Cable buffer layer ablation judgment method, system and equipment and storage medium
By using sinusoidal voltage tests of different frequencies in the cable buffer layer and solving a system of equations based on Ohm's law in complex form, the accuracy problem of resistivity measurement in the cable buffer layer was solved, and the accuracy of cable erosion judgment and repair assessment was achieved.
Patent Information
- Application Number
- CN202511301097.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-12
- Publication Date
- 2025-12-09
AI Technical Summary
Existing technologies make it difficult to accurately test the volume resistivity of cable buffer layers, leading to inaccurate assessments of cable buffer layer erosion and difficulties in repair evaluation.
The cable was tested using sinusoidal voltages of different angular frequencies. An equivalent circuit model of the cable, including the buffer layer resistance and grounding impedance, was established. The buffer layer resistance value was solved by solving a system of equations using Ohm's law in complex form. The measurement time was aligned by combining the satellite synchronization system to eliminate the influence of grounding resistance and inductance.
It achieves high-precision measurement of the resistivity of the cable buffer layer, accurately judges the erosion situation, and evaluates the repair effect by comparing the resistivity before and after repair, providing a scientific basis for cable maintenance.
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Figure CN121090609A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a resistance testing method and system for judging cable buffer layer erosion and evaluating repair, and more particularly to a method, system, device and storage medium for judging cable buffer layer erosion. Background Technology
[0002] In recent years, numerous cases of high-voltage cable buffer layer erosion have emerged. The main reason behind this is that the water-blocking powder in the buffer layer reacts chemically with the metal sheath when damp, forming metal oxides with high resistivity. This causes localized current concentration and heat generation, leading to the erosion of the buffer layer. To address this problem, existing cable buffer layer erosion repair methods typically involve injecting a semi-conductive repair liquid into the cable buffer layer to impregnate it and reduce its resistivity. However, accurately testing the volume resistivity of the buffer layer remains a significant challenge.
[0003] Since the buffer layer is located between the cable's outer shield and the metal sheath, there are two problems if the resistance is simply measured using these two as electrodes: First, the resistance of the buffer layer is comparable to that of the cable's outer shield, which may result in additional resistance along the cable's axial direction and cause the test results to be too high; second, there may be resistance along the surface of the buffer layer, which may cause the test results to be too low. Summary of the Invention
[0004] Purpose of the invention: The purpose of this invention is to provide a method for accurately testing the body resistance of cable buffer layers and for judging and assessing cable buffer layer erosion; the second purpose of this invention is to provide a cable buffer layer erosion judgment system, equipment, and storage medium.
[0005] Technical solution: The method for judging the erosion of the cable buffer layer includes:
[0006] The cable was tested using sinusoidal voltages of different angular frequencies, and the complex effective value of the voltage and the corresponding complex effective value of the current in the cable circuit were collected.
[0007] Based on the cable structure, an equivalent circuit model of the cable including the buffer layer resistance and grounding impedance is established.
[0008] Based on the cable equivalent circuit model, construct a system of simultaneous equations in complex form of Ohm's law;
[0009] Based on the complex effective values of the voltage and the current, the simultaneous equations of Ohm's law are solved to obtain the buffer layer resistance value.
[0010] The resistance value of the buffer layer is used to determine whether the buffer layer has been burned.
[0011] Optionally, the cable structure, from the inside out, consists of a conductor, an inner shielding layer, an insulation layer, an outer shielding layer, a buffer layer, a metal sheath, and an outer sheath, wherein the cable conductor is connected to high voltage, and the metal sheath is grounded.
[0012] Optionally, the equivalent circuit model of the cable is as follows: starting from the test voltage end, the circuit elements of the inner shielding layer, insulation layer, outer shielding layer, and buffer layer are connected in series, and finally connected through the grounding impedance R. G A circuit is formed; wherein, the test voltage is denoted as U; the parameters of the inner shielding layer include the radial resistance R of the shielding per unit length. NP The equivalent circuit of the insulating layer includes a set of parallel insulating capacitors and an insulating resistance. The parameters of the insulating capacitors include the insulating capacitive reactance per unit length R. C The parameters of the insulation resistance include the radial resistance per unit length R. J For cable insulation, R C <<R J The parameters of the outer shielding layer include the radial resistance R per unit length of the outer shielding. WP The parameters of the buffer layer include the radial resistance R per unit length of the buffer layer. H The grounding impedance includes a set of grounding resistors R connected in series. g and grounding resistance R L The length of the test cable is denoted as l.
