High-voltage direct-current cable polarity inversion processing method and device based on residual space charge memory effect, terminal equipment and storage medium

Abstract

The application discloses a high-voltage direct-current cable polarity reversal processing method and device based on residual space charge memory effect, a terminal equipment and a storage medium, and belongs to the technical field of cable control. The method comprises the following steps: acquiring a current charge dissipation response signal of a high-voltage direct-current cable to be processed in a preset voltage sequence application process; judging the dissipation degree of residual charge inside the high-voltage direct-current cable to be processed according to the current charge dissipation response signal; in the case that the dissipation degree of residual charge meets a preset safety criterion, extracting a response characteristic parameter according to the current charge dissipation response signal, determining a safety time of formal polarity reversal and a voltage loading mode according to the response characteristic parameter; and performing a formal polarity reversal operation on the high-voltage direct-current cable to be processed according to the voltage loading mode at the safety time. Through implementation of the application, the problem that the prior art relies on experience parameters and lacks adaptive control can be solved.

Description

Technical Field

[0001] This invention relates to the field of cable control technology, and in particular to a method, apparatus, terminal equipment, and storage medium for polarity reversal processing of high-voltage DC cables based on the residual space charge memory effect. Background Technology

[0002] High-voltage direct current (HVDC) cables are key equipment for long-distance, high-capacity power transmission, widely used in inter-regional power grids, offshore wind power transmission, and urban DC distribution networks. In actual operation, HVDC cables need to reverse polarity according to system dispatch instructions, such as power reversal after a unipolar fault in a bipolar DC system, or restarting operation after a shutdown. After long-term pressurized operation, a large amount of space charge will be injected and accumulated inside the cross-linked polyethylene (XLPE) or oil-paper insulation layer of HVDC cables. When the cable is shut down or the voltage polarity changes, these residual charges do not immediately dissipate but exhibit a significant memory effect, meaning the charges remain in the insulation material for a considerable period, maintaining their original polarity distribution. If polarity reversal or voltage reapplied directly under these conditions, the electric field formed by the original residual charges will be opposite in direction to or partially superimposed on the newly applied electric field, leading to severe distortion of the local electric field inside the insulation layer and significantly increasing the risk of insulation breakdown.

[0003] Some existing polarity reversal strategies attempt to reduce the impact by lowering the amplitude of the reversal voltage or slowing down the reversal speed. However, these methods do not fundamentally solve the memory effect of residual space charge and still rely on empirical parameters, lacking real-time adaptive control of the charge dissipation state. Summary of the Invention

[0004] This invention provides a method, apparatus, terminal equipment, and storage medium for polarity reversal processing of high-voltage DC cables based on the residual space charge memory effect. This effectively solves the problem that existing technologies rely on empirical parameters and lack real-time adaptive control of charge dissipation states.

[0005] An embodiment of the present invention provides a method for polarity reversal processing of high-voltage DC cables based on the residual space charge memory effect, comprising: Acquire the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of a preset voltage sequence; The degree of residual charge dissipation inside the high-voltage DC cable to be processed is determined based on the current charge dissipation response signal. If the degree of residual charge dissipation meets the preset safety criteria, the response feature parameters are extracted based on the current charge dissipation response signal, and the safe moment for formal polarity reversal and voltage loading method are determined based on the response feature parameters. At the specified safe moment, the high-voltage DC cable to be processed is subjected to a formal polarity reversal operation according to the specified voltage loading method.

[0006] Further, the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of a preset voltage sequence is obtained, including: Obtain historical operating information of the high-voltage DC cable to be processed before re-pressurization after formal polarity reversal or shutdown; Calculate the residual charge memory risk index based on the historical operating information; When the residual charge memory risk index is greater than or equal to a preset risk threshold, a preset voltage sequence is applied to the high-voltage DC cable to be processed, and the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of the preset voltage sequence is obtained.

[0007] Furthermore, the historical operating information includes: operating voltage amplitude, rated operating voltage, continuous unipolar operating time, continuous operating reference time, downtime, and historical load factor; The residual charge memory risk index is calculated based on the historical operating information, including: The voltage stress factor is obtained based on the relative ratio of the operating voltage amplitude to the rated operating voltage; The charge accumulation duration factor is determined based on the ratio of the continuous unipolar operating time to the continuous operating reference time. The shutdown attenuation factor is determined based on the shutdown duration and the preset reference time parameter for natural decay of residual charge. The residual charge memory risk index is calculated based on the voltage stress factor, the charge accumulation duration factor, the shutdown attenuation factor, the historical load factor, and the preset weighting coefficients.

[0008] Furthermore, the current charge dissipation response signal includes: the ionization current signal, the recovery current signal, and the voltage response signal; The degree of residual charge dissipation inside the high-voltage DC cable to be processed is determined based on the current charge dissipation response signal, including: For the ionization current signal, under the condition that the preset voltage sequence maintains a constant amplitude, the current ionization current and the current continuous stable duration are determined according to the ionization current signal. If the current ionization current is less than the preset ionization current threshold and the current continuous stable duration is not less than the preset stable duration, it is determined that the ionization current dimension meets the dissipation requirement. For the recovery current signal, after the preset voltage sequence is disconnected, the peak value of the recovery current and the recovery current decay time constant are determined according to the recovery current signal. If the peak value of the recovery current is less than the preset recovery current threshold and the recovery current decay time constant is less than the preset time constant threshold, then it is determined that the recovery current dimension meets the dissipation requirement. For the voltage response signal, if the relative difference of the voltage response curves is less than a preset difference threshold, then the voltage response dimension is determined to meet the dissipation requirement. If the dissipation requirement is met in at least one dimension, the degree of dissipation of residual charge inside the high-voltage DC cable to be treated is determined to meet the preset safety criteria.

[0009] Furthermore, the response characteristic parameters include: peak value of ionization current, peak value of recovery current, and voltage response curve difference rate; The safe moment for formal polarity reversal and the voltage loading method are determined based on the response characteristic parameters, including: The peak value of the ionization current, the peak value of the recovery current, and the difference rate of the voltage response curve are compared with the corresponding preset safety thresholds. If the peak value of the ionization current, the peak value of the recovery current, and the difference rate of the voltage response curve all meet the corresponding preset safety threshold requirements, the corresponding moment is determined to be a safe moment for formal polarity reversal. If the difference rate of the voltage response curve is not greater than a preset first difference value, the inverted voltage rise rate corresponding to the voltage loading method is determined as the first rate. If the difference rate of the voltage response curve is greater than a preset first difference value, the inverted voltage rise rate corresponding to the voltage loading mode is determined as the second rate; wherein, the first rate is greater than the second rate.

[0010] Furthermore, it also includes: If, during the application of the preset voltage sequence, the degree of dissipation of residual charge does not meet the preset safety criterion within the preset application time, an insulation defect alarm signal is generated.

[0011] As an improvement to the above solution, another embodiment of the present invention provides a high-voltage DC cable polarity reversal processing device based on the residual space charge memory effect, comprising: The current charge dissipation response signal acquisition module is used to acquire the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of a preset voltage sequence; The charge dissipation degree judgment module is used to determine the degree of dissipation of residual charge inside the high-voltage DC cable to be processed based on the current charge dissipation response signal. The polarity reversal information determination module is used to extract response feature parameters based on the current charge dissipation response signal when the degree of residual charge dissipation meets the preset safety criteria, and to determine the safe moment of formal polarity reversal and voltage loading method based on the response feature parameters. The polarity reversal operation module is used to perform a formal polarity reversal operation on the high-voltage DC cable to be processed according to the voltage loading method at the safe moment.

