A method for judging the connection quality of unequal diameter submarine cable conductors

Abstract

The present invention discloses a method for judging the connection quality of unequal diameter submarine cable conductors, which relates to the field of submarine cable detection. It aims to solve the problem that the existing technology cannot accurately evaluate the dynamic resistance characteristics and thermal stability of unequal diameter connections. The present invention includes: preparing unequal diameter submarine cable conductors, large-section and small-section conductor samples, measuring their resistance values in the initial, load and recovery states respectively, and converting them into resistance values at standard temperature; applying load current through a series circuit to simulate actual working conditions, and calculating the equivalent resistance value of the unequal diameter section; based on the resistance limit values of large and small-section conductors, combined with the dynamic resistance change law, performing criterion verification. This technical solution realizes a full-dimensional evaluation of the thermal stability, interface resistance characteristics, etc. of unequal diameter connections, significantly improves the detection accuracy; ensures connection reliability, and provides key technical guarantees for the intelligent upgrade and cost reduction and efficiency improvement of submarine cable lines.

Description

Technical Field

[0001] The present invention relates to the field of submarine cable detection, and in particular to a method for judging the connection quality of unequal-diameter submarine cable conductors. Background Art

[0002] In recent years, with the rapid development of offshore wind power and island power supply projects, the scale of submarine cable construction (hereinafter referred to as "submarine cable"), as the core carrier of power transmission, has expanded significantly. A typical submarine cable line can reach tens of kilometers in length and consists primarily of a mid-sea section and a landfall section. The mid-sea section is permanently submerged in seawater or buried beneath the seabed, where the ambient temperature is relatively stable and heat dissipation is excellent. The landfall section, on the other hand, extends from the coastline to the land, encompassing the intertidal zone (which is periodically submerged and exposed) and the shore, facing complex environmental challenges. Field studies have shown that the landfall section, subject to fluctuations in both air and sea temperature, experiences significantly higher ambient temperatures than the mid-sea section. This, coupled with limited heat dissipation (e.g., soil thermal resistance and changes in the overburden caused by tidal scouring), makes this section a bottleneck for the overall power transmission capacity of the entire line. Statistics show that, for cables of equivalent cross-section, the steady-state temperature rise of the landfall section is higher than that of the mid-sea section, directly limiting the overall transmission capacity of the line.

[0003] At present, the industry generally adopts the "short board matching" design principle, that is, the conductor cross-section of the entire submarine cable is determined according to the current-carrying limit of the landing section. Although this method can ensure safe operation, it causes redundant current-carrying capacity of the conductor in the mid-sea section of tens of kilometers, resulting in increased material costs and seriously reducing the economic efficiency of the project. Existing improvement plans focus on optimizing the heat dissipation conditions of the landing section, such as removing the armor layer of the onshore section to enhance convective heat dissipation, but the actual current-carrying capacity improvement effect is insufficient, and the mechanical protection performance may be sacrificed. At the same time, with breakthroughs in laying technology (such as the shipborne 500kV soft joint process), unequal diameter connection technology has been gradually applied to the landing section, and the current-carrying capacity is accurately matched by differentiated design of the conductor cross-section of the mid-sea section and the landing section. However, this technology faces two core problems:

[0004] The current standard only specifies resistance and temperature rise test methods for connections between conductors of equal diameter, and cannot effectively evaluate the stability of the interface resistance at connections of unequal diameters and the thermal-electric coupling effect in the cross-sectional transition zone. Due to material heterogeneity and geometric mutations, unequal diameter connections are prone to local overheating under load fluctuations and changes in ambient temperature. Existing static resistance detection methods are unable to capture such time-varying characteristics.

[0005] Therefore, it is urgent to establish a set of unequal-diameter connection quality evaluation methods covering multi-physical field coupling analysis to solve key technical problems such as cross-sectional difference limit determination, dynamic resistance characteristic characterization and spatial thermal distribution verification, and provide theoretical support for the refined design and safe operation of submarine cable lines. Summary of the Invention

[0006] The technical problem to be solved and the technical task to be addressed by the present invention are to improve and enhance existing technical solutions by providing a method for determining the connection quality of unequal-diameter submarine cable conductors, thereby achieving the purpose of evaluating the connection limits and reliability of unequal-diameter submarine cable conductors. To this end, the present invention adopts the following technical solution.

