A direct current GIS loop resistance field joint test method based on temperature rise gradient

Abstract

This invention discloses a field joint testing method for the circuit resistance of DC GIS based on temperature rise gradient, used for assessing the contact status of the conductive parts of the main circuit of DC GIS or DC gas-insulated switchgear. The method includes determining the test boundary of the circuit under test; measuring the baseline circuit resistance of the DC GIS circuit under test; simultaneously collecting multi-point temperature data near the contact point and upstream and downstream conductor sections; measuring the circuit resistance again under heating or thermal stability scenarios, and performing temperature compensation to obtain the equivalent resistance at the reference temperature; and constructing a joint diagnostic model based on the temperature rise gradient and equivalent resistance to identify contact anomalies and assess their severity. This invention significantly improves the detection sensitivity and consistency of conclusions for defects such as loose contact, contamination, misalignment, and insufficient elasticity without significantly increasing the complexity of field operations, and possesses a traceable data link and automatic reporting output capability.

Description

Technical Field

[0001] This invention relates to the field testing and acceptance technology of high-voltage DC gas-insulated switchgear, specifically to a field joint test method for the resistance of DC GIS circuits based on temperature rise gradient. Background Technology

[0002] The main circuit of a DC GIS consists of multiple conductors and contact interfaces. Long-term current-carrying operation will generate a temperature rise. The temperature rise distribution is related to conductor resistance, contact resistance, and heat dissipation conditions. If there are problems such as looseness, contamination, misalignment, insufficient elasticity, or plating damage at the contact interfaces, the increased local contact resistance will cause localized heating, potentially leading to contact erosion, mechanical performance degradation, and insulation aging risks.

[0003] On-site acceptance testing often uses DC current injection to measure loop resistance and compares it with limits to draw conclusions. This method can evaluate the overall continuity of the loop, but it is not sensitive to some defects under low current conditions and cannot provide information on the spatial distribution of heat generation and risk location. Ambient temperature and wiring errors can also introduce fluctuations, leading to inconsistent conclusions or frequent retesting.

[0004] Temperature rise tests or infrared thermography can be used to identify hot spots, but without controlled flow profiles, standardized measurement point layouts, and quantifiable criteria, it is difficult to reach consistent acceptance conclusions. Infrared thermography is sensitive to surface emissivity and cannot directly reflect the true temperature of internal contact points when shielded by a metal casing.

[0005] Therefore, there is a need for a method that can simultaneously acquire resistance information and temperature spatial distribution information under controlled injection conditions, and can map the two into an executable acceptance conclusion. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the above-mentioned technical defects and provide a method for joint field testing of DC GIS loop resistance based on temperature rise gradient. This method enables the on-site measurement of loop resistance to obtain the temperature rise gradient distribution and dynamic characteristics at the same time, and to construct a criterion system dominated by temperature rise gradient. This improves the detection sensitivity, location capability and conclusion consistency of contact defects, and reduces the missed detection and misjudgment caused by relying solely on single resistance or single temperature rise inspection.

[0007] To solve the above-mentioned technical problems, the technical solution provided by the present invention is: a field joint test method for the resistance of DC GIS circuit based on temperature rise gradient, used for evaluating the contact status of the conductive parts of the main circuit of DC GIS or DC gas-insulated switchgear, comprising the following steps:

[0008] S1: Determine the test boundary of the circuit under test, and arrange temperature monitoring points in the critical contact area of ​​the circuit under test and its upstream and downstream conductor sections;

[0009] S2: Measure the baseline loop resistance of the DC GIS circuit under test;

[0010] S3: Under controlled DC injection heating conditions, simultaneously collect temperature data at multiple points near the contact point and upstream and downstream conductor sections;

[0011] S4: Construct temperature rise distribution and temperature rise gradient distribution based on multi-point temperature data;

[0012] S5: Measure the loop resistance again in the case of temperature rise or thermal stability, and perform temperature compensation to obtain the equivalent resistance at the reference temperature;

[0013] S6: Construct a joint diagnostic model based on temperature rise gradient and equivalent resistance to identify the location of contact anomalies and assess the degree of anomalies;

[0014] S7: Output assessment results including risk location information and treatment recommendations.

[0015] Preferably, in S1, at least three sets of temperature monitoring points are set in the vicinity of each contact point to be evaluated, located on the contact point body, the upstream conductor of the contact point, and the downstream conductor of the contact point, respectively.

