Motor insulation potential fault off-line detection method

Abstract

The invention relates to the technical field of motor insulation fault detection, in particular to a motor insulation potential fault offline detection method. In order to solve the problem that an existing motor insulation off-line detection method cannot completely eliminate motor insulation potential faults, the invention provides a novel motor insulation potential fault off-line detection method which comprises the following steps: 1) normal-temperature electrical parameter detection of a motor; (3) water outlet electrical parameter detection of the motor; (4) fault judgment: (1) determining the health degree range of the normal temperature electrical parameter, the water immersion electrical parameter and the water outlet electrical parameter of the motor with the same running mileage; and (2) motor insulation potential fault judgment. According to the invention, the overall insulation structure of the motor is evaluated based on the dielectric loss and capacitance before and after offline immersion, and the motor insulation fault recognition rate is improved.

Description

Technical Field

[0001] This invention relates to the field of motor insulation fault detection technology, specifically to an offline detection method for potential motor insulation faults. Background Technology

[0002] With the development of variable frequency control, pulse width modulation (PWM) technology has been widely used in AC variable frequency motors. This allows the motor insulation to withstand voltages with higher rates of change and peak values. However, the high rate of change in the voltage waveform further increases the peak voltage reflected from the cable, accelerating the aging of the motor insulation. Common fault types in AC motors include stator faults, bearing faults, and rotor faults; 30%–40% of AC motor faults are related to the stator.

[0003] Offline testing methods for motor insulation structures are relatively mature, including testing insulation resistance, dielectric loss factor, absorption ratio, polarization index, partial discharge, etc., and there are corresponding national standards for these testing methods. Therefore, in the offline state, by testing parameters such as insulation resistance, dielectric loss, and partial discharge, and by setting corresponding parameter thresholds, the state of motor insulation can be determined. However, even if a motor with a good test state is running normally, it is still impossible to completely eliminate potential defects inside the motor insulation, and fundamentally identify motors with potential faults.

[0004] Existing technology 1: The invention patent "An Offline Three-Phase AC Motor Fault Detection Method" by Li Zhongwei et al. discloses an offline method for detecting stator winding inter-turn short circuits, rotor faults, and the severity of faults. This invention calculates phase-phase resistance imbalance by measuring phase-phase resistance, inductance imbalance by measuring phase-phase inductance, impedance imbalance by measuring phase-to-phase impedance, and maximum phase angle by measuring phase angle. Based on the obtained data, it determines whether the motor has a fault and the severity of the fault. However, this technology mainly targets inter-turn and rotor faults and does not detect the condition of the main insulation. Existing technology 2: Standards such as GB / T 20833.4-2021 "Insulation of Windings of Rotating Electrical Machines - Part 4: Measurement of Insulation Resistance and Polarization Index", GB / T 20833.3-2018 "Insulation of Stator Windings of Rotating Electrical Machines - Part 3: Measurement of Dielectric Loss Factor", GB / T 20833.1-2021 "Insulation of Windings of Rotating Electrical Machines - Part 1: Offline Partial Discharge Test", GB / T20833.2-2016 "Insulation of Stator Windings of Rotating Electrical Machines - Part 2: Online Partial Discharge Test", and GB / T 20833.5-2023 "Insulation of Windings of Rotating Electrical Machines - Part 5: Offline Measurement of Partial Discharge Initiation Voltage under Repetitive Impulse Voltage" specify the testing methods for insulation resistance, polarization index, dielectric loss factor, and partial discharge. However, while they specify the testing methods, they do not provide the methods for judging the results, and they do not explain the threshold and health assessment methods for defective motors. Summary of the Invention

[0005] In order to solve the problem that existing offline detection methods for motor insulation cannot completely eliminate potential faults in motor insulation, this invention provides a new offline detection method for potential faults in motor insulation.