[0007] A method for judging the connection quality of unequal-diameter submarine cable conductors comprises the following steps:

[0008] 1) Prepare three straight conductor samples of equal length, including an unequal-diameter submarine cable conductor sample, a large-section conductor sample, and a small-section conductor sample. The unequal-diameter submarine cable conductor sample has an unequal-diameter section located in the middle of the sample, with a large-section section of equal diameter to the large-section conductor sample and a small-section section of equal diameter to the small-section conductor sample connected at both ends. Measure the length of the unequal-diameter section.

[0009] 2) Measure the initial resistance values A1, B1, and C1 of the three samples at room temperature and convert them into resistance values a1, b1, and c1 at standard temperature;

[0010] 3) Connect the three samples in series to form a loop and continuously apply a predetermined load current. When the temperature of the small-section conductor sample exceeds a set threshold, simultaneously measure the temperatures of the three samples and the corresponding load state resistance values A2, B2, and C2, and convert them into resistance values a2, b2, and c2 at the standard temperature;

[0011] 4) After the sample cools to room temperature, measure the recovered resistance values A3, B3, and C3, and convert them to the resistance values a3, b3, and c3 at standard temperature;

[0012] 5) Calculate the equivalent resistance values d1, d2, and d3 of the unequal diameter sections in the initial state, load state, and recovery state based on the resistance values converted to standard temperature; verify the second criterion based on the maximum resistance limit and equivalent resistance values d1, d2, and d3 of the large and small cross-section conductors at standard temperature;

[0013] The connection quality is determined by the criterion results. When the criterion is met, the connection quality of the unequal diameter sections is determined to be qualified.

[0014] This technical solution applies a continuous load current to simulate the long-term current-carrying conditions experienced in actual submarine cable operation. This allows the user to capture resistance changes at unequal-diameter connections during thermal cycling, effectively assessing thermal stability. Resistance measurements (A3 / B3 / C3) after cooling verify the presence of irreversible damage (such as plastic deformation or oxide layer formation) at the connections, preventing the undetected presence of hidden defects. Measured resistance values are uniformly converted to a standard temperature, eliminating the impact of ambient temperature fluctuations on test results and ensuring data comparability. This significantly improves accuracy and provides a key technical foundation for intelligent upgrades, cost reduction, and efficiency improvements to submarine cable lines.

[0015] As a preferred technical means: step 5) also includes: calculating the equivalent resistance values D1, D2 and D3 of the unequal diameter segments in the initial state, the load state and the recovery state based on the directly measured resistance values; and verifying the first criterion based on the maximum resistance limit and the equivalent resistance values D1, D2 and D3 of the large and small cross-section conductors.

[0016] The first criterion can be verified before the second criterion to judge the similarity of the distribution patterns of the resistance values of large, unequal diameter segments and small diameters in the initial state, load state and recovery state. The first criterion verification is performed first to quickly screen abnormal samples. If the first criterion fails, it can be directly prompted that there is an abnormality in the unequal diameter segment to improve efficiency.

[0017] As a preferred technical means: when measuring the resistance value, the distance between the two measuring ends is 1 meter.

[0018] The 1-meter spacing aligns with the standard recommended conductor resistance measurement method, ensuring comparable test results and facilitating conversion of measurement results to resistance per unit length. This eliminates the impact of sample length variations and facilitates engineering design and performance benchmarking. The 1-meter standard spacing is compatible with conventional laboratory equipment, eliminating the need for custom fixtures and reducing the cost of each test. This ensures consistent measurement conditions for each measurement, reducing errors caused by varying measurement lengths, making measurement results more comparable and accurate, and more accurately reflecting the resistance characteristics of sections of unequal diameters. A unified measurement length standard facilitates standardized measurement processes and procedures, allowing different operators to adhere to the same standards when conducting measurements at different times and locations. This improves measurement repeatability and reliability, and facilitates comparison and analysis of measurement results across different samples. 1 meter is the standard probe spacing for resistance testers, eliminating the need for custom fixtures or equipment adjustments, improving testing efficiency.

[0019] The distance between the two measuring ends is 1 meter, so the sample length can be 1.2-2.0 meters. This ensures representativeness of unequal diameter sections, laboratory feasibility, measurement accuracy, cost-effectiveness, and compatibility with measurement equipment. Limiting the sample length to 1.2-2.0 meters achieves a Pareto optimum between electromagnetic simulation accuracy, experimental cost, and defect detection sensitivity, providing a cost-effective, standardized solution for unequal diameter connection quality evaluation.