[0016] It also includes setting reference monitoring points to characterize the overall temperature rise level on a reference conductor segment far from the contact point.

[0017] Preferably, the controlled DC injection heating condition in S3 is a multi-stage stepped current or continuous ramp current method, and temperature data is collected during each current holding stage.

[0018] Preferably, the temperature rise gradient distribution includes the ratio of the temperature rise difference between adjacent monitoring points to the distance between the monitoring points, wherein the location corresponding to the peak value of the temperature rise gradient indicates the suspected location of contact anomaly.

[0019] Preferably, step S4 further includes calculating a gradient anomaly coefficient, which is the ratio of the peak value of the local temperature rise gradient to the overall gradient reference value of the loop, wherein:

[0020] The gradient reference value is the average temperature rise gradient of the non-contact area in the same circuit or the average gradient of multiple control monitoring point pairs.

[0021] Preferably, the thermal stability scenario determination in S5 includes:

[0022] The temperature rise rate of the hot spot monitoring point is less than or equal to the preset threshold and the duration is not less than the preset duration, or the temperature rise gradient rate is less than or equal to the preset threshold and the duration is not less than the preset duration.

[0023] Preferably, the temperature compensation in S5 includes dividing the hot-state circuit resistance by a temperature compensation coefficient, wherein the temperature compensation coefficient is calculated based on the temperature coefficient of the conductor material and the difference between the hot-state equivalent temperature and the reference temperature.

[0024] Preferably, the joint diagnostic model further includes defect type identification, which outputs at least one defect risk warning based on equivalent resistance value, temperature rise gradient peak value, gradient anomaly coefficient, and gradient response characteristics as a function of current, such as loose contact, contact surface contamination, assembly misalignment, insufficient elasticity, or abnormal local cross-section of conductor.

[0025] The advantages of this invention compared to existing technologies are as follows: This invention uses temperature rise gradient as the primary criterion, improving the sensitivity to sudden changes in local thermal resistance at contact points, enabling defect detection even in the early stages when resistance changes are not significant. The gradient peak location can be used to pinpoint risk areas, improving on-site inspection efficiency. The defect type mapping rule enhances the executability of the output. Resistance-temperature compensation conversion improves data comparability under different temperature conditions, and the multi-current scaling relationship enhances the ability to identify nonlinear defects, ultimately forming a traceable data link and automatic reporting output capability. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the DC GIS conduction circuit and measurement point layout;

[0027] Figure 2 This is a flowchart of the overall process for the joint field test method of DC GIS loop resistance based on temperature rise gradient. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings.

[0029] Combined with appendix Figure 1-2 As shown, the core of the method of the present invention is that during the controlled injection heating process, contact defects are usually manifested as a significant increase in temperature near the contact point compared to the upstream and downstream conductor sections, resulting in a sudden change in local thermal resistance.

[0030] The spatial representation of this mutation is not the absolute value of temperature rise, but the rate of change of temperature rise along space, i.e., the temperature rise gradient. Changes in overall heat dissipation conditions will significantly affect the absolute value of temperature rise, while having a relatively small impact on the local gradient peak. Therefore, the temperature rise gradient is more suitable as the main criterion for on-site judgment.

[0031] This invention obtains the contact point temperature profile through standardized measurement point layout, acquires the temperature rise dynamic process by controlled injection heating, calculates the temperature rise gradient according to the measurement point spacing and extracts the gradient peak position for risk location, and simultaneously measures the loop resistance in the hot state and performs temperature compensation conversion to obtain a comparable equivalent resistance R_ref.

[0032] In terms of criterion construction, this invention uses G_max and gradient anomaly coefficient K_G as the leading indicators, and combines them with R_ref to form an acceptance conclusion; when multi-level current loading is applied, a scaling relationship between G_max(I) and I^2 is established, and k_I and the fitting residual are used to characterize the nonlinear heating characteristics, so as to enhance the ability to identify unstable contact defects.

[0033] This invention further provides an adaptive method for determining the temperature rise gradient threshold, avoiding misjudgments caused by a fixed threshold under different on-site heat dissipation conditions; it also provides defect type mapping rules, enabling the system to output actionable risk type prompts and improve on-site handling efficiency. Specifically, this invention includes:

[0034] Standardized measurement point layout: hot spot measurement points are set up at each critical contact point, and reference measurement points are set up in the upstream and downstream conductors to form a "contact point temperature profile";

[0035] Controlled flow heating: The use of stepped or ramp current makes the temperature rise process repeatable and allows for the extraction of dynamic characteristics of thermal stability.