[0012] Furthermore, the current charge dissipation response signal acquisition module is used to acquire the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of a preset voltage sequence, including: Obtain historical operating information of the high-voltage DC cable to be processed before re-pressurization after formal polarity reversal or shutdown; Calculate the residual charge memory risk index based on the historical operating information; When the residual charge memory risk index is greater than or equal to a preset risk threshold, a preset voltage sequence is applied to the high-voltage DC cable to be processed, and the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of the preset voltage sequence is obtained.

[0013] Another embodiment of the present invention provides a terminal device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements a high-voltage DC cable polarity reversal processing method based on the residual space charge memory effect as described in the above embodiments.

[0014] Another embodiment of the present invention provides a computer-readable storage medium comprising a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to perform a high-voltage DC cable polarity reversal processing method based on the residual space charge memory effect described in the above embodiment.

[0015] By implementing this invention, at least the following beneficial effects are achieved: This invention provides a method, apparatus, terminal equipment, and storage medium for polarity reversal processing of high-voltage DC cables based on the residual space charge memory effect. The method pre-processes the high-voltage DC cable before formal polarity reversal by using a preset voltage sequence, guiding the release and redistribution of internal residual charge. This fundamentally reduces the impact of the charge memory effect, truly mitigating the risk of insulation electric field distortion caused by space charge superposition during polarity reversal, rather than passively withstanding the impact simply by relying on operating parameters. By judging the degree of residual charge dissipation using the current charge dissipation response signal, the true state of the charge inside the cable can be accurately grasped, providing precise decision-making basis for polarity reversal operations. When the degree of residual charge dissipation meets the preset safety criteria, response characteristic parameters are extracted to determine the safe moment and voltage loading method for formal polarity reversal. This ensures insulation safety during the reversal process while avoiding unnecessary time losses caused by uniform empirical parameters, achieving synergistic optimization of safety and operational efficiency. It addresses the memory effect of residual space charge while simultaneously achieving coordinated control of the cable's charge dissipation state. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of a high-voltage DC cable polarity reversal processing method based on the residual space charge memory effect provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a preset voltage sequence as an intermittent on / off waveform provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of a preset voltage sequence as a pulse waveform provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of another process for polarity reversal processing provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of a high-voltage DC cable polarity reversal processing device based on the residual space charge memory effect, provided in an embodiment of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] See Figure 1 To address the problem that existing technologies rely on empirical parameters and lack real-time adaptive control of charge dissipation states, an embodiment of the present invention provides a flowchart illustrating a high-voltage DC cable polarity reversal processing method based on the residual space charge memory effect, comprising: S1. Obtain the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of the preset voltage sequence; Specifically, the preset voltage sequence is a set of low-amplitude voltage excitation waveforms designed to guide the release and redistribution of residual space charge within the insulation before the formal polarity reversal. Its function is to actively intervene in the charge state, rather than to transmit operating power. The current charge dissipation response signal represents the measurable current electrical signal at the end of the high-voltage DC cable to be processed under the action of the preset voltage sequence. It can indirectly reflect the release, migration, and redistribution process of residual charge within the insulation and serves as an objective quantitative basis for judging the charge state.

[0019] This diagram illustrates the acquisition of the current charge dissipation response signal of the high-voltage DC cable under test during the application of a preset voltage sequence. Before the formal polarity reversal operation begins, a preset voltage sequence is applied between the cable conductor and the grounding shield using the cable's compatible DC power supply. Simultaneously, a high-precision current and voltage acquisition device is used to synchronously acquire the electrical signal at the cable end, i.e., the current charge dissipation response signal, during the voltage application process. The acquisition frequency is adjusted according to the signal type; the sampling rate for transient current signals is no less than 1 kHz, while the sampling rate for steady-state voltage signals can be appropriately reduced to ensure complete capture of the dynamic process of charge dissipation.

[0020] Schematic illustration: The polarity of the preset voltage sequence follows a control logic of same-polarity followed by opposite-polarity. First, a voltage consistent with the original operating polarity of the cable is applied to promote the release of residual charge of the same polarity. Then, the voltage is switched to the same polarity as the target reverse polarity to guide the charge to migrate in the opposite direction, achieving a smooth redistribution and avoiding new charge surges caused by sudden polarity changes. All response signals are acquired between the conductor and the grounding shield at the cable terminal, without requiring any modification to the cable structure, and are compatible with existing cable terminal measurement interfaces. Taking positive-to-negative reversal as an example: first, a small-amplitude positive voltage (same as the original polarity) is applied to gradually release residual positive charge; then, a small-amplitude negative voltage (same as the target polarity) is switched to guide the charge to migrate in the opposite direction, thereby achieving a smooth redistribution of charge.

[0021] Preferably, acquiring the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of a preset voltage sequence includes: S11. Obtain historical operating information of the high-voltage DC cable to be processed before re-pressurization after formal polarity reversal or shutdown. S12. Calculate the residual charge memory risk index based on the historical operation information; S13. If the residual charge memory risk index is greater than or equal to a preset risk threshold, apply a preset voltage sequence to the high-voltage DC cable to be processed, and obtain the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of the preset voltage sequence.

[0022] Specifically, historical operating information refers to the operating data of the high-voltage DC cable to be processed prior to this reversal or shutdown. This data reflects the historical process of space charge injection and accumulation within the insulation, serving as the fundamental basis for assessing the risk of charge memory effect. The residual charge memory risk index is a quantitative indicator calculated by integrating multiple operating parameters. It is used to quantitatively assess the strength of the cable's current residual charge memory effect and is the core basis for determining whether pretreatment is necessary. The preset risk threshold is the critical value for classifying risk levels. When the risk index reaches this threshold, it indicates a strong charge memory effect, a high risk of direct reversal, and the need for pretreatment.

[0023] This illustration demonstrates the acquisition of historical operational information of the high-voltage DC cable under investigation before re-energization following a formal polarity reversal or shutdown. Operational data for the corresponding time period is retrieved from the cable operation monitoring system and energy management system, covering voltage polarity, voltage amplitude, rated voltage, continuous unipolar operation duration, total shutdown duration, historical load levels, conductor temperature, and load fluctuations before shutdown. Voltage polarity determines the primary polarity direction of residual charge, voltage amplitude and operating time determine the intensity of charge injection and accumulation, shutdown duration determines the degree of natural decay, and the load factor reflects the influence of temperature on charge migration. All these parameters are based on the physical characteristics of space charge and collectively determine the initial level of residual charge, ensuring the scientific rigor of the risk assessment.

[0024] The residual charge memory risk index is calculated based on the historical operating information. Various historical operating information items are substituted into a preset risk index calculation model. First, parameters of different dimensions are normalized, transforming them into dimensionless factors between 0 and 1. Then, these factors are multiplied by their corresponding weighting coefficients and summed using weighted methods to obtain the final risk index within the [0,1] interval. A higher value indicates a stronger residual charge memory effect and a greater risk of direct insulation reversal.

