Insulation testing device, system and method for high-voltage motors with a mountain-shaped structure

Abstract

This application provides a zigzag-structure insulation detection device, system, and method for high-voltage motors, applied in the field of high-voltage motor insulation detection technology. The device includes a zigzag-shaped metal casing and a three-phase high-voltage current-limiting resistor sealed with silicone rubber at its upper end. Inside the casing are six high-voltage isolation relays, a DC high-voltage generation module, a sampling and processing unit, an intelligent processing unit, and an LCD display device. These are permanently connected to the three-phase windings of the motor via flexible wires and circular copper connectors. After determining that the motor meets the safe shutdown conditions, the system sequentially selects the insulation type to ground or between phases, controls the on / off combinations of the six relays to reconstruct the measurement circuit, injects DC voltage, and continuously acquires voltage signals. It calculates the first insulation resistance value, the second insulation resistance value, and the absorption ratio. All insulation objects are divided into ground-to-ground and phase-to-phase groups, and the average value and deviation are calculated for horizontal comparison and vertical comparison with historical data. An early warning sign is generated based on the differences.

Description

Technical Field

[0001] This application relates to the field of high-voltage motor insulation testing technology, and in particular to a device, system and method for testing the insulation of high-voltage motors with a zigzag structure. Background Technology

[0002] High-voltage motors are critical power equipment in industries such as water conservancy, chemical engineering, metallurgy, and power generation. Their insulation condition directly affects production safety and efficiency. Statistics show that approximately 60% of commissioning failures are caused by excessively low insulation resistance. Traditional insulation testing relies on manual operation of a megohmmeter, requiring disconnection of the three-phase windings. This process is cumbersome, time-consuming, and the results are heavily influenced by the operator's experience, easily introducing measurement errors.

[0003] Existing online insulation monitoring devices are typically fixedly installed inside switchgear to monitor insulation resistance to ground. However, their detection circuits are fixed and cannot switch measurement modes, thus failing to achieve automatic detection of phase-to-phase insulation. Furthermore, strong electromagnetic interference exists during operation, limiting measurement accuracy, and they lack the ability to identify insulation aging trends, making it difficult to provide early warnings.

[0004] While a few devices can perform automatic detection after shutdown, they typically use a single relay switching topology, which cannot simultaneously cover three-phase-to-ground and all phase-to-phase insulation. Furthermore, existing solutions rely solely on insulation resistance values ​​at a single point in time, lacking absorption ratio assessment and failing to effectively identify progressive faults such as moisture absorption. Additionally, the lack of horizontal and vertical data analysis results in untimely and inaccurate early warning systems. Summary of the Invention

[0005] The embodiments of this application provide a device, system, and method for detecting the insulation of high-voltage motors with a mountain-shaped structure, achieving fully automatic, comprehensive, high-precision detection and early warning of high-voltage motor insulation. To achieve the above objectives, this application adopts the following technical solution: A triangular insulation testing device for high-voltage motors includes: Mountain-shaped metal casing; High-voltage A-phase current-limiting resistor, high-voltage B-phase current-limiting resistor and high-voltage C-phase current-limiting resistor are installed on the upper end of the mountain-shaped metal casing and sealed with silicone rubber. The following components are installed inside the metal casing: a motor operation status acquisition unit, an output control unit, six high-voltage isolation relays, a DC high-voltage generation module, a sampling and processing unit, and an intelligent processing unit. The high-voltage current-limiting resistor encapsulated in silicone rubber is electrically connected to the DC high-voltage generating module through the high-voltage isolation relay. The DC high-voltage generating module is electrically connected to the sampling and processing unit. The sampling and processing unit is electrically connected to the intelligent processing unit. The intelligent processing unit is electrically connected to the motor operating status acquisition unit and the output control unit, respectively. The device also includes a liquid crystal display device, and the intelligent processing unit is electrically connected to the liquid crystal display device.

[0006] In some possible implementations, the upper end of the mountain-shaped metal casing is connected to three flexible wires, which are electrically connected to the high-voltage A-phase current-limiting resistor, the high-voltage B-phase current-limiting resistor, and the high-voltage C-phase current-limiting resistor, respectively. Each flexible wire has a circular copper connector at its end, which is used to fix the three-phase stator winding of the high-voltage motor.

[0007] A zigzag insulation testing system for high-voltage motors, the system comprising: The status detection and loop control unit is used to acquire the motor's operating status information, determine whether the motor meets the detection conditions, and generate a detection enable flag. When the detection enable flag is valid, it sequentially selects each target insulation type and controls the on / off state of the high-voltage isolation relay to reconstruct the measurement loop according to the target insulation type, and records the loop reconstruction completion flag. The DC voltage application and parameter calculation unit is used to inject DC voltage into the measurement circuit through a high-voltage current-limiting resistor and collect voltage signals when the circuit reconstruction completion flag is detected, and to calculate the first insulation resistance value, the second insulation resistance value, and the absorption ratio corresponding to the target insulation type based on the voltage signals; The storage unit is used to store the historical first insulation resistance value, historical second insulation resistance value, and historical absorption ratio for each target insulation type in the previous cycle; The comparison and early warning unit is used to perform a horizontal comparison of the first insulation resistance value, the second insulation resistance value, and the absorption ratio corresponding to all target insulation types; and to perform a vertical comparison of the first insulation resistance value, the second insulation resistance value, and the absorption ratio corresponding to each target insulation type with the historical first insulation resistance value, the historical second insulation resistance value, and the historical absorption ratio of the same target insulation type in the storage unit; and to generate an early warning flag based on the differences between the horizontal comparison and the vertical comparison.

[0008] In some possible implementations, the state detection and loop control unit is specifically used for: Read the detection enable flag; After confirming that the detection enable flag is in a valid state, a preset detection sequence table is obtained. The detection sequence table records six insulating objects in sequence: the first phase to ground, the second phase to ground, the third phase to ground, the first phase to the second phase, the second phase to the third phase, and the first phase to the third phase. Take out the first untested insulating object in sequence according to the test sequence table; The extracted insulating object is identified as the target insulation type.

[0009] In some possible implementations, the state detection and loop control unit is specifically used for: The six high-voltage isolation relays are divided into three winding-side relays and three ground-side relays; the winding-side relays include a first-phase winding-side relay, a second-phase winding-side relay, and a third-phase winding-side relay; the ground-side relays include a first-phase ground-side relay, a second-phase ground-side relay, and a third-phase ground-side relay. Determine whether the target insulation type is ground-to-ground or phase-to-phase. If the target insulation type is a ground type, then obtain the phase corresponding to the target insulation type; generate a first combination based on the phase; the first combination is: close the winding side relay corresponding to the phase, open the winding side relays of the other two phases, and open all ground side relays; If the target insulation type is phase-to-phase, then obtain the two phases corresponding to the target insulation type; generate a second combination based on the two phases; the second combination is: close the two winding-side relays corresponding to the two phases, open the winding-side relay of the other phase, close the ground-side relay of one of the two phases, and open the remaining ground-side relays; The first combination or the second combination is compiled into an on / off combination instruction, wherein the on / off combination instruction is in six-bit binary form.

[0010] In some possible implementations, the state detection and loop control unit is specifically used for: The on / off combination instruction is parsed to obtain the mapping relationship between each binary bit and the corresponding relay; According to the mapping relationship, each binary bit is sent to the corresponding relay, and after all relays have completed their actions, the auxiliary contact feedback signal of each relay is read. Each feedback signal is compared with the binary bits sent to the relay to generate a comparison result; If all comparison results are consistent, the generation loop reconstruction is complete.

[0011] In some possible implementations, the DC pressurization and parameter calculation unit is specifically used for: Send a start command and voltage amplitude parameters to the DC high voltage generator; The DC high voltage generator produces a DC high voltage according to the start command and the voltage amplitude parameters; The DC high voltage is applied to the motor winding through the corresponding silicone rubber-sealed high voltage current-limiting resistor. After the voltage stabilizes, a voltage injection flag is generated.

[0012] In some possible implementations, the DC pressurization and parameter calculation unit is specifically used for: Set the sampling clock period and the total number of sampling points; Starting from the rising edge of the voltage-injected flag, the digital voltage output of the analog-to-digital converter is read once every sampling clock cycle; The digital voltage values ​​read each time are stored sequentially in a buffer. When the total number of sampling points is reached, the contents of the buffer are output as a voltage sampling sequence.

