A diagnostic method and system for reliability of a switch cabinet wrench contact holding spring

Abstract

The application provides a switch cabinet wye contact holding spring reliability diagnosis method and system, determines the switch cabinet wye contact holding spring type and operation parameters, establishes a creep constitutive model related to temperature and time according to the creep test results of the holding spring under different temperature and stress conditions; based on the creep constitutive model, the size and operation service parameters of the holding spring are combined to determine the spring holding force change curve in the spring stress relaxation process; according to the influence law of the spring holding force on the contact resistance and temperature rise, the critical holding force leading to the overheating fault is determined; based on the spring holding force change curve and the determined critical holding force, according to the measured spring holding force, the time required for the spring stress relaxation to reach the critical holding force, that is, the residual reliable operation time, is calculated, the application can quickly and accurately judge the residual time of the spring reliable operation, and avoids the cost increase and resource waste caused by early replacement.

Description

Technical Field

[0001] The invention belongs to the technical field of equipment diagnosis, and relates to a method and system for diagnosing the reliability of a clamping spring of a plum blossom contact of a switch cabinet. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0004] With the continuous development of the national economy and society, people have placed higher demands on the reliability of power supply equipment. High-voltage switchgear, as a key electrical equipment in the power system, primarily receives and distributes electrical energy. Its quality and reliability are directly related to the safe and stable operation of the main transformer and even the substation. Heating and even overheating are common internally in 10kV to 35kV switchgear, especially in main input cabinets or during peak seasonal power demand periods. Heating of switchgear contacts is one of the most common forms of internal overheating failures in switchgear. The switchgear's plum blossom contacts feature an externally clamped spring structure. Long-term exposure to high temperatures and stresses can lead to stress relaxation and performance degradation, making contact tightness difficult to maintain. This increases contact resistance and causes overheating failures.

[0005] In order to ensure the safety and reliability of switchgear operation and avoid overheating failures, the holding springs need to be regularly inspected and replaced. However, there is still a lack of evaluation basis for the replacement of holding springs. At present, in actual operation and maintenance, operation and maintenance personnel generally make assessments based on experience. This may result in premature replacement, resulting in waste of resources and increased operating costs, and may also result in overheating failures during service due to failure to replace them in time. In order to solve the problem of replacing holding springs during switchgear operation and maintenance, a study disclosed a test device for the holding force of switchgear contact springs. However, the inventors found that although this method measures the magnitude of the holding force, it cannot accurately evaluate the reliability and safety of the spring operation, and cannot identify springs with hidden dangers whose service life is insufficient to serve until the next maintenance, resulting in a lack of reliable basis for spring replacement. Summary of the Invention

[0006] To address the above-mentioned issues, the present invention proposes a method and system for diagnosing the reliability of the clamping spring of a switch cabinet plum blossom contact. Based on the clamping force data, the present invention accurately determines the remaining time for the spring to operate reliably, thus avoiding the cost increase and resource waste caused by premature replacement.

[0007] According to some embodiments, the present invention adopts the following technical solutions:

[0008] A method for diagnosing the reliability of a switch cabinet plum blossom contact holding spring comprises the following steps:

[0009] Determine the type and operating parameters of the switchgear plum blossom contact holding spring. Based on the creep test results of this type of holding spring under different temperature and stress conditions, establish a temperature- and time-dependent creep constitutive model.

[0010] Based on the creep constitutive model and in combination with the size and operating service parameters of the holding spring, a spring holding force variation curve during the spring stress relaxation process is determined;

[0011] According to the influence of spring holding force on contact resistance and temperature rise, the critical holding force that causes overheating failure is determined;

[0012] Based on the spring holding force variation curve and the determined critical holding force, and according to the measured spring holding force, the time required for the spring stress relaxation to reach the critical holding force is calculated, which is the remaining reliable operation time;

[0013] Compare the remaining reliable operating time with the maintenance period to determine whether the retaining spring needs to be replaced during the current maintenance period.

[0014] As an optional implementation method, the specific process of determining the type and operating parameters of the clamping spring of the switch cabinet plum blossom contact includes: determining the clamping spring material, geometric characteristics and dimensional parameters, and operating service parameters based on the shape characteristics and related dimensional parameters of the high-voltage contact and the operating parameters of the switch cabinet.

[0015] As a further limitation, the operation and service parameters include the service temperature of the switch cabinet contact part during normal operation and service and the operation and service time.

[0016] As an optional implementation, the process of establishing a creep constitutive model related to temperature and time includes: conducting creep tests in advance, or obtaining known creep test data of a clamping spring of this type of material, using the creep strain rate of the material as the product of stress, time, and temperature functions to construct a creep constitutive model, and giving the test data to calibrate the model parameters.