[0006] This invention is achieved using the following technical solution: An offline detection method for potential insulation faults in motors includes the following steps: 1) Normal temperature electrical parameter testing of the motor: The room temperature insulation resistance, room temperature dielectric loss factor tanδ0, and room temperature capacitance C0 of the motor are tested at room temperature. If the room temperature insulation resistance is greater than R0 and the room temperature dielectric loss factor is ≤1.5%, it means that the motor has passed the preliminary test and needs to be immersed in water for testing. Otherwise, it means that the motor has failed the test and needs to be reinforced with insulation. 2) Electrical parameter testing of the motor after immersion in water: For motors that pass the initial electrical test at room temperature, immerse them in water and test the immersion insulation resistance, immersion dielectric loss factor tanδ1, and immersion capacitance C1 under immersion conditions. 3) Testing of the motor's outlet electrical parameters: Immediately after the water outlet is discharged, test the water outlet medium loss factor tanδ2 and the water outlet capacitance C2 of the motor. 4) Fault diagnosis: ① Determine the health range of electrical parameters at normal temperature, immersion, and outlet for motors with the same operating mileage. Multiple motors with the same operating mileage were selected, and their electrical parameters at room temperature, immersion in water, and outlet in water were tested. The health range of motors with the same operating mileage was determined based on the concentrated distribution area of ​​the multiple sets of electrical parameters at room temperature, immersion in water, and outlet in water. ② Judgment of potential motor insulation faults When the immersion insulation resistance of the motor under test is less than R0, the motor under test is a faulty motor and requires corresponding insulation reinforcement. When the immersion insulation resistance of the motor under test is greater than R0, further judgment is required. If the electrical parameters at room temperature, immersion, and outlet are all within the health range of motors with the same operating mileage, the motor under test is in normal and healthy condition. If any one of the electrical parameters at room temperature, immersion, or outlet is outside the health range of motors with the same operating mileage, the motor under test has a potential fault.

[0007] Furthermore, step 4) also includes step ③, fault mode judgment: When step ② determines that the motor under test has a potential fault, its fault mode is then judged. When tanδ0 exceeds the health range and C0 is below the health range, it indicates that there are many gaps and delamination in the slot opening. When tanδ0 exceeds the health range and C0 is normal, it indicates that there are a small amount of air gaps and delamination inside the slot opening insulation. When tanδ0 exceeds the health range and C0 is above the health range, it indicates that the slot insulation is damp and needs to be dried and retested. When tanδ1 exceeds the health range and C1 is below the health range, it indicates that water vapor has not entered the insulation, and there is a lot of delamination inside the end or slot opening insulation. When tanδ1 is within the health range and C1 is normal, it indicates that moisture has not entered the insulation interior, and there is less insulation delamination at the ends and slot openings. When tanδ1 exceeds the health range and C1 is higher than the health range, it indicates that moisture has entered the insulation interior, but has not formed a penetrating channel. When tanδ2 exceeds the health range and C2 is lower than the health range, it indicates that moisture has not entered the insulation interior at the ends and slot openings, and there is more delamination inside the insulation. When tanδ2 exceeds the health range and C2 is normal, it indicates that moisture has not entered the insulation interior at the ends and slot openings, and there is relatively less delamination inside the insulation at the ends and slot openings. When tanδ2 exceeds the health range and C2 is higher than the health range, it indicates that moisture has entered the insulation interior at the ends or slot openings, but has not formed a penetrating channel.

[0008] Furthermore, in step 4), the concentration of healthy motors should not be less than 60%. If it is less than 60%, the motor insulation needs to be reinforced before retesting to improve the accuracy of fault detection.

[0009] Furthermore, in step 4), at step ①, more than 30 motors with the same operating mileage are selected to provide a more accurate health range for subsequent fault diagnosis and ensure the accuracy of the test results.

[0010] Furthermore, in step 2), the soaking time is 20 min to 30 min.