[0013] In some possible implementations, the comparison and warning unit is specifically used for: Calculate the first average value of the first insulation resistance of all target insulation types, the second average value of the second insulation resistance of all target insulation types, and the average absorption ratio of all target insulation types; The first deviation is obtained by subtracting the first average value from the first insulation resistance value of each target insulation type; The second deviation is obtained by subtracting the second average value from the second insulation resistance value of each target insulation type; The absorption ratio deviation is obtained by subtracting the average absorption ratio from the absorption ratio of each target insulation type. If the absolute value of the first deviation, the second deviation, or the absorption ratio deviation exceeds a preset threshold, the target insulation type is marked as abnormal. Read the historical first insulation resistance value, historical second insulation resistance value, and historical absorption ratio of the previous cycle; Subtract the historical first insulation resistance value from the current first insulation resistance value to obtain the change in the first resistance value; Subtract the historical second insulation resistance value from the current second insulation resistance value to obtain the change in the second resistance value; Subtracting the historical absorption ratio from the current cycle absorption ratio yields the change in absorption ratio; If the first resistance change or the second resistance change is negative and its absolute value is greater than the first threshold, a resistance degradation flag is generated. If the change in absorption ratio is negative and its absolute value is greater than the second threshold, an absorption ratio degradation flag is generated.

[0014] A method for testing the insulation of a zigzag structure in a high-voltage motor, the method comprising: Obtain the motor's operating status information, determine whether the motor meets the detection conditions based on the operating status information, and generate a detection enable flag; When the detection enable flag is valid, each target insulation type is selected sequentially; For each target insulation type, the on / off state of the high-voltage isolation relay is controlled according to the target insulation type to reconstruct the measurement circuit, and the circuit reconstruction completion flag is recorded; When the circuit reconstruction completion flag is detected, DC voltage is injected into the measurement circuit through the high-voltage current-limiting resistor and the voltage signal is collected. Based on the voltage signal, the first insulation resistance value, the second insulation resistance value and the absorption ratio corresponding to the target insulation type are calculated. Obtain the first insulation resistance, second insulation resistance, and absorption ratio corresponding to each of the target insulation types; A horizontal comparison is made of the first insulation resistance value, the second insulation resistance value, and the absorption ratio corresponding to all target insulation types; The first insulation resistance value, the second insulation resistance value, and the absorption ratio corresponding to each target insulation type are compared longitudinally with the historical first insulation resistance value, historical second insulation resistance value, and historical absorption ratio of the same target insulation type stored in the previous cycle. A warning sign is generated based on the differences between the horizontal and vertical comparisons.

[0015] As can be seen from the above technical solution, this application has the following beneficial effects: 1. This application, through a combination of a "mountain"-shaped symmetrical structure and six high-voltage isolation relays, achieves fully automatic and comprehensive testing of the three-phase stator winding insulation to ground and all phase-to-phase insulation while the high-voltage motor is stopped. This eliminates the need for manual disassembly and reassembly of terminals, significantly reducing testing time. The device incorporates an intelligent processing unit that automatically determines whether the motor is in a safe state with no residual voltage before testing and automatically discharges residual high voltage after testing, eliminating the risk of electric shock. Furthermore, the use of silicone rubber-sealed high-voltage current-limiting resistors and a metal casing provides excellent high-voltage resistance, moisture resistance, and anti-interference performance, enabling long-term stable operation in harsh industrial environments.

[0016] 2. This application continuously collects voltage signals during the DC pressurization process, extracts the voltage values ​​at the first and second moments, and calculates the first insulation resistance, second insulation resistance, and absorption ratio, thus accurately assessing the degree of insulation moisture absorption. Furthermore, all insulation objects are divided into ground-to-ground and phase-to-phase groups, and the average value and deviation are calculated for each group, avoiding the ill-conditioned mean problem caused by the mixing of different dimensions, and enabling sensitive identification of asymmetric insulation defects. Simultaneously, by comparing with historical test results longitudinally, the changes in resistance and absorption ratio are calculated, allowing for the early detection of slow declines in insulation performance. Finally, by comprehensively considering the horizontal and vertical differences, a graded early warning indicator is generated, providing maintenance personnel with precise maintenance guidance, achieving predictive maintenance, and significantly reducing the risk of sudden downtime. Attached Figure Description

[0017] The invention will now be further described with reference to the accompanying drawings.

[0018] Figure 1 This is a structural diagram of the control module provided in an embodiment of this application; Figure 2This is a schematic diagram of the overall structure provided for an embodiment of this application; Figure 3 This is a structural diagram of the device system provided in the embodiments of this application; Figure 4 A flowchart provided for an embodiment of this application.

[0019] 1. Mountain-shaped metal casing; 2. LCD display device; 13. Grounding terminal; 4. High-voltage A-phase current-limiting resistor; 5. High-voltage B-phase current-limiting resistor; 6. High-voltage C-phase current-limiting resistor; 17. C2 high-voltage isolation relay; 18. C1 high-voltage isolation relay; 19. B2 high-voltage isolation relay; 20. B1 high-voltage isolation relay; 21. A2 high-voltage isolation relay; 22. A1 high-voltage isolation relay; 23. DC high-voltage generator module; 24. Intelligent processing unit; 25. Sampling and processing unit; 26. Motor operating status acquisition unit; 28. Output control unit. Detailed Implementation

[0020] The terms "first," "second," and "third," etc., used in this application specification, claims, and drawings are for distinguishing different objects, not for specifying a particular order.

[0021] In the embodiments of this application, the words "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the words "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0022] Research has found that traditional manual testing requires manually disconnecting and reconnecting the three-phase windings after the machine is shut down. This operation is cumbersome, time-consuming, and carries the risk of high-voltage electric shock. The measurement results are greatly affected by human factors. Existing online insulation monitoring devices have fixed detection circuits and can only measure insulation to ground, but cannot achieve automatic detection of phase-to-phase insulation. They also lack the ability to evaluate absorption ratio and analyze historical trends, making it difficult to detect early asymmetric degradation and progressive faults.

[0023] To address the aforementioned issues, this application provides a device, system, and method for testing the insulation of high-voltage motors with a zigzag structure: Example 1

[0024] To solve the above problems, such as Figures 1-4 As shown, to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the preferred embodiments described herein are for illustrative purposes only and are not intended to limit the present invention. The same reference numerals in the drawings denote the same parts.

[0025] Example 1: Hardware structure and installation of a mountain-shaped insulation testing device for high-voltage motors.

[0026] This embodiment details the mechanical structure, electrical connection method, selection criteria for key components, calibration method, and installation and use of the device provided by the present invention in actual high-voltage motor scenarios.

[0027] 1.1 Overview of the overall structure.

[0028] like Figure 1 As shown, a high-voltage motor's zigzag insulation testing device includes: A mountain-shaped metal casing 1 and a liquid crystal display device 2 are electrically connected.

[0029] The mountain-shaped metal casing 1 includes a high-voltage A-phase current-limiting resistor 4, a high-voltage B-phase current-limiting resistor 5, and a high-voltage C-phase current-limiting resistor 6. All three resistors are encapsulated with silicone rubber. Inside the mountain-shaped metal casing 1 are installed a C2 high-voltage isolation relay 17, a C1 high-voltage isolation relay 18, a B2 high-voltage isolation relay 19, a B1 high-voltage isolation relay 20, an A2 high-voltage isolation relay 21, an A1 high-voltage isolation relay 22, a DC high-voltage generator module 23, an intelligent processing unit 24, a sampling processing unit 25, a motor operating status acquisition unit 26, and an output control unit 28. All modules, relays, and units are electrically connected.

[0030] LCD display device 2: As a human-machine interface, it is responsible for displaying, receiving and processing data from the mountain-shaped metal casing 1, displaying the insulation detection results processed by the intelligent processing unit 24, and realizing human-machine exchange function.

[0031] The mountain-shaped metal casing 1 is made of high-quality cold-rolled steel sheet, stamped and welded, with a rust-proof and insulating spray coating. The casing is divided into upper and lower parts. The upper part consists of three upward-protruding "peak"-shaped branches, each hollow inside, used to independently install silicone rubber-sealed high-voltage A-phase current-limiting resistors 4, B-phase current-limiting resistors 5, and C-phase current-limiting resistors 6. The lower part is a closed rectangular metal cavity, internally divided into multiple functional areas by metal partitions, housing a motor operation status acquisition unit 26, an output control unit 28, six high-voltage isolation relays (C2 high-voltage isolation relay 17, C1 high-voltage isolation relay 18, B2 high-voltage isolation relay 19, B1 high-voltage isolation relay 20, A2 high-voltage isolation relay 21, and A1 high-voltage isolation relay 22), a DC high-voltage generator module 23, a sampling and processing unit 25, and an intelligent processing unit 24. The bottom of the casing has mounting feet, which can be fixed to a wall or switch cabinet near the motor using expansion bolts. The casing also has a grounding terminal 13, connected to the field grounding grid via a copper wire.