[0013] Optionally, the system of simultaneous equations in the complex form of Ohm's law includes:
[0014]
[0015] in, The complex effective value of the test voltage U corresponds to the angular frequencies ω1 and ω2, respectively, and the corresponding complex effective values of the generated loop current are as follows: R NP R is the radial resistance of the shield per unit length; wP R is the radial resistance per unit length of the external shield. H The radial resistance per unit length of the buffer layer; Let R be the capacitive reactance per unit length of cable at different frequencies ω1 and ω2, where C is the capacitance per unit length of cable; g R is the grounding resistance. L1 =jω1L、R L2 =jω2L represents the grounding reactance at different frequencies ω1 and ω2, L represents the grounding wire inductance, and j is the imaginary unit. This invention can eliminate the influence of grounding resistance and inductance on the measurement, and realize the accurate measurement of the cable buffer layer resistance.
[0016] Optionally, the method further includes:
[0017] After the buffer layer is repaired, the current buffer layer resistance value is solved again by solving the system of equations according to Ohm's law in complex form, and the buffer layer resistivity is calculated. The values before and after the repair are compared to determine whether the performance of the cable buffer layer has returned to normal after the repair.
[0018] The cable buffer layer erosion detection system includes:
[0019] AC voltage is used to provide sinusoidal voltages of different circular frequencies to the cable; and its own voltage transformer is used to obtain the complex effective value of the voltage of the test cable.
[0020] Current transformers are used to collect the complex RMS value of current in cable circuits;
[0021] The time synchronization module is used to synchronize the test signals of the voltage complex RMS value and the current complex RMS value;
[0022] The microprocessor is used to establish an equivalent circuit model of the cable, including the buffer layer resistance and grounding impedance, based on the cable structure; construct a system of simultaneous equations of Ohm's law in complex form; solve the system of simultaneous equations of Ohm's law in complex form based on the complex effective values of voltage and current to obtain the buffer layer resistance value; and determine whether the buffer layer is ablated based on the buffer layer resistance value.
[0023] Optionally, the microprocessor is further configured to calculate the resistivity of the buffer layer before and after repair based on the buffer layer resistance values before and after repair, and to perform comparative analysis to obtain an evaluation result of the cable repair effect.
[0024] Optionally, the time synchronization module uses GPS or BeiDou system.
[0025] The electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements some or all of the steps of the above-described cable buffer layer ablation judgment method.
[0026] The computer-readable storage medium stores a computer program thereon, which, when executed by a processor, implements some or all of the steps of the above-described method for determining cable buffer layer erosion.
[0027] Beneficial effects: Compared with the prior art, the present invention greatly improves the measurement accuracy of the bulk resistivity of the buffer layer, specifically in the following aspects:
[0028] (1) Test voltages are applied to the cable using sinusoidal voltages of different frequencies. The influence of buffer layer resistance and grounding parameters is decoupled by frequency difference, thus overcoming the defect that single-frequency measurement cannot distinguish each resistance component.
[0029] (2) Simultaneously measure the complex RMS voltage and the corresponding complex RMS current at different frequencies, and obtain amplitude and phase information at the same time, which significantly improves the measurement accuracy compared with traditional real number measurement.
[0030] (3) Establish an equivalent circuit model that includes buffer layer resistance, grounding resistance and grounding inductance to accurately reflect the actual circuit characteristics and solve the problem that the existing model ignores the influence of grounding parameters.
[0031] (4) Solve the equations simultaneously according to Ohm's law in complex form to accurately obtain the buffer layer resistance value and eliminate grounding parameter interference.
[0032] (5) A satellite synchronization system is used to ensure time alignment of dual-frequency measurements and solve the error problem introduced by asynchronous measurements.
[0033] (6) By comparing the changes in the resistance of the buffer layer before and after the repair, the repair effect can be objectively evaluated, providing a scientific basis for cable maintenance. Attached Figure Description
[0034] Figure 1 This is the equivalent circuit model diagram of the present invention;
[0035] Figure 2 This is a schematic diagram of the cable buffer layer ablation judgment system of the present invention. Detailed Implementation
[0036] The technical solution of the present invention will be further described below with reference to the accompanying drawings.