[0011] The beneficial effects of this invention are as follows: This invention evaluates the overall insulation structure of a motor based on dielectric loss and capacitance before and after offline immersion. If the motor insulation resistance meets the requirements, motors with potential defects in the winding ends and slots can be eliminated by using the healthy range of electrical parameters before and after immersion. This reduces the risk of motor online failure and improves the motor insulation fault identification rate. Attached Figure Description

[0012] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 The room temperature dielectric loss factor for multiple motors tested at room temperature; Figure 2 The water immersion medium loss factor for testing multiple motors under water immersion conditions; Figure 3 The water outlet medium loss factor for testing the water outlet status of multiple motors; Figure 4 A room-temperature capacitor for testing multiple motors at room temperature; Figure 5 A water-immersion capacitor used for testing multiple motors under water immersion conditions; Figure 6 The water outlet capacitor is used for testing the water outlet status of multiple motors; Figure 7 This is a flowchart of the offline detection method described in this invention. Detailed Implementation

[0015] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0016] In this description, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. It should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joint" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0017] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0018] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0019] An offline detection method for potential insulation faults in motors includes the following steps: 1) Normal temperature electrical parameter testing of the motor: The room temperature insulation resistance, room temperature dielectric loss factor tanδ0, and room temperature capacitance C0 of the motor are tested at room temperature. If the room temperature insulation resistance is greater than R0 and the room temperature dielectric loss factor is ≤1.5%, it means that the motor has passed the preliminary test and needs to be further tested by immersion. Otherwise, it means that the motor has failed the test and needs to be reinforced with insulation. 2) Electrical parameter testing of the motor after immersion in water: For motors that pass the initial electrical test at room temperature, immerse them in water for 30 minutes and test the immersion insulation resistance, immersion dielectric loss factor tanδ1, and immersion capacitance C1 under immersion conditions. 3) Testing of the motor's outlet electrical parameters: Immediately after the water outlet is discharged, test the water outlet medium loss factor tanδ2 and the water outlet capacitance C2 of the motor. 4) Fault diagnosis: ① Determine the health range of electrical parameters at normal temperature, immersion, and outlet for motors with the same operating mileage. Multiple motors with the same operating mileage were selected, and their electrical parameters at room temperature, immersion in water, and outlet in water were tested. The health range of motors with the same operating mileage was determined based on the concentrated distribution area of ​​the multiple sets of electrical parameters at room temperature, immersion in water, and outlet in water. ② Judgment of potential motor insulation faults When the immersion insulation resistance of the motor under test is less than R0, the motor under test is a faulty motor and requires corresponding insulation reinforcement. When the immersion insulation resistance of the motor under test is greater than R0, further judgment is required. If the electrical parameters at room temperature, immersion, and outlet are all within the health range of motors with the same operating mileage, the motor under test is in normal and healthy condition. If any one of the electrical parameters at room temperature, immersion, or outlet is outside the health range of motors with the same operating mileage, the motor under test has a potential fault.

[0020] Furthermore, step 4) also includes step ③, fault mode judgment: When step ② determines that the motor under test has a potential fault, its fault mode is then judged. When tanδ0 exceeds the health range and C0 is below the health range, it indicates that there are many gaps and delamination in the slot opening. When tanδ0 exceeds the health range and C0 is normal, it indicates that there are a small amount of air gaps and delamination inside the slot opening insulation. When tanδ0 exceeds the health range and C0 is above the health range, it indicates that the slot insulation is damp and needs to be dried and retested. When tanδ1 exceeds the health range and C1 is below the health range, it indicates that water vapor has not entered the insulation, and there is a lot of delamination inside the end or slot opening insulation. When tanδ1 is within the healthy range and C1 is normal, it indicates that moisture has not entered the insulation interior, and there is less insulation delamination at the end and slot opening. When tanδ1 exceeds the healthy range and C1 is higher than the healthy range, it indicates that moisture has entered the insulation interior, but has not formed a penetrating channel. When tanδ2 exceeds the healthy range and C2 is lower than the healthy range, it indicates that moisture has not entered the insulation interior at the end and slot opening, and there is more delamination inside the insulation. When tanδ2 exceeds the healthy range and C2 is normal, it indicates that moisture has not entered the insulation interior at the end and slot opening, and there is relatively less delamination inside the insulation interior at the end and slot opening. When tanδ2 exceeds the healthy range and C2 is higher than the healthy range, it indicates that moisture has entered the insulation interior at the end or slot opening, but has not formed a penetrating channel, as shown in Table 1.

