Submarine cable performance test system and test method

Abstract

The invention discloses a submarine cable performance test system and method, and the system achieves the synchronous application of two voltages through a DC impact superposition module, and a DC blocking saturable reactor effectively isolates a DC source from an impact loop, avoids the impact waveform from the internal resistance of the DC power supply, and improves the performance of a submarine cable. Meanwhile, dynamic distribution of space charges, dielectric loss change and partial discharge characteristic quantity are synchronously acquired through the composite data acquisition module, synchronous acquisition and comprehensive analysis of multiple physical quantities are realized, and the problem that a traditional discrete test cannot reflect the actual working condition coupling effect is solved; and a reliable test means is provided for evaluating the insulation performance degradation rule of the submarine cable under the action of complex electromagnetic stress, so that the performance test accuracy of the submarine cable is improved.

Description

Technical Field

[0001] This application relates to the field of submarine cable performance testing technology, and in particular to a submarine cable testing system and testing method. Background Technology

[0002] With the rapid development of large-capacity, long-distance DC transmission and AC / DC hybrid systems, submarine / land-based extruded insulated cables and their accessories are subjected to steady-state DC electric fields in scenarios such as converter station outgoing lines, submarine cable landing sections, and inter-regional interconnections. They also experience high-steep impulse voltages under events such as lightning strikes, switching overvoltages, grounding faults, switching operations, and converter malfunctions. This complex operating condition causes the cable insulation medium to exhibit not only nonlinear conductivity characteristics related to temperature and field strength, but also carrier injection / capture, space charge accumulation, and interface polarization, leading to local electric field redistribution and threshold drift. When the impulse front arrives at high speed, the charge and polarization states formed under the aforementioned DC prestress will superimpose with the transient voltage, producing peak local field strength and discharge susceptibility far more severe than in a single test.

[0003] Existing type / factory and acceptance tests mostly employ discrete methods, such as DC withstand voltage, lightning or switching impulse, partial discharge, and dielectric loss / dielectric spectrum, which are independent items. While these discrete tests can verify individual cable performance indicators, they cannot realistically simulate the coupled conditions of "DC bias + lightning / switching impulse" commonly encountered in actual operation. Under such coupled conditions, the performance of the cable insulation material deviates significantly from the test results under single test conditions, making it difficult for existing testing methods to accurately assess the cable's true performance under actual operating conditions. Summary of the Invention

[0004] This application provides a submarine cable performance testing system and method to achieve the invention objective of improving the accuracy of cable performance testing.

[0005] To achieve the above-mentioned objectives, the first aspect of this application provides a submarine cable performance testing system, comprising: a control module, a bipolar DC high-voltage source, a temperature control module, an impulse voltage generator, a DC impulse superposition module, and a composite data acquisition module, wherein the DC impulse superposition module comprises: a DC blocking saturated reactor, a coupling capacitor, and a current limiting module, and the temperature control module is used to adjust the test temperature of the cable under test;

[0006] The DC blocking saturated reactor is connected in series with the bipolar DC high voltage source and the cable under test. The impulse voltage generator is connected to the cable under test through the coupling capacitor. The current limiting module is set between the coupling capacitor and the cable under test to limit the current and protect the cable under test.

[0007] The composite data acquisition module includes multiple acquisition components, which are electrically connected to different acquisition points in the cable under test, and are used to acquire performance test data of the cable under test.

[0008] The control module is communicatively connected to the bipolar DC high voltage source, the temperature control module, the impulse voltage generator, and the composite data acquisition module, respectively, and is used to control the operation of the bipolar DC high voltage source, the temperature control module, the impulse voltage generator, and the composite data acquisition module, and to determine the performance test results of the cable under test based on the performance test data received from the composite data acquisition module.

[0009] Preferably, the acquisition components include: a PEA space charge acquisition component, a partial discharge data acquisition component, a dielectric spectrum data acquisition component, and an electric field data acquisition component.

[0010] Preferably, the coupling capacitor is a programmable coupling capacitor.

[0011] Preferably, the DC impulse superposition module is provided with a DC source protection branch, which provides bypass protection for the bipolar DC voltage source when energy is discharged or abnormal after the impulse.

[0012] The second aspect of this application provides a method for testing the performance of submarine cables, applied to the submarine cable performance testing system provided in the first aspect of this application, comprising:

[0013] The control module sends operating commands to the bipolar DC high voltage source, the temperature control module, and the impulse voltage generator, respectively, so that the bipolar DC high voltage source and the impulse voltage generator apply composite stress to the cable under test through the DC impulse superposition module. The temperature control module is used to adjust the test temperature of the cable under test in response to the operating commands.