[0036] Gradient calculation and location: Calculate the temperature rise gradient according to the distance between measuring points, and take the gradient peak and its location as the main risk location result;

[0037] Resistance temperature compensation: R_hot is measured in hot state and converted to R_ref to ensure comparability under different temperature conditions;

[0038] Gradient-dominated criteria: Construct indicators such as G_max and K_G and combine them with R_ref to form an acceptance conclusion. At the same time, you can optionally introduce a multi-current scaling relationship G_max(I)≈k_I×I^2+b_I to enhance the ability to identify nonlinear contact defects.

[0039] Output and Reporting: Outputs a conclusion of pass / retest required / fail, provides the risk contact point number and location, and generates a traceable report.

[0040] The parameters involved in this invention are defined as follows:

[0041] Ambient temperature T_amb: Ambient temperature recorded during the baseline phase, in °C;

[0042] Temperature sequence T_i(t): Temperature at the i-th measuring point at time t, in °C;

[0043] Temperature rise ΔT_i(t): ΔT_i(t) = T_i(t) - T_amb;

[0044] Temperature gradient G_ab(t): G_ab(t) = (ΔT_a(t) - ΔT_b(t)) / d_ab, where d_ab is the distance or equivalent distance between measuring points a and b;

[0045] Gradient peak value G_max: G_max = max_over_pairs( abs(G_ab(t_eval)) ), where t_eval is the evaluation time, which can be the thermally stable time or a specified time;

[0046] Gradient reference G_base: G_base = mean_over_ref_pairs( abs(G_ab(t_eval)) ), where ref_pairs is a set of non-contact point regions or control measurement point pairs;

[0047] Gradient anomaly coefficient K_G: K_G = G_max / max(G_base, G_min), where G_min is a limit value to prevent the denominator from being too small;

[0048] Baseline loop resistance R0: R0 = V0 / I0;

[0049] Hot-state circuit resistance R_hot: R_hot = V_hot / I_hot;

[0050] The resistance calculated based on the reference temperature is R_ref: R_ref = R_hot / (1 + alpha×(T_eq - T_ref)), where alpha is the temperature coefficient, T_eq is the equivalent temperature in the hot state, and T_ref is the reference temperature;

[0051] The thermal stability criterion can be: abs(dΔT_hotspot / dt) <= k_T and duration >= t_stable, or abs(dG_max / dt) <= k_G and duration >= t_stable, where T_hotspot(t) is the hotspot temperature, which is the maximum or average value of the set of measurement points near the contact point, k_T is the threshold for the rate of change of hotspot temperature, k_G is the threshold for the rate of change of temperature gradient, and t_stable is the criterion for the duration of temperature rise stability.

[0052] The multi-current scaling relationship can be fitted as follows: G_max(I) ≈ k_I×I^2 + b_I, where k_I is the scaling coefficient and b_I is the bias term.

[0053] The acceptance criterion of the present invention is dominated by the temperature rise gradient and combined with the resistance result. The following logic can be adopted: it is judged as qualified when R_ref meets the resistance limit, G_max meets the gradient limit, and K_G does not exceed the abnormal threshold; when R_ref meets the limit but G_max or K_G exceeds the limit, it is judged that remeasurement is required or unqualified, and local abnormality of the contact point is preferentially prompted; when R_ref exceeds the limit but G_max is not obvious, insufficient overall conduction ability or abnormality of the conductor segment is prompted, and it is recommended to review the wiring and loop boundary; when both R_ref and G_max exceed the limit or G_max shows a significant non-linear mutation with the current, it is judged as unqualified and it is recommended to stop the test and check the corresponding contact point.

[0054] To make the test output more executable, the present invention provides a defect type mapping rule for mapping indexes such as R_ref, G_max, K_G, k_I, and thermal stability dynamic characteristics obtained from the test into risk type prompts. The mapping rule can adopt the rule library method based on thresholds or can also be used as input features of a machine learning model. The following gives a set of rule descriptions that can be implemented in engineering.

[0055] Rule 1: Priority rule for local abnormality of the contact point. When R_ref does not exceed the limit significantly but G_max or K_G exceeds the limit significantly, it is prompted that there is a local thermal resistance mutation at the contact point, and the risk type is preferentially judged as contact looseness, contact surface contamination or assembly misalignment; the system outputs the measurement point number of the corresponding contact point and the position of the gradient peak value, and it is recommended to tighten, clean or re-assemble and review.

