Intelligent monitoring method for contact resistance fault of ring main unit

Abstract

The application relates to the technical field of power equipment, in particular to an intelligent monitoring method for contact resistance faults of a ring main unit, which comprises the following steps: periodically collecting current data, calculating average current, drawing a period average current curve, converting discrete current data into a continuous trend curve, and intuitively reflecting the dynamic change of the contact resistance, for example, when the contact resistance increases, the current will present a downward trend with the period, and the absolute value of the curve slope will change accordingly, the change can be captured in real time through the curve, compared with static data collection, the method can accurately depict the process of resistance change, provides a more comprehensive trend basis for subsequent analysis, and solves the problem that the current data is not fully applied in the prior art; in the application, the absolute value of the curve slope is calculated and compared with a preset absolute value, so that the strong operation fault tendency or the weak operation fault tendency can be determined at the initial stage of the poor contact problem.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of power equipment, and in particular to an intelligent monitoring method for contact resistance faults of a ring main unit. BACKGROUND

[0002] As a key device in a power distribution network, a ring main unit is widely used in urban power distribution networks, industrial parks and the like, and the core function thereof is to realize ring network power supply, breaking and protection of a power distribution line. The contact state of a wiring terminal in the ring main unit directly affects the stability of power transmission: when the wiring terminal has poor contact, the contact resistance increases, which may cause local joule heat accumulation and lead to overheating, long-term operation may cause insulation aging and equipment burning, and even cause power failure accidents, which seriously threatens the safe operation of the power system.

[0003] At present, the monitoring of contact resistance faults of the ring main unit mainly relies on two ways: one is manual regular inspection, and the temperature of the wiring terminal is detected by an infrared temperature detector. This way has the problems of poor real-time performance, high labor intensity, being easily affected by human experience and the like, and is difficult to capture sudden contact fault. The other is a traditional automatic monitoring system, which mainly collects temperature data through an embedded temperature sensor. However, the system can only passively feed back the overheating result, cannot predict the contact resistance change trend in advance, and is difficult to distinguish different fault reasons such as insufficient contact pressure, oxidation or pollution of the wiring terminal surface, which leads to insufficient fault treatment pertinence. The existing method is difficult to dynamically capture the contact resistance change trend through current data, cannot determine the operation fault tendency type in advance, and leads to lagged fault response.

[0004] Chinese patent application No. CN202510109535.0 discloses an intelligent ring main unit and a monitoring method thereof, which comprises a circuit breaker energy storage spring, a tripping spring, a tripping and closing coil, an energy storage motor, a first pressure sensor, a second pressure sensor, a Hall sensor and a data processing unit. The first pressure sensor and the second pressure sensor are connected with the circuit breaker energy storage spring and the tripping spring respectively. The first pressure sensor collects pressure information of the circuit breaker energy storage spring and transmits the pressure information to the data processing unit. The second pressure sensor collects pressure information of the tripping spring and transmits the pressure information to the data processing unit. The Hall sensor collects action current information of the tripping and closing coil and the energy storage motor and transmits the action current information to the data processing unit. The application can find faults in the early stage and timely eliminate the faults to ensure the continuity of power supply, and can accurately determine the fault position.

[0005] However, the prior art still has the following problems:

[0006] The existing method is difficult to dynamically capture the contact resistance change trend through current data, and cannot determine the running fault tendency type in advance, resulting in lagging fault response. SUMMARY

[0007] Therefore, the application provides an intelligent monitoring method for contact resistance faults of a ring main unit to overcome the problem that it is difficult to dynamically capture the contact resistance change trend through current data in the prior art, and the running fault tendency type cannot be determined in advance, resulting in lagging fault response.

[0008] To achieve the above-mentioned purpose, the application provides an intelligent monitoring method for contact resistance faults of a ring main unit. The method comprises the following steps:

[0009] Step S1, periodically collecting current data information at each wiring terminal in the cable chamber, calculating the average current value of each period, and drawing a period-average current curve;

[0010] Step S2, calculating the curve slope of the curve in the current detection period, and determining the running fault tendency type of the ring main unit based on the absolute value of the curve slope;

[0011] Step S3, determining the analysis mode for the ring main unit based on the running fault tendency type of the ring main unit, comprising:

[0012] determining that the running condition of the ring main unit is unqualified and the unqualified reason is the existence of a wiring terminal with poor contact, and adjusting the contact pressure based on the curve slope, and analyzing whether to correct the contact pressure based on the proportion of the number of abnormal wiring terminals,

[0013] or, determining that the running condition of the ring main unit is qualified;

[0014] Step S4, outputting the analysis result.