[0014] The composite data acquisition module collects performance test data of the cable under test under the conditions of composite stress and test temperature.

[0015] Based on the performance test data, the composite stress tolerance index and the straightening interactive aging coefficient are obtained by using the preset comprehensive index calculation formula and the straightening interactive aging coefficient calculation formula, respectively.

[0016] Based on the composite stress tolerance index and the straightening interaction aging coefficient, and combined with the comparison results of the performance test data and the preset performance data threshold, the performance test results of the cable under test are determined.

[0017] Preferably, the performance test data includes: partial discharge amplitude, impact overthreshold count, relative change of space charge relaxation time, relative change of dielectric loss tangent, relative change of local electric field peak value, polarity reversal index, and drift of partial discharge initiation voltage under different polarities, wherein the impact overthreshold count is the number of partial discharge signal pulses whose pulse amplitude exceeds a preset threshold in a set of impact tests.

[0018] Preferably, the formula for calculating the comprehensive index is:

[0019]

[0020] In the formula, CSI is the composite stress tolerance index. This is the normalized value of the partial discharge amplitude; This is the normalized value of the threshold count. This represents the relative change in space charge relaxation time. This represents the relative change of the dielectric loss tangent. This represents the relative change in the peak value of the local electric field. This is the normalized value of the polarity reversal index; This represents the drift of the partial discharge initiation voltage under different polarities. ~ These are the weighting coefficients for each performance test data point.

[0021] Preferably, the formula for calculating the straightening interaction aging coefficient is:

[0022]

[0023] In the formula, The straight-line interaction aging coefficient, This is the DC bias voltage. For impulse voltage, A, B, and C are fitting coefficients related to voltage level, and m, n, p, and q are exponential coefficients obtained through fitting, used to represent the nonlinear relationship of the impact of different types of voltage on equipment damage.

[0024] Preferably, when the coupling capacitor in the DC impulse superposition module is a programmable capacitor, it further includes:

[0025] The capacitance value of the coupling capacitor is adjusted according to the preset impact voltage division formula.

[0026] Preferably, the impact pressure distribution relationship is as follows:

[0027]

[0028] In the formula, This refers to the impulse voltage that the cable under test experiences. The impulse voltage output by the impulse voltage generator. This is the capacitance value of the coupling capacitor. This is the capacitance value of the cable under test.

[0029] As can be seen from the above technical solutions, this application has the following advantages:

[0030] The solution provided in this application achieves the synchronous application of two voltages through a DC impulse superposition module. The DC blocking saturated reactor effectively isolates the DC source and the impulse circuit, avoiding the influence of the DC power supply's internal resistance on the impulse waveform. It reproduces composite stress and collects multiple physical quantity characteristics. At the same time, the composite data acquisition module synchronously acquires the dynamic distribution of space charge, the change of dielectric loss, and the characteristics of partial discharge, realizing the synchronous acquisition and comprehensive analysis of multiple physical quantities. This solves the problem that traditional discrete tests cannot reflect the coupling effect of actual working conditions, and provides a reliable test method for evaluating the insulation performance degradation law of submarine cables under complex electromagnetic stress, thereby improving the accuracy of performance testing of submarine cables. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the architecture of an embodiment of a submarine cable performance testing system provided in this application.

[0033] Figure 2 This is a flowchart illustrating an embodiment of a submarine cable performance testing method provided in this application.

[0034] Figure 3 This is an overall logic block diagram of an embodiment of a submarine cable performance testing method provided in this application. Detailed Implementation

[0035] In traditional technologies, the rapid development of DC power transmission and AC / DC hybrid systems has resulted in submarine cables enduring the combined stress of a steady-state DC electric field and a high-slope impulse voltage over extended periods. Traditional discrete testing methods, which involve independent DC withstand voltage testing, impulse testing, and partial discharge detection, cannot simulate the coupling effect of DC bias and transient impulse under actual operating conditions. When the cable insulation medium accumulates space charge and reaches a polarized state under DC prestress, the superimposed transient impulse voltage leads to local electric field distortion and increased discharge sensitivity, causing significant deviations between laboratory test results and actual operational performance.

[0036] To address the aforementioned issues, it is necessary to construct a composite stress testing environment capable of simultaneously applying DC bias voltage and impulse voltage, while also achieving dynamic temperature control and multi-dimensional data acquisition. Therefore, this application provides a submarine cable performance testing system and method to achieve the inventive objective of improving the accuracy of cable performance testing.

