A device and method for testing response time of direct current grounding protection with adjustable resistance and controllable time length

Abstract

The application discloses a DC grounding protection response time testing device and method with controllable resistance and adjustable time length, and relates to the technical field of power systems.The technical scheme is as follows: a controllable high-resistance grounding testing unit is arranged in series between a DC load side and a grounding bus, and is used for establishing a single controllable single-point grounding loop;the controllable high-resistance grounding testing unit comprises an adjustable high-resistance grounding resistor, a high-speed electronic switch, a millisecond-level time sequence control module and a switching value acquisition module;the millisecond-level time sequence control module and the switching value acquisition module share the same time reference, so that double-time stamp synchronous acquisition of a fault starting time stamp and an alarm time stamp is realized, and the response time is automatically calculated.The application realizes millisecond-level accurate control of a grounding fault time length and automatic high-precision measurement of the response time, has small testing error, and can cover multiple working condition simulation.

Description

Technical Field

[0001] This invention relates to the field of power system technology, and more specifically, to a test device and method for DC grounding protection response time with controllable duration and adjustable resistance. Background Technology

[0002] DC power supply systems are the core operating power sources for relay protection devices, automatic control devices, and circuit breaker operating mechanisms in substations and power plants. Their operational reliability directly affects the safety and stability of the power system. When a single-point ground fault occurs in a DC system, although it may not immediately cause protection malfunctions, if it is not detected and addressed in time, a second ground fault could trigger relay malfunctions or protection failures, leading to major accidents such as cascading trips. Therefore, DC systems are generally equipped with insulation monitoring devices to monitor the system's insulation to ground in real time and issue alarm signals when the insulation drops to a set threshold. The response time of the insulation monitoring device is one of its most critical performance indicators, directly determining the speed of fault detection and the timeliness of the system's response.

[0003] Currently, various calibration devices for DC system insulation monitoring devices exist both domestically and internationally. These devices are primarily used to verify the accuracy of grounding resistance detection, the correctness of grounding line selection, and the ability to identify AC cross-current. These calibration devices typically use fixed resistors or relay arrays to simulate grounding faults with different resistance values. The displayed values ​​of the insulation monitoring device are manually read and compared to determine if the measurement accuracy meets the standards. However, existing calibration devices generally suffer from the following shortcomings: First, fault simulation methods often involve manual instantaneous grounding or long-term fixed grounding, failing to achieve millisecond-level precise controllable switching and making it difficult to simulate the instantaneous and intermittent grounding faults that may occur in actual DC systems. Second, response time testing relies on manual stopwatch timing, resulting in low accuracy, large errors, and the inability to achieve automated closed-loop testing. The test results lack traceability and standardized basis. Third, existing equipment lacks a hardware interface for automatically acquiring alarm signals from insulation monitoring devices, failing to automatically capture the alarm level transition time and correlate it with the fault injection time, leading to low efficiency and poor repeatability in response time testing.

[0004] Therefore, researching and designing a DC grounding protection response time testing device and method that can overcome the above-mentioned defects with controllable duration and adjustable resistance is an urgent problem to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a DC grounding protection response time testing device and method with controllable duration and adjustable resistance. It achieves precise control over the grounding fault duration at the millisecond level through a unique controllable single-point grounding loop, and realizes automatic high-precision measurement of response time through synchronous acquisition of dual timestamps. At the same time, it enables flexible simulation of multiple insulation leakage conditions through adjustable high-resistance grounding resistance.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: In a first aspect, a DC grounding protection response time testing device with controllable duration and adjustable resistance is provided for series connection to a DC system including a DC bus, a monitored insulation under test, a DC load, and a grounding busbar, comprising: A controllable high-resistance grounding test unit is connected in series between the DC load side and the grounding busbar to establish a unique and controllable single-point grounding loop between the DC load side and the ground. The controllable high-resistance grounding test unit includes: Adjustable high-resistance grounding resistor, whose resistance value is continuously adjustable, is used to simulate grounding faults with different degrees of insulation leakage; A high-speed electronic switch, connected in series with the adjustable high-resistance grounding resistor, forms a pure resistance grounding circuit, and the operating delay of the high-speed electronic switch is lower than a preset threshold. A millisecond-level timing control module with a built-in high-precision clock source is used to output a programmable trigger signal to control the conduction duration of the high-speed electronic switch, which can be arbitrarily set within the millisecond range. The switch quantity acquisition module is electrically connected to the switch quantity alarm output terminal of the insulation monitoring device under test, and is used to monitor the alarm level flip and capture the alarm timestamp in real time. The millisecond-level timing control module and the switch quantity acquisition module share the same time base to achieve synchronous acquisition of the fault start time stamp and alarm time stamp, and automatically calculate the response time.