[0020] As a preferred technical means: in step 5), the calculation formulas for the equivalent resistance values D1, D2, and D3 of the unequal diameter segments in the initial state, the load state, and the recovery state are: ,Where, n=1, 2, 3, corresponding to different test stages; is the length of the small cross-section between the two measuring ends, is the length of the large cross-section between the two measuring ends; is the length of the unequal diameter segment.

[0021] By formula: , the total resistance A n Decompose into large cross-section segments ( )、small cross-section segment( ) and unequal diameter segments ( ) contribution, accurately isolate the equivalent resistance characteristics of the connection, and by separating the resistance of each segment, the quality of the connection can be more accurately evaluated. For the initial, load, and recovery states (n=1,2,3), calculate D n , reflecting the resistance change pattern of unequal diameter segments under thermal cycling (such as reversible expansion and irreversible oxidation). This is beneficial to improving defect detection rate and economic efficiency.

[0022] As a preferred technical means: in step 5), the calculation formula of the equivalent resistances d1, d2 and d3 of the unequal diameter segments at standard temperature is: The resistance values of each state are uniformly converted to the standard temperature to eliminate the influence of ambient temperature fluctuation on the test results, so that the data measured at different times and places are directly comparable. Calculate the normalized resistance contribution of the large and small cross-section segments, and after accurately deducting their influence, the remaining resistance It fully characterizes the true characteristics of unequal diameter sections, avoids the "signal drowning" problem of traditional overall measurement methods, and provides a highly sensitive, low-cost, standardized quality control tool for submarine cable projects.

[0023] As a preferred technical means: Step 5) also includes: performing multi-point resistance measurement on the unequal diameter submarine cable conductor sample in the length direction, calculating the average equivalent resistance value y of the unequal diameter section through the multi-point resistance measurement value, calculating the average resistance value d through the equivalent resistance values d1, d2 and d3, and performing the third criterion verification based on the average resistance values y and the average resistance values d.

[0024] Measuring resistance at different locations on unequal diameter sections (e.g., near the large cross-section end, in the middle, and near the small cross-section end) facilitates identification of spatially distributed defects such as poor local contact, material inclusions, or geometric deformation. The average of these multiple measurement points effectively suppresses random errors.

[0025] d is the average value of the equivalent resistance based on the dynamic load test (initial, load, and recovery states), which reflects the comprehensive performance of the unequal-diameter section under thermal cycling; y is the average value of the spatial equivalent resistance measured at multiple points at room temperature, which reflects the static distribution characteristics; comparing y and d can reflect the difference between dynamic and static, prevent performance deviations caused by thermal damage (such as oxidation and creep) or process fluctuations, and realize full-dimensional verification of the quality of unequal-diameter connections, providing key support for the safe operation and full life cycle management of submarine cables.

[0026] As a preferred technical means: the calculation formula of the average equivalent resistance value y is: , where: is the equivalent resistance value of the unequal diameter segment at the i-th position, and m is the total number of positions; , where: No. The resistance value measured at the position is converted into the total resistance value at standard temperature; For the The length of the small cross-section between the two measuring ends when in position; For the The length of the large cross-section between the two measuring ends when in position.

[0027] Multi-point spatial averaging improves data stability and reliability. By calculating the average value of the equivalent resistance values of multiple measurement points, it significantly suppresses local random errors (such as poor contact and microscopic material inhomogeneity), reduces data dispersion, and ensures that the overall evaluation results are closer to the true value. All resistance values are converted to a standard temperature, eliminating the influence of ambient temperature fluctuations on the resistance value. This allows direct comparison of test results across time, location, and season. By dividing by the length of the unequal-diameter segment, L3, the total resistance value is converted to resistance per unit length (Ω / m), making test results for samples of different sizes directly comparable. This solution utilizes multi-point spatial averaging, dynamic parameter decoupling, and temperature-length dual normalization to achieve high-precision, comprehensive assessment of unequal-diameter connection quality.

[0028] As a preferred technical means: in step 5), the quality of the connection of the unequal diameter sections is judged based on the following three criteria:

[0029] First criterion: each D n The value does not exceed the corresponding B n with C n 1.1 times the maximum value;

[0030] The second criterion: each d n The value does not exceed the corresponding b n with c n 1.05 times the maximum value;

[0031] The third criterion: |yd|≤5%;

[0032] The connection quality of unequal diameter sections is considered qualified if and only if the three criteria are met at the same time.