[0037] To make the inventive objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] First, a detailed description of an embodiment of a submarine cable performance testing system provided in this application is as follows:

[0039] Please see Figure 1 This application provides an embodiment of a submarine cable performance testing system, comprising: a control module, a bipolar DC high voltage source, a temperature control module, an impulse voltage generator, a DC impulse superposition module, and a composite data acquisition module. The DC impulse superposition module includes: a DC blocking saturated reactor, a coupling capacitor, and a current limiting module. The temperature control module is used to adjust the test temperature of the cable under test.

[0040] The DC blocking saturated reactor is connected in series with the bipolar DC high voltage source and the cable under test. The impulse voltage generator is connected to the cable under test through the coupling capacitor. The current limiting module is set between the coupling capacitor and the cable under test to limit the current and protect the cable under test.

[0041] The composite data acquisition module includes multiple acquisition components, which are electrically connected to different acquisition points in the cable under test, and are used to acquire performance test data of the cable under test.

[0042] The control module is communicatively connected to the bipolar DC high voltage source, the temperature control module, the impulse voltage generator, and the composite data acquisition module, respectively, and is used to control the operation of the bipolar DC high voltage source, the temperature control module, the impulse voltage generator, and the composite data acquisition module, and to determine the performance test results of the cable under test based on the performance test data received from the composite data acquisition module.

[0043] Among them, the DC blocking saturated reactor refers to an inductive device with DC current saturation characteristics. It can be implemented using an iron-based amorphous alloy magnetic core, exhibiting low DC impedance and high AC impedance, used to isolate DC sources from impulse circuits. The coupling capacitor is a capacitive element used for impulse voltage transmission, specifically composed of polypropylene film capacitors connected in series, achieving efficient coupling of impulse voltage to the cable under test. The current limiting module is a protection device with nonlinear volt-ampere characteristics, specifically implemented using a combination of a zinc oxide varistor and a fast-acting fuse, used to suppress the amplitude of impulse current. The composite data acquisition module includes multiple acquisition components, which are sensor arrays for different physical quantities. Specifically, it can be implemented by combining a distributed fiber optic temperature measurement unit with a high-frequency current transformer to simultaneously acquire space charge distribution and partial discharge signals. A bipolar DC high voltage source (HVDC, High Voltage Direct Current) is used to provide bipolar DC bias, covering a range of ±50 kV to ±800 kV. The ripple is <0.1% to avoid the bias ripple affecting the repeatability of PD / PEA. The impulse voltage generator can be a Marx-type generator, which can output a 1.2 / 50 μs (lightning) or 250 / 2500 μs (operation) standard waveform with adjustable amplitude and leading / falling edges, for applying transient high stress.

[0044] In order to prevent the impulse voltage from flowing back to HVDC, the DC blocking saturated reactor is selected such that the equivalent angular frequency at the impulse leading edge is [value missing]. (1.2 μs front is acceptable) Under the level of (number), the requirements are:

[0045]

[0046] This makes it exhibit high resistance to impacts and low voltage drop to DC. A saturated core is also selected to reduce DC power consumption and improve volume utilization.

[0047] Specifically, a bipolar DC high-voltage source applies positive and negative DC voltages to the cable under test through a DC-blocking saturated reactor, forming a steady-state electric field environment. An impulse voltage generator injects standard lightning or operational waves into the cable through a coupling capacitor, while a current-limiting module suppresses the impulse current amplitude to prevent cable damage. A temperature control module regulates the cable conductor temperature using a circulating oil bath or resistance heating method, simulating actual operating temperature rise. The space charge detection unit in the composite data acquisition module measures the charge distribution in the insulation layer using the electroacoustic pulse method, the partial discharge detection unit captures discharge pulses using a high-frequency current sensor, and the dielectric loss detection unit measures the loss tangent using the bridge method. The control module coordinates the working sequence of each unit through an industrial bus, collects multi-dimensional data, and calculates the composite stress tolerance index and aging coefficient to obtain the characteristics of the cable under test.

[0048] This scheme achieves simultaneous application of two voltages through a DC impulse superposition module. A DC blocking saturated reactor effectively isolates the DC source from the impulse circuit, avoiding the influence of the DC power supply's internal resistance on the impulse waveform. The composite data acquisition module overcomes the limitations of single-parameter detection, simultaneously acquiring dynamic distribution of space charge, changes in dielectric loss, and partial discharge characteristics, providing a data foundation for evaluating insulation performance degradation under combined stress. Through the above technical solutions, this application can realistically simulate the combined stress environment of DC bias and transient impulse superposition, precisely control the test temperature gradient, and achieve simultaneous acquisition and comprehensive analysis of multiple physical quantities. This scheme effectively solves the problem that traditional discrete tests cannot reflect the coupling effect of actual operating conditions, providing a reliable testing method for evaluating the insulation performance degradation law of submarine cables under complex electromagnetic stress.