[0017] As an optional implementation method, the specific process of determining the spring clamping force change curve during the spring stress relaxation process includes establishing an accurate spring simulation model and dividing the grid based on the spring characteristics and related dimensional parameters, using the spring creep constitutive model, setting boundary conditions based on the actual elongation during service, carrying out spring stress relaxation simulation and experimental verification, and determining the clamping force change curve during the spring stress relaxation process.

[0018] As an optional implementation method, based on the influence of the spring holding force on the contact resistance and temperature rise of the contacts, the specific process of determining the critical holding force that causes an overheating failure includes: conducting a temperature rise test on the contacts under different holding force conditions in advance, or obtaining the temperature rise test results of the contacts under different holding force conditions, clarifying the influence of the spring holding force on the contact resistance and temperature rise of the contacts, and further obtaining the critical holding force for the temperature rise failure caused by insufficient holding force.

[0019] Furthermore, it is determined that the temperature rise required for the operation safety of the corresponding model of switchgear does not exceed the set threshold. Then, contact temperature rise tests or numerical simulations are performed under different clamping force conditions to obtain the clamping force when the temperature rise exceeds the set threshold, which is the critical clamping force of the switchgear model.

[0020] As an optional implementation method, the remaining reliable operation time is compared with the maintenance cycle to determine whether the clamping spring needs to be replaced in the current maintenance cycle. The specific process includes converting the remaining reliable operation time and the maintenance cycle to the same unit, comparing the remaining reliable operation time and the maintenance cycle, and if the remaining reliable operation time is less than the maintenance cycle, the clamping spring needs to be replaced in the current maintenance cycle.

[0021] A switch cabinet plum blossom contact holding spring reliability diagnosis system, comprising:

[0022] The creep constitutive model building module is configured to determine the type and operating parameters of the switchgear plum blossom contact holding spring and establish a temperature- and time-dependent creep constitutive model based on creep test results of this type of holding spring under different temperature and stress conditions.

[0023] a spring holding force variation curve determination module configured to determine a spring holding force variation curve during a spring stress relaxation process based on the creep constitutive model and in combination with dimensions and operational service parameters of the holding spring;

[0024] a critical holding force determination module configured to determine a critical holding force that causes an overheating fault based on a law of influence of the spring holding force on contact resistance and temperature rise of the contacts;

[0025] a remaining reliable operation time determination module configured to calculate, based on the spring holding force variation curve and the determined critical holding force and according to the measured spring holding force, a time required for the spring stress relaxation to reach the critical holding force, which is the remaining reliable operation time;

[0026] The comparison module is configured to compare the remaining reliable operating time with the maintenance cycle to determine whether the retaining spring needs to be replaced in the current maintenance cycle.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) Monitoring is more convenient and the prediction accuracy is high. By reliably establishing a stress relaxation model of the spring, the change of the spring holding force is predicted. By comparing the actual holding force measured during operation and maintenance with the prediction results of the stress relaxation model, monitoring is simpler, safer and more reliable.

[0029] (2) The cost is lower than that of traditional methods. Compared with traditional temperature measurement methods, the present invention can accurately predict the life of the spring, avoid premature replacement, and save costs.

[0030] (3) The entire operation method is simple, low-cost, and universal. The test model can be directly integrated with the existing clamping spring force measurement system to achieve production application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0032] Figure 1 Flowchart for contact spring aging reliability diagnosis.

[0033] Figure 2 This is the contact spring reliability criterion diagram. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0035] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0036] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0037] As mentioned above, heating and even overheating are common inside 10kV to 35kV switchgear, especially in main input cabinets or during seasonal peak electricity consumption periods. In actual operation, it is generally necessary to regularly inspect the contacts and replace aging springs in a timely manner. However, there is currently a lack of reliable diagnostic methods for the reliability of the operation of service springs, which makes the replacement of contact springs rely more on the subjective opinions of operation and maintenance personnel. In order to reliably evaluate the operational reliability of the switchgear contact clamping springs, the present invention proposes a diagnostic method for the reliability of the switchgear plum blossom contact clamping springs. Through numerical simulation and experimental testing, the changing law of the reduction of the spring stress relaxation clamping force is accurately predicted, and the spring operational reliability is reliably evaluated. The specific steps are as follows:

[0038] Step 1: Based on the switchgear model and related nameplate information, obtain the contact shape characteristics and related dimensional parameters and switchgear operating parameters, and determine the holding spring material, geometric characteristics and dimensional parameters, and operating service parameters;

[0039] According to the specific switchgear model parameters and nameplate information, the corresponding holding spring material information, size parameters and operating service parameters can be obtained.

