Comprehensive test device and method for preventive test of 10kV switch cabinet

Abstract

The invention discloses a comprehensive test device and method for a preventive test of a 10kV switch cabinet, and belongs to the technical field of electrical equipment testing, and the device comprises a main control unit, a power module, a test module, a human-computer interaction interface, a communication interface and an external test interface. The power supply module comprises an auxiliary power supply unit and a plurality of special test power supply units, and the main control unit controls the power supply module to be automatically switched among different special test power supply units. And the test module comprises a direct current resistance test unit, a loop resistance test unit, a switch action time test unit, an insulation resistance test unit and a power frequency withstand voltage test unit which are controlled by the main control unit to execute tests in sequence. According to the invention, integration of multiple test functions, automatic power supply switching and automatic test flow scheduling are realized, all test items are completed through one-time wiring, the test efficiency and precision are improved, and digital management of test data is realized.

Description

A comprehensive test apparatus and method for preventive testing of 10kV switchgear Technical Field

[0001] This invention relates to the field of power equipment testing technology, specifically to a comprehensive test device and method for preventive testing of 10kV switchgear. Background Technology

[0002] As a core piece of equipment in the power distribution system, the 10kV switchgear's operating status directly affects the reliability of power supply and the safety of the system. To ensure the safe and stable operation of the switchgear, preventive tests need to be carried out regularly, mainly including DC resistance testing, loop resistance testing, switch operating time testing, insulation resistance testing, and power frequency withstand voltage testing.

[0003] Existing preventative testing typically employs multiple independent devices, such as DC resistance testers, loop resistance testers, switch characteristic testers, insulation resistance testers, and power frequency withstand voltage testers, to perform each test separately. This testing model has the following technical drawbacks: the test equipment is functionally limited and dispersed, with each device capable of completing only one or two tests. Multiple instruments must be carried on-site, and after each test, equipment must be replaced and rewiring repeated, resulting in long testing cycles and complex on-site operations. Frequent wiring operations not only increase the risk of wiring errors but also easily affect test accuracy due to changes in contact resistance, especially in resistance tests where the introduction of lead resistance directly impacts the accuracy of measurement results.

[0004] Existing equipment lacks unified test process management and automated control capabilities. Switching test items, configuring power supplies, and setting test parameters all require individual operations, making it impossible to achieve automatic scheduling of test processes and intelligent switching of power supplies. This results in low test efficiency and reliance on operational experience.

[0005] The recording, storage, and analysis of test data mainly rely on traditional methods. The data is stored in a scattered manner and the format is not uniform, making it difficult to form a systematic test archive. This is not conducive to trend analysis of equipment status and fault prediction, and cannot meet the development needs of intelligent and digital power equipment operation and maintenance management. Summary of the Invention

[0006] In view of the above-mentioned problems, the present invention provides a comprehensive test device and method for preventive testing of 10kV switchgear.

[0007] Therefore, the technical problem solved by this invention is: how to integrate multiple test functions of 10kV switchgear preventive testing into a single device, realize automatic power switching and automatic scheduling of test processes, improve test accuracy and efficiency, and realize digital management of test data.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a comprehensive test device for preventive testing of 10kV switchgear, comprising: a main control unit for executing test process control and power switching control, and receiving and processing test data; a power module electrically and signal-connected to the main control unit, including an auxiliary power unit and multiple dedicated test power units, wherein the auxiliary power unit provides working power to the main control unit, and the dedicated test power units are controlled by the main control unit to provide corresponding test power to the test module; the main control unit controls the power module to automatically switch between different dedicated test power units according to the currently executed test item through signal connection; and a test module signal-connected to the main control unit and connected to the main control unit. The power supply module is electrically connected and used to perform multiple preventive tests on the 10kV switchgear. The test module includes a DC resistance test unit, a loop resistance test unit, a switch action time test unit, an insulation resistance test unit, and a power frequency withstand voltage test unit. Under the control of the main control unit, the test module sequentially performs tests and transmits the test data to the main control unit. A human-machine interface, communicatively connected to the main control unit, is used to receive test commands and parameters input by the user and display the test results. A communication interface, also communicatively connected to the main control unit, is used to upload test data to an external management system. An external test interface, electrically connected to the test module, is used to connect the test module to the test points of the 10kV switchgear.

[0009] As a preferred embodiment of the comprehensive preventive testing device for 10kV switchgear described in this invention, the dedicated test power supply unit includes: a DC constant current power supply unit for providing adjustable DC constant current power to the DC resistance testing unit and the loop resistance testing unit; a DC high voltage power supply unit for providing DC high voltage power to the insulation resistance testing unit; and a power frequency high voltage power supply unit for providing continuously adjustable power frequency AC high voltage power to the power frequency withstand voltage testing unit.

[0010] As a preferred embodiment of the comprehensive test device for preventive testing of 10kV switchgear according to the present invention, the DC resistance testing unit includes: a precision constant current source for outputting a constant test current; a first current line and a second current line for applying the constant test current to both ends of the resistor under test; a first voltage sampling line and a second voltage sampling line connected to both ends of the resistor under test for acquiring voltage signals across the resistor under test; a high-precision differential amplifier connected to the first voltage sampling line and the second voltage sampling line for amplifying the voltage signals; and a high-precision analog-to-digital converter connected to the high-precision differential amplifier for converting the amplified voltage signals into digital voltage values ​​and transmitting them to the main control unit.

[0011] The beneficial effects of this preferred technical solution are as follows: Employing the four-wire measurement principle, the current injection circuit and voltage measurement circuit are separated through independent current transmission lines and voltage sampling lines. The current line applies a constant test current to the resistor under test, while the voltage sampling line is directly connected across the resistor to acquire the voltage signal. This eliminates the presence of lead resistance in the measurement circuit, thus completely eliminating the influence of lead resistance and contact resistance on the measurement results. A high-precision differential amplifier accurately amplifies weak voltage signals, and in conjunction with a high-precision analog-to-digital converter, achieves high-resolution data acquisition, significantly improving the measurement accuracy of DC resistance testing.

[0012] As a preferred embodiment of the comprehensive test device for preventive testing of 10kV switchgear according to the present invention, the loop resistance testing unit includes: a high-current constant current source for outputting a constant test current of a high current level; a high-current contactor connected to the high-current constant current source for controlling the on / off state of the constant test current of a high current level; a first current line and a second current line for applying the constant test current of a high current level to both ends of the loop resistance under test; a high-precision shunt connected in series with the second current line for converting the constant test current of a high current level into a voltage signal for sampling; a first voltage sampling line and a second voltage sampling line connected to both ends of the loop resistance under test for acquiring the voltage signal across the loop resistance under test; a differential amplifier connected to the first voltage sampling line and the second voltage sampling line for amplifying the voltage signal; and an analog-to-digital converter connected to the differential amplifier and the high-precision shunt for converting the amplified voltage signal and the voltage signal generated by the high-precision shunt into a digital signal and transmitting it to the main control unit.