[0037] The cable structure typically consists of, from the inside out, conductor, inner shield, insulation, outer shield, buffer layer, metal sheath, and outer sheath. The cable conductor is connected to high voltage, and the metal sheath is grounded.
[0038] If the cable conductors are connected to the test voltage, the circuit diagram of each part of the cable is as follows: Figure 1 As shown. Where U is the test voltage, R... NP R is the radial resistance of the shield per unit length. C R is the insulation capacitance per unit length. J R is the radial resistance per unit length of insulation. WP R is the radial resistance per unit length of the external shield. H R is the radial resistance per unit length of the buffer layer. G Where R is the grounding impedance, and l is the length of the test cable. For cable insulation, R... C < <R J Therefore, in Figure 1 In the parallel circuit shown, R can be ignored. J Additionally, R G It can be considered as two parts connected in series, namely the grounding resistance R g and grounding resistance R L .
[0039] Using an AC power source to generate sinusoidal voltages with different angular frequencies ω1 and ω2, the complex effective values of the voltages are collected. and the complex effective value of the current in the corresponding cable circuit.
[0040] The complex form of Ohm's law is represented by the following system of equations:
[0041]
[0042] In the formula, R represents the capacitive reactance per unit length of cable at different frequencies ω1 and ω2, where C is the capacitance per unit length of cable; L1 =jω1L,R L2 =jω²L represents the grounding reactance at different frequencies, where L is the grounding wire inductance and j is the imaginary unit. In the above formula, R C1 R C2 R g All values are known. By combining equations (1) and (2), the unknown quantity R can be solved. H And L.
[0043] Based on this, the specific process of the cable buffer layer ablation judgment method is as follows:
[0044] (1) An AC voltage source is used to generate a sine wave with an angular frequency of ω1. The voltage transformer (PT) of the AC voltage source is used to obtain the complex effective value of the voltage of the test cable. At the same time, the complex effective value of the grounding current is obtained synchronously using a current transformer (CT). The synchronization of the test signals is based on the Beidou or GPS synchronization timing method.
[0045] (2) Use an AC voltage source to generate a sine wave with an angular frequency of ω2, use the voltage transformer of the AC voltage source to obtain the complex effective value of the voltage of the test cable, and use the current transformer to synchronously obtain the complex effective value of the grounding current. The synchronization method is the same as above.
[0046] (3) Substituting the test data obtained in the first two steps into the above formulas (1) and (2), the buffer layer resistance R can be obtained. H ;
[0047] (4) For cable buffer layers that have been burned at the engineering site, the above steps can be used to test the resistance of the buffer layer before and after repair and conduct comparative analysis.
[0048] The following example, the resistance test of the buffer layer of a 220kV cross-linked polyethylene (XLPE) insulated cable, will be used to further illustrate this point.
[0049] (1) Cable selection and related parameters
[0050] A 600m section of 220kV cross-linked polyethylene (XLPE) insulated cable with buffer layer erosion (i.e., increased buffer layer resistance) that needs repair was selected. Field testing showed that the cable's grounding resistance R... g It is 2Ω.
[0051] The axial structural dimensions of the 220kV XLPE insulated cable are as follows: conductor cross-section 2500mm². 2 The inner shield has an inner radius of 31mm and an outer radius of 33mm; the insulation thickness is 24mm, and its inner insulation radius is r. N The outer radius of the inner shield is equal to 33mm, and its outer radius of insulation is r. W The inner radius of the outer shield is 57mm; the inner radius of the outer shield is 57mm, and the outer radius is 58mm; the inner radius of the buffer layer is 58mm, and the outer radius is 60mm. Considering that the resistivity of both the inner and outer shields is 10Ω·m, R can be calculated based on the cable structure. NP =0.1Ω, R WP =0.03Ω.