[0032] The geometry of the three raised branches: Each raised branch has a fixed-length wiring groove for the high-voltage leads to pass through. The geometric center distance between the wiring grooves is equal (the center distance between two adjacent raised branches is 60mm), and the bending radius of the high-voltage leads is uniformly set to 20mm. The physical length of the high-voltage leads between the three-phase current-limiting resistors and the corresponding high-voltage isolation relays is consistent. Thus, the symmetry of the distributed capacitance and inductance of each phase is guaranteed at the hardware level, providing a structural basis for subsequent lateral comparisons.

[0033] High-voltage phase A current-limiting resistor 4, high-voltage phase B current-limiting resistor 5, and high-voltage phase C current-limiting resistor 6 are respectively fixed inside the three protrusions at the upper end of the mountain-shaped metal casing 1. Each resistor body uses a precision metal oxide film resistor with a nominal resistance value of [value missing]. (Other values ​​can be selected as needed), accuracy ±1%, temperature coefficient less than The rated power is 5W. Silver-plated copper wires are led out from both ends of the resistor body, one end serving as the high-voltage input and the other as the low-voltage output. The entire resistor body is cast and sealed in a vacuum environment using two-component addition-type liquid silicone rubber, with a silicone rubber layer thickness of not less than 5 mm. The volume resistivity of silicone rubber is... Dielectric strength greater than It also exhibits hydrophobicity (water contact angle greater than 100°). This high volume resistivity ensures minimal leakage current at the solid dielectric surface under 5kV high voltage. This is far below the minimum resolution of the measurement loop, thus avoiding errors introduced by surface creepage.

[0034] Resistor selection criteria: The 100MΩ resistance value is calculated based on a typical test voltage of 5kV and safe current limits. Ohm's law provides the maximum possible current. This current is far less than the current felt by the human body (approximately 0.5mA), and also less than the overcurrent protection threshold of a typical DC high-voltage source (usually 2mA). Furthermore, the Joule heating generated when a current of 0.05mA flows through the insulation resistance is extremely low. The true value of the insulation resistance will not change due to heat generation. Therefore, this resistance value strikes a balance between safety and measurement accuracy.

[0035] The device also includes three flexible conductors and a circular copper connector: each flexible conductor is a high-voltage resistant cable with silicone rubber insulation and a withstand voltage rating of 15kV. One end is fixed to the corresponding output terminal (A phase, B phase, C phase) inside the device, and the other end is crimped to a circular copper connector. The copper connector has an inner diameter of 8mm and is silver-plated to reduce contact resistance. The flexible conductors are typically 1.5m to 3m long to accommodate the different positions of junction boxes for different motor models. The circular copper connector can be permanently fixed to the motor terminal bolts without needing to be re-clamped for each test, avoiding randomness in contact resistance. The silver plating further reduces contact resistance; typical contact resistance is less than 0.1Ω, which is negligible compared to insulation resistance (hundreds of megohms), thus not introducing measurement errors.

[0036] The internal electrical connections of the device are as follows: The high-voltage output terminal (positive) of the DC high-voltage generator module 23 is simultaneously connected to the input terminals of the high-voltage A-phase current-limiting resistor 4, the high-voltage B-phase current-limiting resistor 5, and the high-voltage C-phase current-limiting resistor 6; that is, the input terminals of the three resistors are connected in parallel. This parallel structure ensures that the voltage applied to each current-limiting resistor is exactly the same, providing the same excitation conditions for subsequent lateral comparisons.

[0037] The output of the high-voltage A-phase current-limiting resistor 4 is divided into two paths: the first path is connected to the A-phase output terminal of the device through the contact of the A1 high-voltage isolation relay 22, and this terminal is connected to the A-phase winding of the motor through a flexible wire and a circular copper connector; the second path is connected to the grounding bus inside the device through the contact of the A2 high-voltage isolation relay 21, and this bus is finally connected to the grounding terminal 13.

[0038] The output terminals of the high-voltage B-phase current-limiting resistor 5 are similar: connected to the B1 high-voltage isolation relay 20 and the B2 high-voltage isolation relay 19 respectively.

[0039] The output terminal of the high-voltage C-phase current-limiting resistor 6 is connected to the C1 high-voltage isolation relay 18 and the C2 high-voltage isolation relay 17, respectively.

[0040] The low-voltage sampling output of the DC high-voltage generator module 23 is used to monitor the actual output voltage connected to an input channel of the sampling processing unit 25. This sampling channel is used to accurately measure the voltage actually applied to the input of the current-limiting resistor to eliminate setting errors and temperature drift.

[0041] The sampling processing unit 25 is also connected to the two ends of three current-limiting resistors via a differential amplifier to acquire the voltage drop across the resistors. The reason for using a differential amplifier is that the voltage across the current-limiting resistors may be very small. When the insulation resistance is large, the current is very small, and the voltage drop across the resistor is only a few hundred microvolts, making it impossible to effectively extract the signal using ordinary single-ended measurements.

[0042] The digital output of the sampling processing unit 25 is connected to the intelligent processing unit 24 via the SPI bus.

[0043] The output (analog voltage and digital level) of the motor operation status acquisition unit 26 is connected to the ADC input and GPIO input of the intelligent processing unit 24.

[0044] The input terminal (GPIO) of the output control unit 28 is connected to the intelligent processing unit 24, and its output terminal (12V drive signal) is connected to the coils of six high-voltage isolation relays respectively.

[0045] The LCD display device 2 is connected to the UART port of the intelligent processing unit 24 via an RS485 bus. This is used for auxiliary display or redundant design.

[0046] Intelligent processing unit 24: Employs an ARM Cortex-M4 microcontroller, such as the STM32F407, with a main frequency of 168MHz, and integrates ADC, DAC, timers, multiple USARTs, and SPI peripherals. Running the FreeRTOS real-time operating system, it processes data from the sampling processing unit 25 and the motor operating status acquisition unit 26, determines the equipment's operating status and insulation performance, and controls the operation of C2 high-voltage isolation relay 17, C1 high-voltage isolation relay 18, B2 high-voltage isolation relay 19, B1 high-voltage isolation relay 20, A2 high-voltage isolation relay 21, A1 high-voltage isolation relay 22, the DC high-voltage generator module 23, and the output control unit 28. Non-volatile memory (EEPROM) is used to store calibration parameters and historical detection results.

[0047] C2 high-voltage isolation relay 17, C1 high-voltage isolation relay 18, B2 high-voltage isolation relay 19, B1 high-voltage isolation relay 20, A2 high-voltage isolation relay 21, and A1 high-voltage isolation relay 22: Under the control of the intelligent processing unit 24, they are used to control the on / off state of the measurement circuit. When the motor is running, the above relays disconnect the measurement circuit from the high-voltage motor stator winding to protect the safety of the intelligent processing unit 24; when the motor is stopped and the detection conditions are met, the relays connect the measurement circuit to the high-voltage motor stator winding, initiating insulation measurement; by switching the measurement mode through different relay combinations, the insulation resistance between the three-phase stator winding and the casing of the high-voltage motor, as well as the insulation measurement between the three-phase stator windings, can be realized.

[0048] DC high voltage generator module 23: Utilizing a flyback topology, it takes a low-voltage DC input (24V), which is boosted by a high-frequency transformer and then rectified by a voltage doubler to output an adjustable DC high voltage (0-10kV). This voltage is used to raise the voltage to the required test voltage level (e.g., 5kV). The module has an internal voltage feedback loop to stabilize the output voltage at the set value with an accuracy of ±2%. It also features overcurrent protection, automatically shutting off when the output current exceeds 2mA.

[0049] The high-voltage A-phase current-limiting resistor 4, high-voltage B-phase current-limiting resistor 5, and high-voltage C-phase current-limiting resistor 6 work in conjunction with the C2 high-voltage isolation relay 17, C1 high-voltage isolation relay 18, B2 high-voltage isolation relay 19, B1 high-voltage isolation relay 20, A2 high-voltage isolation relay 21, and A1 high-voltage isolation relay 22. Through the control commands of the intelligent processing unit 24, different relay combinations are switched to achieve multiple measurement modes, thereby completing the full coverage detection of the three-phase stator winding insulation to ground and phase-to-phase insulation of the high-voltage motor.

[0050] Sampling and processing unit 25: Includes four independent differential amplification and analog-to-digital conversion channels, used to acquire the voltage signal across the current-limiting resistor during the test, and transmit the digitized voltage data to the intelligent processing unit 24 for software calculation and processing.