[0049] Based on the above basic embodiments, this application further proposes a data acquisition component including a PEA space charge acquisition component, a partial discharge data acquisition component, a dielectric spectrum data acquisition component, and an electric field data acquisition component.

[0050] The PEA space charge acquisition component refers to a device that measures the distribution of space charge inside insulating materials based on the principle of electroacoustic pulse method. Specifically, it can be implemented using a high-voltage pulse generator and a piezoelectric sensor, applying nanosecond-level high-voltage pulses to excite acoustic signals and invert the charge distribution state. The partial discharge data acquisition component is a system for detecting partial discharge signals caused by defects in cable insulation. Specifically, it can be implemented using a combination of a high-frequency current transformer and a digital oscilloscope to capture the amplitude, phase, and repetition rate of the discharge pulse. The dielectric spectrum data acquisition component is a device for measuring the dielectric response spectrum characteristics of cable insulation materials. Specifically, it can be implemented using a wideband LCR tester and a temperature control unit to acquire changes in dielectric loss and capacitance at different frequencies. The electric field data acquisition component is a device for monitoring the electric field strength inside or at the interface of cable insulation layers. Specifically, it can be implemented using an embedded electric field sensor and a fiber optic transmission system to record the dynamic electric field distribution in real time.

[0051] Specifically, during the composite stress test, the PEA space charge acquisition component measures the accumulation of space charge within the cable insulation layer using the electroacoustic pulse method. The partial discharge data acquisition component simultaneously acquires the partial discharge signal induced by the superposition of DC bias and impulse. The dielectric spectrum data acquisition component measures the spectral lines of the dielectric loss tangent as a function of frequency under different temperature conditions. The electric field data acquisition component records the spatiotemporal evolution of the electric field intensity within the insulation layer through a distributed sensor network. These four components achieve data synchronization through the timing control unit of the composite data acquisition module, comprehensively covering four key parameters: charge dynamics, discharge behavior, dielectric response, and electric field distribution.

[0052] This scheme, through the collaborative acquisition of multiple physical quantities, achieves for the first time spatiotemporal correlation analysis of four types of data: charge injection, polarization response, discharge development, and field strength distortion. Using the above technical solution, this application can comprehensively capture key phenomena such as charge migration, interface polarization, discharge initiation, and sudden field strength changes in cable insulation materials under the superimposed coupling of DC bias and impact, providing multi-dimensional data support for accurately assessing composite stress tolerance and solving the problem of performance misjudgment caused by the lack of parameter correlation in discrete testing.

[0053] Based on the above basic embodiments, this application further proposes that the coupling capacitor be a programmable coupling capacitor. A programmable coupling capacitor refers to a capacitive device whose capacitance value can be dynamically adjusted by an external control signal. Specifically, it can be implemented using a digitally controlled variable capacitor array or a vacuum-sealed capacitor structure based on electromechanical adjustment. This feature ensures that the impulse voltage division relationship meets the test requirements by changing the capacitance value to match the equivalent capacitance of different cables under test.

[0054] Specifically, during the testing process, when the equivalent capacitance of the cable under test changes, the capacitance value of the programmable coupling capacitor is automatically adjusted through a preset program or real-time feedback. For example, when the length of the cable under test increases, leading to an increase in the equivalent capacitance, the capacitance value of the coupling capacitor can be simultaneously increased to more than ten times the equivalent capacitance, ensuring that more than 90% of the impulse voltage is applied to the cable under test, with the remaining portion borne by the coupling capacitor. This adjustment process is based on the voltage divider formula. By controlling the ratio of the capacitance values ​​of the coupling capacitor and the cable under test, the impulse voltage waveform is faithfully transmitted on the cable, avoiding deviations from the preset value due to voltage divider errors. This solution, through the active adjustment capability of the programmable capacitor, can dynamically adapt to the equivalent capacitance parameters of different cables, eliminating voltage divider errors caused by sample differences. Through the above technical solution, this application achieves precise control of the impulse voltage applied to cables of different specifications, ensuring that the superposition relationship between the impulse voltage component and the DC bias voltage in the composite stress test conforms to the actual working conditions, thus guaranteeing that most of the impulse voltage falls on the cable under test.