[0033] Since the total length of L is 1 meter, B can be used directly in the calculation. n 、C n Calculation, no need to divide by L. By criterion D n ≤1.1×max(B n ,C n), it is mandatory that the equivalent resistance of the unequal diameter section in the initial state, load state, and recovery state does not exceed 1.1 times the resistance of the large and small cross-section conductors, ensuring that the connection remains stable under the impact of thermal cycles and avoiding uncontrolled temperature rise caused by overload (such as the common thermal bottleneck problem in the landing section of submarine cables). n ≤1.05×max(b n ,c n ), based on the resistance value at standard temperature, eliminates interference from ambient temperature fluctuations and accurately evaluates the inherent resistance characteristics of the connection. This is more stringent (1.05 times) than the dynamic criterion (1.1 times), ensuring that the conductor material meets design requirements after thermal expansion and contraction. ∣yd∣≤5% can identify local defects or uneven workmanship. Through a three-criteria mechanism combining dynamic performance verification, temperature standardization control, and spatial distribution verification, a full-lifecycle, multi-physics field coupled assessment of the quality of unequal-diameter connections is achieved. This triple line of defense intercepts thermal damage, material defects, and local anomalies, effectively improving the reliability of submarine cable projects and reducing full-lifecycle costs.

[0034] As the preferred technical means: the standard temperature is 20℃.

[0035] Direct use avoids secondary conversion errors. Furthermore, 20°C is close to the normal laboratory ambient temperature, eliminating the need for additional temperature control equipment to maintain stable measurement conditions and reduce testing costs.

[0036] As a preferred technical means: in step 3), the predetermined load current is continuously applied for 24 hours before subsequent temperature measurement is performed.

[0037] A 24-hour continuous load current simulates the actual operating conditions of a submarine cable during long-term operation, allowing the temperature distribution within the conductor to reach a steady state. Measuring temperature under this steady-state condition accurately reflects the thermal characteristics of the conductor under sustained high load, avoiding measurement errors caused by transient temperature fluctuations. Continuous load helps expose potential defects that may go undetected in short-term testing but could be extremely detrimental to long-term operation. By simulating long-term operation, design or process defects at the connection points can be identified in advance, preventing actual submarine cable failures caused by thermal failure and reducing operation and maintenance costs.

[0038] Beneficial effects: This technical solution proposes a resistance measurement and evaluation method for unequal-diameter conductors based on comparative analysis, targeting the structural characteristics of unequal-diameter conductors. It realizes a full-dimensional evaluation of the thermal stability and interface resistance characteristics of unequal-diameter connections, effectively improves accuracy, and solves the problem of difficulty in measuring the DC resistance of unequal-diameter submarine cable conductors. It can be used to guide related measurement and analysis work; it provides key technical guarantees for the intelligent upgrade and cost reduction and efficiency improvement of submarine cable lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a sample diagram of the present invention.

[0040] Figure 2 This is a multi-point resistance measurement position diagram of the present invention.

[0041] In the figure: 1. Sample of unequal-diameter submarine cable conductor; 101. Unequal-diameter section; 102. Large-section section; 103. Small-section section 103; 2. Large-section conductor sample; 3. Small-section conductor sample. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings.

[0043] The present invention comprises the following steps:

[0044] S1: First, prepare the conductor resistance samples. Take samples of equal length for unequal diameter submarine cable conductors, large cross-section conductors and small cross-section conductors. Figure 1 As shown, there are three samples in total, namely, unequal diameter submarine cable conductor sample 1, large cross-section conductor sample 2 and small cross-section conductor sample 3; each sample is 1.5m long, and the three samples remain straight. Among them, the unequal diameter submarine cable conductor sample 1 should ensure that the unequal diameter section 101 is in the middle of the sample, that is, the large cross-section section 102 and the small cross-section section 103 at both ends of the unequal diameter section 101 are equal in length.

[0045] S2: Measure the length of the unequal diameter section 101 in the unequal diameter submarine cable conductor sample 1; if the length of the unequal diameter section 101 is 0.2m, the lengths of the large and small cross-section sections 103 are 0.4m respectively; all subsequent steps are calculated based on the length of the unequal diameter section 101 being 0.2m.

[0046] The length of the unequal diameter section 101 in the unequal diameter submarine cable conductor sample 1 can be measured using a vernier caliper or a laser rangefinder.

[0047] S3: After the three samples have been left to stand at room temperature, the conductor resistance is measured according to relevant standards (the conductor resistance is measured at a distance of 1m, and the unequal diameter section 101 of the unequal diameter submarine cable conductor sample 1 should be in the middle of the 1m). These are recorded as A1, B1, and C1 respectively, and converted to the resistance values at 20°C, which are recorded as a1, b1, and c1 respectively.