[0040] Step 2: Conduct a creep test on the corresponding spring material or obtain the creep test results of the corresponding spring material, and establish a creep constitutive model of the spring material based on the test results;

[0041] Step 3: Conduct a stress relaxation test on the corresponding type of spring, establish a spring stress relaxation model and perform experimental calibration to obtain a clamping force variation curve of the spring under service conditions;

[0042] Step 4: Conduct contact temperature rise tests under different holding force conditions or establish a contact thermoelectric coupling numerical model and perform experimental calibration to measure the contact resistance between the contact petal and the contact arm under different spring holding forces. Apply this resistance to the contact thermoelectric coupling numerical model to predict the contact temperature rise and obtain the relationship between the holding force and the contact temperature rise.

[0043] In this embodiment, the contact thermoelectric coupling numerical model can be a model in the existing technology, for example, the contact thermoelectric coupling numerical model provided in the invention patent application number 202111664462X "A method and system for predicting temperature rise of switch cabinet contacts".

[0044] Step 5: Based on the switchgear operation safety requirements and the contact temperature rise predicted in step 4, determine the critical spring clamping force for the switchgear contact to cause an overheating fault;

[0045] Specifically, for example, if the operating safety requirement for a certain type of switchgear is that the temperature rise does not exceed a certain set threshold, a contact temperature rise test or numerical simulation is performed under different clamping force conditions to obtain the clamping force when the temperature rise exceeds the set threshold, which is the critical clamping force of the switchgear model.

[0046] Step 6: Based on the critical holding force and the measured holding force, and according to the spring stress relaxation curve, determine the remaining time for the holding spring to operate safely, such as Figure 2 As shown;

[0047] Step 7: Determine the maintenance interval based on the daily maintenance specifications and requirements of the switchgear being tested;

[0048] Step 8: Determine the spring operation safety and maintenance requirements based on the relationship between the maintenance time interval and the predicted remaining spring operation time, such as whether maintenance is required within the current maintenance cycle.

[0049] The spring of the contact can be made of different materials, such as stainless steel, alloy steel, carbon steel, copper alloy, nickel-based alloy, beryllium bronze, etc.

[0050] The current passing through the switch cabinet contacts can be changed, such as 630A, 1250A, 2500A, 3200A, 4000A, etc.

[0051] The voltage of the switchgear can be changed, such as 12kV, 10kV, etc.

[0052] The dimensions of the switchgear contacts can vary.

[0053] The shape, size and preload force generated by the switch cabinet contact springs can be different.

[0054] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0055] Example 1

[0056] The switchgear holding spring tested is made of 304L stainless steel, with a coil diameter of 5.00mm, a coil pitch of 1.31mm, and a wire diameter of 1.0mm. The specific evaluation method includes the following steps:

[0057] (1) According to the shape characteristics and relevant dimensional parameters of the high-voltage switchgear contacts and the switchgear operating parameters, the material of the holding spring is determined to be 304L stainless steel, the geometric dimensional parameters are a ring diameter of 5.00 mm, a ring pitch of 1.3 mm, and a wire diameter of 1.0 mm. The temperature of the switchgear contact during normal operation is 85°C.

[0058] (2) Conduct creep tests under typical temperature and stress conditions based on the spring material; the creep strain rate of the material It can be written as the product of stress σ, time t, and temperature T functions, such as (where A and C are material parameters, ΔH is activation energy, k is the Boltzmann constant, n is stress order, and m is time order). The model parameters are calibrated using the test results, and the creep constitutive model of 304L spring material is obtained as follows:

[0059] (3) According to the spring characteristics and related dimensional parameters, an accurate CAD model of the spring is established and the mesh is divided. The spring creep constitutive model obtained in step (2) is used to set boundary conditions according to the actual elongation during service, and the spring stress relaxation simulation and experimental verification are carried out to determine the clamping force change curve during the spring stress relaxation process;

[0060] (4) Carry out temperature rise tests and simulations of contacts under different holding force conditions to clarify the influence of spring holding force on contact resistance and temperature rise, and obtain the critical holding force for temperature rise failure caused by insufficient holding force to be 120N.

[0061] (5) During the operation, maintenance and inspection of the switch cabinet, the clamping force of the contact clamping spring is measured. The actual clamping force of the spring is 150N.