[0055] Based on the above basic embodiments, this application further proposes that the DC impulse superposition module is equipped with a DC source protection branch, which is used to provide bypass protection for the bipolar DC voltage source when energy is discharged or abnormal after the impulse.

[0056] The DC source protection branch refers to a discharge circuit consisting of a fast-switching device and a current-limiting resistor connected in series. Specifically, a thyristor or IGBT can be used as the switching device, along with a zinc oxide varistor for overvoltage triggering. This branch forms a low-impedance path after the impulse voltage is applied, dissipating residual energy through the current-limiting resistor and preventing reverse current from impacting the DC source. The bypass protection isolates the DC source from the impulse circuit by switching devices when an abnormal DC source port voltage is detected. Specifically, a voltage sensor can monitor the DC source output voltage in real time, triggering protection action when the voltage exceeds a set threshold.

[0057] Specifically, during the application of the impulse voltage, the DC source protection branch is in an open state to ensure the normal superposition of composite stress. After the impulse ends, when residual energy is transferred in reverse to the DC source port through the coupling capacitor, the fast switching device is triggered to conduct, forming a discharge circuit. If an overvoltage or short circuit abnormality occurs in the DC source during the impulse test, the current-limiting resistor in the protection branch can suppress the surge current, and at the same time, the bypass switch will disconnect the DC source from the main circuit. This protection mechanism is implemented through the coordinated use of hardware circuits and software criteria, such as using multi-level voltage threshold judgment logic, combined with the impulse waveform timing control to control the delay time of the protection action.

[0058] This solution actively discharges energy through an independently designed protection branch, resolving the energy interference issue between the DC source and the impact circuit in composite stress testing, while also reducing the risk of equipment damage due to abnormal operating conditions. Through the above technical solution, this application achieves multiple protections for the bipolar DC voltage source, effectively preventing cumulative damage to the DC source power module from reverse pulse voltage during impact testing, ensuring the stable operation of the test system under continuous impact conditions, and extending the service life of critical equipment.

[0059] The above is a detailed description of an embodiment of a submarine cable performance testing system provided in this application. The following is a detailed description of an embodiment of a submarine cable performance testing method applied to the above testing system provided in this application.

[0060] Please see Figure 2 and Figure 3 An embodiment of a submarine cable performance testing method provided in this application includes:

[0061] Step 101: The control module sends operation commands to the bipolar DC high voltage source, temperature control module, and impulse voltage generator respectively, so that the bipolar DC high voltage source and impulse voltage generator apply composite stress to the cable under test through the DC impulse superposition module. The temperature control module is used to adjust the test temperature of the cable under test in response to the operation command.

[0062] Step 102: Collect performance test data of the cable under test under composite stress and test temperature conditions using the composite data acquisition module;

[0063] Step 103: Based on the performance test data, obtain the composite stress tolerance index and the straightening interactive aging coefficient by using the preset comprehensive index calculation formula and the straightening interactive aging coefficient calculation formula, respectively.

[0064] Step 104: Based on the composite stress tolerance index and the straightening interaction aging coefficient, and combined with the comparison results of the performance test data and the preset performance data threshold, determine the performance test results of the cable under test.

[0065] The composite stress refers to the electrical stress formed by the superposition of the DC bias voltage output from the bipolar DC high-voltage source and the transient impulse voltage output from the impulse voltage generator. Specifically, this can be achieved by coupling the DC and impulse signals through the DC blocking saturated reactor and coupling capacitor in the DC impulse superposition module, simulating the superposition of DC steady-state and impulse transient conditions during actual cable operation. Test temperature regulation refers to changing the temperature of the environment in which the cable under test is located through a temperature control module, such as using a circulating liquid heating or cooling device, to simulate temperature changes in submarine cables at different depths or in different seasons. The composite data acquisition module includes various acquisition components, such as partial discharge sensors and dielectric loss measurement units, to simultaneously acquire multi-dimensional performance parameters of the cable under composite stress. The comprehensive index calculation formula is a weighted normalization model, integrating parameters such as partial discharge amplitude and impulse over-threshold count into a single index according to weights, to quantify the cable's ability to withstand composite stress. The impulse-DC interaction aging coefficient calculation formula is a nonlinear fitting equation, characterizing the synergistic effect of the DC voltage and impulse voltage on the accelerated aging of insulation through the product term of the two.

[0066] Based on this, the performance test data mentioned in this embodiment specifically includes: partial discharge amplitude, impact overthreshold count, relative change of space charge relaxation time, relative change of dielectric loss tangent, relative change of local electric field peak value, polarity reversal index, and drift of partial discharge initiation voltage under different polarities. The impact overthreshold count is the number of partial discharge signal pulses whose pulse amplitude exceeds a preset threshold in a set of impact tests.