[0007] Furthermore, the adjustable high-resistance grounding resistor has a resistance adjustment range of 10kΩ to 100kΩ; The operating delay of the high-speed electronic switch does not exceed 0.5ms; The time resolution of the millisecond-level timing control module is no greater than 0.1ms; Furthermore, the setting range for the conduction duration is from 1ms to 2000ms.

[0008] Furthermore, the high-speed electronic switch is a metal-oxide-semiconductor field-effect transistor, whose parasitic capacitance is less than a preset threshold, so that the parasitic effect of the pure resistive grounding loop can be ignored during the millisecond-level switching process, and it can be regarded as an ideal pure resistive characteristic.

[0009] Furthermore, the adjustable high-impedance grounding resistor is composed of multiple precision resistors combined by a relay array; The relay array is controlled by the millisecond-level timing control module to achieve step-by-step or continuous adjustment of the resistance value.

[0010] Furthermore, the millisecond-level timing control module is also used to latch the fault start timestamp at the instant the high-speed electronic switch is triggered to turn on; The digital input module is used to latch the alarm timestamp when it detects an alarm level flip of the insulation monitoring device under test. The millisecond-level timing control module or host computer calculates the response time by subtracting the fault start timestamp from the alarm timestamp.

[0011] Furthermore, the switch quantity acquisition module includes an opto-isolation circuit, which is used to convert the passive dry contact signal of the insulation monitoring device under test into a level signal and filter out jitter interference.

[0012] Furthermore, it also includes a human-computer interaction module; The human-computer interaction module is communicatively connected to the millisecond-level timing control module, and is used to receive the grounding resistance value, grounding duration and number of tests set by the user, and display the test results.

[0013] Furthermore, the DC load side is the negative terminal of the DC bus; One end of the controllable high-resistance grounding test unit is connected to the negative terminal of the DC bus, and the other end is connected to the grounding bus.

[0014] Secondly, a method for testing the response time of DC grounding protection with controllable duration and adjustable resistance is provided. This method is applied to the DC grounding protection response time testing device with controllable duration and adjustable resistance described in any one of the first aspects, and includes the following steps: S1: The test device performs a power-on initialization self-test to confirm that there is no original grounding fault in the DC system; S2: Set the target grounding resistance value and grounding duration; S3: The millisecond-level timing control module outputs a trigger signal to turn on the high-speed electronic switch. The adjustable high-impedance grounding resistor is connected between the DC load side and the grounding busbar to form a unique single-point grounding fault. At the same time, the millisecond-level timing control module latches the fault start timestamp. S4: The switch quantity acquisition module monitors the alarm output terminal of the insulation monitoring device under test in real time, and latches the alarm timestamp when it detects an alarm level flip. S5: The response time is automatically calculated based on the difference between the alarm timestamp and the fault start timestamp, and the millisecond-level timing control module controls the high-speed electronic switch to turn off after the preset grounding duration is reached, thereby eliminating the grounding fault; S6: Repeat steps S2 to S5, iterating through different combinations of resistance values ​​and durations to complete the multi-condition test.