[0062] (6) Based on the clamping force variation curve during the spring stress relaxation process obtained in step (3), determine the time required for the spring to decrease from 150N to the critical clamping force of 120N under normal use conditions. It is calculated that the remaining time for the normal and reliable operation of the clamping spring is 5000h.

[0063] (7) According to the daily maintenance time cycle of the switch cabinet being tested, if the operation and maintenance cycle of this switch cabinet is half a year, it is about 4392 hours (calculated as 183 days).

[0064] (8) Comparing the remaining time of the spring's reliable operation with the maintenance cycle, it can be seen that the spring's reliable operation time is much longer than the maintenance cycle. Therefore, the spring is safe and reliable in this inspection and does not need to be replaced this time.

[0065] Example 2

[0066] The simulated holding spring material is a beryllium bronze spring with a spring coil diameter of 6.00mm, a coil pitch of 1.2mm, and a wire diameter of 0.8mm. The specific evaluation method includes the following steps:

[0067] (1) According to the shape characteristics and relevant dimensional parameters of the high-voltage switchgear contacts and the switchgear operating parameters, the material of the holding spring is determined to be beryllium bronze, the geometric dimensional parameters are a ring diameter of 6.00 mm, a ring pitch of 1.20 mm, and a wire diameter of 0.8 mm. The internal temperature of the switchgear during normal operation and service is 105°C.

[0068] (2) According to the creep test of spring material under typical temperature and stress conditions, the creep strain rate of the material can be written as the product of stress, time and temperature functions, such as The test results are used to calibrate the model parameters and the corresponding creep constitutive model of the spring material can be obtained.

[0069] (3) According to the spring characteristics and related dimensional parameters, an accurate CAD model of the spring is established and the mesh is divided. The spring creep constitutive model obtained in step (2) is used to set boundary conditions according to the actual elongation during service, and the spring stress relaxation simulation and experimental verification are carried out to determine the clamping force change curve during the spring stress relaxation process;

[0070] (4) Conduct temperature rise tests on contacts under different holding force conditions to clarify the influence of spring holding force on contact resistance and temperature rise, and obtain the critical holding force for temperature rise failure caused by insufficient holding force to be 180N.

[0071] (5) During the operation, maintenance and inspection of the switch cabinet, a force measuring device is used to measure the clamping force of the contact clamping spring. The measured clamping force of the spring is 210N.

[0072] (6) Based on the clamping force variation curve during the spring stress relaxation process obtained in step (3), determine the time required for the spring to decrease from 210N to the critical clamping force of 180N under normal use conditions, and determine that the remaining time for reliable operation of the clamping spring is 1500h.

[0073] (7) According to the daily maintenance time cycle of the switch cabinet being tested, if the periodic maintenance time of this switch cabinet is one year, it is about 8760 hours (calculated based on 365 days).

[0074] (8) Comparing the remaining time of the spring's reliable operation with the maintenance cycle, it can be seen that the spring's reliable operation time is much shorter than the maintenance cycle. Therefore, the spring has a safety hazard during this inspection and needs to be replaced.

[0075] The present invention also provides a switch cabinet plum blossom contact holding spring reliability diagnosis system, comprising:

[0076] The creep constitutive model building module is configured to determine the type and operating parameters of the switchgear plum blossom contact holding spring and establish a temperature- and time-dependent creep constitutive model based on creep test results of this type of holding spring under different temperature and stress conditions.

[0077] a spring holding force variation curve determination module configured to determine a spring holding force variation curve during a spring stress relaxation process based on the creep constitutive model and in combination with dimensions and operational service parameters of the holding spring;

[0078] a critical holding force determination module configured to determine a critical holding force that causes an overheating fault based on a law of influence of the spring holding force on contact resistance and temperature rise of the contacts;

[0079] a remaining reliable operation time determination module configured to calculate, based on the spring holding force variation curve and the determined critical holding force and according to the measured spring holding force, a time required for the spring stress relaxation to reach the critical holding force, which is the remaining reliable operation time;

[0080] The comparison module is configured to compare the remaining reliable operating time with the maintenance cycle to determine whether the retaining spring needs to be replaced in the current maintenance cycle.

[0081] Although the above describes the specific embodiments of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without any creative work are still within the scope of protection of the present invention.