[0067] The partial discharge amplitude refers to the peak value of the instantaneous current or voltage generated during partial discharge, which can be achieved using a high-frequency current transformer or a capacitively coupled sensor, and is used to characterize the discharge intensity of insulation defects. The impact threshold count refers to the number of times the partial discharge pulse exceeds a preset voltage threshold during an impact test, which can be achieved using a high-speed data acquisition card in conjunction with a threshold comparison circuit, and is used to quantify the instantaneous impact damage degree of the impact voltage on the insulation system. The relative change in space charge relaxation time refers to the offset of the space charge dissipation time in the cable insulation relative to the initial state, which can be measured using the electroacoustic pulse method or the pressure wave method, and is used to reflect the changes in material polarization characteristics caused by charge accumulation under DC bias voltage. The relative change in the dielectric loss tangent refers to the offset ratio of the dielectric loss characteristics of the insulating material relative to a reference value, which can be measured using a broadband dielectric impedance spectrometer, and is used to characterize the nonlinear changes in dielectric polarization loss under composite stress. The relative change in the peak value of the local electric field refers to the offset ratio of the maximum electric field intensity in the cable insulation layer relative to the initial state, which can be obtained using an electric field probe or an inversion algorithm based on the Poisson equation, and is used to evaluate the dynamic influence of space charge distortion on the electric field distribution. The polarity reversal index refers to the ratio of transient overvoltage to steady-state voltage generated during DC voltage polarity switching. It can be measured using a high-speed voltage recorder in conjunction with a polarity switching control unit to quantify the additional stress of polarity reversal on the insulation system. The drift of the partial discharge initiation voltage under different polarities refers to the difference in the partial discharge initiation voltage under positive and negative DC voltage conditions. It can be measured using a stepped voltage boost method in conjunction with a partial discharge detection system to characterize the asymmetric influence of the electric field direction on the discharge characteristics of insulation defects.

[0068] Specifically, during the test, the control module first coordinates the output of the bipolar DC high-voltage source and the impulse voltage generator to achieve the preset DC bias voltage and impulse waveform. A DC blocking saturated reactor suppresses DC interference to the impulse source, while a coupling capacitor transmits the impulse voltage to the cable under test. The temperature control module adjusts the temperature of the medium surrounding the cable according to a preset program, for example, by gradually increasing the temperature within a range of 30℃ to 90℃. The composite data acquisition module records data such as partial discharge and dielectric loss of the cable under composite stress in real time and uploads the data to the control module. The control module inputs the collected data into a comprehensive index calculation formula, for example, normalizing the partial discharge amplitude and multiplying it by a weighting coefficient, then weighted and summing it with other parameters to obtain the composite stress tolerance index. Simultaneously, the synergistic aging effect of DC and impulse voltage is calculated using the impulse-DC interactive aging coefficient calculation formula, for example, by nonlinearly superimposing the quadratic term of the DC voltage with the linear term of the impulse voltage. Finally, by comparing the tolerance index, aging coefficient, and preset thresholds, for example, it determines whether the composite stress tolerance index is below a critical value, thus determining whether the cable meets the actual operating requirements.

[0069] More specifically, the data processing and cable evaluation analysis process proposed in this embodiment can be seen in the following example:

[0070] (1) Acquire raw data at different times. During the DC superimposed impact period: continuously sample PD (UHF / HFCT) and record. ;

[0071] (2) During the disturbance-free window (after each set of impacts, all transients that would interfere with the measurement have decayed to below the preset threshold, the applied voltage is in a stable DC bias state, and the on-site electromagnetic / acoustic environment has recovered to near the baseline): trigger PEA and reconstruct Calculate the interface charge integral And fit the relaxation time Perform FDS / tanδ three-point scan;

[0072] Criteria for determining the disturbance-free window period: a stable voltage, such as a DC bias. Ripple ≤ 0.1%; Residual voltage of coupling circuit drops to ≤ 1% of initial value; UHF band energy returns to within ±3dB of the pre-group baseline; HFCT over-threshold count drops to below the baseline mean +2σ; PEA oscilloscope reference channel noise ≤ calibration limit (e.g., 1–2% of full scale), and no visible ringing on the oscilloscope.

[0073] (3) During polarity reversal (referring to changing the applied polarity in the test sequence, mainly DC bias) The positive and negative values, including impulse voltage when necessary. The positive or negative sign of the charge / polarization and the time it takes for the test sample to transition from the charge / polarization state established by the old polarity to the steady state of the new polarity, which is between two sets of impact tests, is used to ensure that the space charge and threshold under the new polarity have formed a repeatable initial state before proceeding to the next set of impact tests: (Complete) Four-quadrant sequences form comparable data with the same conditions but different polarities.