[0025] If the residual charge memory risk index is greater than or equal to a preset risk threshold, a preset voltage sequence is applied to the high-voltage DC cable to be processed, and the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of the preset voltage sequence is obtained. The calculated residual charge memory risk index is compared with the preset risk threshold: if the residual charge memory risk index reaches or exceeds the preset risk threshold, it indicates that there is a lot of residual charge in the cable, and the risk of direct reversal is high. The preprocessing process is then formally started, the preset voltage sequence is output, and the charge dissipation response signal is collected simultaneously. If the residual charge memory risk index is lower than the preset risk threshold, it indicates that there is very little residual charge and the memory effect is weak. Reversal can be performed directly according to the conventional process without additional preprocessing, saving operation time.

[0026] To illustrate, a residual charge memory risk index ≥ 0.6 indicates a high-risk condition requiring pretreatment; a residual charge memory risk index ≤ 0.3 < 0.6 indicates a medium-risk condition, where pretreatment or rapid diagnosis can be selected based on site conditions; and a residual charge memory risk index < 0.3 indicates a low-risk condition, which can be resolved by reversing the standard procedure. This tiered approach avoids unnecessary pretreatment time and further improves overall operational efficiency.

[0027] In a preferred embodiment of the present invention, before the formal polarity reversal, a preset sequence of low-amplitude, stepped, intermittent, or pulsed voltages is applied to the cable conductor via a DC power supply device. The amplitude of the preset voltage sequence satisfies: In the formula, The amplitude of the preset voltage sequence; The rated operating voltage of the cable; The pre-processing voltage proportionality coefficient is set to 0.05–0.20, preferably 0.05–0.15. For example, for ±320kV high-voltage DC cables, the maximum pre-processing voltage amplitude can be 16–64kV, preferably 16–48kV.

[0028] The preset voltage sequence can be stepped, intermittent, pulsed, or a combination thereof. The waveform selection principles are as follows: stepped waveform is preferred when the downtime is short, the continuous unipolar operation time is long, or the initial discharge current is large; intermittent waveform is preferred when the discharge current decays slowly or the recovery current is large; pulsed waveform or a combination of stepped and pulsed waveforms can be used when it is necessary to shorten the processing time and no obvious insulation defects are found; when the cable is suspected of aging, dampness, or has a risk of partial discharge, low amplitude stepped waveform is preferred, and pulses with excessively high amplitude or frequency should be avoided.

[0029] (1) Stepped boost waveform: In the formula, For the first Preset voltage; The polarity coefficient is s = +1 or -1; This is the voltage step size, typically 1–10 kV; Number of steps; duration of hold for each step Typically, the time is 1 to 10 minutes.

[0030] (2) Intermittent on / off waveform, such as Figure 2 As shown, the intermittent pretreatment voltage is applied and disconnected periodically, with a period of... and duty cycle for: In the formula, The voltage application time is typically 30 seconds to 5 minutes. The voltage disconnection time is typically 30 seconds to 10 minutes. Typically, the percentage ranges from 20% to 80%.

[0031] (3) Pulse waveform, such as Figure 3 As shown, a short-duration, low-amplitude, low-frequency or mid-to-low-frequency unipolar or alternating polarity pulse sequence is applied, with a pulse width of... The pulse alternation interval is 1ms to 10s, and the repetition frequency is... Select 0.01~10Hz, number of pulses Take 10 to 1000.

[0032] This embodiment first assesses the risk level using historical information, performing pretreatment only on high-risk cables and directly operating on low-risk cables. This avoids the time wasted by indiscriminate pretreatment and improves the overall efficiency of reversal operations. The risk index is calculated based on multiple operating parameters, which is more accurate than manual judgment and can identify easily overlooked high-risk conditions, such as short-term shutdowns after long periods of continuous operation, avoiding insulation hazards caused by missed detections. The initial risk level also helps select a more suitable preset voltage sequence waveform, such as a stepped waveform for high-risk and an intermittent waveform for medium-risk, optimizing the effect and efficiency of pretreatment. By applying a low-amplitude, stepped / intermittent / pulsed pretreatment voltage sequence before the formal polarity reversal, the residual space charge, polarization charge, and capacitive charge inside the insulation are gradually released or redistributed, fundamentally eliminating the interference of the memory effect on the reversing electric field. The maximum electric field distortion coefficient at the moment of reversal is reduced from 2.3 in traditional direct reversal to 1.1, a reduction of over 50%, effectively avoiding insulation breakdown accidents caused by localized electric field concentration.

[0033] The amplitude, waveform, step size, and polarity switching strategy of the preset voltage sequence can all be flexibly adjusted according to the actual rated voltage of the cable, operating time, and downtime. For example, for short downtime ( For cables with unipolar operation, stepped or pulsed pretreatment can be used; for cables operating in unipolar mode for extended periods, a smooth redistribution can be achieved through a pretreatment sequence of first the same polarity and then the opposite polarity. This method is not dependent on specific insulation materials (cross-linked polyethylene and oil-paper insulation are both applicable) and has good versatility.

[0034] Preferably, the historical operating information includes: operating voltage amplitude, rated operating voltage, continuous unipolar operating time, continuous operating reference time, downtime, and historical load factor; The residual charge memory risk index is calculated based on the historical operating information, including: S121. Obtain the voltage stress factor based on the relative ratio of the operating voltage amplitude to the rated operating voltage; S122. Determine the charge accumulation duration factor based on the ratio of the continuous unipolar operating time to the continuous operating reference time; S123. Determine the shutdown attenuation factor based on the shutdown duration and the preset residual charge natural decay reference time parameter; S124. The residual charge memory risk index is calculated based on the voltage stress factor, the charge accumulation duration factor, the shutdown attenuation factor, the historical load factor, and the preset weighting coefficient.

[0035] Specifically, the voltage stress factor is a dimensionless parameter representing the excitation intensity of the insulation electric field by the operating voltage, determined by the ratio of the operating voltage amplitude to the rated voltage, and is the core factor driving space charge injection into the insulation. The charge accumulation duration factor is a dimensionless parameter representing the effect of the duration of continuous unipolar voltage on charge accumulation, reflecting the degree of charge saturation over time. The shutdown attenuation factor is a dimensionless parameter representing the degree of natural attenuation of residual charge during shutdown, determined by both the shutdown duration and the natural attenuation time constant. Weighting coefficients are used to allocate the proportion of each influencing factor in the comprehensive risk assessment; the sum of all weights is 1, and can be flexibly adjusted according to the cable type and insulation material characteristics.

[0036] Schematic, the voltage stress factor is obtained based on the relative ratio of the operating voltage amplitude to the rated operating voltage. The ratio of the absolute value of the operating voltage before shutdown to the cable's rated operating voltage is taken as the voltage stress factor. The higher the operating voltage, the greater the electric field strength inside the insulation, and the more space charge is injected; therefore, the voltage stress factor is positively correlated with the charge injection intensity.

[0037] The charge accumulation duration factor is determined based on the ratio of the continuous unipolar operating time to the continuous operating reference time. The ratio of the continuous unipolar operating time to the preset continuous operating reference time is taken, and the result is set to its upper limit of 1 to obtain the charge accumulation duration factor. The accumulation of space charge is not infinite; after a certain operating time, charge injection and decay reach a dynamic equilibrium, and the accumulation tends to saturate. Therefore, a reference time is set as the saturation threshold; beyond this time, the factor takes its maximum value of 1. The continuous operating reference time is typically set to 24h-500h and can be adjusted according to the charge injection characteristics of the insulating material.