[0051] Motor operation status acquisition unit 26: includes three voltage transformer signal conditioning circuits, three current transformer signal conditioning circuits, and a digital input port (connected to the auxiliary contact of the motor circuit breaker), used to acquire the three-phase voltage, three-phase current and circuit breaker status information of the high-voltage motor in real time, and transmit this information to the intelligent processing unit 24.

[0052] Output control unit 28: Composed of multiple optocoupler-isolated MOSFET drivers, each outputting 12V / 200mA, capable of directly driving relay coils. When the GPIO output of intelligent processing unit 24 is low, the optocoupler conducts, the MOSFET conducts, and the relay coil is energized, closing the contacts; when the output is high, the relay is de-energized. A freewheeling diode is connected in parallel across each relay coil to prevent the reverse induced electromotive force generated during power-off from damaging the MOSFET.

[0053] 1.2 Detailed functions and principles of each component: Mountain-shaped metal casing 1: It provides mechanical protection and electromagnetic shielding, while also serving as a mounting base for three current-limiting resistors. The "mountain"-shaped structure isolates the three current-limiting resistors from each other, reducing interphase electric field coupling and providing an independent creepage surface for each resistor. When a DC high voltage is applied to one phase, the current-limiting resistors of the other two phases remain in a high-resistance state, preventing interference. This shape also ensures the spatial symmetry of the three current-limiting resistors, making their thermal characteristics, stray capacitance, and other parasitic parameters essentially consistent when measuring insulation resistance to ground of different phases. This provides a structural basis for subsequent lateral comparison (comparing the three-phase resistance to ground).

[0054] High-voltage phase A current-limiting resistor 4, high-voltage phase B current-limiting resistor 5, high-voltage phase C current-limiting resistor 6: When a DC high voltage is applied to the measuring circuit, if the insulation resistance is very low or even short-circuited, the current-limiting resistor will limit the circuit current to a safe range. For example... ,when , At that time, the maximum current was only This current is far less than the safe current for the human body and also less than the overload capacity of a typical DC power source. The silicone rubber seal provides high pressure resistance and moisture protection, and its elasticity can buffer the mechanical stress caused by temperature changes.

[0055] Temperature compensation explanation: Because the resistance of the current-limiting resistor changes with temperature ( When the ambient temperature changes by 20°C, the relative change in resistance can reach 0.1%. For a 100MΩ resistor, this corresponds to an absolute change of 0.1MΩ, which may cause an error of approximately 0.1% in the insulation resistance calculation. To eliminate this error, the firmware of the intelligent processing unit 24 integrates a temperature compensation algorithm: a digital temperature sensor (not shown) is installed inside the device to read the ambient temperature in real time. And according to the temperature coefficient of resistance specified by the manufacturer. Make corrections: .

[0056] Calibration method: Each current-limiting resistor is measured at 25°C using a high-precision ohmmeter (0.05% accuracy) at the factory, and the actual resistance value is stored in the EEPROM of the intelligent processing unit 24. Since the three resistors may have slight differences, they are stored separately as follows: , , During use, it can be recalibrated once a year to eliminate resistance drift caused by aging.

[0057] Six high-voltage disconnect relays (C2 high-voltage disconnect relay 17, C1 high-voltage disconnect relay 18, B2 high-voltage disconnect relay 19, B1 high-voltage disconnect relay 20, A2 high-voltage disconnect relay 21, A1 high-voltage disconnect relay 22): They are divided into two groups: Winding-side relays: A1 high-voltage isolation relay 22, B1 high-voltage isolation relay 20, C1 high-voltage isolation relay 18. When a winding-side relay of a certain phase is closed, the output terminal of the current-limiting resistor of the corresponding phase is connected to the motor winding of that phase.

[0058] Ground-side relays: A2 high-voltage isolation relay 21, B2 high-voltage isolation relay 19, C2 high-voltage isolation relay 17. When a ground-side relay of a certain phase is closed, the output terminal of the current-limiting resistor of the corresponding phase is directly short-circuited to the ground (device grounding terminal).

[0059] The switching rules for the six relays: By independently controlling the winding side and ground side of each phase, six measurement topologies can be achieved. Details are as follows: Measuring the insulation resistance of phase A winding to ground: Close high-voltage isolation relay 22 (A1), and disconnect high-voltage isolation relays 21 (A2), 20 (B1), 19 (B2), 18 (C1), and 17 (C2). At this time, the DC high-voltage positive terminal flows through the high-voltage phase A current-limiting resistor 4, the contact of high-voltage isolation relay 22 (A1), and the flexible wire to the motor's phase A winding. It then flows through the insulation resistance to the motor casing (ground), and finally returns to the high-voltage negative terminal via grounding terminal 13. The sampling and processing unit 25 measures the voltage across the high-voltage phase A current-limiting resistor 4.

[0060] To measure the insulation of phase B winding to ground: close high-voltage isolation relay 20 (B1) and disconnect all other relays.

[0061] To measure the insulation of the C-phase winding to ground: close the C1 high-voltage isolation relay 18 and disconnect all other relays.

[0062] Measuring the insulation between phase A and phase B windings: Close high-voltage isolation relays A1 (22), B1 (20), and A2 (21, ground side relay for phase A), and disconnect high-voltage isolation relays B2 (19), C1 (18), and C2 (17). The current path is: high-voltage positive terminal → high-voltage phase A current-limiting resistor 4 → A1 high-voltage isolation relay 22 → A winding → A / B phase insulation resistance → B winding → B1 high-voltage isolation relay 20 → high-voltage phase B current-limiting resistor 5 → high-voltage negative terminal, forming a complete circuit. The additionally closed high-voltage isolation relay A2 21 connects the output of the phase A current-limiting resistor to ground potential, providing a stable common-mode reference potential for the differential amplifier. Due to the large resistance of the current-limiting resistor (100MΩ), the shunt current caused by the A2 branch is extremely small (5kV / 100MΩ=0.05mA), and the measured impact on the main circuit current is less than 0.1%, which is negligible in engineering applications.

[0063] To measure the insulation between phase B and phase C windings: Close high-voltage isolation relays B1 (20), C1 (18), and B2 (19, the B-phase ground relay), and disconnect high-voltage isolation relays A1 (22), A2 (21), and C2 (17). The principle is similar to that between phases A and B.

[0064] To measure the insulation between phase A and phase C windings: Close high-voltage isolation relays A1 (22), C1 (18), and A2 (21, the phase A ground relay); open high-voltage isolation relays B1 (20), B2 (19), and C2 (17). The same procedure applies.

[0065] Based on the above rules, the six-bit binary mask for generating the on / off combination instruction (in the order A1, A2, B1, B2, C1, C2) is as follows: A relative location: 100000 B relative to: 001000 C relative to: 000010 AB alternation: 101000 BC alternation: 001010 AC phase-to-phase: 100010 The above conventions are fixedly implemented in the firmware of the intelligent processing unit 24.

[0066] DC high-voltage generator module 23: Employs a flyback topology, receiving a low-voltage DC input (24V). The voltage is boosted by a high-frequency transformer and then rectified by a voltage doubler to output an adjustable DC high voltage (0-10kV). The intelligent processing unit 24 sets the output voltage amplitude via PWM. An internal voltage feedback loop ensures the output voltage remains stable at the set value with an accuracy of ±2%. The module also features overcurrent protection, automatically shutting off when the output current exceeds 2mA. The module provides a 0-10V analog feedback signal, linearly corresponding to the 0-10kV output voltage; this signal is connected to channel 4 of the sampling and processing unit 25.

[0067] Feedback signal voltage divider circuit: Since the ADC's input range is 0–3.3V, a voltage divider circuit consisting of 990kΩ and 10kΩ precision resistors is added to the front end of channel 4 to attenuate the 0–10V feedback voltage to 0–0.1V, which is then input to the ADC via a voltage follower (op-amp buffer). Voltage division ratio. This design ensures that the high-voltage feedback signal does not damage the ADC, while maintaining high input impedance.

[0068] Feedback signal calibration: At the factory, the output voltage is measured using a high-voltage meter, and the ADC reading after voltage division is recorded to establish linear fitting coefficients. This coefficient is stored in the EEPROM and used for accurate calculation of the actual voltage later.