[0021] Table 1

[0022] In step 4), at ①, more than 30 motors with the same operating mileage are selected to provide a more accurate health range for subsequent fault diagnosis and ensure the accuracy of the test results.

[0023] Furthermore, in step 4), the concentration of healthy motors should not be less than 60%. If it is less than 60%, the motor insulation needs to be reinforced before retesting to improve the accuracy of fault detection.

[0024] The following analysis uses a motor with a certain operating mileage as an example: 1) Electrical parameter testing: This section unifies the dielectric loss and capacitance data of the motor windings at room temperature, after immersion in water, and after removal from water for easy comparison and analysis. Separate explanations are not provided for room temperature testing, immersion, and removal from water. If the insulation resistance is lower than R0 during immersion, the motor is rejected. For motors whose insulation resistance meets the requirements after immersion, electrical parameter tests include dielectric loss factor and capacitance before immersion, after immersion, and after removal from water. Table 2 shows the test data for 32 motors under maintenance at a certain maintenance mileage (the data in the table may contain human error; obvious human errors can be eliminated through retesting).

[0025] Table 2 Electrical parameter values ​​tested at a certain maintenance mileage

[0026] 2) Result Evaluation Determine the health range of motor insulation electrical parameters The electrical parameters of multiple motors undergoing the same repair process are assessed for their health range. The area where most motors are concentrated is selected as the healthy range of normal electrical parameters. The degree of dispersion varies depending on the insulation status of the motors. The distribution of healthy motors should not be less than 60%. If the electrical parameters of the motors are highly dispersed and the health range cannot be determined, the insulation of the motors must be uniformly reinforced. Figures 2-7 This is a distribution chart showing the health status ranges of multiple motors.

[0027] The health range of the motor during this repair process can be determined through testing and statistical analysis of electrical parameters, as shown in Table 3. Table 3 Assessment of the health range of electrical parameters Dielectric loss before entering water 0.5%~2% Water immersion loss 0.5%~3% Water outflow medium loss 0.5%~7% Capacitor before water immersion 22nF~45nF Water-immersed capacitors 50nF~72nF Water outlet capacitor 42nF~79nF ② Identification of potential motor insulation faults Motors 7, 12, 14, and 24 exhibited relatively high dielectric loss factor (tanδ0) at room temperature. Motor 24 showed a lower capacitance (C0) at room temperature, likely due to severe air stratification within the tank, leading to a decrease in capacitance. Motor 7 had a normal capacitance (C0) at room temperature, possibly because the internal air gap was small, minimizing its impact on capacitance. Motors 12 and 14 had higher capacitances at room temperature, possibly related to moisture absorption. Dielectric loss and capacitance at room temperature were retested after baking. Motors 6, 11, 26, and 31 had a large dielectric loss factor (tanδ1) when immersed in water. The immersion capacitors of motors 6, 11, 26, and 31 were normal. Delamination and air gaps appeared inside the end insulation, but water did not enter the insulation. The dielectric loss tanδ2 of the water outlet of motor No. 25 is significantly higher than the normal range, while tanδ0 and tanδ1 are normal. The accuracy of the test is verified by retesting. If the loss is still high after retesting, it is considered that the insulation condition inside the tank is relatively good, and there are a large number of bulges and delaminations at the tank opening and end, resulting in large air gaps. Water can enter the insulation, but there is no penetrating channel.

[0028] Based on the above assessment, motors 6, 7, 11, 12, 14, 24, 25, 26, and 31 may have varying degrees of potential insulation faults. After testing, the identified potential faults were confirmed to be correct, proving the feasibility of the detection method.

[0029] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered within the protection scope of the claims.