[0052] Considering the relative permittivity ε of XLPE insulation r =2.3, that is, the dielectric constant ε = ε r ε0=2×10 -11 F / m. Therefore, the capacitance C per unit length of cable is:
[0053]
[0054] (2) Buffer layer resistance test
[0055] The buffer layer resistance test process is as follows: First, test the resistance of the buffer layer that has already been burned (i.e., step ① below); then, repair the cable buffer layer; next, test the resistance of the repaired buffer layer (i.e., step ② below). The specific test description is as follows:
[0056] ① Ablation buffer layer
[0057] First, an angular frequency of ω1 = 3.14 × 10⁻⁶ is generated using an AC power supply. 6 Hz sinusoidal voltage Synchronous testing of current using CT
[0058] Then, an angular frequency of ω2 = 6.28 × 10⁻⁶ is generated using an AC power supply. 6 Hz sinusoidal voltage Synchronous testing of current using CT
[0059] Next, based on the angular frequencies ω1 and ω2, calculate the capacitive reactance R per unit length of cable. C1 = -1384.66j(Ω), R C2 = -692.33j(Ω);
[0060] Finally, the relevant parameters R in steps (1) and (2) are... NP R WP R C1 R C2 Substituting into equations (1) and (2) and solving, we obtain: the resistance R of the buffer layer per unit length. H =54Ω, that is, the resistivity ρ of the buffer layer H =1×10 4 Ω·m. Analysis of the resistivity of the buffer layer shows that this value exceeds the standard requirements, indicating that the cable buffer layer is malfunctioning and exhibits signs of erosion.
[0061] ② The buffer layer has been repaired.
[0062] First, an angular frequency of ω1 = 3.14 × 10⁻⁶ is generated using an AC power supply. 6 Hz sinusoidal voltage Using CT synchronous testing, the current I1 is
[0063] Then, an angular frequency of ω2 = 6.28 × 10⁻⁶ is generated using an AC power supply. 6 Hz sinusoidal voltage Synchronous testing of current using CT for
[0064] Next, based on the angular frequencies ω1 and ω2, calculate the cable capacitive reactance R. C1 = -1384.66j(Ω), R C2 = -692.33j(Ω);
[0065] Finally, the relevant parameters R obtained in steps (1) and (2) are... NP R WP R C1 R C2 Substituting into equations (1) and (2) and solving, we obtain: the resistance R of the buffer layer per unit length. H =0.09Ω, that is, the resistivity ρ of the buffer layer H =16.67Ω·m. Analysis of the buffer layer resistivity indicates that the cable buffer layer performed normally after repair.
[0066] like Figure 2The present invention also provides a cable buffer layer ablation judgment system, including an AC voltage source, a current transformer, a time synchronization module, and a microprocessor.
[0067] The AC voltage is used to provide sinusoidal voltages of different circular frequencies to the cable; and its own voltage transformer is used to obtain the complex effective value of the voltage of the test cable. The sinusoidal voltages of different circular frequencies are selected using a dual-frequency test voltage, denoted as the first frequency ω1 and the second frequency ω2, respectively. The corresponding complex effective values of the voltage at the two frequencies are denoted as...
[0068] The current transformer is used to collect the complex RMS value of the current in the cable circuit. When the AC voltage provides a dual-frequency test voltage, the complex RMS values of the current measured simultaneously at the two frequencies are recorded as follows:
[0069] The time synchronization module is used to synchronize the test signals of the voltage complex RMS value and the current complex RMS value.
[0070] The microprocessor is used to establish, based on the cable structure, a buffer layer resistor R. H Grounding impedance R G The equivalent circuit model of the cable, wherein the impedance R G It may include a set of resistors R connected in series. g And the grounding inductance L; construct a system of simultaneous equations of Ohm's law in complex form, and solve the system of simultaneous equations of Ohm's law in complex form according to the complex effective values of voltage and current to obtain the buffer layer resistance value; determine whether the buffer layer is ablated based on the buffer layer resistance value.
[0071] The system of equations for Ohm's law in complex form can be solved using the above formulas (1) and (2).
[0072] The time synchronization module can use GPS or BeiDou systems to achieve measurement synchronization.
[0073] The microprocessor is also used to calculate the resistivity of the buffer layer before and after repair based on the buffer layer resistance values before and after repair, and to perform comparative analysis to obtain an evaluation result of the cable repair effect, including determining whether the repair was successful.
[0074] To implement the above-mentioned method for judging cable buffer layer erosion, the present invention also provides an electronic device and a computer-readable storage medium.
[0075] The electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements some or all of the steps of the above-described cable buffer layer ablation judgment method.
[0076] The computer-readable storage medium stores a computer program, which, when executed by a processor, implements some or all of the steps of the above-described method for determining cable buffer layer erosion.