[0069] Sampling processing unit 25: Contains four independent analog channels: Channels 1-3: Used for differential voltage measurement across the current-limiting resistors of phases A, B, and C, respectively. Each channel is equipped with an instrumentation amplifier (e.g., INA826, fixed gain). The system consists of a low-pass filter and a 12-bit successive approximation ADC. The instrumentation amplifier amplifies the small voltage difference across the current-limiting resistor by a factor of 100, outputting 0–10V. Since the ADC reference voltage is 3.3V, the amplified signal needs to be attenuated to 0–3.3V by a voltage divider circuit. In this embodiment, two 10kΩ resistors are used to form a 1 / 2 voltage divider (voltage divider factor). Final ADC readings The original differential voltage corresponding to (0~4095) The calculation formula is: Should That is, the voltage across the current-limiting resistor. .

[0070] Channel 4: Used to measure the feedback voltage of the DC high-voltage generator module 23, its voltage divider circuit and buffer are as described above. ADC readings Corresponding feedback voltage for: Then, the actual DC voltage is obtained based on the calibration coefficient. .

[0071] Oversampling and digital filtering: To improve the signal-to-noise ratio, the system continuously acquires data in each measurement. The original ADC readings are analyzed by removing the maximum and minimum values, and then the arithmetic mean of the remaining 8 points is taken to obtain the filtered ADC reading. The firmware of the intelligent processing unit 24 uses long integer (32-bit) variables for accumulation operations to avoid data overflow. This operation can effectively suppress measurement jitter caused by quantization noise and random interference.

[0072] System resolution analysis: The measured effective bit number (ENOB) of the ADC at this sampling rate is approximately 11 bits (the actual effective bit number is less than 12 bits due to noise and quantization errors). Therefore, the voltage resolution corresponding to the least significant bit (LSB) of the ADC is... After the aforementioned 1 / 2 voltage divider and 100x amplification, the original voltage resolution across the current-limiting resistor is: Therefore, the minimum resolvable current change of the system can be calculated as follows: This resolution is much smaller than the typical value of leakage current in high-voltage motor insulation (nanoampere level), proving that the hardware selection can meet the measurement requirements.

[0073] Calibration process: Gain and zero-point deviation for each channel are eliminated through factory calibration. Specifically, when the input is short-circuited, the ADC reading is recorded as the zero-point offset; when a known standard voltage (e.g., 1V) is input, the ADC reading is recorded, and the actual gain is calculated. These calibration coefficients are stored in EEPROM and automatically compensated for on each measurement.

[0074] The motor operation status acquisition unit 26 includes three voltage transformer (PT) signal conditioning circuits, three current transformer (CT) signal conditioning circuits, and a digital input port (connected to the auxiliary contacts of the motor circuit breaker). The voltage input range is 0–120V (secondary side), which is reduced to 0–3.3V after resistor division and isolation amplifier; the current input range is 0–5A, which is reduced to 0–3.3V after passing through the CT and sampling resistor. The digital input is an optocoupler-isolated dry contact signal. These signals are directly fed into the analog and digital input pins of the intelligent processing unit 24.

[0075] Threshold determination: For a 6kV motor, the rated secondary voltage is 100V, and 5% of that is 5V. Since the actual signal is divided by voltage, the corresponding ADC threshold needs to be calculated based on the voltage division ratio. Specifically, 100V corresponds to an ADC input of 3.3V, and 5V corresponds to 0.165V, with the corresponding ADC reading being approximately... Therefore, when the ADC readings of all three-phase voltages are less than 204, the voltage is considered to meet safety requirements. These percentage values ​​can be configured by the user through the interface to suit different motors.

[0076] Intelligent Processing Unit 24: Employs an ARM Cortex-M4 microcontroller with a 168MHz clock speed, featuring built-in ADC, DAC, timers, multiple USARTs, and SPI peripherals. Running the FreeRTOS real-time operating system, it handles data acquisition, logic processing, relay control, numerical calculations, communication, and display. Non-volatile memory (EEPROM) stores calibration parameters (the actual resistance value of each current-limiting resistor). (Voltage amplitude calibration coefficient, instrument amplifier gain calibration value) and historical test results.

[0077] Data storage strategy: The EEPROM has a capacity of 32KB, and each detection cycle's data (6 objects × 3 parameters × 4 bytes = 72 bytes) plus a timestamp (8 bytes) totals 80 bytes. It can store data from the most recent 400 cycles, cyclically overwriting in chronological order. Simultaneously, it maintains copies of the current and previous cycle's data in RAM to accelerate access speed.

[0078] Output control unit 28: Composed of 8 optocoupler-isolated MOSFET drivers (such as TLP250), each outputting 12V / 200mA, which can directly drive the relay coil. When the GPIO output of the intelligent processing unit 24 is low, the optocoupler is turned on, the MOSFET is turned on, the relay coil is energized and the contacts are closed; when the GPIO output is high, the relay is de-energized.

[0079] Protection circuit: A freewheeling diode is connected in parallel across the two ends of each relay coil to prevent the reverse induced electromotive force generated when the power is off from damaging the MOSFET.

[0080] LCD Display Device 2: LCD Display Device 2 is a 7-inch industrial-grade TFT color touchscreen that communicates with Intelligent Processing Unit 24 via RS485. The screen displays the current testing progress, the measured insulation resistance value of each insulated object, the absorption ratio, a horizontal comparison bar chart, a vertical trend curve, and warning information. Operators can manually start the test, set the testing cycle, and view historical data via the touchscreen.

[0081] User interface example: Main interface: Displays the overall status of the most recent detection ("Normal" / "Level 1 Warning" / "Level 2 Warning"), as well as three buttons: "Start Detection", "History", and "Parameter Settings".

[0082] The detection process interface displays the current detection object with a progress bar (e.g., "Measuring A relative to ground... 45 seconds remaining"), and displays the collected voltage waveform in real time (simplified display).

[0083] Results screen: Lists the six objects in a table format. , The absorption ratio is displayed, and items exceeding the threshold are marked with color. Warning messages are also displayed, such as "B-phase ground insulation resistance is low; inspection recommended."

[0084] 1.3 Installation and field application scenarios.

[0085] At a thermal power plant, the insulation of a 6kV high-voltage feedwater pump motor needs to be tested regularly. According to this embodiment, the installation personnel shall perform the following operations: 1. Fixing device: Install the device in an unoccupied location in the switch cabinet near the motor using expansion bolts, ensuring that the grounding terminal 13 is reliably connected to the grounding grid.

[0086] 2. Connecting the flexible wires: Lead the three flexible wires from the device, pass them through the cable inlet of the motor junction box, and place the circular copper connectors at the ends under the nuts of the terminals of the motor's A, B, and C phase windings respectively. Tighten the nuts to ensure good contact. Use a torque wrench with a torque of 5 N·m to prevent loosening.

[0087] 3. Connection status signal: Cables are led out from the secondary circuits of the voltage transformer and the secondary circuit of the current transformer in the motor switch cabinet and connected to the corresponding input terminals of the motor operation status acquisition unit 26 of the device; the circuit breaker auxiliary contact signal is also connected.

[0088] 4. Power-on self-test: When the device power is turned on, LCD display device 2 starts up and displays the standby interface. The system automatically performs an internal self-test: checking whether the calibration parameters in the EEPROM are valid, whether the relays operate normally (no-load test), and whether the ADC channel readings are stable. After the self-test passes, "Ready" is displayed.

[0089] After installation, the device maintains a permanent connection with the motor's three-phase windings. During normal motor operation, all high-voltage isolation relays are in the open state, physically isolating the measurement circuit from the high-voltage circuit and ensuring uninterrupted motor operation. When insulation testing is required, such as after a planned shutdown for maintenance or a fault trip, the operator simply clicks "Start Testing" on the LCD screen, and the device automatically completes the entire process.

[0090] Parameter adjustment for motors of different voltage levels: For 10kV motors, the test voltage should be increased to 10kV accordingly, and the current-limiting resistor value should be increased to 200MΩ to ensure that the maximum current remains at 0.05mA. The device can be set with different voltage levels via software, and the corresponding current-limiting resistor modules (high voltage A-phase current-limiting resistor 4, high voltage B-phase current-limiting resistor 5, high voltage C-phase current-limiting resistor 6) can be replaced.

[0091] Example 2: Software modules and workflow of a mountain-shaped insulation testing system for high-voltage motors.

[0092] This embodiment describes a real-time software system running in the intelligent processing unit 24. This system consists of multiple functional units that work in conjunction with hardware to achieve fully automated detection. All code is written in C language and is based on… Task scheduling.

[0093] 2.1 Status detection and loop control unit.

[0094] Functions: Acquire motor operating status, determine whether safety detection conditions are met, maintain the list of detection objects, control relay switching, and verify circuit reconstruction.