[0013] The beneficial effects of this preferred technical solution are as follows: Addressing the requirement of high current conditions in loop resistance testing, a high-precision shunt is used to convert the high current into a measurable voltage signal, achieving accurate sampling of the test current. A high-current contactor reliably controls the switching of currents in the hundreds of amperes, ensuring the safety of the testing process. This solution also employs the four-wire method, eliminating the influence of lead resistance through an independent voltage sampling circuit, ensuring accurate resistance measurements even under high-current testing conditions. The use of a high-precision shunt avoids the inaccuracy problem of traditional current transformers in measuring small resistance values ​​with large currents, thus improving the accuracy of loop resistance testing.

[0014] As a preferred embodiment of the comprehensive test device for preventive testing of 10kV switchgear described in this invention, the switch action time test unit includes: a contact state sensor for detecting the state changes of each phase contact of the circuit breaker; a switch input channel connected to the contact state sensor and having photoelectric isolation function for transmitting the contact state signal to the main control unit; and a high-precision timer located in the main control unit for starting the timer when the main control unit issues a closing or opening command, recording the time of state changes of each phase contact, and calculating the closing time, opening time, and asynchrony time based on the recorded time.

[0015] As a preferred embodiment of the comprehensive preventive testing device for 10kV switchgear described in this invention, the insulation resistance testing unit includes: a DC high-voltage generator for generating and outputting a DC high voltage to the insulator under test; a sampling resistor network connected in series with the DC high-voltage generator for collecting leakage current flowing through the insulator under test; a micro-current amplifier connected to the sampling resistor network for amplifying the leakage current signal; and an analog-to-digital converter connected to the micro-current amplifier for converting the amplified leakage current signal into a digital signal and transmitting it to the main control unit. The main control unit calculates the insulation resistance value based on the DC high voltage and the leakage current.

[0016] As a preferred embodiment of the comprehensive preventive testing device for 10kV switchgear described in this invention, the power frequency withstand voltage test unit includes: a power frequency high voltage generator for generating and outputting a continuously adjustable power frequency AC high voltage to the insulator under test; a leakage current detection circuit for real-time monitoring of the leakage current flowing through the insulator under test; an overcurrent protection circuit connected to the leakage current detection circuit for cutting off the output of the power frequency high voltage generator when the leakage current exceeds a preset threshold; and an analog-to-digital converter connected to the leakage current detection circuit for converting the leakage current signal into a digital signal and transmitting it to the main control unit.

[0017] As a preferred embodiment of the 10kV switchgear preventive test integrated test device described in this invention, the power supply module further includes: a power switching control unit, which is signal-connected to the main control unit, including multiple high-voltage relays and contactors. The high-voltage relays and contactors are respectively connected to the output terminal of the dedicated test power supply unit, and are used to selectively connect the output of the dedicated test power supply unit to the test module under the control of the main control unit, so as to ensure that only the output of one dedicated test power supply unit is connected to the test module at any given time.

[0018] The beneficial effects of this preferred technical solution are as follows: By setting up a power switching control unit, automatic switching and mutual exclusion control of power supplies for different test items are achieved. Under the control of the main control unit, the high-voltage relays and contactors can accurately select the dedicated test power supply unit required for the current test item, and a hardware interlock mechanism ensures that only one power supply unit is connected to the test module at any given time, effectively avoiding mutual interference and short-circuit risks between power supplies of different voltage and current levels. This design not only ensures the safety of the testing process but also eliminates the potential for equipment damage caused by power switching operation errors.

[0019] In a preferred embodiment of the 10kV switchgear preventive test integrated test device of the present invention, a test path switching unit is provided between the test module and the external test interface. The test path switching unit is signal-connected to the main control unit and is used to selectively connect the corresponding units of the DC resistance test unit, the loop resistance test unit, the switch action time test unit, the insulation resistance test unit and the power frequency withstand voltage test unit to the external test interface under the control of the main control unit.

[0020] This invention provides a comprehensive test method for preventive testing of 10kV switchgear.

[0021] To address the aforementioned technical problems, this invention provides the following technical solution: a comprehensive preventive testing method for 10kV switchgear, comprising: connecting a test module to the test point of the 10kV switchgear under test via an external test interface; receiving test instructions via a human-machine interface; the main control unit determining the test items to be executed based on the test instructions; the main control unit controlling the power module to switch to the dedicated test power unit corresponding to the first test item, and starting the corresponding test unit to execute the first test item and collect test data; the main control unit determining whether all test items have been completed; if not, controlling the power module to switch to the dedicated test power unit corresponding to the next test item, and starting the corresponding test unit to execute the next test item and collect test data, repeating this step; if yes, executing the next step; the main control unit processing the collected test data, generating a test report, and displaying the test results via the human-machine interface and uploading test data via a communication interface.

[0022] The present invention provides a computer device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the comprehensive test method for preventive testing of a 10kV switchgear.

[0023] The present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the comprehensive test method for preventive testing of a 10kV switchgear.

[0024] The beneficial effects of this invention are: integrating DC resistance, loop resistance, switching action time, insulation resistance and power frequency withstand voltage testing into a single device, and achieving one-time wiring through an external test interface, avoiding multiple disassembly and assembly of test circuits, significantly shortening the test cycle and improving on-site operation efficiency.

[0025] The DC resistance test unit and the loop resistance test unit adopt the four-wire method measurement principle. Through independent current transmission lines and voltage sampling lines, the influence of lead resistance on the measurement results is eliminated. The application of high-precision differential amplifiers and high-precision analog-to-digital converters ensures the accurate acquisition and conversion of small voltage signals. The high-precision shunt converts large currents into voltage signals for sampling, ensuring the measurement accuracy of loop resistance under high current conditions.

[0026] The power module automatically switches between power supplies for different test items through a power switching control unit. The mutual exclusion control of high-voltage relays and contactors ensures that only one dedicated test power supply unit is connected to the test module at any given time, avoiding power conflicts and mutual interference. The overcurrent protection circuit configured in the power frequency withstand voltage test unit can automatically cut off the high-voltage output when the leakage current exceeds the preset threshold, ensuring the safety of the test process.

[0027] The main control unit automatically schedules the test modules to execute each test in sequence according to the test instructions, and automatically controls the power module to switch between different dedicated test power units. The test process does not require manual intervention, which reduces the possibility of operational errors and improves the standardization and consistency of the test.