[0015] Further, in the step S2, the absolute value of the curve slope is used to determine the running fault tendency type of the ring main unit, comprising:

[0016] If the absolute value of the curve slope is greater than or equal to a preset absolute value, it is determined that the running fault tendency type of the ring main unit is strong running fault tendency;

[0017] If the absolute value of the curve slope is less than the preset absolute value, it is determined that the running fault tendency type of the ring main unit is weak running fault tendency.

[0018] Further, in the step S3, the analysis mode for the ring main unit is determined based on the running fault tendency type of the ring main unit, comprising:

[0019] If the running fault tendency type of the ring net cabinet is a strong running fault tendency, it is determined that the running condition of the ring net cabinet is unqualified and the unqualified reason is that there is a poor contact wiring terminal, and the contact pressure is adjusted based on the curve slope, and whether the contact pressure is corrected is analyzed based on the proportion of the number of abnormal wiring terminals;

[0020] If the running fault tendency type of the ring net cabinet is a weak running fault tendency, it is determined that the running condition of the ring net cabinet is qualified.

[0021] Further, the adjusting the contact pressure based on the curve slope comprises:

[0022] The absolute value of the curve slope is calculated, and the difference between the preset absolute value is obtained, and the absolute difference value, wherein the increase range of the contact pressure is positively correlated with the absolute difference value.

[0023] Further, when the adjustment to the contact pressure is completed, whether the contact pressure is corrected is analyzed based on the proportion of the number of abnormal wiring terminals, comprising:

[0024] Filtering the abnormal wiring terminal and counting the number of abnormal wiring terminals,

[0025] The ratio of the number of abnormal wiring terminals to the total number of wiring terminals is calculated to obtain an abnormal proportion,

[0026] If the abnormal proportion is greater than or equal to the preset abnormal proportion, it is determined that the contact pressure is not corrected;

[0027] If the abnormal proportion is less than the preset abnormal proportion, it is determined that the contact pressure is corrected, wherein the decrease amount of the contact pressure in the correction process is negatively correlated with the abnormal proportion.

[0028] Further, when the adjustment to the contact pressure is completed, the current difference between the preset current and the actual current at each wiring terminal is calculated, and the contact pressure for a single wiring terminal is corrected based on the current difference, wherein the increase amount of the contact pressure is positively correlated with the current difference.

[0029] Further, when the adjustment to the contact pressure is completed, steps S1-S3 are repeated, if it is determined that the running condition of the ring net cabinet is unqualified, it is determined that the contact pressure is adjusted based on the reacquired curve slope, and it is determined that the running condition of the ring net cabinet is unqualified. The reason is that the surface of the wiring terminal is unqualified.

[0030] Further, when it is determined that the surface of the wiring terminal is unqualified, the curve data in the current detection period is extracted, the curve integral value is calculated, and the processing mode is determined based on the curve integral value, comprising:

[0031] If the curve integral is less than or equal to the preset curve integral, it is determined that a replacement joint notification signal is sent;

[0032] If the curve integral is greater than the preset curve integral, it is determined to adjust the heat dissipation operation power.

[0033] Further, when determining to adjust the heat dissipation operation power, the integral difference between the curve integral and the preset curve integral is calculated, wherein the increase amount of the heat dissipation operation power is positively correlated with the integral difference.

[0034] Further, when the adjustment to the heat dissipation operation power is completed, steps S1-S3 are re-executed, and if it is determined that the operating condition of the ring main unit is unqualified, it is determined to issue a replacement joint notification signal.

[0035] Compared with the prior art, the beneficial effects of the present application are that, in the present application, by periodically collecting current data, calculating the average current, and drawing the period average current curve, the discrete current data is converted into a continuous trend curve, which intuitively reflects the dynamic change of the contact resistance. For example, when the contact resistance increases, the current will show a downward trend with the period, and the absolute value of the curve slope will change accordingly. This change can be captured in real time through the curve. Compared with static data collection, this method can accurately depict the process of resistance change and provide a more comprehensive trend basis for subsequent analysis, solving the problem of insufficient application of current data in the prior art. In the present application, by calculating the absolute value of the curve slope and comparing it with the preset absolute value, the strong operation failure tendency or weak operation failure tendency can be determined at the initial stage of the contact failure problem. When the absolute value of the slope is greater than or equal to the preset value, the strong tendency that may cause serious failure is locked in advance. At this time, although the contact resistance has not reached the failure threshold, the change rate is already abnormal. By intervening in advance, the failure can be avoided. This trend prediction mode moves the failure judgment node from after the failure occurs to the failure brewing period, solving the core pain point of the response lag of the prior art.