[0056] Rule 2: Rule for insufficient overall conduction ability. When R_ref exceeds the limit while G_max and K_G are not significant, it is prompted that the overall conduction ability is insufficient or the loop boundary contains additional series resistances, and the risk type is preferentially judged as improper loop connection, insufficient overall contact pressure or conductor segment abnormality; the system recommends reviewing the wiring boundary, measurement loop and conductor connection status, and performing further disassembly and inspection after confirmation.

[0057] Rule 3: Non-linear contact instability rule. When k_I obtained by multi-current fitting is significantly large or the fitting residual Res_I significantly increases, and at the same time G_max shows a mutation trend with the current level, it is prompted that the contact spot is unstable or the thermal contact instability caused by local micro-arc discharge, and the risk type can be prompted as insufficient elastic force, contact surface ablation or coating damage; the system recommends stopping the current increase and preferentially checking the corresponding contact interface.

[0058] Rule 4: Rule for identifying the influence of heat dissipation conditions. When the temperature rise of all measurement points is generally high but the gradient statistic μ_G of the control area also increases synchronously and K_G does not exceed the limit significantly, it is prompted that the heat dissipation conditions are abnormal or affected by environmental factors, such as external wind speed change, occlusion or abnormal heat dissipation of the shell; the system recommends re-measuring under the same environmental conditions or updating the threshold by using the control area statistical method before judging.

[0059] The above mapping rules can be parameterized by combining equipment models and enterprise experience. For example, different threshold groups can be set for different contact structures, or the risk types output by the rules can be bound to the suggested handling templates to form standardized acceptance reports.

[0060] The specific implementation method of this invention is as follows: Figure 1 As shown.

[0061] Experimental preparation and measurement point setup:

[0062] This invention focuses on key continuity interfaces in the main circuit of a DC GIS (Gas-Insulated Switchgear) system as the testing object. These continuity interfaces include, but are not limited to, plug contacts, conductor lap / flange connections, and continuity circuits between disconnecting switches and grounding switches. During field implementation, the test boundaries of the circuit under test are first determined, i.e., the inlet and outlet of the DC current injection, the series connection path of the circuit, and the location of the contact points of particular interest. After confirming the circuit boundaries, it should be ensured that the equipment is in a safe and testable state, including but not limited to safety measures such as power outage, voltage testing, reliable grounding, tagging and interlocking, and isolation of the work area.

[0063] Next press Figure 2 The measurement points are arranged and numbered. For each critical contact point, at least four types of temperature measurement points are arranged: the first is the hot spot measurement point T_H, which is arranged in the vicinity of the contact point where local heating is most likely to occur; the second is the upstream control measurement point T_U, which is arranged in the conductor section upstream of the contact point, in a position where thermal coupling is stable and the structure is consistent; the third is the downstream control measurement point T_D, which is arranged in the conductor section downstream of the contact point, and the location selection principle is the same as T_U; the fourth is the reference measurement point T_R, which is arranged far away from the critical contact point, in a position that represents the overall temperature background or environmental disturbance, and is used to calculate the ambient / baseline temperature T_amb and assist in the gradient statistics of the control area.

[0064] When arranging measurement points, record the distances or equivalent distances between them, including at least the distances d_HU and d_HD between the hot spot and the upstream and downstream control points, or record d_ab for any pair of adjacent measurement points. If point-type temperature sensors (such as patch thermocouples, PT100, surface-mount thermometers, etc.) are used, d_ab is the geometric distance between the sensors; if distributed fiber optic temperature measurement is used, d_ab is the spacing between fiber optic sampling points or the equivalent spatial resolution. To ensure measurement consistency, measurement points should be fixed using a uniform method and thermally conductive interface material to avoid temperature drift caused by loosening or poor contact. Simultaneously, establish a mapping table of "measurement point number—physical location—distance parameter" in the acquisition system as the basis for subsequent temperature rise gradient positioning output.

[0065] In addition to the temperature measurement point, the site also needs to be equipped with a DC current injection and stabilization device, a four-wire loop resistance measurement device (or equivalent voltage drop measurement channel), and a data acquisition and processing device. The current injection device should have controlled output capability and overcurrent protection; the resistance measurement should use a four-wire connection to reduce the influence of lead resistance; the data acquisition should support synchronous sampling of temperature, current, and voltage, and retain timestamps for dynamic characteristic and stability criterion calculations.