[0048] S4: Connect the three samples into a loop and apply a single load current (select an appropriate current value based on the conductor cross-section) for 24 hours. Measure the temperature of each sample. The minimum conductor temperature among the three samples should be greater than 50°C. For unequal-diameter submarine cable conductor sample 1, measure the temperature at unequal-diameter section 101. Immediately and simultaneously measure the conductor resistance according to relevant standards, recording them as A2, B2, and C2, respectively. Convert these values to the resistance at 20°C, recording them as a2, b2, and c2, respectively.

[0049] S5: After cooling to room temperature, measure the conductor resistance according to relevant standards, record them as A3, B3, and C3 respectively, and convert them to obtain the resistance value at 20℃, record them as a3, b3, and c3 respectively.

[0050] Calculate separately (A1-B1 0.4-C1 0.4) / 0.2=D1, (A2-B2 0.4-C2 0.4) / 0.2=D2, (A3-B3 0.4-C3 0.4) / 0.2=D3.

[0051] The first criterion: D1 should be within the resistance value range of B1 and C1, that is, the confidence interval. If it is not within the confidence interval, it should not be greater than 1.1 times the maximum value of B1 and C1. Similarly, D2 should be within the confidence interval of B2 and C2. If it is not within the confidence interval, it should not be greater than 1.1 times the maximum value of B2 and C2. D3 should be within the confidence interval of B3 and C3. If it is not within the confidence interval, it should not be greater than 1.1 times the maximum value of B3 and C3.

[0052] If the first criterion is satisfied, d1, d2 and d3 can be calculated; if criterion 1 is not satisfied, the quality of the unequal diameter section 101 is considered to be questionable.

[0053] Calculate (a1-b1 0.4-c1 0.4) / 0.2=d1, (a2-b2 0.4-c2 0.4) / 0.2=d2, (a3-b3 0.4-c3 0.4) / 0.2=d3.

[0054] The second criterion: d1 should be within the confidence interval of b1 and c1, d2 should be within the confidence interval of b2 and c2, and d3 should be within the confidence interval of b3 and c3; if there is a situation that is not within the confidence interval, it should not be greater than 1.05 times the maximum value.

[0055] If the second criterion is not met, it is considered that the quality of the unequal diameter section 101 is questionable.

[0056] This embodiment comprehensively considers the overall characteristics of the submarine cable line, the connection structure of the unequal-diameter conductors of the submarine cable and its manufacturing characteristics, the conductor resistance value and its variation characteristics, combines the technical requirements for the connection of the unequal-diameter submarine cable conductor 1, and analyzes the data of the conductor resistance value variation characteristics when connecting different conductor cross-sections to realize a method for evaluating the limit value and reliability of the connection of the unequal-diameter submarine cable conductor 1, so as to improve the reliability of the operation of the unequal-diameter submarine cable line.

[0057] Example 2:

[0058] The same points as those in the first embodiment are not repeated here. The difference is that step S5 further includes:

[0059] At room temperature, press Figure 2 The DC resistance values of the unequal diameter submarine cable conductor sample 1 are measured at the positions and recorded as X1, X2, and X3 respectively, and the resistance values at 20°C are converted and recorded as x1, x2, and x3 respectively.

[0060] Calculate y1=x1-0.4b1-0.4c1, y2=x2-0.2b1-0.6c1, y3=x3-0.6b1-0.2c1 respectively; Y1=y1 / 0.2, Y2=y2 / 0.2, Y3=y3 / 0.2; calculate the average value y of Y1, Y2, and Y3; calculate the average value d of d1, d2, and d3.

[0061] The third criterion: compare y and d, and the difference is no more than 5%. If the third criterion is not met, the quality of the unequal diameter section 101 is considered to be questionable.

[0062] Based on the first embodiment, this embodiment adds the measurement of DC resistance value and the third criterion. Through more comprehensive data analysis, the quality of the connection of the unequal diameter submarine cable conductors is further verified, and the reliability of the operation of the unequal diameter submarine cable line is improved.

[0063] The method for judging the connection quality of unequal-diameter submarine cable conductors shown above is a specific embodiment of the present invention, which has reflected the substantial characteristics and progress of the present invention. It can be modified equivalently according to actual use needs under the guidance of the present invention, and all of them are within the scope of protection of this solution.