[0074] (4) Characteristic quantities, CSI and lifetime model:

[0075] PD index: Overthreshold count for each group =5 pC or 3 × noise rms, whichever is greater), where each group is counted for over-threshold ( This refers to the number of partial discharge (PD) signal pulses whose amplitude exceeds a preset partial discharge threshold during each set of impact tests. When the PD signal exceeds this threshold, it is considered to be a valid partial discharge signal.

[0076] Space charge measurement results: interface peak value, profile centroid displacement relaxation half-life and relative changes , ;

[0077] Polarity-sensitive characteristic: Reversal index Charge extraction is performed using the interface integral of PEA;

[0078] To evaluate the cable insulation's ability to withstand combined stress from DC superimposed impulse voltage, a comprehensive evaluation index (CSI) is obtained by weighted summation of multiple key characteristics, as follows:

[0079]

[0080] in: This is the normalized value (after stabilization) of the partial discharge (PD) amplitude; This is the normalized value of the over-threshold count for each group of impact tests; Characterizes the relative change in space charge relaxation time and quantifies the stability change in charge distribution; The relative change in the dielectric loss tangent (tan δ) characterizes the performance changes of the insulating material. To quantify the fluctuation of electric field intensity by representing the relative change in the peak value of the local electric field; polarity reversal index. Describes the sensitivity to charge reversal under different polarities; The weighting coefficients represent the drift of PDIV (partial discharge initiation voltage) under different polarities, characterizing the change in voltage threshold. This ensures that the contribution of each feature to CSI is reasonable, and that the sum of all weights is equal. To ensure overall normalization (using the median / MAD of the samples for normalization, so that all features are on the same scale (between 0 and 1)).

[0081] While obtaining performance test data through the aforementioned accelerated aging test (applying a DC superimposed impulse voltage to simulate the overvoltage impact on the cable under actual operating conditions), this application further uses DC bias voltage... and impulse voltage Combined with the preset formula for calculating the aging coefficient of the straightening interaction

[0082] The formula for calculating the aging coefficient of straightening interaction is:

[0083]

[0084] Among them, A, B, and C are fitting coefficients related to voltage level, which are usually obtained by fitting the accelerated aging test data mentioned above, and represent the degree of influence of DC voltage and impulse voltage on equipment performance. These are the DC bias voltage and the impulse voltage, respectively; m, n, p, and q are exponential coefficients representing the nonlinear relationship between the impact of different types of voltage on equipment damage.

[0085] Straightening interaction aging coefficient It is used to quantize "DC bias" "and impulse voltage" The interaction term in KDI refers to the strength parameter of the mutual promotion of aging rate by the two factors. For example, when DC bias and shock factors act independently, the aging rate is simply approximated as additive. If the superposition is faster than the simple addition of the aging results, the interaction term corresponding to KDI is positive ("synergistic"); if there is no mutual promotion, the interaction term ≈ 0; if "antagonism" occurs, the interaction term can be small or even negative, for example:

[0086] <0.1: weak interaction (almost like linear superposition);

[0087] Interaction level is moderate;

[0088] >0.3: Strong interaction (strong collaboration, significantly shortened lifespan).

[0089] Finally, based on the tolerance index, aging coefficient, and the comparison results of various performance test data with the corresponding preset thresholds, it is determined whether the cable meets the actual working conditions requirements, for example:

[0090] Performance test pass conditions: Any group ; ; ; and ;

[0091] Critical conditions for performance test results: ; or any single item is close to the limit (within ±20%); K DI Show cross items Furthermore, the isochronous lifetime curve is shortened by 20–40% compared to the baseline.

[0092] Performance test failed: ; or any group ; Or a persistent charge reversal may occur (not recovering after 30 minutes); and .

[0093] In addition, when the capacitance value of the cable under test changes, the programmable capacitor automatically adjusts its capacitance value according to the impulse voltage division formula. For example, the coupling capacitor is set to more than 10 times the cable capacitance to ensure that the impulse voltage is effectively applied to the cable.

[0094] More specifically, the relationship between the impact partial pressures is:

[0095]

[0096] In order to make ≈ Based on engineering experience ≥10 This can reduce the voltage division error to less than 10% and preserve waveform fidelity. Programmable switching is used to match different samples. .