[0028] Test data is collected in real time via an analog-to-digital converter and transmitted to the main control unit for processing and calculation, generating standardized test reports. These reports are then uploaded to an external management system via a communication interface, enabling centralized storage, querying, and analysis of test data, and providing data support for equipment status assessment and fault prediction. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 is an overall structural diagram of a 10kV switchgear preventive testing integrated test device provided in an embodiment of the present invention.

[0031] Figure 2 is a schematic diagram of the four-wire resistance measurement principle of a comprehensive test device for preventive testing of 10kV switchgear provided in an embodiment of the present invention.

[0032] Figure 3 is a timing diagram of the switch action time test of a comprehensive test device for preventive testing of 10kV switchgear provided in an embodiment of the present invention.

[0033] Figure 4 is a schematic diagram of the insulation / withstand voltage test principle of a comprehensive preventive test device for 10kV switchgear provided in an embodiment of the present invention. Detailed Implementation

[0034] To make the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0035] Example 1, referring to Figures 1-4, illustrates an embodiment of the present invention. This embodiment provides a comprehensive test device for preventive testing of 10kV switchgear, comprising: a main control unit for executing test process control and power switching control, and receiving and processing test data; a power module electrically and signal-connected to the main control unit, including an auxiliary power unit and multiple dedicated test power units, wherein the auxiliary power unit provides operating power to the main control unit, and the dedicated test power units, under the control of the main control unit, provide corresponding test power to the test module; the main control unit controls the power module to automatically switch between different dedicated test power units according to the currently executed test item via signal connection; and a test module signal-connected to the main control unit. The system is electrically connected to the power supply module and is used to perform multiple preventative tests on the 10kV switchgear. The test module includes a DC resistance test unit, a loop resistance test unit, a switch action time test unit, an insulation resistance test unit, and a power frequency withstand voltage test unit. Under the control of the main control unit, the test module sequentially performs tests and transmits the test data to the main control unit. A human-machine interface, communicatively connected to the main control unit, is used to receive test commands and parameters input by the user and display the test results. A communication interface, also communicatively connected to the main control unit, is used to upload test data to an external management system. An external test interface, electrically connected to the test module, is used to connect the test module to the test points of the 10kV switchgear.

[0036] Furthermore, the dedicated test power supply unit includes: a DC constant current power supply unit for providing an adjustable DC constant current power supply to the DC resistance test unit and the loop resistance test unit; a DC high voltage power supply unit for providing a DC high voltage power supply to the insulation resistance test unit; and a power frequency high voltage power supply unit for providing a continuously adjustable power frequency AC high voltage power supply to the power frequency withstand voltage test unit.

[0037] Furthermore, the DC resistance testing unit includes: a precision constant current source for outputting a constant test current; a first current line and a second current line for applying the constant test current to both ends of the resistor under test; a first voltage sampling line and a second voltage sampling line connected to both ends of the resistor under test for acquiring voltage signals across the resistor under test; a high-precision differential amplifier connected to the first voltage sampling line and the second voltage sampling line for amplifying the voltage signals; and a high-precision analog-to-digital converter connected to the high-precision differential amplifier for converting the amplified voltage signals into digital voltage values ​​and transmitting them to the main control unit.

[0038] Furthermore, the loop resistance testing unit includes: a high-current constant current source for outputting a constant test current of a high current level; a high-current contactor connected to the high-current constant current source for controlling the on / off state of the constant test current of a high current level; a first current line and a second current line for applying the constant test current of a high current level to both ends of the loop resistance under test; a high-precision shunt connected in series with the second current line for converting the constant test current of a high current level into a voltage signal for sampling; a first voltage sampling line and a second voltage sampling line connected to both ends of the loop resistance under test for acquiring the voltage signal across the loop resistance under test; a differential amplifier connected to the first voltage sampling line and the second voltage sampling line for amplifying the voltage signal; and an analog-to-digital converter connected to the differential amplifier and the high-precision shunt for converting the amplified voltage signal and the voltage signal generated by the high-precision shunt into a digital signal and transmitting it to the main control unit.

[0039] Furthermore, the switch action time testing unit includes: a contact state sensor for detecting state changes of each phase contact of the circuit breaker; a switch input channel connected to the contact state sensor and having photoelectric isolation function for transmitting the contact state signal to the main control unit; and a high-precision timer located in the main control unit for starting timing when the main control unit issues a closing or opening command, recording the time of state changes of each phase contact, and calculating the closing time, opening time, and asynchrony time based on the recorded time.

[0040] Furthermore, the insulation resistance testing unit includes: a DC high-voltage generator for generating and outputting a DC high voltage to the insulator under test; a sampling resistor network connected in series with the DC high-voltage generator for collecting the leakage current flowing through the insulator under test; a micro-current amplifier connected to the sampling resistor network for amplifying the leakage current signal; and an analog-to-digital converter connected to the micro-current amplifier for converting the amplified leakage current signal into a digital signal and transmitting it to the main control unit, wherein the main control unit calculates the insulation resistance value based on the DC high voltage and the leakage current.

[0041] Furthermore, the power frequency withstand voltage test unit includes: a power frequency high voltage generator for generating and outputting a continuously adjustable power frequency AC high voltage to the insulator under test; a leakage current detection circuit for real-time monitoring of the leakage current flowing through the insulator under test; an overcurrent protection circuit connected to the leakage current detection circuit for cutting off the output of the power frequency high voltage generator when the leakage current exceeds a preset threshold; and an analog-to-digital converter connected to the leakage current detection circuit for converting the leakage current signal into a digital signal and transmitting it to the main control unit.

[0042] Furthermore, the power module also includes a power switching control unit, which is signal-connected to the main control unit and includes multiple high-voltage relays and contactors. The high-voltage relays and contactors are respectively connected to the output terminals of the dedicated test power unit, and are used to selectively connect the output of the dedicated test power unit to the test module under the control of the main control unit, so as to ensure that only the output of one dedicated test power unit is connected to the test module at any given time.

[0043] Furthermore, a test path switching unit is provided between the test module and the external test interface. The test path switching unit is signal-connected to the main control unit and is used to selectively connect the corresponding units of the DC resistance test unit, the loop resistance test unit, the switch action time test unit, the insulation resistance test unit, and the power frequency withstand voltage test unit to the external test interface under the control of the main control unit.

[0044] In this embodiment, the main control unit uses the STM32H743 high-performance microcontroller, which features high-speed data processing capabilities and rich peripheral interfaces. The main control unit integrates a high-precision timer for accurate timing in switching action time testing, with a clock frequency of 200MHz and a timing accuracy of 5ns. The main control unit communicates with each module via GPIO, SPI, I2C, and UART interfaces for signal connection and data exchange.