Claims

1. A method for diagnosing the reliability of a switch cabinet plum blossom contact holding spring, characterized in that: The following steps are involved: Determine the type and operating parameters of the switchgear plum blossom contact holding spring. Based on the creep test results of this type of holding spring under different temperature and stress conditions, establish a temperature- and time-dependent creep constitutive model. Based on the creep constitutive model and in combination with the size and operating service parameters of the holding spring, a spring holding force variation curve during the spring stress relaxation process is determined; According to the influence of spring holding force on contact resistance and temperature rise, the critical holding force that causes overheating failure is determined; Based on the spring holding force variation curve and the determined critical holding force, and according to the measured spring holding force, the time required for the spring stress relaxation to reach the critical holding force is calculated, which is the remaining reliable operation time; Compare the remaining reliable operating time with the maintenance period to determine whether the retaining spring needs to be replaced during the current maintenance period.

2. A switch cabinet plum blossom contact holding spring reliability diagnosis method according to claim 1, characterized in that: The specific process of determining the type and operating parameters of the switch cabinet plum blossom contact holding spring includes: determining the holding spring material, geometric characteristics and dimensional parameters, and operating service parameters based on the shape characteristics and related dimensional parameters of the high-voltage contact and the switch cabinet operating parameters.

3. A switch cabinet plum blossom contact holding spring reliability diagnosis method according to claim 1, characterized in that: The operation and service parameters include the service temperature of the switch cabinet contact part during normal operation and the operation and service time.

4. A switch cabinet plum blossom contact holding spring reliability diagnosis method according to claim 1, characterized in that: The process of establishing a temperature- and time-dependent creep constitutive model includes: conducting a creep test in advance, or obtaining known creep test data of the clamping spring, using the creep strain rate of the material of the clamping spring to construct a creep constitutive model, and giving the test data to calibrate the model parameters, where the creep strain rate is the product of stress, time, and temperature functions.

5. A switch cabinet plum blossom contact holding spring reliability diagnosis method according to claim 1, characterized in that: The specific process of determining the spring holding force variation curve during the spring stress relaxation process includes establishing an accurate spring simulation model and dividing the grid according to the spring characteristics and related dimensional parameters, using the spring creep constitutive model, setting boundary conditions according to the actual elongation during service, conducting spring stress relaxation simulation and experimental verification, and determining the spring holding force variation curve during the spring stress relaxation process.

6. A switch cabinet plum blossom contact holding spring reliability diagnosis method according to claim 1, characterized in that: Based on the influence of spring holding force on contact resistance and temperature rise, the specific process of determining the critical holding force that causes overheating failure includes: based on the temperature rise results, clarifying the influence of spring holding force on contact resistance and temperature rise, and further obtaining the critical holding force for temperature rise failure caused by insufficient holding force.

7. A switch cabinet plum blossom contact holding spring reliability diagnosis method according to claim 6, characterized in that: Determine that the temperature rise required for the operation safety of the corresponding model of switchgear does not exceed the set threshold, then conduct contact temperature rise tests or numerical simulations under different holding force conditions to obtain the holding force when the temperature rise exceeds the set threshold, which is the critical holding force of the switchgear model.

8. A switch cabinet plum blossom contact holding spring reliability diagnosis method according to claim 6, characterized in that: The temperature rise results are results obtained by pre-performing temperature rise tests on the contacts under different holding force conditions, or obtained temperature rise test results of the contacts under different holding force conditions.

9. A method for diagnosing the reliability of a switch cabinet plum blossom contact holding spring according to claim 6, characterized in that: The specific process of comparing the remaining reliable operating time with the maintenance cycle to determine whether the holding spring needs to be replaced in the current maintenance cycle includes converting the remaining reliable operating time and the maintenance cycle to the same unit, comparing the remaining reliable operating time with the maintenance cycle, and if the remaining reliable operating time is less than the maintenance cycle, the holding spring needs to be replaced in the current maintenance cycle.

10. A diagnostic system for the reliability of the plum blossom contact holding spring of a switch cabinet, characterized by: include: The creep constitutive model building module is configured to determine the type and operating parameters of the switchgear plum blossom contact holding spring and establish a temperature- and time-dependent creep constitutive model based on creep test results of this type of holding spring under different temperature and stress conditions. a spring holding force variation curve determination module configured to determine a spring holding force variation curve during a spring stress relaxation process based on the creep constitutive model and in combination with dimensions and operational service parameters of the holding spring; a critical holding force determination module configured to determine a critical holding force that causes an overheating fault based on a law of influence of the spring holding force on contact resistance and temperature rise of the contacts; a remaining reliable operation time determination module configured to calculate, based on the spring holding force variation curve and the determined critical holding force and according to the measured spring holding force, a time required for the spring stress relaxation to reach the critical holding force, which is the remaining reliable operation time; The comparison module is configured to compare the remaining reliable operating time with the maintenance cycle to determine whether the retaining spring needs to be replaced in the current maintenance cycle.

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