[0095] Implementation details: This unit is based on periodic tasks (every The task is executed in a single run format. The task first reads data from the motor operating status acquisition unit 26: Three-phase voltage RMS value .

[0096] RMS value of three-phase current .

[0097] Circuit breaker auxiliary contact status A high level indicates the circuit is closed, and a low level indicates the circuit is open.

[0098] Safety detection condition determination logic (non-blocking state machine): The system maintains a state variable The value can be 1. .

[0099] when and All are less than the threshold (rated voltage). )and When all values ​​are less than the threshold (1% of the rated current), if Then start a A non-blocking software timer based on system tick interrupts, with high precision. and switch the state to .

[0100] exist In this state, the timer is checked for timeout each cycle. If any of the above conditions are not met before the timeout, the timer is immediately reset and the process returns. .

[0101] If the timer times out normally, then Set as And set the detection enable flag. .

[0102] When the detection begins or the conditions are not met, Qingwei and reset the state to .

[0103] Detection sequence table: This unit internally stores a fixed array of enumerated insulation objects, in the following order: Phase winding to ground Phase winding to ground Phase winding to ground phase and Between phase windings phase and Between phase windings phase and Between phase windings .

[0104] Select target insulation type: When When the value is true and testing has not yet begun, the cell creates a global index variable. Initially .according to Retrieve the corresponding insulation type from the sequential list and assign it to the global variable. .

[0105] Generate on / off combination instructions: based on The value, the unit call function This function returns a 6-bit binary mask (corresponding to the most significant bit from the least significant bit). The mapping rules follow a convention: Execute relay instructions and verify: The unit will The bitmask is written to the corresponding output control unit 28. port, through a Bit variable cache, write once, then wait (Relay operating time). Next, the auxiliary contact feedback signal of each relay is read sequentially, through... Input. Each auxiliary contact is connected to a pull-up resistor. When the contact is closed, the input is low; when open, it is high. Note that the logic may be reversed and needs to be adjusted according to the actual hardware configuration. This embodiment assumes that the feedback is high when closed. For each bit, if the mask is... (Expected closure) and the feedback signal is high (contact is closed), or the mask is... If the feedback is low, it is considered consistent; otherwise, it is considered inconsistent. If all are consistent, a global flag is set. If they do not match, then retry a maximum of [number] times. Each time, before retrying, all relays are disconnected and the command is resent. If If all attempts fail, set an error status. The LCD display device 2 outputs the message "Relay fault, please check," and simultaneously disconnects all relays (outputting all relays). And terminate the test.

[0106] 2.2 DC pressurization and parameter calculation unit.

[0107] Function: After the circuit reconstruction is completed, start the DC high voltage, collect the voltage signal, and calculate the first and second insulation resistance values ​​and absorption ratio of each insulated object.

[0108] Implementation details: This unit is also a task, involving continuous inspection. The flag indicates that once a true result is detected, the measurement sequence will be executed immediately.

[0109] Setting voltage: via Output an analog voltage or set the target voltage value of the DC high voltage generator module 23 via a digital potentiometer. For Motors, typically used Test voltage; for Motor, use Test voltage. This value can be set by the user via the LCD screen. Send a start command, i.e., a pulse.

[0110] Waiting for voltage stabilization (non-blocking): The unit starts a non-blocking timer to... For periodic reading of channel 4 in sampling processing unit 25 Value, converted to actual DC voltage The conversion formula is: Then obtain based on the calibration coefficient When the voltage change rate is less than 1% after 5 consecutive readings, the voltage is considered stable, and the reading is cleared. Logo, setting Record the current absolute time as the pressurization start time. If it exceeds If it is still not stable, report a fault.

[0111] Continuous voltage signal acquisition: The sampling and processing unit 25 is configured with channels, and the corresponding differential channel is selected according to the current insulation type: for ground measurement, the channel of the corresponding phase is selected; for phase-to-phase measurement, the channel of the first phase is selected by convention, for example... Alternating selection Phase channel, with a fixed sampling rate, for example That is, each One job per second. From At the beginning, each time After conversion, the current-limiting resistor channel is oversampled and continuously sampled. The filtered digital voltage is obtained by averaging the values ​​from each point after removing the maximum and minimum values. This is converted to the actual voltage across the current-limiting resistor. Appended to a pre-allocated circular buffer Meanwhile, the relative time of the sampling point is recorded, from... The number of seconds since the start. The total number of sampling points is preset to [number]. Points, coverage Seconds, when the points reach Data collection stops when the time is right. Throughout the data collection process, the unit does not block other tasks.

[0112] Extracting voltage values ​​at the first and second time points: Based on the predetermined first time point, Second and second moment Calculate the corresponding sampling index for each second: in Since the sampling times may not be perfectly aligned, the nearest neighbor sample value is used, i.e., the integer point with the closest index is selected. If the sample point falls exactly between two integer points, linear interpolation is used: Retrieve the voltage values ​​corresponding to these two indices from the buffer, and record them as follows: and .

[0113] Calculate the insulation resistance and absorption ratio: Read pre-stored The actual resistance value of the current limiting resistor corresponding to the current measurement channel in the current measurement channel. For phase-to-phase measurements, select the actual resistance value corresponding to the selected channel, for example... Alternating selection Phase channel, then use .

[0114] Read the actual DC voltage amplitude measured in the step .

[0115] Calculate the first insulation resistance value: Calculate the second insulation resistance value: Calculate the absorption ratio: Formula derivation: Based on the voltage divider principle of series circuits, the current-limiting resistor... With insulation resistance In series, the total applied voltage is The voltage drop across the current-limiting resistor is Then the voltage drop across the insulation resistance is The current flowing through the two resistors is equal: Solving Store the results: the calculated Including the type of the currently insulated object, such as Store them together in the global result array In the middle, mark the data as valid. Then Clear to zero and increment index. The state detection and loop control unit is re-triggered to configure the next insulated object, and the above process is repeated.

[0116] When all All objects have been measured ( achieve If all data is valid, the system will automatically enter the comparison and analysis phase. If a data point becomes invalid due to a fault, such as a relay verification failure, the system will report an error and terminate, and will not enter the comparison phase.

[0117] Troubleshooting: If during pressurization, Unable to be stable, for example, exceeding Seconds, still fluctuating for more than If the DC high voltage generator module 23 fails, an error message will be output and the process will terminate.

[0118] 2.3 Storage unit.

[0119] Function: Stores the detection results of each cycle in non-volatile memory for longitudinal comparison. Also handles the case of the first detection.

[0120] Implementation details: The storage unit maintains an array of structures. ,in Saves the data from the previous period, and history[1] saves the data from the current period (temporarily stored during measurement). Each element contains three floating-point numbers ( ) and a validity indicator .

[0121] When all of the current period After the measurement of each object is completed and valid, the unit will... Copy the content In the middle, then Clear the data and reuse it for the next cycle. Simultaneously, write the current cycle data to... The write address is incremented cyclically. CRC checksum is used during the write process to ensure data integrity.

[0122] For the first detection cycle (without data from the previous cycle), during system initialization... All validity flags are initialized to Meanwhile, the system scans... Find the most recent valid detection record; if found, load it into... In, and will Set as Otherwise, keep This way, even if the device is powered off and restarted, historical data will not be lost.

[0123] First check when making a longitudinal comparison If If the longitudinal comparison is not found, the warning sign will indicate that it is the first detection and there is no historical data.

[0124] 2.4 Comparison and Early Warning Unit.

[0125] Function: Performs horizontal (inter-object comparison) and vertical (comparison with historical data) comparisons of three parameters for all insulated objects, generating warning indicators. To avoid ill-conditioned means, the horizontal comparison divides insulated objects into two groups: the ground group ( ) and alternating groups ( The average and deviation are calculated for each group.

[0126] Implementation details: When all The unit is triggered once the measurement of an object is completed.

[0127] First, perform a data validity check: traverse... Array, if any If the comparison fails, the comparison will terminate and an error will be reported.

[0128] Horizontal comparison: Ground group (index) ): Calculate three ground objects average , average The average value of DAR For each ground target, calculate the deviation: if or or If so, it is marked as an exception. For example, the threshold value for deviation from ground resistance. .

[0129] Alternating groups (index) Similarly, calculate the average value of the three alternating objects. , , And calculate the deviation, using an additional threshold. ,For example Because the phase-to-phase insulation resistance is usually equal to the phase-to-ground resistance. The absolute value of any deviation exceeds the corresponding threshold, and is then marked as a lateral anomaly.

[0130] Vertical comparison: from Read data from the previous cycle. For each object... ,if ,but: if and ,or and , For example, the resistance degradation threshold. or relative value If so, set a resistance degradation flag.