[0045] Specifically, the auxiliary power supply unit receives an AC220V main power input and outputs multiple isolated DC voltages, including ±12V, +5V, and +3.3V, through a switching power supply module. ±12V powers the analog circuitry in the test module, +5V powers the digital circuitry, and +3.3V powers the main control unit. The auxiliary power supply unit has a total output power of 50W and features overvoltage, overcurrent, and short-circuit protection.

[0046] In this embodiment, the human-machine interface (HMI) uses a 7-inch color LCD touchscreen with a resolution of 800×480 pixels, supporting multi-touch. The HMI communicates with the main control unit via a UART interface with a baud rate of 115200bps. The main interface displays the device status, current test item, test progress, and real-time data. Users can select test modes (automatic or manual), set test parameters, start or stop tests, query historical test records, and export test reports via the touchscreen. The HMI also features fault indication and alarm functions; when wiring errors, abnormal power supply, overcurrent, overvoltage, or equipment failure are detected, an alarm window pops up and a buzzer sounds.

[0047] In this embodiment, the communication interface supports multiple communication methods, including an RS485 interface, an Ethernet interface, and a Wi-Fi wireless communication interface. The RS485 interface uses the Modbus RTU communication protocol, with an adjustable baud rate from 9600 to 115200 bps. The Ethernet interface uses the TCP / IP protocol and supports 10 / 100 Mbps auto-sensing. The Wi-Fi interface supports the IEEE 802.11b / g / n standard at a frequency of 2.4 GHz. The communication interface can upload test data to an external management system (such as a substation automation system or a distribution network dispatching system) in real time, enabling centralized storage, remote monitoring, and statistical analysis of the test data. Encrypted transmission of communication data ensures data security.

[0048] In this embodiment, the external test interface is located on the front panel of the device and includes a current output terminal, a voltage sampling terminal, a high-voltage output terminal, and a grounding terminal. The current output terminal includes two terminals, C1 and C2, corresponding to the first current line and the second current line. The voltage sampling terminal includes two terminals, P1 and P2, corresponding to the first voltage sampling line and the second voltage sampling line. The high-voltage output terminal is used to connect high-voltage test leads and is suitable for insulation resistance testing and power frequency withstand voltage testing. The grounding terminal connects to the device housing and grounding busbar to ensure reliable grounding of the device. The terminals of the external test interface are made of high-strength insulating material and have anti-misinsertion functionality.

[0049] In this embodiment, the DC constant current power supply unit has a low-current output mode and a high-current output mode. The low-current output mode provides a constant DC current of 1A with a current stability better than 0.1%, used for DC resistance testing. The high-current output mode provides a constant DC current of 100A or 200A with a current stability better than 0.5%, used for loop resistance testing. The current output can be automatically adjusted by the main control unit according to the test requirements. The DC constant current power supply unit employs a constant current control circuit and negative feedback current stabilization technology to ensure the stability of the output current.

[0050] In this embodiment, the DC high-voltage power supply unit uses a DC-DC boost converter with three output voltage levels: 500V, 1000V, and 2500V. The appropriate level can be selected according to the voltage level of the insulator under test. The output current capability is 5mA, the output voltage stability is better than 1%, and the ripple factor is less than 1%. The DC high-voltage power supply unit is equipped with a discharge resistor, which can automatically discharge the insulator under test after the test is completed, ensuring safety.

[0051] In this embodiment, the power frequency high-voltage power supply unit consists of an autotransformer, a high-voltage transformer, and a control circuit. The autotransformer receives AC220V input and outputs an adjustable voltage from 0 to 220V, with voltage regulation achieved by a stepper motor driving the sliding contact of the regulator. The high-voltage transformer boosts the output voltage of the regulator to 0 to 50kV, with a turns ratio of 1:227 and a frequency of 50Hz. The main control unit controls the stepper motor to slowly increase the output voltage to the preset value at a set rate (e.g., 2kV / s) and maintain it for a period of time (e.g., 1 minute). The power frequency high-voltage power supply unit is equipped with an overcurrent protection circuit, which automatically cuts off the power supply when the output current exceeds the set value.

[0052] In this embodiment, the precision constant current source outputs a typical constant DC current of 1A, with a current stability better than 0.1% and an output ripple of less than 0.01%. The precision constant current source uses a constant current control circuit composed of a precision reference source and an operational amplifier, and ensures the stability of the output current through negative feedback current stabilization technology.

[0053] In this embodiment, referring to Figure 2, the first current line is connected to the upper end of the contact of the circuit breaker under test, and the second current line is connected to the lower end of the contact of the circuit breaker under test, forming a current loop. The first and second current lines are made of copper wire with a cross-sectional area of ​​not less than 2.5 mm² and a length of 3 meters. Standardized terminal clamps are provided at both ends of the wires to ensure a reliable connection with the test point.

[0054] In this embodiment, referring to Figure 2, the first voltage sampling line is connected to the voltage sampling point at the upper end of the contact of the circuit breaker under test, and the second voltage sampling line is connected to the voltage sampling point at the lower end of the contact of the circuit breaker under test. The first and second voltage sampling lines are separate from the first and second current lines, and are made of shielded twisted-pair cable with a diameter of 0.5 mm² and a length of 3 meters. The connection point of the voltage sampling lines is as close as possible to the resistor being measured to eliminate the influence of the lead resistance and realize the four-wire measurement principle.

[0055] In this embodiment, the high-precision differential amplifier uses the AD620 instrumentation amplifier, which has adjustable gain, a typical gain of 100, an input impedance greater than 10MΩ, and a common-mode rejection ratio greater than 80dB. The high-precision differential amplifier effectively suppresses common-mode interference and accurately amplifies the weak voltage signal across the measured resistor. The amplifier gain is set via a resistor and calibrated by the main control unit to ensure the accuracy of the amplification factor.

[0056] In this embodiment, the high-precision analog-to-digital converter (ADC) employs a 24-bit Σ-Δ ADC (such as the ADS1256), achieving microvolt-level resolution, a sampling rate of 1 kHz, and an effective bit depth of at least 20 bits. The high-precision ADC connects to the main control unit via an SPI interface, transmitting the digital voltage value to the main control unit in real time. The main control unit receives the digital voltage value U and the known test current I, calculates the measured resistance value according to Ohm's law R = U / I, and performs temperature correction and digital filtering to obtain an accurate DC resistance measurement result.