[0015] Furthermore, the power-on initialization self-test of the test device includes: The presence of an original grounding fault is determined by measuring whether the sum of the positive and negative voltages of the DC bus to ground is equal to the rated voltage of the bus. When automatically calculating the response time, the inherent action delay of the high-speed electronic switch is deducted, and the inherent action delay is pre-stored in the millisecond-level timing control module.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention provides a DC grounding protection response time testing device with controllable duration and adjustable resistance. By connecting a controllable high-resistance grounding test unit in series between the DC load side and the grounding busbar, a unique and controllable single-point grounding loop is established between the DC load side and the earth. In this loop, the adjustable high-resistance grounding resistor is continuously adjustable, simulating grounding faults with different degrees of insulation leakage. A high-speed electronic switch and the adjustable high-resistance grounding resistor are connected in series to form a pure resistance grounding loop, whose action delay is lower than a preset threshold, ensuring rapid switching of the grounding loop. The millisecond-level timing control module has a built-in high-precision clock source, outputting a programmable trigger signal to control the conduction duration of the high-speed electronic switch, allowing the conduction duration to be arbitrarily set within a millisecond range. The switch quantity acquisition module is electrically connected to the switch quantity alarm output terminal of the insulation monitoring device under test, monitoring the alarm level flip-off in real time and capturing the alarm timestamp. Specifically, the millisecond-level timing control module and the switch quantity acquisition module share the same time base, realizing synchronous acquisition of both the fault start timestamp and the alarm timestamp, and automatic calculation of the response time. This invention overcomes the shortcomings of traditional testing, which relies on manual stopwatch timing, has uncontrollable fault switching duration, and cannot simulate millisecond-level instantaneous grounding faults. It achieves precise control over the duration of grounding faults at the millisecond level and automated high-precision measurement of response time, with a test error not exceeding ±0.1ms.

[0017] 2. The adjustable high-resistance grounding resistor in this invention can simulate various insulation fault scenarios ranging from weak to moderate leakage. The millisecond to second-level duration settings cover all types of transient, intermittent, and steady-state continuous grounding faults. The high-speed electronic switch uses a metal-oxide-semiconductor field-effect transistor, whose parasitic capacitance is less than a preset threshold. This allows the parasitic effects of the pure resistive grounding loop to be ignored during millisecond-level switching, treating it as an ideal pure resistive characteristic and avoiding interference from switch parasitic parameters on test accuracy. The adjustable high-resistance grounding resistor is composed of multiple precision resistors combined through a relay array. The relay array is controlled by a millisecond-level timing control module to achieve step-by-step or continuous adjustment of the resistance value, ensuring the accuracy and repeatability of the resistance setting. This invention ensures that the testing device maintains high-precision and high-repeatability testing performance across the entire operating range.

[0018] 3. This invention utilizes a millisecond-level timing control module to latch the fault start timestamp the instant the high-speed electronic switch is turned on. The switch quantity acquisition module latches the alarm timestamp when it detects an alarm level reversal in the insulation monitoring device under test. The millisecond-level timing control module or the host computer calculates the response time by subtracting the fault start timestamp from the alarm timestamp, achieving fully automatic response time calculation and eliminating subjective errors from manual stopwatch timing. The switch quantity acquisition module includes an opto-isolation circuit to convert the passive dry contact signal of the insulation monitoring device under test into a level signal and filter out jitter interference, ensuring accurate capture of the alarm timestamp and avoiding false triggering caused by contact jitter. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the topological structure of the overall device in Embodiment 1 of the present invention; Figure 2 This is a circuit diagram of the controllable high-resistance grounding test unit in Embodiment 1 of the present invention; Figure 3 This is a timing diagram of millisecond-level timing switching and signal acquisition in Embodiment 1 of the present invention; Figure 4 This is a test flowchart in Embodiment 2 of the present invention. Detailed Implementation

[0020] 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 embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0021] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly or indirectly attached to that other component. When a component is referred to as being "connected to" another component, it can be directly or indirectly connected to that other component.