[0066] Baseline measurement:

[0067] Baseline measurements are performed before the heating and injection phase. First, the ambient temperature T_amb is recorded. In this invention, T_amb can preferably be the average value of the reference measurement point T_R during the baseline phase, or it can be the average value of multiple reference points or the temperature recorded on-site (to improve anti-disturbance capability). Then, the baseline loop resistance R0 is measured using a four-wire DC injection method. The baseline measurement current I0 can be set according to the equipment's allowable value to ensure measurement stability and prevent significant temperature rise. After measuring the baseline voltage drop V0, R0 = V0 / I0 is calculated, and R0, I0, V0, T_amb, and the initial temperature T_i(t0) of each measurement point are archived.

[0068] To reduce the impact of random noise and contact fluctuations on R0, the baseline resistance can be sampled multiple times within a short time window to obtain the average value, or the voltage drop signal can be processed by low-pass / moving average. The processing method needs to be fixed in the data processing module to ensure consistency across different sites / work groups.

[0069] Controlled flow heating and synchronous data acquisition:

[0070] The controlled flow heating stage begins. The flow curve I_heat(t) can be implemented using two typical methods: a stepped or a ramp type. The stepped type involves increasing the current in preset increments, maintaining each current level for a period to allow the temperature field to reach a quasi-steady state. The ramp type involves a smooth current increase within a preset time to reduce thermal shock and improve on-site safety. Regardless of the method used, the flow must not exceed the equipment's allowable current carrying capacity and the on-site thermal limits.

[0071] During the injection heating process, the data acquisition device simultaneously collects the current I(t), loop voltage drop V(t), and temperature T_i(t) at each measurement point. The sampling period Δt can be set according to the on-site acquisition capability (e.g., within the range of 1 s to 10 s) and should remain consistent throughout the same experiment. To facilitate subsequent stability assessment and gradient calculation, it is recommended to retain a data window of at least sufficient length in each step holding period for calculating the rate of temperature rise or gradient change. The data processing module calculates the temperature rise ΔT_i(t) = T_i(t) - T_amb at each measurement point in real time and follows the... Figure 1The distance relationships shown are used to calculate the temperature rise gradient of adjacent measuring point pairs. For critical contact points, the following calculations can be performed: G_HU(t) = (ΔT_H(t) - ΔT_U(t)) / d_HU, G_HD(t) = (ΔT_H(t) - ΔT_D(t)) / d_HD. Simultaneously, the gradients of other control measuring point pairs can also be calculated to form statistics for the control area. By continuously updating G_ab(t), the gradient peak value G_max(t) and its corresponding measuring point pair / contact point number can be obtained in real time, thus enabling hotspot location and risk prediction during the experiment.

[0072] Stability determination and evaluation timing:

[0073] This invention sets up a stability determination node to determine the evaluation time t_eval and the hot resistance measurement time. Stability determination can use one of the following two types of conditions (or a combination of both): The first type is the temperature rise stability criterion. The rate of change dΔT_H / dt is calculated for the temperature rise ΔT_H(t) at the hot spot measurement point. When abs(dΔT_H / dt) ≤ k_T and the duration is not less than t_stable, the hot spot temperature rise is determined to have entered a quasi-steady state. The second type is the gradient stability criterion. The rate of change dG_max / dt is calculated for the gradient peak value G_max(t). When abs(dG_max / dt) ≤ k_G and the duration is not less than t_stable, the temperature rise gradient distribution is determined to have entered a quasi-steady state. Compared to using only temperature rise stability as a criterion, gradient stability more directly reflects whether the sudden change in local thermal resistance at the contact point tends to stabilize, and has a stronger resistance to external heat dissipation disturbances; therefore, it can be used as a preferred criterion.

[0074] When the stability criterion is met, the specified time point at or after that moment is used as t_eval to calculate the final G_max and the control region statistics; if the stability criterion is not met, then... Figure 1 The process continues with the current injection flow, extends the holding time, or proceeds to the next current level to continue heating and data acquisition until the criteria are met or the test time limit is reached. If the criteria are not met even after reaching the time limit, a "steady state not reached" message should be recorded and included in the report for comprehensive consideration during acceptance testing.