[0057] In this embodiment, the DC resistance testing unit also includes an analog switch for multi-channel switching, enabling a single device to measure the resistance of the three-phase contacts (A, B, and C phases) of the circuit breaker. The analog switch uses a CD4051 or similar chip, is controlled by the main control unit, and can quickly switch between different measurement channels with a switching time of less than 1ms.

[0058] In this embodiment, the high-current constant current source outputs a typical constant DC current of 100A or 200A, with a current stability better than 0.5%. The high-current constant current source employs a high-power switching power supply and a constant current control circuit, achieving an output power of several kilowatts. The current output is controlled by the main control unit via a DAC and current feedback to ensure the stability and adjustability of the output current.

[0059] In this embodiment, the high-current contactor is a vacuum contactor with a rated current of 300A and a rated voltage of DC24V. The high-current contactor is controlled by the main control unit via a relay drive circuit, enabling reliable control of rapid switching of high currents. Both contact closing and opening times are less than 100ms, preventing arc damage to the contacts. The high-current contactor is also equipped with auxiliary contacts for feedback of the contactor's actual status to the main control unit.

[0060] In this embodiment, the first and second current lines are made of large-section copper wire with a cross-sectional area of ​​not less than 50 mm² and a length of 5 meters to reduce line voltage drop. The first current line is connected to the incoming bushing of the switchgear, and the second current line is connected to the grounding switch or the outgoing bushing, forming a complete conductive loop. Both ends of the wires are equipped with high-current clamps or terminals, capable of withstanding currents of over 200A without overheating.

[0061] In this embodiment, the high-precision shunt is made of manganin or constantan, with a typical resistance of 100μΩ, an accuracy of 0.5 class, and a temperature coefficient of less than 20ppm / ℃. When a 100A current passes through the high-precision shunt, a 10mV voltage signal is generated. The high-precision shunt outputs the voltage signal through an independent voltage sampling terminal. This voltage signal is amplified by a differential amplifier, acquired by an analog-to-digital converter, and transmitted to the main control unit to achieve accurate sampling of the test current. The high-precision shunt is mounted on a heat sink to ensure that the temperature rise is controlled within the allowable range when a large current passes through.

[0062] In this embodiment, the first and second voltage sampling lines are shielded twisted-pair cables with a diameter of 1 mm² and a length of 5 meters to reduce electromagnetic interference. The first voltage sampling line is connected to the upper sampling point of the resistance of the circuit under test, and the second voltage sampling line is connected to the lower sampling point of the resistance of the circuit under test. The connection points are as close as possible to the circuit under test to realize the four-wire method measurement principle and eliminate the influence of lead resistance and contact resistance.

[0063] In this embodiment, the differential amplifier employs a design with enhanced anti-interference capabilities to address the high-current environment of loop resistance testing. The differential amplifier includes an input filter circuit, an instrumentation amplifier, and an output filter circuit. The input filter circuit uses RC filtering and a common-mode choke to suppress high-frequency and common-mode interference. The instrumentation amplifier has a gain of 50 and a common-mode rejection ratio greater than 90dB. The output filter circuit uses a low-pass filter with a cutoff frequency of 100Hz to further filter out high-frequency noise. The overall design of the differential amplifier ensures accurate amplification of the voltage signal across the tested loop resistance even under high-current testing conditions.

[0064] In this embodiment, the analog-to-digital converter (ADC) uses a 16-bit SAR-type ADC (such as ADS8688) with a sampling rate of 100kHz, capable of simultaneously acquiring the voltage signal output from the differential amplifier and the voltage signal generated by the high-precision shunt. The ADC is connected to the main control unit via an SPI interface. The main control unit obtains the voltage value U across the resistor under test and the current value I flowing through it through synchronous sampling, and calculates the circuit resistance value according to Ohm's law R=U / I.

[0065] The loop resistance test takes a very short time, typically within 3 to 5 seconds, to prevent the tested loop from overheating due to prolonged high current flow, which could affect the measurement results. The main control unit monitors current stability and temperature changes in real time during the test to ensure the accuracy of the results.

[0066] In this embodiment, referring to Figure 3, the contact status sensor is connected to the auxiliary contacts of the circuit breaker or determines the on / off state of the main contacts through voltage detection. The contact status sensor outputs a switching signal; it outputs a high level (DC24V) when the contacts are closed and a low level (0V) when the contacts are open. The contact status sensor includes three independent sensors for phase A, phase B, and phase C, which monitor the status of the three-phase contacts respectively.

[0067] In this embodiment, referring to Figure 3, the digital input channel uses a high-speed optocoupler (such as 6N137) for opto-isolation, with an isolation voltage of not less than 2500V and a response time of less than 1μs, ensuring the safety of the main control unit under high-voltage conditions without affecting the time measurement accuracy. The digital input channel includes three independent channels: phase A, phase B, and phase C. Each channel includes a current-limiting resistor, an optocoupler, and a signal conditioning circuit. The optocoupler output signal is shaped by a Schmitt trigger and then input to the GPIO port of the main control unit to trigger an interrupt or timer capture function.

[0068] In this embodiment, referring to Figure 3, the high-precision timer is implemented using a hardware timer based on the STM32H743, with a clock frequency of 200MHz and a timing accuracy of 5ns. The high-precision timer operates as follows: the main control unit issues a closing (or opening) command at time T0, and simultaneously starts the high-precision timer. The contacts of phase A, phase B, and phase C are respectively at T... a When state changes occur at times Tᵦ and Tᴄ, the digital input channels capture these state changes and notify the main control unit via interrupts. The main control unit records Tᵦ. a The main control unit calculates the closing time (or opening time) and the time difference based on the recorded timestamps: Closing time (or opening time) = Max(Tᵦ, Tᴄ). a ,Tᵦ,Tᴄ)-T0 different time periods = Max(T a ,Tᵦ,Tᴄ)-Min(T a ,Tᵦ,Tᴄ) where Max(T a Min(Tᵦ,Tᴄ) represents the moment of the latest action in the three phases. a (Tᵦ, Tᴄ) represents the earliest action time among the three phases. The main control unit stores the calculation results and displays them through the human-machine interface, with measurement accuracy reaching the millisecond or even microsecond level.

[0069] In this embodiment, referring to Figure 4, the DC high-voltage generator uses a DC-DC boost converter, with output voltage levels including 500V, 1000V, and 2500V. The DC high-voltage generator has an output current capability of 5mA and an output voltage stability better than 1%. The DC high-voltage generator is connected to the conductor under test (such as the upper end of a circuit breaker contact) via a high-voltage test lead, and its low-voltage side (ground) is connected to the switchgear grounding busbar. The DC high-voltage generator is controlled by a main control unit and can automatically select the output voltage level according to the testing requirements.