[0131] if and , For example, the absorption ratio degradation threshold Then set an "absorption ratio degradation flag".

[0132] Generate warning flags: Based on the above information, construct a data structure containing the following fields: (0) = Normal, (1) = Level 1 Warning (Attention), (2) = Level 2 Warning (Warning). Judgment rule: If any deterioration indicator exists, it is at least a Level 1 Warning; if there is a lateral anomaly and the absolute value of the deviation exceeds the corresponding of If so, it will be upgraded to a Level II warning.

[0133] List of abnormal objects and their causes: "Large-to-ground deviation", "Phase-to-phase lateral deviation", "Resistance decrease", "Absorption ratio decrease".

[0134] Overall trend description, such as overall resistance decreasing. .

[0135] The warning sign passes The data is sent to the LCD display device 2 for display and can optionally be uploaded to the background monitoring system.

[0136] Threshold setting basis: :according to standard, The insulation resistance of the motor should be greater than ,according to correspond , As a deviation threshold, it can effectively identify situations where a certain phase is significantly lower than other phases. For The motor can be adjusted to .

[0137] Based on experimental statistics, the phase-to-phase insulation resistance is approximately equal to the phase-to-ground resistance. Therefore, the threshold is taken as a multiple of the ground threshold. times.

[0138] The absorption ratio should be greater than the normal value. ,deviation This means that the absorption ratio of a certain object differs from the group average by more than [a certain percentage]. For example, average A certain object Still higher However, it is already close to the lower limit, and a warning should be issued.

[0139] or Take the larger value. If the reference resistance is very high, such as... Relative to 10% To avoid false alarms; if the reference resistance is low, such as... ,absolute The value may be too large; in this case, using a relative percentage is more reasonable.

[0140] Absorption ratio decreases This indicates a clear trend of deterioration.

[0141] Example 3: Detailed steps of the insulation testing method for the zigzag structure of high-voltage motors.

[0142] This embodiment demonstrates the complete execution flow of the method of the present invention using a specific field operation example. Assume that in a thermal power plant, one... The high-pressure feedwater pump motor was shut down for planned maintenance, and the maintenance personnel decided to use this device for insulation testing. The device has been installed and powered on, and historical data from the previous cycle is available (not the first time).

[0143] Step 1: Obtain motor operating status information, determine whether the detection conditions are met, and generate a detection enable flag.

[0144] After the device is powered on, the intelligent processing unit 24 continuously performs status detection tasks. When maintenance personnel click "Start Detection" on the LCD screen, the system begins a non-blocking safe wait.

[0145] The circuit breaker auxiliary contacts are in a low-level state (open state). The effective values ​​of the three-phase voltages are respectively... All are less than Threshold, effective value of three-phase current are both .start up A non-blocking timer will continue to function if the condition is still met after the timer expires. Set as .

[0146] Step 2: When the enable flag is valid, select each target insulation type in sequence.

[0147] The first object in the system's sequential list is A, relative to the ground. The system will... Set as .

[0148] Step 3: For each target insulation type, perform the following sub-steps (3.1 to 3.4).

[0149] 3.1 Based on the target insulation type, control the on / off state of the high-voltage isolation relay to reconstruct the measurement circuit and record the circuit reconstruction completion flag.

[0150] The system according to Call the instruction generation function to obtain a 6-bit binary instruction. (A1 closed, the rest open). The command is output through the output control unit 28.

[0151] wait Then, read the feedback from each relay auxiliary contact: A1 feedback is high, the rest are low, consistent with the command. System Settings The symbol is 1.

[0152] 3.2 When the circuit reconfiguration completion flag is detected, DC voltage is injected into the measurement circuit through the high-voltage current-limiting resistor and the voltage signal is acquired.

[0153] The system detected Then, the output of the DC high voltage generator module 23 is set via the DAC. And send a start command. After the voltage stabilizes, approximately The system begins continuous voltage sampling. Each The voltage across the current-limiting resistor is read once per second (by oversampling averaging) and stored in the buffer.

[0154] The continuous sampling process totals Seconds, get The filtered voltage value.

[0155] 3.3 Calculate the first insulation resistance, second insulation resistance, and absorption ratio corresponding to the current target insulation type based on the voltage signal.

[0156] After sampling, the system extracts the voltage values ​​corresponding to 15 seconds from the buffer. Voltage value corresponding to the 60th second That is, the corrected reasonable value. (Known) Read the actual resistance value of the current-limiting resistor in phase A from the EEPROM. .

[0157] The system will Store the index of the result array .

[0158] 3.4 Select the next target insulation type and repeat the above sub-steps.

[0159] The system will increment the index and select... ,repeat We obtained phase B data; then After completing all the steps, 6 sets of valid data were obtained.

[0160] Step 4: Obtain the first insulation resistance value, second insulation resistance value, and absorption ratio for each of the target insulation types.

[0161] At this point, the result array is full and all results are valid, and the system enters the comparative analysis phase.

[0162] Step 5: Perform a horizontal comparison (grouping) of the three parameters corresponding to all target insulation types.

[0163] Ground group: three ground objects They are respectively ,average value Phase B deviation less than Threshold, no abnormalities.

[0164] Alternating group: Three alternating objects They are respectively ,average value The deviations are all less than Threshold, no abnormalities.

[0165] Step 6: Compare the three parameters of each insulation object in the current cycle with the historical values ​​of the same target insulation type stored in the previous cycle.

[0166] The system reads historical data stored in the previous cycle: The history of the phase for Calculate the change The absolute value is less than the threshold. The degradation flag was not triggered.

[0167] All other changes to objects are within the allowed range.

[0168] Step 7: Generate warning signs based on the differences between horizontal and vertical comparisons.

[0169] Overall Information: The warning sign is normal, and the LCD screen shows that the insulation status is good.

[0170] Example 4: Special treatment during the first test.

[0171] When the device is first installed or data is cleared, the initial test will not include historical data from the previous cycle. At this time, all historical validity flags in the storage unit will be empty. In the steps In the longitudinal comparison, the system detected If no historical data is found, the system will skip all longitudinal comparison calculations and directly proceed to generating an early warning flag. The early warning flag will indicate "No historical data, longitudinal comparison not performed." Simultaneously, after the current period's data is completed, the system will store the data in the historical storage area for the next test. This avoids false alarms caused by a lack of historical data. Furthermore, after the initial test, the system will automatically use the current data as the historical baseline for subsequent comparisons.

[0172] Example 5: Comparison test with existing technology.

[0173] To verify the technical effectiveness of the present invention, the inventors conducted a comparative test. The test object was a machine. High-voltage motors were tested using traditional manual methods. The megohmmeter and the device of this invention were tested, and the comparison results are as follows: Detection time: Traditional methods require (Hours, including power outage permit, disconnection of wires, measurement, and reconnection) The device of this invention only requires Minutes, fully automatic, no need to disconnect or reconnect cables. Efficiency increased by more than 10 times.

[0174] Testing items: Traditional methods typically only measure three-phase to ground and some phase-to-phase connections (due to the cumbersome disconnection and reconnection of wires). This invention's device automatically completes all six tests, achieving high coverage. .

[0175] Repeatability: Due to human factors such as contact resistance and megohmmeter speed, traditional methods can result in significant deviations in repeated measurements by the same operator. The repeatability deviation of the device of the present invention is less than % %.

[0176] Early warning capability: Traditional methods only provide resistance values, requiring manual comparison with standards; the device of this invention automatically provides lateral comparisons and longitudinal trends, issuing an early warning when the insulation of a phase begins to decrease but has not yet fallen below the standard value, with an advance time of approximately [missing information]. (Based on simulated aging tests).

[0177] Safety: Traditional methods require operators to be near the high-voltage junction box, posing a risk of electric shock; the device of this invention automatically detects and isolates residual voltage after the motor stops, eliminating the need for personnel to come into contact with high voltage throughout the process.

[0178] Summary of technical effects.

[0179] This invention achieves automation and safety: no manual terminal disassembly or assembly is required; measurement only begins when there is no residual voltage, avoiding the danger of electric arcs. Relay feedback verification ensures circuit correctness and eliminates malfunctions.

[0180] Highly efficient and comprehensive: One-time connection for permanent use; continuous automatic measurement of six insulated objects; total time less than [time value missing]. Traditional manual methods require .

[0181] Early warning: Horizontal comparison (group statistics) can detect asymmetric insulation defects (such as one phase being damp), and vertical comparison can detect the overall insulation aging trend. Warnings are issued before the insulation resistance value drops to the dangerous threshold, enabling predictive maintenance.