Claims

1. A method for determining the connection quality of unequal diameter submarine cable conductors, characterized by: The following steps are involved: 1) Prepare three straight conductor samples of equal length, including unequal diameter submarine cable conductor samples, large cross-section conductor samples, and small cross-section conductor samples; The unequal diameter submarine cable conductor sample has an unequal diameter section located in the middle of the sample, with both ends of the unequal diameter section respectively connected to a large cross-section section of the same diameter as the large cross-section conductor sample and a small cross-section section of the same diameter as the small cross-section conductor sample; the length of the unequal diameter section is measured; 2) Measure the initial resistance values A1, B1, and C1 of the three samples at room temperature and convert them into resistance values a1, b1, and c1 at standard temperature; 3) Connect the three samples in series to form a loop and continuously apply a predetermined load current. When the temperature of the small-section conductor sample exceeds a set threshold, simultaneously measure the temperatures of the three samples and the corresponding load state resistance values A2, B2, and C2, and convert them into resistance values a2, b2, and c2 at the standard temperature; 4) After the sample cools to room temperature, measure the recovered resistance values A3, B3, and C3, and convert them to the resistance values a3, b3, and c3 at standard temperature; 5) Calculate the equivalent resistance values d1, d2, and d3 of the unequal diameter sections in the initial state, load state, and recovery state based on the resistance values converted to standard temperature; verify the second criterion based on the maximum resistance limit and equivalent resistance values d1, d2, and d3 of the large and small cross-section conductors at standard temperature; The connection quality is determined by the criterion results. When the criterion is met, the connection quality of the unequal diameter sections is determined to be qualified.

2. The method for determining the connection quality of unequal-diameter submarine cable conductors according to claim 1, wherein: Step 5) also includes: calculating the equivalent resistance values D1, D2 and D3 of the unequal diameter segments in the initial state, the load state and the recovery state based on the directly measured resistance values; and verifying the first criterion based on the maximum resistance limits of the large and small cross-section conductors and the equivalent resistance values D1, D2 and D3.

3. The method for determining the connection quality of unequal-diameter submarine cable conductors according to claim 2, wherein: When measuring resistance, the distance between the two measuring ends is 1 meter.

4. The method for determining the connection quality of unequal-diameter submarine cable conductors according to claim 3, wherein: In step 5), the calculation formulas for the equivalent resistance values D1, D2, and D3 of the unequal diameter segments in the initial state, load state, and recovery state are: ,Where, n=1, 2, 3, corresponding to different test stages; is the length of the small cross-section between the two measuring ends, is the length of the large cross-section between the two measuring ends; is the length of the unequal diameter segment.

5. The method for judging the connection quality of unequal diameter submarine cable conductors according to claim 4, characterized in that: In step 5), the calculation formula for the equivalent resistances d1, d2, and d3 of the unequal diameter segments at standard temperature is: .

6. A method for determining the connection quality of unequal-diameter submarine cable conductors according to claim 5, characterized in that: Step 5) also includes: performing multi-point resistance measurement on the unequal-diameter submarine cable conductor sample in the length direction, calculating the average equivalent resistance value y of the unequal-diameter section through the multi-point resistance measurement values, calculating the average resistance value d through the equivalent resistance values d1, d2 and d3, and performing third criterion verification based on the average resistance values y and the average resistance values d.

7. A method for determining the connection quality of unequal-diameter submarine cable conductors according to claim 6, characterized in that: The calculation formula for the average equivalent resistance value y is: , where: is the equivalent resistance value of the unequal diameter segment at the i-th position, and m is the total number of positions; , where: No. The resistance value measured at the position is converted into the total resistance value at standard temperature; For the The length of the small cross-section between the two measuring ends when in position; For the The length of the large cross-section between the two measuring ends when in position.

8. The method for judging the connection quality of unequal diameter submarine cable conductors according to claim 7, characterized in that: In step 5), the connection quality of the unequal diameter sections is judged to be qualified based on the following three criteria: First criterion: each D n The value does not exceed the corresponding B n with C n 1.1 times the maximum value; The second criterion: each d n The value does not exceed the corresponding b n with c n 1.05 times the maximum value; The third criterion: |yd|≤5%; The connection quality of unequal diameter sections is considered qualified if and only if the three criteria are met at the same time.

9. The method for judging the connection quality of unequal diameter submarine cable conductors according to claim 1, characterized in that: The standard temperature is 20℃.

10. The method for judging the connection quality of unequal diameter submarine cable conductors according to claim 1, characterized in that: In step 3), the predetermined load current is continuously applied for 24 hours before subsequent temperature measurements are performed.

Images