[0070] In this embodiment, the sampling resistor network consists of high-resistance precision resistors, typically with a resistance of 1MΩ, an accuracy of 1%, and a power of 2W. The sampling resistor network is connected in series in the output circuit of the DC high-voltage generator. When leakage current flows through the sampling resistor network, a corresponding voltage drop is generated. This voltage drop signal is then passed through a voltage divider circuit and a buffer amplifier before being output to a micro-current amplifier for further processing.

[0071] In this embodiment, since the leakage current in insulation resistance testing is typically in the microampere or even nanoampere range, the microcurrent amplifier employs a low-noise, high-input-impedance operational amplifier (such as the OPA128), with a gain of up to 10,000 times, an input bias current of less than 1 pA, and an input impedance greater than 1 TΩ. The microcurrent amplifier uses a multi-stage amplification design: the first stage is a low-noise preamplifier with a gain of 100 times; the second stage is an adjustable-gain amplifier with a gain adjustable from 10 to 100 times. The output of the microcurrent amplifier is then sent to the analog-to-digital converter after being filtered by a low-pass filter to remove high-frequency noise.

[0072] In this embodiment, the analog-to-digital converter (ADC) employs a 24-bit Σ-Δ ADC with a sampling rate of 10Hz and a resolution reaching the nanoampere level. The ADC is connected to the main control unit via an SPI interface. The main control unit receives the digitized leakage current signal and, combined with the known DC high voltage value U, calculates the insulation resistance value using Ohm's law R=U / I.

[0073] During the insulation resistance test, the main control unit monitors the stability of the leakage current. After the test begins, the main control unit controls the DC high-voltage generator to output the set voltage and continuously monitors the leakage current. Once the leakage current stabilizes (typically 15 to 60 seconds after voltage application), the main control unit performs data acquisition and calculation to improve measurement accuracy. After the test is completed, the main control unit controls the DC high-voltage generator to shut off its output and discharges the tested insulator through its built-in discharge resistor. The discharge time is no less than four times the test time to ensure that any residual charge on the tested insulator is completely discharged, ensuring safety.

[0074] In this embodiment, referring to Figure 4, the power frequency high-voltage generator consists of an autotransformer, a high-voltage transformer, and a control circuit. The autotransformer receives AC 220V mains power and outputs an adjustable voltage from 0 to 220V. The sliding contact of the autotransformer is driven by a stepper motor, which is controlled by the main control unit through a stepper motor driver to achieve precise voltage regulation. The high-voltage transformer boosts the output voltage of the autotransformer to 0 to 50kV, with a turns ratio of 1:227, a frequency of 50Hz, and a rated capacity of 3kVA.

[0075] The output of the power frequency high voltage generator is connected to the insulator under test via a high voltage test lead, and the casing and low voltage end of the high voltage transformer are reliably grounded. The main control unit controls the stepper motor to slowly increase the output voltage to a preset value (e.g., 42kV) at a set rate (e.g., 2kV / s) and maintain it for a period of time (e.g., 1 minute), during which the leakage current is monitored in real time to ensure it is within the allowable range.

[0076] In this embodiment, the leakage current detection circuit uses a current transformer to convert the leakage current signal on the high-voltage side into a voltage signal on the low-voltage side. The current transformer has a turns ratio of 1000:1, enabling it to measure leakage current in the range of 0.1mA to 100mA. A sampling resistor with a resistance of 100Ω is connected to the secondary side of the current transformer to convert the current signal into a voltage signal. This voltage signal is then rectified, filtered, and amplified before being output to an analog-to-digital converter for digital acquisition.

[0077] In this embodiment, the overcurrent protection circuit consists of a hardware comparator and a relay. The hardware comparator compares the voltage signal output by the leakage current detection circuit with a preset threshold voltage (corresponding to a 50mA leakage current). When the detected leakage current exceeds the preset threshold, the comparator outputs a switching signal, triggering the relay to disconnect the input power supply to the autotransformer. Simultaneously, the main control unit short-circuits the output terminal of the high-voltage transformer via a contactor to quickly discharge residual charge. The overcurrent protection response time is less than 10ms, ensuring timely power disconnection in case of insulation breakdown, thus protecting equipment and personnel safety.

[0078] The overcurrent protection circuit also has a resettable function. After troubleshooting, the user can reset the protection circuit through the human-machine interface and restart the test. The main control unit records the time of each overcurrent protection action and the leakage current value, and stores them in the test report for easy fault analysis.

[0079] In this embodiment, the analog-to-digital converter (ADC) uses a 16-bit ADC with a sampling rate of 1kHz, and is connected to the main control unit via an SPI interface. The main control unit acquires the digital signal of leakage current in real time and monitors the trend of leakage current changes. If the leakage current remains stable under the test voltage and does not exceed the value specified in the national standard (such as the leakage current limit specified in GB / T16927.1), the main control unit determines that the insulation performance of the tested insulator is qualified. If the leakage current increases sharply or exceeds the preset threshold, the main control unit determines that the insulation performance of the tested insulator is unqualified or that a breakdown has occurred, and immediately triggers the overcurrent protection circuit to cut off the power supply.

[0080] After the power frequency withstand voltage test is completed, the main control unit controls the autotransformer to slowly reduce the output voltage to zero, and then disconnects the power supply to ensure safe operation. The test results, including the test voltage, holding time, leakage current value, and pass / fail determination, are stored in the main control unit and displayed through the human-machine interface.

[0081] In this embodiment, the power switching control unit employs a hardware interlock mechanism. A high-voltage relay is used to switch the output of the DC high-voltage power supply unit and the power frequency high-voltage power supply unit. The high-voltage relay has a withstand voltage rating of no less than 60kV and a rated contact current of 10A. A contactor is used to switch the low-current mode and high-current mode of the DC constant-current power supply unit. The contactor's rated contact current is 200A. The main control unit controls the operation of the high-voltage relay and contactor through a digital output port (GPIO) and a relay drive circuit. When a test item needs to be performed, the main control unit sends a control signal to close the corresponding high-voltage relay or contactor, establishing an electrical connection between the dedicated test power supply unit and the test module. Simultaneously, the hardware interlock circuit ensures that other high-voltage relays and contactors are in the open state, avoiding mutual interference and short-circuit risks between power supplies of different voltage and current levels. The status of the power switching control unit is monitored in real time by the main control unit. Each high-voltage relay and contactor is equipped with auxiliary contacts that feed back the actual operating status to the main control unit. The main control unit confirms whether the power switching is successful by reading the auxiliary contact status. If an abnormal switching is detected, the test is immediately stopped and an alarm is triggered through the human-machine interface.