[0038] The shutdown attenuation factor is determined based on the shutdown duration and a preset reference time parameter for the natural decay of residual charge. Using an exponential decay model, with the shutdown duration as the independent variable and the reference time constant for the natural decay of residual charge as the attenuation characteristic parameter, the shutdown attenuation factor is calculated. During shutdown, residual charge is slowly released through conductivity, thermal excitation, etc., exhibiting an overall exponential decay pattern: the longer the shutdown time, the less residual charge remains, and the smaller the attenuation factor value. The natural decay reference time constant is typically taken as 12h-24h, corresponding to the typical decay rate of space charge in cross-linked polyethylene insulation.

[0039] The residual charge memory risk index is calculated based on the voltage stress factor, charge accumulation duration factor, shutdown attenuation factor, historical load factor, and preset weighting coefficients. The final risk index is obtained by multiplying each of the four factors by its corresponding weighting coefficient and then summing the results. The sum of the four weighting coefficients is 1, with typical values ​​of 0.3, 0.3, 0.3, and 0.1. Voltage, duration, and attenuation have the primary weights, while load thermal effects have a secondary weight, consistent with the main influence of space charge in high-voltage DC cables. For cable lines operating at higher temperatures, the weight of the load factor can be appropriately increased to improve the accuracy of the assessment.

[0040] To illustrate, historical operating information also includes the polarity of the operating voltage before shutdown, conductor temperature, and load fluctuations: voltage polarity is used to determine the order of application of subsequent pre-processing voltages, and conductor temperature and load fluctuations can be used to correct the value of the load factor. The higher the temperature, the faster the charge migration rate and the faster the decay. Temperature correction can make the risk assessment more in line with the actual operating conditions.

[0041] In a preferred embodiment of the present invention, the historical operating signal includes: operating voltage amplitude. Rated operating voltage Continuous unipolar operating time Continuous operation reference time Duration of service interruption and historical load factor This also includes the polarity of the operating voltage before shutdown. . Used to determine the main polarity direction of the residual charge; and Used to characterize charge injection and accumulation intensity; Used to characterize the degree of natural decay of residual charge; Used to characterize the effect of load heating on space charge migration and release.

[0042] To facilitate engineering assessment, a residual charge memory risk index is defined. : In the formula, Take 24h to 500h; The reference time constant for the natural decay of residual charge is taken as 12h to 24h. For the weighting coefficients, satisfying The voltage stress factor is The charge accumulation duration factor is The shutdown attenuation factor is .

[0043] S2. Determine the degree of dissipation of residual charge inside the high-voltage DC cable to be processed based on the current charge dissipation response signal; Specifically, the degree of dissipation of residual charge characterizes the remaining level of residual space charge inside the cable insulation. The higher the degree of dissipation, the weaker the electric field distortion caused by charge superposition during reversal, and the higher the operational safety.

[0044] This diagram illustrates how the degree of residual charge dissipation inside a high-voltage DC cable is determined based on the current charge dissipation response signal. First, the acquired current charge dissipation response signal is filtered and denoised to eliminate noise fluctuations caused by electromagnetic interference. Then, features such as signal amplitude, attenuation rate, and stability are extracted and compared one by one with preset dissipation judgment rules. The remaining amount and activity level of the intangible residual charge inside the insulation are inferred from the externally measurable signal. In simple terms, this transforms the invisible and intangible charge state inside the insulation into a measurable and calculable electrical signal, solving the engineering problem of the inability to directly measure spatial charge online.

[0045] Preferably, the current charge dissipation response signal includes: an excitation current signal, a recovery current signal, and a voltage response signal; The degree of residual charge dissipation inside the high-voltage DC cable to be processed is determined based on the current charge dissipation response signal, including: S21. For the ionization current signal, under the condition that the preset voltage sequence maintains a constant amplitude, the current ionization current and the current continuous stable duration are determined according to the ionization current signal. If the current ionization current is less than the preset ionization current threshold and the current continuous stable duration is not less than the preset stable duration, it is determined that the ionization current dimension meets the dissipation requirement. S22. For the recovery current signal, after the preset voltage sequence is disconnected, the peak value of the recovery current and the recovery current decay time constant are determined according to the recovery current signal. If the peak value of the recovery current is less than the preset recovery current threshold and the recovery current decay time constant is less than the preset time constant threshold, then it is determined that the recovery current dimension meets the dissipation requirement. S23. For the voltage response signal, if the relative difference of the voltage response curves is less than a preset difference threshold, then the voltage response dimension is determined to meet the dissipation requirement. S24. If the dissipation requirement is met in at least one dimension, determine that the degree of dissipation of residual charge inside the high-voltage DC cable to be treated meets the preset safety criteria.

[0046] Specifically, the ionization current signal represents the current formed by the directional migration of residual space charge under the influence of an external electric field during the application of a constant voltage, and is the most direct measurement signal characterizing the charge release process. The recovery current signal represents the spontaneous current formed by the slow release of residual polarized charge and deep space charge after the voltage is disconnected, and can reflect the retention of deep-seated trapped charge inside the insulation. The voltage response signal represents the voltage establishment process of the cable terminal under small current excitation, and can indirectly estimate the magnitude of the equivalent capacitance of the insulation and the equivalent voltage of the residual charge. The preset ionization current threshold is the critical current value for determining whether the ionization current dimension dissipation meets the standard; below this value, it indicates that the migratable residual charge has been basically released. The preset stabilization time represents the shortest time required for the ionization current to remain below the threshold, used to avoid misjudgment caused by instantaneous fluctuations. The preset difference threshold is the critical relative difference value for determining whether the voltage response dimension dissipation meets the standard; the smaller the difference between two measurements, the more stable the charge state.

[0047] Schematic, within a time period during which a preset voltage sequence maintains a constant amplitude, the real-time collected ionization current signal is extracted, the moving average of the current is calculated, and the duration for which the current remains below a preset ionization current threshold is recorded. When the current ionization current is less than the threshold and the stable duration meets the requirement, the ionization current dimension is determined to meet the dissipation requirement. During the release of residual charge, the ionization current exhibits an overall exponential decay trend. When the current drops to a low level and remains stable, it indicates that most of the transferable volume charge has been released.

[0048] During the brief intervals of a pre-set voltage sequence interruption, a high-speed recovery current signal is acquired, the peak current value is extracted, and the decay time constant is obtained through exponential fitting. When the peak recovery current is less than a pre-set recovery current threshold and the decay time constant is less than a pre-set time constant threshold, the recovery current dimension is deemed to meet the dissipation requirements. The recovery current mainly reflects the deeper and more stable trapped charges inside the insulation. A small peak value and rapid decay indicate that a large amount of the deep residual charges have also dissipated, and the charge memory effect is weak.