[0022] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0024] Example 1: A DC grounding protection response time testing device with controllable duration and adjustable resistance, such as... Figure 1 As shown, this is used for series connection to a DC system including a DC bus, the insulation monitoring device under test, the DC load, and the grounding bus. The test setup includes a controllable high-resistance grounding test unit. (See diagram.) Figure 2 As shown, this controllable high-resistance grounding test unit is connected in series between the DC load side and the grounding busbar to establish a unique and controllable single-point grounding loop between the DC load side and the earth. The DC load side refers to the end point of the branch where the DC load is located, usually the negative terminal of the DC bus. The grounding busbar is a common grounding reference point used to collect the grounding wires of various devices in the DC system and is directly connected to the earth.

[0025] The controllable high-resistance grounding test unit includes an adjustable high-resistance grounding resistor, a high-speed electronic switch, a millisecond-level timing control module, and a switch quantity acquisition module.

[0026] The adjustable high-resistance grounding resistor has a continuously adjustable resistance value and is used to simulate grounding faults with varying degrees of insulation leakage. This resistor is composed of multiple precision resistors connected in a relay array. The relay array is controlled by a millisecond-level timing control module. By controlling the on / off state of different relays, the resistors can be connected in series or parallel, thus achieving step-by-step or continuous adjustment of the resistance value. The adjustable high-resistance grounding resistor has an adjustable value range of 10kΩ to 100kΩ, covering typical grounding fault scenarios from weak to moderate leakage.

[0027] A high-speed electronic switch is connected in series with an adjustable high-resistance grounding resistor to form a purely resistive grounding loop. The high-speed electronic switch uses a metal-oxide-semiconductor field-effect transistor, whose parasitic capacitance is less than a preset threshold. This allows the parasitic effects of the purely resistive grounding loop to be negligible during millisecond-level switching processes, thus exhibiting ideal purely resistive characteristics. The operating delay of the high-speed electronic switch does not exceed 0.5ms, ensuring that the grounding loop can respond quickly to control commands when turning on and off.

[0028] like Figure 3As shown, the millisecond-level timing control module incorporates a high-precision clock source to output a programmable trigger signal to control the conduction duration of the high-speed electronic switch. This conduction duration can be arbitrarily set within a millisecond range, from 1ms to 2000ms. The time resolution of the millisecond-level timing control module is no greater than 0.1ms, enabling precise control of the duration of ground faults, thereby simulating transient, intermittent, or steady-state continuous ground faults. This module also latches the fault start timestamp at the instant the high-speed electronic switch is triggered to conduct, denoted as... .

[0029] The digital input module is electrically connected to the digital alarm output terminal of the insulation monitoring device under test. It is used to monitor alarm level transitions in real time and capture alarm timestamps. The digital input module includes an opto-isolation circuit to convert the passive dry contact signal of the insulation monitoring device under test into a voltage level signal and filter out jitter interference. When an alarm level transition is detected, the digital input module latches the alarm timestamp and records it as... .

[0030] The millisecond-level timing control module and the switch quantity acquisition module share the same time base to achieve synchronous acquisition of both the fault start timestamp and the alarm timestamp. The millisecond-level timing control module or the host computer calculates the response time by subtracting the fault start timestamp from the alarm timestamp. Because the two timestamps are based on the same time base, the accuracy of the calculation results is guaranteed.

[0031] The testing device also includes a human-machine interface (HMI) module. This HMI module communicates with the millisecond-level timing control module, receiving user-defined grounding resistance values, grounding duration, and test counts, and displaying the test results. The HMI module can be implemented using a touchscreen, allowing users to set parameters and start / stop tests via the touchscreen.