Claims
1. A method of judging cable buffer layer ablation, characterized by, The method comprises: The cable is tested by using sine wave voltages with different circular frequencies, and the complex effective value of the voltage and the complex effective value of the current in the cable loop corresponding to the voltage are collected; An equivalent circuit model of the cable is established according to the cable structure, and the equivalent circuit model comprises a buffer layer resistance and a grounding impedance; Based on the equivalent circuit model of the cable, a simultaneous equation group of Ohm's law in a complex form is constructed; The simultaneous equation group of Ohm's law is solved according to the complex effective value of the voltage and the complex effective value of the current, so as to obtain the buffer layer resistance value; Whether the buffer layer is ablated is determined according to the buffer layer resistance value.
2. The method of claim 1, wherein, The cable structure comprises, from inside to outside, a conductor, an inner shielding layer, an insulation layer, an outer shielding layer, a buffer layer, a metal sleeve and an outer sheath, wherein the cable conductor is connected to high voltage, and the metal sleeve is grounded.
3. The method of claim 2, wherein the step of determining the presence of a cable buffer burn is performed by the steps of: The equivalent circuit model of the cable constructed based on the described cable structure is as follows: starting from the test voltage end, the circuit elements of the inner shielding layer, insulation layer, outer shielding layer, and buffer layer are connected in series, and finally connected through the grounding impedance R. G A circuit is formed; wherein, the test voltage is denoted as U; the parameters of the inner shielding layer include the radial resistance R of the shielding per unit length. NP The equivalent circuit of the insulating layer includes a set of parallel insulating capacitors and an insulating resistance. The parameters of the insulating capacitors include the insulating capacitive reactance per unit length R. C The parameters of the insulation resistance include the radial resistance per unit length R. J For cable insulation, R C <<R J The parameters of the outer shielding layer include the radial resistance R per unit length of the outer shielding. WP The parameters of the buffer layer include the radial resistance R per unit length of the buffer layer. H The grounding impedance includes a set of grounding resistors R connected in series. g and grounding resistance R L The length of the test cable is denoted as l. 4. The method of claim 1, wherein the step of determining the cable buffer burnout is characterized by, The simultaneous equation group of Ohm's law in a complex form comprises: wherein For the complex effective value of the test voltage U, corresponding to the circular frequencies ω1, ω2, the complex effective value of the loop current generated is respectively R NP r is the radial resistance of the inner shield per unit length; WP R is the radial resistance of the outer shield per unit length; H r is the radial resistance of the buffer layer per unit length; C is the capacitance per unit length of the cable; R g R is the grounding resistance; L1 = jω1K, R L2 = jω2L is the grounding inductive reactance at different frequencies ω1, ω2, L is the grounding line inductance, and j is the imaginary unit.
5. The method of claim 1, wherein, The method further comprises: After the buffer layer is repaired, the current buffer layer resistance value is solved again according to the simultaneous equation group of Ohm's law in a complex form, and the buffer layer resistivity is calculated, and the values before and after the repair are compared to determine whether the performance of the buffer layer of the cable after the repair is restored to normal.
6. A cable buffer ablation judgment system characterized by comprising: The system comprises: An alternating voltage is used to provide sine wave voltages with different circular frequencies to the cable, and a voltage mutual inductor of the alternating voltage is used to obtain the complex effective value of the voltage of the test cable; A current mutual inductor is used to collect the complex effective value of the current in the cable loop; A time synchronization module is used to synchronize the test signals of the complex effective value of the voltage and the complex effective value of the current; A microprocessor is used to establish an equivalent circuit model of the cable comprising a buffer layer resistance and a grounding impedance according to the cable structure, to construct a simultaneous equation group of Ohm's law in a complex form, to solve the simultaneous equation group of Ohm's law in a complex form according to the complex effective value of the voltage and the complex effective value of the current, to obtain the buffer layer resistance value, and to determine whether the buffer layer is ablated according to the buffer layer resistance value.
7. The cable buffer ablation judgment system of claim 6, wherein, The microprocessor is further used to calculate the buffer layer resistivity before and after the repair according to the buffer layer resistance values before and after the repair, to compare and analyze the buffer layer resistivity, and to obtain an evaluation result of the repair effect of the cable.
8. The cable buffer ablation judgment system of claim 6, wherein, The time synchronization module adopts a GPS or Beidou system.
9. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the program to implement the steps of the cable buffer layer ablation determination method according to any one of claims 1 to 5.
10. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the steps of the cable buffer layer ablation determination method according to any one of claims 1 to 5.