[0075] Hot resistance measurement and temperature compensation conversion:

[0076] After the stability criterion is met or the specified measurement time is reached, the hot-state loop resistance measurement is performed. The hot-state loop resistance R_hot can be obtained in one of two ways: First, while maintaining the injection current, R_hot can be calculated directly using the synchronously acquired V(t) and I(t) = V_hot / I_hot, where V_hot and I_hot are the average values ​​within the stable time window; second, while maintaining the hot-state temperature, the measurement current is switched (or, within the range supported by the injection device, the current is switched to a more suitable current for resistance measurement), the corresponding voltage drop is collected, and R_hot is calculated. When using either method, the four-wire connection of the measurement loop should be kept unchanged to reduce system errors. To eliminate the influence of temperature on resistance, R_hot is converted to a reference temperature T_ref (usually taken as 20°C) to obtain R_ref, and the conversion formula is: R_ref = R_hot / (1 + alpha×(T_eq - T_ref)). Where alpha is the equivalent resistance temperature coefficient of the loop, and T_eq is the hot-state equivalent temperature. T_eq can be preferably taken as the temperature of the hot spot measurement point T_H, or it can be taken as the average temperature of multiple measurement points near the hot spot, in order to improve noise immunity. The calculated R_ref is used for consistency comparison with the resistance limit, improving the comparability under different ambient temperatures and different heating conditions.

[0077] Anomaly detection and location output:

[0078] This invention uses the temperature rise gradient as the primary criterion and combines it with the resistance index to output an acceptance conclusion. At time t_eval, the gradient peak value G_max is calculated, and the gradient baseline G_base (e.g., the average gradient value of the control region) is calculated to construct the gradient anomaly coefficient.

[0079] K_G = G_max / max(G_base, G_min). G_min is the minimum limit to avoid numerical divergence caused by an excessively small denominator. K_G is a dimensionless index that reflects the degree of anomaly of the local peak relative to the background gradient.

[0080] based on Figure 2 The system maps measurement point numbers to distances, allowing the point pairs or contact point numbers corresponding to G_max to be directly output as "risk location results." When using multiple contact point measurement point groups, the system can calculate the local gradient peak value for each contact point and sort and output it, thus forming a "risk contact point priority list," significantly improving on-site investigation efficiency.

[0081] Combined conclusions and defect type suggestions:

[0082] The output conclusions of this invention include at least three categories: qualified, requiring retesting, and unqualified. When making a joint judgment, the temperature rise gradient index is preferably the primary factor, constrained by the resistance index, forming the following typical logic: Qualified when R_ref meets the resistance limit, G_max meets the gradient limit, and K_G does not exceed the abnormal threshold; qualified when R_ref meets the limit but G_max or K_G exceeds the limit, requiring retesting or unqualified, with a priority warning of "risk of sudden change in local thermal resistance at the contact point"; unqualified when R_ref exceeds the limit but G_max and K_G are not significant, indicating "insufficient overall conductivity or the loop boundary contains additional series resistance," suggesting a review of the wiring and loop boundary before further judgment; unqualified when both R_ref and G_max exceed the limit, or when the gradient continuously increases and is difficult to stabilize during the heating process, and it is recommended to stop the current rise and disassemble and inspect the corresponding contact point.

[0083] To improve the executability of the output, the system can provide defect type suggestions based on R_ref, G_max, K_G, and stability characteristics. Typical suggestion rules include: when R_ref is not significantly exceeded but G_max or K_G is significantly exceeded, it indicates a high probability of loose contact, contact surface contamination, or assembly misalignment; when R_ref exceeds the limit but the gradient is not obvious, it indicates insufficient overall contact pressure, improper circuit connection, or conductor segment abnormality; when the temperature rise or gradient is difficult to stabilize over a long period, it indicates a risk of intermittent contact or abnormal mechanical fit. The above suggestions, along with the location results, are output together and can serve as a basis for on-site handling.

[0084] Report generation and data archiving:

[0085] After the test is completed, the system generates a standardized test report and archives the data. The report should include at least: a description of the boundary conditions of the circuit under test and... Figure 1 The diagram shows the layout, numbering, and distance parameters of the measuring points; baseline measurement data R0, I0, V0, and T_amb; the injection curve I_heat(t) and the synchronously acquired V(t) and T_i(t); the temperature rise ΔT_i(t) curve and the temperature rise gradient G_ab(t) curve, including G_max and t_eval; the hot resistance R_hot, the equivalent resistance R_ref, and the compensation parameters alpha, T_eq, and T_ref; risk location and defect type indications, and suggested remedial measures.