[0082] In this embodiment, referring to Figure 1, the test path switching unit includes a relay matrix and a signal switch. The relay matrix consists of multiple relays, with appropriate relay specifications selected according to the voltage and current levels of different test items. High-current relays are used for the DC resistance test path and the loop resistance test path, with a rated contact current of not less than 200A. High-voltage relays are used for the insulation resistance test path and the power frequency withstand voltage test path, with a withstand voltage level of not less than 60kV. The switch action time test path uses a signal relay with a rated contact current of 1A and a response time of less than 10ms.

[0083] The main control unit, based on the currently executed test item, controls the closing of the relays in the corresponding test unit within the test path switching unit via digital output ports and relay drive circuits. This establishes the electrical connection between the test unit and the external test interface, while simultaneously ensuring that the relays of other test units are in the open state. The test path switching unit achieves a one-time wiring function; the user only needs to connect the test leads of the external test interface to the corresponding test points of the 10kV switchgear before the test begins. Subsequent switching of all test items is automatically completed by the device, eliminating the need for rewiring.

[0084] The test path switching unit also has a safety interlock function. When a high voltage output is detected, it automatically disconnects the low voltage test path; when a large current output is detected, it automatically disconnects the small current and signal test paths to avoid equipment damage or personal injury caused by misoperation.

[0085] In this embodiment, the loop resistance test unit and the DC resistance test unit share the same hardware platform and adopt the same four-wire method measurement principle and signal processing circuit architecture. The main difference is that they use a high-current level test power supply and corresponding high-current processing components.

[0086] The DC high-voltage generator is connected to the conductor under test (such as the upper end of a circuit breaker contact) via high-voltage shielded test leads. The test leads use a coaxial shielded structure, and the shielding layer is grounded to reduce the influence of external interference and leakage current. The low-voltage end (ground) is connected to the switchgear grounding busbar.

[0087] The high-voltage test cable uses high-voltage shielded wire with a withstand voltage rating of not less than 100kV. It is equipped with an insulating sheath and a grounding shield to reduce leakage current and electromagnetic interference. The test cable is 10 meters long and equipped with high-voltage insulating connectors at both ends, featuring an anti-corona design.

[0088] Example 2, an embodiment of the present invention, provides a comprehensive preventive testing method for 10kV switchgear based on the previous embodiment, comprising: connecting a test module to the test point of the 10kV switchgear under test through an external test interface; receiving test instructions through a human-machine interface; the main control unit determining the test items to be executed according to the test instructions; the main control unit controlling the power module to switch to the dedicated test power unit corresponding to the first test item, and starting the corresponding test unit to execute the first test item and collect test data; the main control unit determining whether all test items have been completed; if not, controlling the power module to switch to the dedicated test power unit corresponding to the next test item, and starting the corresponding test unit to execute the next test item and collect test data, repeating this step; if yes, executing the next step; the main control unit processing the collected test data, generating a test report, and displaying the test results through the human-machine interface and uploading the test data through the communication interface.

[0089] Specifically, step S1 involves system initialization and self-test. After the device is powered on, the main control unit performs system initialization, detecting the operating status of each module, including the output voltage of the power module, the sensor status of the test module, the communication status of the human-machine interface, and the network connection status of the communication interface. After the self-test is completed, the human-machine interface displays that the system is ready.

[0090] Step S2, Mode Selection. The user selects the test mode through the human-computer interaction interface, including automatic mode or manual mode. In automatic mode, the device will execute all five tests sequentially; in manual mode, the user can select a single test.

[0091] Step S3, Wiring Confirmation. The user connects the test leads of the external test interface to the corresponding test points on the 10kV switchgear according to the on-screen prompts. The main control unit uses a detection circuit to determine if the wiring is correct. If an error or missing connection is detected, the interface prompts the user to troubleshoot. After confirming the wiring is correct, proceed to the next step.

[0092] Step S4, Parameter Setting. Users set test parameters through the human-machine interface or by calling preset parameter templates. Test parameters include the current value for DC resistance testing, the current value and test time for loop resistance testing, the voltage level for insulation resistance testing, and the test voltage and holding time for power frequency withstand voltage testing, etc.

[0093] Step S5: The user inputs the start command. The user clicks the "Start Test" button on the interface, and the main control unit receives the test command and starts the test process.

[0094] Step S6: Switch test items and power supply. The main control unit determines the test items to be executed according to the test procedure, and switches the power switching control unit of the power module to the corresponding dedicated test power unit through signal connection. At the same time, it controls the test path switching unit to connect the corresponding test unit to the external test interface.

[0095] Step S7: Run the corresponding test module. The main control unit starts the corresponding test unit to execute the test. During the test, the main control unit monitors the test status and safety parameters in real time.

[0096] Step S8, Real-time Safety Monitoring. The main control unit monitors parameters such as voltage, current, and temperature in real time during the test process through the sensors and protection circuits of each test unit. If an abnormality is detected (such as overcurrent, overvoltage, or insulation breakdown), the main control unit immediately stops the test, cuts off the power output, records the abnormal information, and displays the alarm information through the human-machine interface.

[0097] Step S9: Collect and record data. During normal testing, the main control unit collects test data via an analog-to-digital converter, performs digital filtering, temperature compensation, and calculations to obtain the test results. The main control unit stores the test data in its internal memory.

[0098] Step S10: Display the results on the interface. The main control unit displays the test results in real time through the human-machine interface, including measured values, pass / fail criteria, and comparison with historical data.

[0099] Step S11: Determine if all items are completed. The main control unit determines if all test items are completed. If not, return to step S6, switch to the next test item and continue execution; if all test items are completed, proceed to the next step.

[0100] Step S12, test ends. The main control unit shuts down all test power outputs, disconnects the test path switching unit, and the device returns to standby mode.

[0101] Step S13: Generate a report. The main control unit summarizes and analyzes all test data to generate a standardized test report. The test report includes equipment information, test information, test results, and conclusions / recommendations.

[0102] Step S14: Upload data. The main control unit uploads the test data and test report to the external management system via the communication interface.

[0103] This embodiment also provides an electronic device applicable to a comprehensive preventive test method for 10kV switchgear, comprising: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to realize the comprehensive preventive test method for 10kV switchgear as proposed in the above embodiment.

[0104] This embodiment also provides a storage medium storing a computer program, which, when executed by a processor, implements a comprehensive test method for preventive testing of a 10kV switchgear as proposed in the above embodiment.