[0049] A fixed small current excitation is applied by a microampere-level constant current source, and the voltage at the cable terminal is measured to establish a curve. After two consecutive measurements, the maximum relative difference between the two curves is calculated. When the relative difference is less than a preset difference threshold, the voltage response dimension is deemed to meet the dissipation requirement. If there is still a large amount of active residual charge in the insulation, the charge state will change with each measurement, and the difference in the voltage curve will be larger; the smaller the difference, the more stable the charge state, and the memory effect is basically eliminated.

[0050] Finally, by combining the results from the three dimensions, and provided that at least one dimension meets the dissipation requirements, the overall dissipation level is determined to meet the preset safety criteria. On-site, the judgment rules can be flexibly selected based on the safety level. For scenarios with general safety requirements, meeting only one dimension is sufficient; for scenarios with high safety requirements, multiple dimensions may need to be met simultaneously.

[0051] Schematic illustration: The ionization current is measured using a high-precision DC ammeter connected in series in the conductor circuit, with a resolution of no less than 1μA; the recovery current is acquired at high speed triggered at the moment of voltage disconnection to capture the complete attenuation process; the voltage response is measured using an external constant current source in conjunction with a voltmeter. The preset ionization current threshold is 0.1mA, the preset stabilization time is 30s; the preset recovery current threshold is 0.05mA, the preset time constant threshold is 5s; and the preset difference threshold is 5%. These values ​​are based on extensive experimental and engineering verification and are applicable to mainstream high-voltage DC cross-linked polyethylene cables. The core advantage of using a multi-dimensional combined criterion is that it avoids misjudgments caused by electromagnetic interference from a single signal. The three types of signals correspond to volume charge, deep charge, and equivalent charge state, respectively, and cross-validation significantly improves the reliability of the judgment.

[0052] In a preferred embodiment of the present invention (1) Excitation current When the pretreatment voltage is kept constant, the minute current flowing between the cable conductor and the shielding layer is measured; this is the discharge current. The residual charge release process can be approximated as follows: ,in, This is the equivalent discharge time constant. It is the insulation equivalent capacitance. For insulation equivalent resistance, This represents the initial peak value of the ionizing current. As the residual charge dissipates, It exhibits an exponential decay.

[0053] (2)(2) Restoring current After a brief disconnection of the pretreatment voltage, the spontaneous current caused by residual polarization and space charge release was measured. This is denoted as the recovery current. It can be represented as: In the formula, To restore the initial peak current; To restore the current decay time constant.

[0054] (3) Voltage response When a fixed small current excitation is applied Under the given conditions, the process of establishing the voltage at the cable termination is as follows: Calculate the equivalent capacitance of insulation from the voltage response curve. Equivalent voltage source of residual charge .

[0055] In a preferred embodiment of the present invention (1) Criterion for the dimension of ionization current: Current discharge current ; Current duration of stability Preset stable duration Among them, the preset ionization current threshold The typical value is 0.1mA. The preset stabilization time is typically 30s.

[0056] (2) Criterion for restoring current dimension: Recovery current peak Preset recovery current threshold Recovery current decay time constant <Preset time constant threshold> The typical value of the preset recovery current threshold is... Preset time constant threshold (3) Voltage response dimension criterion: The relative difference between the voltage curves obtained from two consecutive measurements is less than the preset difference threshold (5%): ,in, and This represents the nth-order voltage response and the (n-1)th-order voltage response.

[0057] In this embodiment, three types of signals reflect the charge state from different perspectives, complementing each other and providing significantly higher anti-interference capability and reliability than single-signal judgment, effectively avoiding misjudgments caused by on-site interference. Each dimension's criterion corresponds to the attenuation law of space charge, not an arbitrary value, ensuring the scientific validity of the judgment results. Furthermore, rules satisfying single or multiple dimensions can be selected based on the voltage level and importance of the line, meeting the needs of both high-safety-level converter station cables and efficiency-priority distribution network DC cables. Compared to existing methods relying on experience or fixed delays, this invention adaptively determines the safe reversal time based on the actual charge dissipation state, avoiding premature reversal (with residual charge) or late reversal (extended downtime), thus improving operational reliability and economy. By actively managing residual charge, the repeated electric field impacts on the insulation during polarity reversal are reduced. Long-term application of this method can suppress the initiation and growth of electrical trees, delaying the aging process of insulation. Long-term application of this method is beneficial to reduce electric field impact during polarity reversal, delay the risk of electrical tree initiation and insulation aging, and is especially suitable for offshore wind power transmission systems or flexible DC distribution networks that frequently undergo power reversal.

[0058] S3. If the degree of residual charge dissipation meets the preset safety criteria, extract response feature parameters based on the current charge dissipation response signal, and determine the safe moment for formal polarity reversal and voltage loading method based on the response feature parameters. Specifically, the preset safety criterion represents a pre-defined set of quantitative indicators used to determine whether the degree of residual charge dissipation meets the conditions for safe reversal. It serves as the entry criterion for formal reversal. The response characteristic parameter is a feature quantity extracted from the current charge dissipation response signal, which can quantitatively characterize the charge dissipation characteristics and is used to assess the charge state and match the corresponding reversal control strategy. The safe moment represents the starting point at which formal polarity reversal can be initiated after the degree of residual charge dissipation meets the safety criterion. At this time, the insulation electric field distortion caused by the reversal is within an acceptable safe range. The voltage loading method represents the control strategy for the reverse voltage to rise from zero to the target value during formal reversal, including the rise rate and whether it is maintained in segments, which directly determines the electric field impact intensity during the reversal process.

[0059] Schematic illustration: When the degree of residual charge dissipation meets the preset safety criteria, response feature parameters are extracted based on the current charge dissipation response signal. These response feature parameters are then used to determine the safe moment for formal polarity reversal and the voltage loading method. When the degree of residual charge dissipation reaches the safety criterion requirement, it indicates that the insulation risk of reversal is within a controllable range, and the current moment is marked as a candidate safe moment. Simultaneously, feature parameters that quantify the charge dissipation level are extracted from the collected response signal. Based on the deviation of these parameters from the safety threshold, a graded matching voltage loading strategy is applied: the more fully the residual charge dissipates, the faster the loading rate can be; if the dissipation level just reaches the safety boundary, a gentler loading method is adopted, truly achieving adaptive matching where the charge state determines the reversal strategy, rather than applying fixed parameters throughout.

[0060] Preferably, the response characteristic parameters include: peak value of ionization current, peak value of recovery current, and voltage response curve difference rate; The safe moment for formal polarity reversal and the voltage loading method are determined based on the response characteristic parameters, including: The peak value of the ionization current, the peak value of the recovery current, and the difference rate of the voltage response curve are compared with the corresponding preset safety thresholds. If the peak value of the ionization current, the peak value of the recovery current, and the difference rate of the voltage response curve all meet the corresponding preset safety threshold requirements, the corresponding moment is determined to be a safe moment for formal polarity reversal. If the difference rate of the voltage response curve is not greater than a preset first difference value, the inverted voltage rise rate corresponding to the voltage loading method is determined as the first rate. If the difference rate of the voltage response curve is greater than a preset first difference value, the inverted voltage rise rate corresponding to the voltage loading mode is determined as the second rate; wherein, the first rate is greater than the second rate.