[0032] The DC load side is specifically the negative terminal of the DC bus. One end of the controllable high-resistance grounding test unit is connected to the negative terminal of the DC bus, and the other end is connected to the grounding busbar. Thus, when the high-speed electronic switch is turned on, the negative terminal of the DC bus forms a unique grounding loop with the earth through the adjustable high-resistance grounding resistor, simulating a positive or negative grounding fault on the DC load side. It should be noted that this embodiment uses negative grounding as an example, but positive grounding is equally applicable; simply connect the test unit to the positive terminal of the DC bus.

[0033] Example 2: A method for testing the response time of DC grounding protection with controllable duration and adjustable resistance. This method is applied to the DC grounding protection response time testing device with controllable duration and adjustable resistance described in Example 1. The testing device includes a controllable high-resistance grounding test unit, which is connected in series between the DC load side and the grounding busbar. It contains an adjustable high-resistance grounding resistor, a high-speed electronic switch, a millisecond-level timing control module, and a switch quantity acquisition module. Figure 4 As shown, the specific steps include:

[0034] Step S1: The testing device powers on and initializes a self-test to confirm that there is no original grounding fault in the DC system. The self-test measures the voltage between the positive and negative terminals of the DC bus to ground and calculates their sum. If the sum equals the rated voltage of the bus, the DC system is determined to have no original grounding fault, and the test can continue; otherwise, an alarm is issued and the test is terminated to avoid misjudgment or equipment damage caused by testing on top of an existing grounding fault. This self-test logic utilizes the basic principle of symmetrical positive and negative voltages to ground during normal operation of the DC system.

[0035] Step S2: Set the target grounding resistance value and grounding duration. The user inputs the desired grounding resistance value through the human-machine interface module. This value can be arbitrarily selected within the range of 10kΩ to 100kΩ to simulate insulation leakage faults of varying degrees. Simultaneously, the grounding duration is set, which can be arbitrarily set within the range of 1ms to 2000ms to simulate transient, intermittent, or steady-state continuous grounding faults. After setting, the millisecond-level timing control module receives and stores these parameters.

[0036] In step S3, the millisecond-level timing control module outputs a trigger signal to turn on the high-speed electronic switch. An adjustable high-resistance grounding resistor is connected between the DC load side and the grounding busbar, forming a unique single-point grounding fault. At this time, the DC load side forms a loop with the ground through the adjustable high-resistance grounding resistor, simulating a real DC grounding fault. Simultaneously, the millisecond-level timing control module latches the fault start timestamp at the instant the trigger signal is issued, denoted as […]. The timestamp is based on a high-precision clock source built into the module, with a time resolution of no more than 0.1ms, ensuring accurate recording of the start time.

[0037] Step S4: The switch quantity acquisition module monitors the switch quantity alarm output terminal of the insulation monitoring device under test in real time. When the insulation monitoring device under test detects a ground fault and issues an alarm signal, the level of its alarm output terminal flips, for example, from high level to low level or from open to closed. The switch quantity acquisition module captures this level flip event through the opto-isolation circuit and immediately latches the alarm timestamp, recording it as... The opto-isolation circuit effectively filters out interference caused by contact jitter, ensuring the accuracy of the timestamp.

[0038] Step S5: Automatically calculate the response time based on the difference between the alarm timestamp and the fault start timestamp. This calculation can be performed internally by the millisecond-level timing control module, or it can be performed by the host computer after receiving two timestamps. During the calculation, the inherent action delay of the high-speed electronic switch needs to be deducted; this delay is pre-stored in the millisecond-level timing control module. For example, if the action delay of the high-speed electronic switch is 0.5ms, the actual response time will be corrected to... ,in The inherent action delay of the switch is included. After the preset grounding duration is reached, the millisecond-level timing control module automatically outputs a shutdown signal to control the high-speed electronic switch to open, eliminate the grounding fault, and restore the system to normal operation.