[0097] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application 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 this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0098] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances. The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A submarine cable performance testing system, characterized in that, include: The system includes a control module, a bipolar DC high-voltage source, a temperature control module, an impulse voltage generator, a DC impulse superposition module, and a composite data acquisition module. The DC impulse superposition module includes a DC blocking saturated reactor, a coupling capacitor, and a current limiting module. The temperature control module is used to adjust the test temperature of the cable under test. The DC blocking saturated reactor is connected in series with the bipolar DC high voltage source and the cable under test. The impulse voltage generator is connected to the cable under test through the coupling capacitor. The current limiting module is set between the coupling capacitor and the cable under test to limit the current and protect the cable under test. The composite data acquisition module includes multiple acquisition components, which are electrically connected to different acquisition points in the cable under test, and are used to acquire performance test data of the cable under test. The control module is communicatively connected to the bipolar DC high voltage source, the temperature control module, the impulse voltage generator, and the composite data acquisition module, respectively, and is used to control the operation of the bipolar DC high voltage source, the temperature control module, the impulse voltage generator, and the composite data acquisition module, and to determine the performance test results of the cable under test based on the performance test data received from the composite data acquisition module.

2. The submarine cable performance testing system according to claim 1, characterized in that, The acquisition components include: a PEA space charge acquisition component, a partial discharge data acquisition component, a dielectric spectrum data acquisition component, and an electric field data acquisition component.

3. The submarine cable performance testing system according to claim 1, characterized in that, The coupling capacitor is specifically a programmable coupling capacitor.

4. The submarine cable performance testing system according to claim 1, characterized in that, The DC impulse superposition module is equipped with a DC source protection branch, which provides bypass protection for the bipolar DC voltage source when energy is discharged or abnormal after the impulse.

5. A method for testing the performance of submarine cables, applied to the submarine cable performance testing system as described in any one of claims 1 to 4, characterized in that, include: The control module sends operating commands to the bipolar DC high voltage source, the temperature control module, and the impulse voltage generator, respectively, so that the bipolar DC high voltage source and the impulse voltage generator apply composite stress to the cable under test through the DC impulse superposition module. The temperature control module is used to adjust the test temperature of the cable under test in response to the operating commands. The composite data acquisition module collects performance test data of the cable under test under the conditions of composite stress and test temperature. Based on the performance test data, the composite stress tolerance index and the straightening interactive aging coefficient are obtained by using the preset comprehensive index calculation formula and the straightening interactive aging coefficient calculation formula, respectively. Based on the composite stress tolerance index and the straightening interaction aging coefficient, and combined with the comparison results of the performance test data and the preset performance data threshold, the performance test results of the cable under test are determined.

6. The method for testing the performance of a submarine cable according to claim 5, characterized in that, The performance test data includes: partial discharge amplitude, impact overthreshold count, relative change of space charge relaxation time, relative change of dielectric loss tangent, relative change of local electric field peak value, polarity reversal index, and the drift of partial discharge initiation voltage under different polarities. The impact overthreshold count is the number of partial discharge signal pulses whose pulse amplitude exceeds a preset threshold in a set of impact tests.

7. The method for testing the performance of a submarine cable according to claim 6, characterized in that, The formula for calculating the comprehensive index is as follows: In the formula, CSI is the composite stress tolerance index. This is the normalized value of the partial discharge amplitude; This is the normalized value of the threshold count. This represents the relative change in space charge relaxation time. This represents the relative change of the dielectric loss tangent. This represents the relative change in the peak value of the local electric field. This is the normalized value of the polarity reversal index; This represents the drift of the partial discharge initiation voltage under different polarities. ~ These are the weighting coefficients for each performance test data point.

8. The method for testing the performance of a submarine cable according to claim 6, characterized in that, The formula for calculating the straightening interaction aging coefficient is as follows: In the formula, The straight-line interaction aging coefficient, This is the DC bias voltage. For impulse voltage, A, B, and C are fitting coefficients related to voltage level, and m, n, p, and q are exponential coefficients obtained through fitting, used to represent the nonlinear relationship of the impact of different types of voltage on equipment damage.

9. The method for testing the performance of a submarine cable according to claim 5, characterized in that, When the coupling capacitor in the DC impulse superposition module is a programmable capacitor, it also includes: The capacitance value of the coupling capacitor is adjusted according to the preset impact voltage division formula.

10. A method for testing the performance of a submarine cable according to claim 9, characterized in that, The specific impact pressure relationship is as follows: In the formula, This refers to the impulse voltage that the cable under test experiences. The impulse voltage output by the impulse voltage generator. This is the capacitance value of the coupling capacitor. This is the capacitance value of the cable under test.

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