Claims

1. An offline detection method for potential insulation faults in motors, characterized in that, Includes the following steps: 1) Electrical parameter testing of motor at room temperature: Test the insulation resistance, dielectric loss factor tanδ0, and capacitance C0 of the motor at room temperature. If the insulation resistance is greater than R0 and the dielectric loss factor is ≤1.5%, where R0 is the insulation resistance threshold obtained based on experience, it means that the motor has passed the preliminary test and needs to be immersed in water for testing. Otherwise, it means that the motor has failed the test and needs to be reinforced with insulation. 2) Electrical parameter testing of the motor after immersion in water: For motors that pass the initial electrical test at room temperature, immerse them in water and test the immersion insulation resistance, immersion dielectric loss factor tanδ1, and immersion capacitance C1 under immersion conditions. 3) Testing of the motor's outlet electrical parameters: Immediately after the water outlet is discharged, test the water outlet medium loss factor tanδ2 and the water outlet capacitance C2 of the motor. 4) Fault diagnosis: ① Determine the health range of electrical parameters at room temperature, immersion, and outlet for motors with the same operating mileage; Multiple motors with the same operating mileage were selected, and their electrical parameters at room temperature, immersion in water, and outlet in water were tested. The health range of motors with the same operating mileage was determined based on the concentrated distribution area of ​​the multiple sets of electrical parameters at room temperature, immersion in water, and outlet in water. ② Judgment of potential motor insulation faults When the immersion insulation resistance of the motor under test is less than R0, the motor under test is a faulty motor and requires corresponding insulation reinforcement. When the immersion insulation resistance of the motor under test is greater than R0, further judgment is required. If the electrical parameters of the motor under test at room temperature, immersion, and outlet are all within the health range of motors with the same operating mileage, the motor under test is in normal and healthy condition. If any one of the electrical parameters of the motor under test at room temperature, immersion, or outlet is outside the health range of motors with the same operating mileage, the motor under test has a potential fault.

2. The offline detection method for potential insulation faults in motors according to claim 1, characterized in that, Step 4) also includes step ③, fault mode judgment: When step ② determines that the motor under test has a potential fault, its fault mode is then judged. When tanδ0 exceeds the health range and C0 is below the health range, it indicates that there are many gaps and delamination in the slot opening. When tanδ0 exceeds the health range and C0 is normal, it indicates that there are a small amount of air gaps and delamination inside the slot opening insulation. When tanδ0 exceeds the health range and C0 is above the health range, it indicates that the slot insulation is damp and needs to be dried and retested. When tanδ1 exceeds the health range and C1 is below the health range, it indicates that water vapor has not entered the insulation, and there is a lot of delamination inside the end or slot opening insulation. When tanδ1 is within the healthy range and C1 is normal, it indicates that moisture has not entered the insulation interior, and there is less insulation delamination at the ends and slot openings. When tanδ1 exceeds the healthy range and C1 is higher than the healthy range, it indicates that moisture has entered the insulation interior, but has not formed a penetrating channel. When tanδ2 exceeds the healthy range and C2 is lower than the healthy range, it indicates that moisture has not entered the insulation interior at the ends and slot openings, and there is more delamination inside the insulation. When tanδ2 exceeds the healthy range and C2 is normal, it indicates that moisture has not entered the insulation interior at the ends and slot openings, and there is relatively less delamination inside the insulation interior at the ends and slot openings. When tanδ2 exceeds the healthy range and C2 is higher than the healthy range, it indicates that moisture has entered the insulation interior at the ends or slot openings, but has not formed a penetrating channel.

3. The offline detection method for potential insulation faults in motors according to claim 2, characterized in that, In step 4), the concentration of healthy motors should not be less than 60%. If it is less than 60%, the motor insulation needs to be reinforced before retesting.

4. The offline detection method for potential insulation faults in motors according to claim 3, characterized in that, In step 4), ①, more than 30 motors with the same operating mileage are selected.

5. The offline detection method for potential motor insulation faults according to claim 4, characterized in that, In step 2), the soaking time is 20 to 30 minutes.

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