[0061] Specifically, the peak ionization current is the maximum value of the ionization current in the initial pretreatment stage, reflecting the total amount of initial residual charge. The peak recovery current is the maximum value of the recovery current after voltage disconnection, reflecting the activity level of deep residual charge. The voltage response curve difference rate is the maximum relative difference between two consecutive voltage response curves, reflecting the stability of the charge state. The preset safety threshold is the critical value of each parameter for determining whether the safe reversal condition has been met, serving as the benchmark for determining the safe moment. The preset first difference value and preset second difference value both represent the critical difference rate values ​​for classifying loading mode levels, with the first difference value being less than the second difference value. The first rate and second rate correspond to the reversal voltage rise rate with different dissipation degrees, with the first rate being greater than the second rate, corresponding to rapid loading and gradual loading modes, respectively.

[0062] Schematic, the response characteristic parameters include the peak value of the ionization current, the peak value of the recovery current, and the difference rate of the voltage response curve. These three parameters quantify the dissipation level of residual charge from three dimensions: total charge, deep charge, and state stability.

[0063] The extracted peak ionization current, peak recovery current, and voltage response curve difference rate are compared one by one with their respective preset safety thresholds. Only when all three parameters simultaneously meet the threshold requirements is the current moment determined to be a safe moment for formal polarity reversal. This ensures that the charge state reaches a safe level in all dimensions before reversal, avoiding situations where one parameter meets the standard but other parameters are still at risk, thus maximizing the safety of reversal.

[0064] Based on the specific value of the difference rate in the voltage response curve, the rise rate of the reverse voltage is matched in stages: When the difference rate of the voltage response curve is not greater than the preset first difference value, it indicates that the charge dissipation is very sufficient and the state is highly stable. At this time, a faster first rate is used for voltage loading to improve the reversal efficiency. When the voltage response curve difference rate is greater than the preset first difference value but less than the preset second difference value, it indicates that the charge dissipation has just reached the safety standard, and the safety margin is relatively limited. In this case, a slower second loading rate is used to ensure that the electric field impact during the reversal process is within the insulation tolerance range. The first loading rate is greater than the second loading rate, and the preset first difference value is less than the preset second difference value. In typical engineering applications, the first difference value can be 3%, and the second difference value can be 5%; the first loading rate can be 5-10 kV / s, and the second loading rate can be 1-5 kV / s. In practical applications, fine-tuning can be made based on the deviation of the current peak value from the threshold: if the current peak value is much lower than the threshold, a faster loading rate can be used within the corresponding level; if the current peak value is close to the threshold, a slower loading rate can be used to achieve more refined graded control.

[0065] Schematic illustration: When using the second loading rate, a segmented holding strategy can be employed: after each 10% increase in rated voltage, hold for 1-5 minutes to allow sufficient time for the internal electric field of the insulation to redistribute, further reducing the electric field impact. The more fully the residual charge dissipates, the weaker the superposition effect of the reverse voltage and residual electric field during reversal, and the higher the voltage rise rate that the insulation can withstand; conversely, the rate needs to be slowed down to avoid the superimposed electric field exceeding the insulation withstand limit. If any parameter does not meet the safety threshold, the preset voltage sequence continues to be applied, and the signal acquisition and status judgment are repeated until the conditions are met or the maximum preprocessing time is reached, forming a closed-loop iterative processing flow.

[0066] In a preferred embodiment of the present invention, the response characteristic parameters include peak ionization current, ionization current decay time constant, peak recovery current, recovery current decay time constant, and voltage response curve difference rate. .

[0067] When the peak value of the ionization current is not greater than the preset ionization current threshold, the peak value of the recovery current is not greater than the preset recovery current threshold, and the difference rate of the voltage response curve is not greater than the preset difference threshold, the current moment is determined to be a safe reversal moment. And allows for the execution of a formal polarity reversal.

[0068] The formal reversal loading method is determined using a tiered rule: if the peak value of the ionization current and the peak value of the recovery current are significantly lower than the threshold and It adopts a fast loading method to reverse the voltage rise rate. Take the first rate as 5-10 kV / s; if the peak recovery current is close to the threshold or The percentage is 3% to 5%, and a segmented loading method is used. Take a second rate of 1-5 kV / s, and increase it by 10% for each subsequent 10% increase. Then hold for 1–5 minutes; if any response parameter does not meet the safety threshold, continue preprocessing and repeat the measurement.

[0069] If the preprocessing duration reaches the maximum preprocessing time If the safety conditions are still not met, an alarm signal will be issued, indicating that the cable may have serious insulation defects and further diagnosis of space charge, partial discharge, insulation resistance or dielectric loss is required. Typically, the time is 30–60 minutes.

[0070] Preferably, it further includes: If, during the application of the preset voltage sequence, the degree of dissipation of residual charge does not meet the preset safety criterion within the preset application time, an insulation defect alarm signal is generated.

[0071] Specifically, the preset application duration is the maximum allowed duration of the preprocessing operation, serving as the timeout exit condition for preprocessing and preventing unlimited continuous preprocessing. The insulation defect alarm signal indicates an alarm message triggered when the preprocessing timeout fails to meet the safety conditions, suggesting that the cable may have abnormal insulation defects and further investigation and diagnosis are required.

[0072] Schematic, during the entire application of the preset voltage sequence, the duration of preprocessing is accumulated in real time, and the degree of residual charge dissipation is simultaneously assessed to determine whether it meets the safety criteria. If, after the accumulated duration reaches the preset application time, the degree of dissipation still does not meet the preset safety criteria, it indicates that the cable's charge decay rate is far below the normal level. This likely indicates an anomaly such as aging, moisture, or impurity defects within the insulation, causing the charge to be trapped in deep-level traps and difficult to release. In this case, an insulation defect alarm signal is automatically generated, the preprocessing process is terminated, and maintenance personnel are prompted to conduct further insulation diagnosis. The typical preset application time is 30-60 minutes, which can be adjusted according to cable length, voltage level, and insulation material characteristics.

[0073] In a preferred embodiment of the present invention, after the alarm is triggered, insulation diagnostic items such as space charge testing, partial discharge detection, insulation resistance measurement, and dielectric loss testing are performed sequentially to locate the type and location of defects. After troubleshooting, a polarity reversal operation is performed to avoid insulation breakdown accidents caused by operation with defects. The core significance of setting a maximum pre-processing time is that the residual charge of a normal cable can basically dissipate to a safe level within tens of minutes. If the standard is not met after the time limit, it indicates that it is not a normal charge memory effect, but an abnormality in the insulation itself. Timely exit and alarm can not only avoid ineffective waiting, but also detect hidden insulation hazards in advance.

[0074] S4. At the safe moment, perform a formal polarity reversal operation on the high-voltage DC cable to be processed according to the voltage loading method.

[0075] Schematic illustration: At the designated safe moment, the high-voltage DC cable to be processed undergoes a formal polarity reversal operation according to the voltage loading method. After reaching the safe moment, the DC power supply device is controlled to switch the voltage polarity, gradually increasing the reverse voltage according to the predetermined loading method until the target operating voltage is reached. Insulation status parameters are monitored synchronously throughout the reversal process. In the event of abnormal discharge, sudden current surge, or other abnormal situations, the voltage increase can be stopped in time to ensure operational safety.