[0105] The storage medium proposed in this embodiment belongs to the same inventive concept as the comprehensive test method for preventive testing of 10kV switchgear proposed in the above embodiment. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0106] Based on the above description of the implementation methods, those skilled in the art can clearly understand that the present invention can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0107] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A comprehensive test device for preventive testing of 10kV switchgear, characterized in that: Includes a main control unit, used to execute test process control and power switching control, and to receive and process test data; The power supply module, electrically and signal-connected to the main control unit, includes an auxiliary power supply unit and multiple dedicated test power supply units. The auxiliary power supply unit provides operating power to the main control unit, and the dedicated test power supply units, controlled by the main control unit, provide corresponding test power to the test modules. The main control unit controls the power supply module to automatically switch between different dedicated test power supply units according to the currently executed test item via signal connection. The test module, signal-connected to the main control unit and electrically connected to the power supply module, is used to perform multiple preventative tests on the 10kV switchgear. The test module includes a DC resistance test unit, a loop resistance test unit, a switch action time test unit, an insulation resistance test unit, and a power frequency withstand voltage test unit. Under the control of the main control unit, the test module sequentially performs tests and transmits test data to the main control unit. The human-machine interface, communicatively connected to the main control unit, is used to receive user-input test commands and test parameters and display test results. The communication interface is connected to the main control unit and is used to upload test data to an external management system; the external test interface is electrically connected to the test module and is used to connect the test module to the test point of the 10kV switchgear.

2. The comprehensive test device for preventive testing of 10kV switchgear as described in claim 1, characterized in that: The dedicated test power supply unit includes: a DC constant current power supply unit for providing an adjustable DC constant current power supply to the DC resistance test unit and the loop resistance test unit; a DC high voltage power supply unit for providing a DC high voltage power supply to the insulation resistance test unit; and a power frequency high voltage power supply unit for providing a continuously adjustable power frequency AC high voltage power supply to the power frequency withstand voltage test unit.

3. The comprehensive test device for preventive testing of 10kV switchgear as described in claim 2, characterized in that: The DC resistance testing unit includes: a precision constant current source for outputting a constant test current; a first current line and a second current line for applying the constant test current to both ends of the resistor under test; a first voltage sampling line and a second voltage sampling line connected to both ends of the resistor under test for acquiring voltage signals across the resistor under test; a high-precision differential amplifier connected to the first voltage sampling line and the second voltage sampling line for amplifying the voltage signals; and a high-precision analog-to-digital converter connected to the high-precision differential amplifier for converting the amplified voltage signals into digital voltage values ​​and transmitting them to the main control unit.

4. The comprehensive test device for preventive testing of 10kV switchgear as described in claim 3, characterized in that: The loop resistance testing unit includes: a high-current constant current source for outputting a constant test current of a high current level; a high-current contactor connected to the high-current constant current source for controlling the on / off state of the constant test current of a high current level; a first current line and a second current line for applying the constant test current of a high current level to both ends of the loop resistance under test; a high-precision shunt connected in series with the second current line for converting the constant test current of a high current level into a voltage signal for sampling; a first voltage sampling line and a second voltage sampling line connected to both ends of the loop resistance under test for acquiring the voltage signal across the loop resistance under test; a differential amplifier connected to the first voltage sampling line and the second voltage sampling line for amplifying the voltage signal; and an analog-to-digital converter connected to the differential amplifier and the high-precision shunt for converting the amplified voltage signal and the voltage signal generated by the high-precision shunt into a digital signal and transmitting it to the main control unit.

5. The comprehensive test device for preventive testing of 10kV switchgear as described in claim 4, characterized in that: The switch action time testing unit includes: a contact status sensor for detecting the status changes of each phase contact of the circuit breaker; a switch input channel connected to the contact status sensor and having photoelectric isolation function for transmitting the contact status signal to the main control unit; and a high-precision timer located in the main control unit for starting the timer when the main control unit issues a closing or opening command, recording the time of each phase contact status change, and calculating the closing time, opening time, and asynchrony time based on the recorded time.

6. The comprehensive test device for preventive testing of 10kV switchgear as described in claim 5, characterized in that: The insulation resistance testing unit includes: a DC high-voltage generator for generating and outputting a DC high voltage to the insulator under test; a sampling resistor network connected in series with the DC high-voltage generator for collecting leakage current flowing through the insulator under test; a micro-current amplifier connected to the sampling resistor network for amplifying the leakage current signal; and an analog-to-digital converter connected to the micro-current amplifier for converting the amplified leakage current signal into a digital signal and transmitting it to the main control unit. The main control unit calculates the insulation resistance value based on the DC high voltage and the leakage current.

7. The comprehensive test device for preventive testing of 10kV switchgear as described in claim 6, characterized in that: The power frequency withstand voltage test unit includes: a power frequency high voltage generator for generating and outputting a continuously adjustable power frequency AC high voltage to the insulator under test; a leakage current detection circuit for real-time monitoring of the leakage current flowing through the insulator under test; an overcurrent protection circuit connected to the leakage current detection circuit for cutting off the output of the power frequency high voltage generator when the leakage current exceeds a preset threshold; and an analog-to-digital converter connected to the leakage current detection circuit for converting the leakage current signal into a digital signal and transmitting it to the main control unit.

8. The comprehensive test device for preventive testing of 10kV switchgear as described in claim 7, characterized in that: The power module further includes a power switching control unit, which is signal-connected to the main control unit and includes multiple high-voltage relays and contactors. The high-voltage relays and contactors are respectively connected to the output terminals of the dedicated test power unit, and are used to selectively connect the output of the dedicated test power unit to the test module under the control of the main control unit, so as to ensure that only the output of one dedicated test power unit is connected to the test module at any given time.

9. The comprehensive test device for preventive testing of 10kV switchgear as described in claim 8, characterized in that: A test path switching unit is provided between the test module and the external test interface. The test path switching unit is signal-connected to the main control unit and is used to selectively connect the corresponding units of the DC resistance test unit, the loop resistance test unit, the switch action time test unit, the insulation resistance test unit, and the power frequency withstand voltage test unit to the external test interface under the control of the main control unit.

10. A comprehensive test method for preventive testing of 10kV switchgear, using a comprehensive test device for preventive testing of 10kV switchgear as described in any one of claims 1 to 9, characterized in that, include: The test module is connected to the test point of the 10kV switchgear under test via an external test interface; test commands are received through the human-machine interface, and the main control unit determines the test items to be executed according to the test commands; the main control unit controls the power module to switch to the dedicated test power unit corresponding to the first test item, and starts the corresponding test unit to execute the first test item and collect test data; the main control unit determines whether all test items have been completed. If not, it controls the power module to switch to the dedicated test power unit corresponding to the next test item, and starts the corresponding test unit to execute the next test item and collect test data. This step is repeated. If yes, the next step is executed. The main control unit processes the collected test data, generates test reports, displays the test results through a human-machine interface, and uploads test data through a communication interface.

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