[0039] Step S6: Repeat steps S2 to S5, iterating through different combinations of resistance values ​​and durations to complete the multi-condition test. By changing the resistance value of the adjustable high-resistance grounding resistor and the conduction duration of the high-speed electronic switch, the response performance of the insulation monitoring device under test under different fault conditions can be comprehensively evaluated. For example, three resistance values ​​of 10kΩ, 50kΩ, and 100kΩ can be set respectively, and five durations of 1ms, 10ms, 100ms, 1000ms, and 2000ms can be set for each resistance value, for a total of fifteen operating conditions. All tests are automatically completed and the response time of each group is recorded to form a complete performance curve.

[0040] This embodiment achieves precise, millisecond-level control over the duration of ground faults through the coordinated operation of a millisecond-level timing control module and a high-speed electronic switch. By using dual-timestamp synchronous acquisition and automatic calculation, errors caused by manual stopwatch timing are completely eliminated. Adjustable high-resistance grounding resistance enables flexible simulation of multiple resistance conditions. The entire method is highly automated, with a testing accuracy of ±0.1ms, making it suitable for rapid on-site verification of insulation monitoring devices in DC systems such as substations and power plants.

[0041] Working Principle: This invention establishes a unique, controllable single-point grounding loop between the DC load side and the grounding busbar by connecting a controllable high-resistance grounding test unit in series between the DC load side and the ground. In this loop, the adjustable high-resistance grounding resistor is continuously adjustable, simulating grounding faults with varying degrees of insulation leakage. A high-speed electronic switch connected in series with the adjustable high-resistance grounding resistor forms a purely resistive grounding loop with an action delay lower than a preset threshold, ensuring rapid switching of the grounding loop. The millisecond-level timing control module has a built-in high-precision clock source, outputting a programmable trigger signal to control the conduction duration of the high-speed electronic switch, allowing the conduction duration to be arbitrarily set within a millisecond range. The switch quantity acquisition module is electrically connected to the switch quantity alarm output terminal of the insulation monitoring device under test, monitoring alarm level flips in real time and capturing alarm timestamps. Specifically, the millisecond-level timing control module and the switch quantity acquisition module share the same time base, achieving synchronous acquisition of both the fault start timestamp and the alarm timestamp, and automatically calculating the response time. This invention overcomes the shortcomings of traditional testing, which relies on manual stopwatch timing, has uncontrollable fault switching duration, and cannot simulate millisecond-level instantaneous grounding faults. It achieves precise control over the duration of grounding faults at the millisecond level and automated high-precision measurement of response time, with a test error not exceeding ±0.1ms.

[0042] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A DC grounding protection response time testing device with controllable duration and adjustable resistance, characterized in that, For series connection of a DC system including a DC bus, an insulation monitoring device under test, a DC load, and a grounding bus, including: A controllable high-resistance grounding test unit is connected in series between the DC load side and the grounding busbar to establish a unique and controllable single-point grounding loop between the DC load side and the ground. The controllable high-resistance grounding test unit includes: Adjustable high-resistance grounding resistor, whose resistance value is continuously adjustable, is used to simulate grounding faults with different degrees of insulation leakage; A high-speed electronic switch, connected in series with the adjustable high-resistance grounding resistor, forms a pure resistance grounding circuit, and the operating delay of the high-speed electronic switch is lower than a preset threshold. A millisecond-level timing control module with a built-in high-precision clock source is used to output a programmable trigger signal to control the conduction duration of the high-speed electronic switch, which can be arbitrarily set within the millisecond range. The switch quantity acquisition module is electrically connected to the switch quantity alarm output terminal of the insulation monitoring device under test, and is used to monitor the alarm level flip and capture the alarm timestamp in real time. The millisecond-level timing control module and the switch quantity acquisition module share the same time base to achieve synchronous acquisition of the fault start time stamp and alarm time stamp, and automatically calculate the response time.