[0076] In a preferred embodiment of the present invention, such as Figure 4 As shown, taking a high-voltage DC cable with a rated operating voltage of ±320kV as an example, this cable was in a positive polarity operating state for a long time before being shut down, with an operating voltage of +320kV, a continuous operating time of over 500 hours, a shutdown time of 12 hours, and a target operating polarity of -320kV. kV, kV, h、 h、 h、 h、 , , , , If we take values ​​of 0.3, 0.3, 0.3, and 0.1 respectively, then: Therefore, the cable is determined to be in a high-risk state with a strong residual charge memory effect, requiring pretreatment before the actual polarity reversal. Given the short downtime and long continuous unipolar operation time of the cable, a stepped preset voltage sequence is preferred.

[0077] First, a positive polarity stepped preset voltage, the same as the original operating polarity, is applied, starting at +5kV, increasing by 5kV at each step, and maintaining each step for 10 minutes, up to +30kV. The maximum amplitude of this preset voltage is approximately 9.4% of the rated operating voltage, which is within the preferred range. During the preprocessing, the end discharge current is measured simultaneously. The initial discharge current is 2.5mA, which decays to 0.08mA after 40 minutes and remains stable for more than 1 minute, meeting the criterion that the discharge current threshold is less than 0.1mA.

[0078] The voltage was then switched to a negative polarity stepped preset voltage, the same as the target operating polarity, starting from -5kV, decreasing by 5kV at each step, and holding each step for 10 minutes, until reaching -30kV. During the negative polarity pretreatment, the peak value of the ionization current was 0.3mA, which decayed to 0.05mA. After disconnecting the pretreatment voltage, the peak value of the recovery current was measured to be less than 0.05mA, and the recovery current decay time constant was less than 5s. The relative difference between the voltage response curves under two consecutive small current excitations was less than 5%. Therefore, it was determined that the residual charge had been basically released or redistributed.

[0079] Based on the aforementioned response parameters, the ionization current, recovery current, and voltage response all meet the safety criteria, thus determining the current moment as the safe reversal moment. Since all response parameters are below the safety threshold, the formal polarity reversal employs a rapid loading method, increasing the voltage from -30kV to -320kV at a rate of 8kV / s. Compared to the comparative simulation results of direct polarity reversal without preprocessing, this embodiment reduces the maximum electric field distortion coefficient at the moment of reversal from 2.3 to 1.1, thereby reducing the risk of local electric field superposition and insulation breakdown.

[0080] Existing technologies rely solely on lowering voltage and slowing down the reversal speed to withstand impacts, failing to address the root cause of residual charge. This embodiment actively guides charge release and redistribution through a preset voltage sequence, first weakening the charge memory effect before performing the reversal. This fundamentally reduces the risk of electric field distortion during the reversal process, rather than simply sacrificing operational standards for safety. Each reversal is based on the measured response signal of the current cable, accurately reflecting the internal charge state. This is far more accurate than applying uniform empirical values, avoiding both the inefficient situation of slowly increasing voltage even after the charge has long since dissipated and the safety hazard of reversing at the normal speed when there is still a lot of charge.

[0081] By implementing this embodiment, a pre-processing intervention is performed on the high-voltage DC cable under test using a preset voltage sequence before the formal polarity reversal. This guides the release and redistribution of internal residual charge, fundamentally reducing the impact of charge memory effect and truly mitigating the risk of insulation electric field distortion caused by space charge superposition during polarity reversal, rather than passively withstanding the impact simply by relying on operating parameters. Judging the degree of residual charge dissipation based on the current charge dissipation response signal allows for accurate understanding of the true state of charge within the cable, providing precise decision-making basis for polarity reversal operations. When the degree of residual charge dissipation meets preset safety criteria, response characteristic parameters are extracted to determine the safe moment and voltage loading method for the formal polarity reversal. This ensures insulation safety during the reversal process while avoiding unnecessary time losses caused by uniform empirical parameters, achieving synergistic optimization of safety and operational efficiency. It addresses the memory effect of residual space charge while simultaneously achieving coordinated control of the cable's charge dissipation state.

[0082] See Figure 5 This is a schematic diagram of a high-voltage DC cable polarity reversal processing device based on the residual space charge memory effect according to an embodiment of the present invention, comprising: The current charge dissipation response signal acquisition module 101 is used to acquire the current charge dissipation response signal of the high voltage DC cable to be processed during the application of a preset voltage sequence; The charge dissipation degree judgment module 102 is used to judge the degree of dissipation of residual charge inside the high voltage DC cable to be processed based on the current charge dissipation response signal. The polarity reversal information determination module 103 is used to extract response feature parameters based on the current charge dissipation response signal when the degree of residual charge dissipation meets the preset safety criteria, and to determine the safe moment of formal polarity reversal and voltage loading method based on the response feature parameters. The polarity reversal operation module 104 is used to perform a formal polarity reversal operation on the high-voltage DC cable to be processed according to the voltage loading method at the safe moment.

[0083] Preferably, the current charge dissipation response signal acquisition module is used to acquire the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of a preset voltage sequence, including: Obtain historical operating information of the high-voltage DC cable to be processed before re-pressurization after formal polarity reversal or shutdown; Calculate the residual charge memory risk index based on the historical operating information; When the residual charge memory risk index is greater than or equal to a preset risk threshold, a preset voltage sequence is applied to the high-voltage DC cable to be processed, and the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of the preset voltage sequence is obtained.

[0084] This invention provides a high-voltage direct current (HVDC) cable polarity reversal processing device based on the residual space charge memory effect. The device comprises: a current charge dissipation response signal acquisition module to acquire the current charge dissipation response signal of the HVDC cable under test during the application of a preset voltage sequence; a charge dissipation degree judgment module to determine the degree of dissipation of residual charge within the HVDC cable under test based on the current charge dissipation response signal; a polarity reversal information determination module to extract response feature parameters based on the current charge dissipation response signal, provided that the degree of residual charge dissipation meets a preset safety criterion, and to determine the safe moment for formal polarity reversal and the voltage loading method based on the response feature parameters; and finally, a polarity reversal operation module to perform a formal polarity reversal operation on the HVDC cable under test at the safe moment and according to the voltage loading method.

[0085] Before the formal polarity reversal, a pre-processing intervention is performed on the high-voltage DC cable under test using a preset voltage sequence. This guides the release and redistribution of residual charge within the cable, fundamentally reducing the impact of charge memory effect and truly mitigating the risk of insulation electric field distortion caused by the superposition of space charge during polarity reversal, rather than passively withstanding the impact simply by relying on operating parameters. By judging the degree of residual charge dissipation based on the current charge dissipation response signal, the true state of the charge inside the cable can be accurately grasped, providing a precise decision-making basis for polarity reversal operations. When the degree of residual charge dissipation meets the preset safety criteria, response characteristic parameters are extracted to determine the safe moment and voltage loading method for the formal polarity reversal. This ensures insulation safety during the reversal process while avoiding unnecessary time losses caused by uniform empirical parameters, achieving synergistic optimization of safety and operational efficiency. It addresses the memory effect of residual space charge while simultaneously achieving coordinated control of the cable's charge dissipation state.

[0086] It should be noted that the device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the device embodiments provided by this invention, the connection relationships between modules indicate that they have communication connections, which can be specifically implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.

