate operation defect; if the operation time corresponding to the first mutation point of the curve is reduced (the contact just closes in advance), it is judged that the disconnector to be detected has a three-phase out-of-phase defect with one phase ahead; if the power value increases as a whole (power mean), it is judged that there is a transmission jam defect. When using this diagnostic technology to diagnose the mechanical defects of the disconnector, it is necessary to comprehensively consider the deformation of the appearance of the disconnector, the operation process, the operating environment and other factors. This method is suitable for the diagnosis of mechanical defects of disconnectors of different models, but it should be appropriately adjusted according to the model differences.

[0046] The present invention provides a method for detecting mechanical defects of an isolating switch, which detects the voltage and current on the power supply side of a motor during the operation of the isolating switch in an online operation state, calculates the corresponding input power, and on this basis, subtracts the loss caused by the power transmission inside the motor to obtain the output power of the motor, and then draws the corresponding motor output power-time curve, so as to judge the mechanical state of the isolating switch through the motor output power curve during the operation of the isolating switch.

[0047] It should be noted that in the above embodiments, the description of each embodiment has its own emphasis, and for parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0048] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0049] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for detecting mechanical defects of an isolating switch, characterized in that: include: Obtain the motor voltage signal and current signal during the closing operation of the diagnosed disconnector; Calculate the motor output power according to the voltage signal and the current signal, and draw a corresponding motor output power-time curve; The motor output power-time curve is compared and analyzed with the normal state curve of the same type of disconnector as the diagnosed object to determine whether the diagnosed disconnector has mechanical defects and the type of defects.

2. The method for detecting mechanical defects of disconnectors according to claim 1, characterized in that: The step of obtaining the motor voltage signal and current signal during the closing operation of the diagnosed isolating switch includes: Based on the two-wattmeter detection principle, two voltage sensors are used to measure the line voltage of the drive motor in the operating mechanism box. u ab and u bc is used for detection, and two current sensors are used to detect the input phase current of the motor a and b respectively. i a. i b.

3. The method for detecting mechanical defects of disconnectors according to claim 2, characterized in that: According to the voltage signal and the current signal, the motor output power is calculated, and the corresponding motor output power-time curve is drawn, including: According to the line voltage of the motor u ab, u bc and motor a, b two-phase input current i a. i b. Calculate the motor input power and power loss. The power loss includes copper loss, iron loss, and mechanical loss. The motor output power = motor input power - power loss.

4. The method for detecting mechanical defects of disconnectors according to claim 3, characterized in that: The line voltage of the motor u ab, u bc and motor a, b two-phase input current i a. i b. Calculate the motor input power, including: Determine a calculation cycle, wherein there are N sampling points in one calculation cycle; Calculate the instantaneous power of phase A: ； Calculate the instantaneous power of phase B: ； Calculate the instantaneous power of phase C: ； in, ； ； In the formula, , , They represent the line voltage of phases A and B, the line voltage of phases B and C, and the line voltage of phases A and C at the nth sampling point in the calculation cycle, respectively. , , They represent the A-phase current, B-phase current and C-phase current of the n-th sampling point respectively. , , They represent the instantaneous power of phase A, phase B and phase C at the nth sampling point in the calculation period respectively; The average power Pavg during the calculation period is: ； = ； Among them, the average power Pavg within the cycle is the motor input power within the calculation cycle.

5. The method for detecting mechanical defects of disconnectors according to claim 3, characterized in that: Calculation of power dissipation, including: Copper loss is expressed as: ； Among them, i=1,2,3, respectively represents phase A, phase B and phase C, represents the copper loss of the i-th phase, represents the phase current of the i-th phase, represents the resistance of the i-th phase winding; Get the iron loss of the motor according to the motor nameplate; And obtain the mechanical loss of the motor through experimental measurement.

6. The method for detecting mechanical defects of disconnectors according to claim 4, characterized in that: The relationship between the calculation period T and the power supply frequency period cycle is: 1 / 2cycle≤T≤2cycle.

7. The method for detecting mechanical defects of disconnectors according to claim 1, characterized in that: The mechanical defects include bearing jamming, three-phase out of sync and improper operation. The motor output power-time curve is compared and analyzed with the normal state curve of the same type of disconnector as the diagnosed object to determine whether the diagnosed disconnector has mechanical defects and the defect type, including: Obtain the motor output power-time curve within the calculation period; Extracting a first characteristic quantity, a second characteristic quantity and a third characteristic quantity of the motor output power-time curve respectively; The first characteristic quantity, the second characteristic quantity and the third characteristic quantity are respectively compared with the first characteristic quantity, the second characteristic quantity and the third characteristic quantity of the motor output power-time curve under normal conditions, and according to the comparison results, it is determined whether the diagnosed isolating switch has mechanical defects such as bearing sticking, three-phase synchronization and improper operation.

8. The method for detecting mechanical defects of disconnect switches according to claim 7, characterized in that: The first characteristic quantity is the average output power within the calculation period, the second characteristic quantity is the closing operation time corresponding to the first mutation point of the power curve, and the third characteristic quantity is the closing end time.

9. The method for detecting mechanical defects of disconnectors according to claim 8, characterized in that: The first characteristic quantity, the second characteristic quantity and the third characteristic quantity are respectively compared with the first characteristic quantity, the second characteristic quantity and the third characteristic quantity of the motor output power-time curve in a normal state, and judging whether the diagnosed disconnector has mechanical defects such as bearing jamming, three-phase out of phase and improper operation according to the comparison result, including: If the difference between the output power average value of the diagnosed isolating switch within the calculation cycle and the output power value under normal conditions exceeds the set range, it is determined that the diagnosed isolating switch has a bearing jamming mechanical defect; If the closing operation time corresponding to the first mutation point of the power curve of the diagnosed disconnector is earlier than the closing operation time corresponding to the first mutation point under normal state by a first set time, it is determined that the diagnosed disconnector has a three-phase out-of-phase mechanical defect; If the closing completion time of the diagnosed disconnector is earlier than the closing completion time under normal conditions by a second set time, it is determined that the diagnosed disconnector has a mechanical defect of improper operation.

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