2. The DC grounding protection response time testing device with controllable duration and adjustable resistance according to claim 1, characterized in that, The adjustable high-resistance grounding resistor has a resistance range of 10kΩ to 100kΩ; The operating delay of the high-speed electronic switch does not exceed 0.5ms; The time resolution of the millisecond-level timing control module is no greater than 0.1ms; Furthermore, the setting range for the conduction duration is from 1ms to 2000ms.

3. The DC grounding protection response time testing device with controllable duration and adjustable resistance according to claim 1, characterized in that, The high-speed electronic switch is a metal-oxide-semiconductor field-effect transistor, whose parasitic capacitance is less than a preset threshold, so that the parasitic effect of the pure resistive grounding loop can be ignored during the millisecond-level switching process, and it can be regarded as an ideal pure resistive characteristic.

4. The DC grounding protection response time testing device with controllable duration and adjustable resistance according to claim 1, characterized in that, The adjustable high-impedance grounding resistor is composed of multiple precision resistors combined by a relay array; The relay array is controlled by the millisecond-level timing control module to achieve step-by-step or continuous adjustment of the resistance value.

5. The DC grounding protection response time testing device with controllable duration and adjustable resistance according to claim 1, characterized in that, The millisecond-level timing control module is also used to latch the fault start timestamp at the moment the high-speed electronic switch is triggered to turn on; The digital acquisition module is used to latch the alarm timestamp when it detects an alarm level flip of the insulation monitoring device under test. The millisecond-level timing control module or the host computer calculates the response time by subtracting the fault start timestamp from the alarm timestamp.

6. The DC grounding protection response time testing device with controllable duration and adjustable resistance according to claim 1, characterized in that, The switch quantity acquisition module includes an opto-isolation circuit, which is used to convert the passive dry contact signal of the insulation monitoring device under test into a level signal and filter out jitter interference.

7. The DC grounding protection response time testing device with controllable duration and adjustable resistance according to claim 1, characterized in that, It also includes a human-computer interaction module; The human-computer interaction module is communicatively connected to the millisecond-level timing control module, and is used to receive the grounding resistance value, grounding duration and number of tests set by the user, and display the test results.

8. The DC grounding protection response time testing device with controllable duration and adjustable resistance according to claim 1, characterized in that, The DC load side is the negative terminal of the DC bus; One end of the controllable high-resistance grounding test unit is connected to the negative terminal of the DC bus, and the other end is connected to the grounding bus.

9. A method for testing the response time of DC grounding protection with controllable duration and adjustable resistance, characterized in that, This method, applied to a DC grounding protection response time testing device with controllable duration and adjustable resistance as described in any one of claims 1-8, includes the following steps: S1: The test device performs a power-on initialization self-test to confirm that there is no original grounding fault in the DC system; S2: Set the target grounding resistance value and grounding duration; S3: The millisecond-level timing control module outputs a trigger signal to turn on the high-speed electronic switch. The adjustable high-impedance grounding resistor is connected between the DC load side and the grounding busbar to form a unique single-point grounding fault. At the same time, the millisecond-level timing control module latches the fault start timestamp. S4: The switch quantity acquisition module monitors the alarm output terminal of the insulation monitoring device under test in real time, and latches the alarm timestamp when it detects an alarm level flip. S5: The response time is automatically calculated based on the difference between the alarm timestamp and the fault start timestamp, and the millisecond-level timing control module controls the high-speed electronic switch to turn off after the preset grounding duration is reached, thereby eliminating the grounding fault; S6: Repeat steps S2 to S5, iterating through different combinations of resistance values ​​and durations to complete the multi-condition test.

10. The method for testing the response time of DC grounding protection with controllable duration and adjustable resistance according to claim 9, characterized in that, The test device performs a power-on initialization self-test, including: The presence of an original grounding fault is determined by measuring whether the sum of the positive and negative voltages of the DC bus to ground is equal to the rated voltage of the bus. When automatically calculating the response time, the inherent action delay of the high-speed electronic switch is deducted, and the inherent action delay is pre-stored in the millisecond-level timing control module.

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