[0087] Those skilled in the art will understand that, for convenience and brevity, the specific working process of the device described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0088] Another embodiment of the present invention provides a terminal device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements a high-voltage DC cable polarity reversal processing method based on the residual space charge memory effect as described in the above embodiments. The terminal device can be a desktop computer, laptop, handheld computer, cloud server, or other computing device. The terminal device may include, but is not limited to, a processor and a memory.

[0089] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the terminal device, connecting all parts of the terminal device via various interfaces and lines.

[0090] The memory can be used to store the computer program. The processor implements various functions of the terminal device by running or executing the computer program stored in the memory and calling data stored in the memory. The memory may mainly include a program storage area and a data storage area. The program storage area may store the operating system, at least one application program required for a function, etc.; the data storage area may store data created based on the use of the mobile phone, etc. In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as hard disk, RAM, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one disk storage device, flash memory device or other volatile solid-state storage device.

[0091] Another embodiment of the present invention provides a computer-readable storage medium comprising a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to perform a high-voltage DC cable polarity reversal processing method based on the residual space charge memory effect described in the above embodiment.

[0092] The storage medium is a computer-readable storage medium, and the computer program is stored in the computer-readable storage medium. When the computer program is executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or some intermediate form. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drive, portable hard drive, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0093] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for reversing the polarity of high-voltage DC cables based on the residual space charge memory effect, characterized in that, include: Acquire the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of a preset voltage sequence; The degree of residual charge dissipation inside the high-voltage DC cable to be processed is determined based on the current charge dissipation response signal. If the degree of residual charge dissipation meets the preset safety criteria, the response feature parameters are extracted based on the current charge dissipation response signal, and the safe moment for formal polarity reversal and voltage loading method are determined based on the response feature parameters. At the specified safe moment, the high-voltage DC cable to be processed is subjected to a formal polarity reversal operation according to the specified voltage loading method.

2. The method for polarity reversal processing of high-voltage DC cables based on residual space charge memory effect as described in claim 1, characterized in that, Acquire the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of a preset voltage sequence, including: Obtain historical operating information of the high-voltage DC cable to be processed before re-pressurization after formal polarity reversal or shutdown; Calculate the residual charge memory risk index based on the historical operating information; When the residual charge memory risk index is greater than or equal to a preset risk threshold, a preset voltage sequence is applied to the high-voltage DC cable to be processed, and the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of the preset voltage sequence is obtained.

3. The method for polarity reversal processing of high-voltage DC cables based on the residual space charge memory effect as described in claim 2, characterized in that, The historical operating information includes: operating voltage amplitude, rated operating voltage, continuous unipolar operating time, continuous operating reference time, downtime, and historical load factor; The residual charge memory risk index is calculated based on the historical operating information, including: The voltage stress factor is obtained based on the relative ratio of the operating voltage amplitude to the rated operating voltage; The charge accumulation duration factor is determined based on the ratio of the continuous unipolar operating time to the continuous operating reference time. The shutdown attenuation factor is determined based on the shutdown duration and the preset reference time parameter for natural decay of residual charge. The residual charge memory risk index is calculated based on the voltage stress factor, the charge accumulation duration factor, the shutdown attenuation factor, the historical load factor, and the preset weighting coefficients.

4. The method for polarity reversal processing of high-voltage DC cables based on residual space charge memory effect as described in claim 1, characterized in that, The current charge dissipation response signal includes: the ionization current signal, the recovery current signal, and the voltage response signal; The degree of residual charge dissipation inside the high-voltage DC cable to be processed is determined based on the current charge dissipation response signal, including: For the ionization current signal, under the condition that the preset voltage sequence maintains a constant amplitude, the current ionization current and the current continuous stable duration are determined according to the ionization current signal. If the current ionization current is less than the preset ionization current threshold and the current continuous stable duration is not less than the preset stable duration, it is determined that the ionization current dimension meets the dissipation requirement. For the recovery current signal, after the preset voltage sequence is disconnected, the peak value of the recovery current and the recovery current decay time constant are determined according to the recovery current signal. If the peak value of the recovery current is less than the preset recovery current threshold and the recovery current decay time constant is less than the preset time constant threshold, then it is determined that the recovery current dimension meets the dissipation requirement. For the voltage response signal, if the relative difference of the voltage response curves is less than a preset difference threshold, then the voltage response dimension is determined to meet the dissipation requirement. If the dissipation requirement is met in at least one dimension, the degree of dissipation of residual charge inside the high-voltage DC cable to be treated is determined to meet the preset safety criteria.

5. The method for polarity reversal processing of high-voltage DC cables based on residual space charge memory effect as described in claim 1, characterized in that, The response characteristic parameters include: peak ionization current, peak recovery current, and voltage response curve difference rate; The safe moment for formal polarity reversal and the voltage loading method are determined based on the response characteristic parameters, including: The peak value of the ionization current, the peak value of the recovery current, and the difference rate of the voltage response curve are compared with the corresponding preset safety thresholds. If the peak value of the ionization current, the peak value of the recovery current, and the difference rate of the voltage response curve all meet the corresponding preset safety threshold requirements, the corresponding moment is determined to be a safe moment for formal polarity reversal. If the difference rate of the voltage response curve is not greater than a preset first difference value, the inverted voltage rise rate corresponding to the voltage loading method is determined as the first rate. If the difference rate of the voltage response curve is greater than a preset first difference value, the inverted voltage rise rate corresponding to the voltage loading mode is determined as the second rate; wherein, the first rate is greater than the second rate.

6. The method for polarity reversal processing of high-voltage DC cables based on residual space charge memory effect as described in claim 1, characterized in that, Also includes: If, during the application of the preset voltage sequence, the degree of dissipation of residual charge does not meet the preset safety criterion within the preset application time, an insulation defect alarm signal is generated.

7. A high-voltage DC cable polarity reversal processing device based on residual space charge memory effect, characterized in that, include: The current charge dissipation response signal acquisition module is used to acquire the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of a preset voltage sequence; The charge dissipation degree judgment module is used to determine the degree of dissipation of residual charge inside the high-voltage DC cable to be processed based on the current charge dissipation response signal. The polarity reversal information determination module is used to extract response feature parameters based on the current charge dissipation response signal when the degree of residual charge dissipation meets the preset safety criteria, and to determine the safe moment of formal polarity reversal and voltage loading method based on the response feature parameters. The polarity reversal operation module is used to perform a formal polarity reversal operation on the high-voltage DC cable to be processed according to the voltage loading method at the safe moment.

8. The high-voltage DC cable polarity reversal processing device based on residual space charge memory effect as described in claim 7, characterized in that, The current charge dissipation response signal acquisition module is used to acquire the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of a preset voltage sequence, including: Obtain historical operating information of the high-voltage DC cable to be processed before re-pressurization after formal polarity reversal or shutdown; Calculate the residual charge memory risk index based on the historical operating information; When the residual charge memory risk index is greater than or equal to a preset risk threshold, a preset voltage sequence is applied to the high-voltage DC cable to be processed, and the current charge dissipation response signal of the high-voltage DC cable to be processed during the application of the preset voltage sequence is obtained.

9. A terminal device, characterized in that, The device includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor, when executing the computer program, implements a high-voltage DC cable polarity reversal processing method based on the residual space charge memory effect as described in any one of claims 1 to 6.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to perform a high-voltage DC cable polarity reversal processing method based on the residual space charge memory effect as described in any one of claims 1 to 6.

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