[0086] In summary, the present invention combines Figure 2Under the framework of the on-site joint test procedure shown, quantitative on-site evaluation and risk location output of the contact status of the DC GIS conduction loop are achieved through baseline loop resistance measurement, controlled injection temperature rise synchronous acquisition, multi-point temperature rise and temperature rise gradient calculation, stability judgment, hot resistance measurement and temperature compensation conversion, and joint criterion judgment. This method uses the temperature rise gradient as the primary criterion and combines it with the loop resistance conversion value as a constraint, which can improve the detection sensitivity and location capability of local contact anomalies, and enhance the consistency of judgment under different ambient temperatures and heat dissipation conditions. It is suitable for on-site application scenarios such as DC GIS handover acceptance, repair and maintenance, and condition verification.

[0087] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0088] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0089] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A field joint test method for the resistance of DC GIS circuits based on temperature rise gradient, used for evaluating the contact status of the conductive parts of the main circuit of DC GIS or DC gas-insulated switchgear, characterized in that: Includes the following steps: S1: Determine the test boundary of the circuit under test, and arrange temperature monitoring points in the critical contact area of ​​the circuit under test and its upstream and downstream conductor sections; S2: Measure the baseline loop resistance of the DC GIS circuit under test; S3: Under controlled DC injection heating conditions, simultaneously collect temperature data at multiple points near the contact point and upstream and downstream conductor sections; S4: Construct temperature rise distribution and temperature rise gradient distribution based on multi-point temperature data; S5: Measure the loop resistance again in the case of temperature rise or thermal stability, and perform temperature compensation to obtain the equivalent resistance at the reference temperature; S6: Construct a joint diagnostic model based on temperature rise gradient and equivalent resistance to identify the location of contact anomalies and assess the degree of anomalies; S7: Output assessment results including risk location information and treatment recommendations.

2. The method for joint field testing of DC GIS loop resistance based on temperature rise gradient according to claim 1, characterized in that: In S1, at least three sets of temperature monitoring points are set in the vicinity of each contact point to be evaluated, located on the contact point body, the upstream conductor of the contact point and the downstream conductor of the contact point, respectively. It also includes setting reference monitoring points to characterize the overall temperature rise level on a reference conductor segment far from the contact point.

3. The method for joint field testing of DC GIS loop resistance based on temperature rise gradient according to claim 1, characterized in that: The controlled DC injection heating condition in S3 is a multi-stage stepped current or continuous ramp current method, and temperature data is collected during each current holding stage.

4. The method for joint field testing of DC GIS loop resistance based on temperature rise gradient according to claim 2, characterized in that: The temperature rise gradient distribution includes the ratio of the temperature rise difference between adjacent monitoring points to the distance between the monitoring points, wherein the location corresponding to the peak value of the temperature rise gradient indicates the suspected location of contact anomaly.

5. The method for joint field testing of DC GIS loop resistance based on temperature rise gradient according to claim 2, characterized in that: S4 further includes calculating a gradient anomaly coefficient, which is the ratio of the peak value of the local temperature rise gradient to the overall gradient reference value of the loop, wherein: The gradient reference value is the average temperature rise gradient of the non-contact area in the same circuit or the average gradient of multiple control monitoring point pairs.

6. The method for joint field testing of DC GIS loop resistance based on temperature rise gradient according to claim 1, characterized in that: The thermal stability scenario determination in S5 includes: The temperature rise rate of the hot spot monitoring point is less than or equal to the preset threshold and the duration is not less than the preset duration, or the temperature rise gradient rate is less than or equal to the preset threshold and the duration is not less than the preset duration.

7. The method for joint field testing of DC GIS loop resistance based on temperature rise gradient according to claim 6, characterized in that: The temperature compensation in S5 is obtained by dividing the hot-state loop resistance by the temperature compensation coefficient, wherein the temperature compensation coefficient is calculated based on the temperature coefficient of the conductor material and the difference between the hot-state equivalent temperature and the reference temperature.

8. The method for joint field testing of DC GIS loop resistance based on temperature rise gradient according to claim 1, characterized in that: The joint diagnostic model also includes defect type identification, which outputs at least one defect risk warning based on equivalent resistance value, temperature rise gradient peak, gradient anomaly coefficient, and gradient response characteristics as a function of current, such as loose contact, contact surface contamination, assembly misalignment, insufficient elasticity, or abnormal local cross-section of conductor.

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