[0182] Adaptability: Flexible wires and circular copper connectors are suitable for different motor junction boxes, and silicone rubber-sealed resistors are suitable for harsh environments.

[0183] Data traceability: Stores historical data, supports trend analysis, and provides a scientific basis for equipment management.

[0184] The foregoing has shown and described the basic principles, main features, and advantages of this application. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the appended claims and their equivalents.

Claims

1. A delta configuration insulation detection device for a high voltage electric machine, characterized by, include: Mountain-shaped metal casing; High-voltage A-phase current-limiting resistor, high-voltage B-phase current-limiting resistor and high-voltage C-phase current-limiting resistor are installed on the upper end of the mountain-shaped metal casing and sealed with silicone rubber. The following components are installed inside the metal casing: a motor operation status acquisition unit, an output control unit, six high-voltage isolation relays, a DC high-voltage generation module, a sampling and processing unit, and an intelligent processing unit. The high-voltage current-limiting resistor encapsulated in silicone rubber is electrically connected to the DC high-voltage generating module through the high-voltage isolation relay. The DC high-voltage generating module is electrically connected to the sampling and processing unit. The sampling and processing unit is electrically connected to the intelligent processing unit. The intelligent processing unit is electrically connected to the motor operating status acquisition unit and the output control unit, respectively. The device also includes a liquid crystal display device, and the intelligent processing unit is electrically connected to the liquid crystal display device.

2. The apparatus of claim 1, wherein, The upper end of the mountain-shaped metal casing is connected to three flexible wires, which are electrically connected to the high-voltage A-phase current-limiting resistor, the high-voltage B-phase current-limiting resistor, and the high-voltage C-phase current-limiting resistor, respectively. Each flexible wire has a circular copper connector at its end, which is used to fix and connect the three-phase stator winding of the high-voltage motor.

3. A delta configuration insulation detection system for a high voltage electric machine, characterized in that, The system includes: The status detection and loop control unit is used to acquire the motor's operating status information, determine whether the motor meets the detection conditions, and generate a detection enable flag. When the detection enable flag is valid, it sequentially selects each target insulation type and controls the on / off state of the high-voltage isolation relay to reconstruct the measurement loop according to the target insulation type, and records the loop reconstruction completion flag. The DC voltage application and parameter calculation unit is used to inject DC voltage into the measurement circuit through a high-voltage current-limiting resistor and collect voltage signals when the circuit reconstruction completion flag is detected, and to calculate the first insulation resistance value, the second insulation resistance value, and the absorption ratio corresponding to the target insulation type based on the voltage signals; The storage unit is used to store the historical first insulation resistance value, historical second insulation resistance value, and historical absorption ratio for each target insulation type in the previous cycle; The comparison and early warning unit is used to perform a horizontal comparison of the first insulation resistance value, the second insulation resistance value, and the absorption ratio corresponding to all target insulation types; and to perform a vertical comparison of the first insulation resistance value, the second insulation resistance value, and the absorption ratio corresponding to each target insulation type with the historical first insulation resistance value, the historical second insulation resistance value, and the historical absorption ratio of the same target insulation type in the storage unit; and to generate an early warning flag based on the differences between the horizontal comparison and the vertical comparison.

4. The system of claim 3, wherein, The state detection and loop control unit is specifically used for: Read the detection enable flag; After confirming that the detection enable flag is in a valid state, a preset detection sequence table is obtained. The detection sequence table records six insulating objects in sequence: the first phase to ground, the second phase to ground, the third phase to ground, the first phase to the second phase, the second phase to the third phase, and the first phase to the third phase. Take out the first untested insulating object in sequence according to the test sequence table; The extracted insulating object is identified as the target insulation type.

5. The system of claim 3, wherein, The state detection and loop control unit is specifically used for: The six high-voltage isolation relays are divided into three winding-side relays and three ground-side relays; the winding-side relays include a first-phase winding-side relay, a second-phase winding-side relay, and a third-phase winding-side relay; the ground-side relays include a first-phase ground-side relay, a second-phase ground-side relay, and a third-phase ground-side relay. Determine whether the target insulation type is ground-to-ground or phase-to-phase. If the target insulation type is a ground type, then obtain the phase corresponding to the target insulation type; generate a first combination based on the phase; the first combination is: close the winding side relay corresponding to the phase, open the winding side relays of the other two phases, and open all ground side relays; If the target insulation type is phase-to-phase, then obtain the two phases corresponding to the target insulation type; generate a second combination based on the two phases; the second combination is: close the two winding-side relays corresponding to the two phases, open the winding-side relay of the other phase, close the ground-side relay of one of the two phases, and open the remaining ground-side relays; The first combination or the second combination is compiled into an on / off combination instruction, wherein the on / off combination instruction is in six-bit binary form.

6. The system of claim 5, wherein, The state detection and loop control unit is specifically used for: The on / off combination instruction is parsed to obtain the mapping relationship between each binary bit and the corresponding relay; According to the mapping relationship, each binary bit is sent to the corresponding relay, and after all relays have completed their actions, the auxiliary contact feedback signal of each relay is read. Each feedback signal is compared with the binary bits sent to the relay to generate a comparison result; If all comparison results are consistent, the generation loop reconstruction is complete.

7. The system of claim 3, wherein, The DC voltage application and parameter calculation unit is specifically used for: Send a start command and voltage amplitude parameters to the DC high voltage generator; The DC high voltage generator produces a DC high voltage according to the start command and the voltage amplitude parameters; The DC high voltage is applied to the motor winding through the corresponding silicone rubber-sealed high voltage current-limiting resistor. After the voltage stabilizes, a voltage injection flag is generated.

8. The system of claim 7, wherein, The DC voltage application and parameter calculation unit is specifically used for: Set the sampling clock period and the total number of sampling points; Starting from the rising edge of the voltage-injected flag, the digital voltage output of the analog-to-digital converter is read once every sampling clock cycle; The digital voltage values ​​read each time are stored sequentially in a buffer. When the total number of sampling points is reached, the contents of the buffer are output as a voltage sampling sequence.

9. The system of claim 3, wherein, The comparison and early warning unit is specifically used for: Calculate the first average value of the first insulation resistance of all target insulation types, the second average value of the second insulation resistance of all target insulation types, and the average absorption ratio of all target insulation types; The first deviation is obtained by subtracting the first average value from the first insulation resistance value of each target insulation type; The second deviation is obtained by subtracting the second average value from the second insulation resistance value of each target insulation type; The absorption ratio deviation is obtained by subtracting the average absorption ratio from the absorption ratio of each target insulation type. If the absolute value of the first deviation, the second deviation, or the absorption ratio deviation exceeds a preset threshold, the target insulation type is marked as abnormal. Read the historical first insulation resistance value, historical second insulation resistance value, and historical absorption ratio of the previous cycle; Subtract the historical first insulation resistance value from the current first insulation resistance value to obtain the change in the first resistance value; Subtract the historical second insulation resistance value from the current second insulation resistance value to obtain the change in the second resistance value; Subtracting the historical absorption ratio from the current cycle absorption ratio yields the change in absorption ratio; If the first resistance change or the second resistance change is negative and its absolute value is greater than the first threshold, a resistance degradation flag is generated. If the change in absorption ratio is negative and its absolute value is greater than the second threshold, an absorption ratio degradation flag is generated.

10. A method for detecting the delta configuration insulation of a high voltage electric machine, characterized in that, The method includes: Obtain the motor's operating status information, determine whether the motor meets the detection conditions based on the operating status information, and generate a detection enable flag; When the detection enable flag is valid, each target insulation type is selected sequentially; For each target insulation type, the on / off state of the high-voltage isolation relay is controlled according to the target insulation type to reconstruct the measurement circuit, and the circuit reconstruction completion flag is recorded; When the circuit reconstruction completion flag is detected, DC voltage is injected into the measurement circuit through the high-voltage current-limiting resistor and the voltage signal is collected. Based on the voltage signal, the first insulation resistance value, the second insulation resistance value and the absorption ratio corresponding to the target insulation type are calculated. Obtain the first insulation resistance, second insulation resistance, and absorption ratio corresponding to each of the target insulation types; A horizontal comparison is made of the first insulation resistance value, the second insulation resistance value, and the absorption ratio corresponding to all target insulation types; The first insulation resistance value, the second insulation resistance value, and the absorption ratio corresponding to each target insulation type are compared longitudinally with the historical first insulation resistance value, historical second insulation resistance value, and historical absorption ratio of the same target insulation type stored in the previous cycle. A warning sign is generated based on the differences between the horizontal and vertical comparisons.

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