[0036] Further, in the present application, considering that the prior art often lacks clear risk classification standards, either over-processing slight current fluctuations (leading to increased equipment wear and tear) or reacting slowly to significant abnormal signals (missing the best intervention opportunity), step S2 clearly divides the failure tendency into two categories: "strong operation failure tendency" and "weak operation failure tendency" through the comparison of the absolute value of the curve slope with the preset absolute value. When the absolute value of the slope is greater than or equal to the preset value, the high-risk state (such as rapid increase of contact resistance) is directly locked. When the absolute value of the slope is less than the preset value, it is determined to be a low-risk state (such as normal fluctuation). This clear definition avoids ambiguous risk judgment, prevents over-intervention on slight abnormalities, and ensures that serious risks are identified in a timely manner, achieving precise classification and control of failure risks.

[0037] Further, in the present application, it is considered that the essence of poor contact is the increase of contact resistance, and the contact pressure is the key factor affecting the resistance. Insufficient pressure will cause the resistance to rise, and excessive pressure may cause the terminal to deform. In step S3, the logic of adjusting the contact pressure based on the curve slope, by calculating the absolute difference (the difference between the absolute value of the curve slope and the preset absolute value), makes the pressure increase positively correlated with the degree of abnormality. This dynamic adjustment mechanism avoids the limitations of "fixed value adjustment": when the abnormality is slight (small difference), a small increase in pressure can improve the contact; when the abnormality is significant (large difference), the resistance is quickly reduced by a larger increase in pressure. Compared with the traditional "uniformly increase fixed pressure" method, this method not only ensures the repair effect, but also prevents excessive adjustment from causing secondary damage to the equipment, achieving "on-demand adjustment" for precise repair.

[0038] Further, in the present application, it is considered that when the proportion of abnormal terminals is greater than or equal to the preset abnormality proportion, it means that there may be systematic problems, such as overall failure of the pressure device or general aging of the terminals. At this time, if the contact pressure is still corrected, it will not only fail to solve the root problem, but also may exacerbate equipment wear due to repeated adjustments. The determination of not correcting in the step can timely terminate invalid pressure adjustment and guide the maintenance personnel to investigate the systematic reasons (such as checking whether the pressure device is malfunctioning), avoiding wasting resources on surface adjustment and improving the directionality and efficiency of fault handling.

[0039] Further, in the present application, it is considered that in the ring network cabinet, most terminals are usually in normal operation state (current difference close to 0). If the pressure of all terminals is uniformly adjusted, it will cause unnecessary high pressure on normal terminals, accelerating their aging and deformation (such as plastic deformation of copper terminals under long-term overpressure). In the step, only the terminals with current difference are adjusted, and the normal terminals maintain the original pressure, avoiding the "non-discriminatory adjustment" of normal components.

[0040] Further, in the present application, it is considered that the contact pressure is not the bigger the better: exceeding the pressure limit of the terminal material (such as copper terminals exceeding 750N) will cause deformation and cracking, and excessive frequent adjustment (such as more than 4 times) will accelerate the mechanical wear of the pressure device. In the step, the rule of "adjusting to reach the critical value or stopping when the number of adjustments reaches the critical value" restricts the adjustment behavior from both physical limits and mechanical life through "pressure critical value" and "number of times critical value".

[0041] Further, the present application considers that the severity of the terminal surface unqualified is not completely consistent, slight oxidation may only cause the contact resistance to slowly rise, and serious ablation may cause local overheating in a short time. In the step, the curve integral value (reflecting the cumulative effect of current in a certain period, which is positively correlated with the heat generation) is calculated and compared with the preset curve integral, and the surface fault is divided into two categories of "low emergency degree" and "high emergency degree". For the surface fault with integral ≤ preset value (such as slight oxidation), it will not cause serious risk in a short time, so the replacement notice is sent instead of immediate shutdown for repair, which can avoid the production interruption (such as factory production line shutdown, data center downtime) caused by emergency shutdown. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 Flow chart for intelligent monitoring method of contact resistance fault of ring network cabinet;

[0043] Figure 2 Flow chart for determining operation fault tendency type of ring network cabinet;

[0044] Figure 3 Flow chart for determining analysis mode for ring network cabinet. DETAILED DESCRIPTION

[0045] In order to make the objects and advantages of the present application clearer, the present application will be further described below in combination with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present application, and do not limit the present application.

[0046] It should be pointed out that the data in the present embodiment are obtained by comprehensive analysis and evaluation of historical data and corresponding historical determination results of the present system in the past 6 months before the present determination. Those skilled in the art can understand that the determination mode of the present system for a single parameter can be to select the value with the highest proportion as the preset standard parameter according to the data distribution, to use weighted summation to obtain the value as the preset standard parameter, to substitute each historical data into a specific formula and to obtain the value by using the formula as the preset standard parameter, or other selection modes, as long as the present system can clearly define different specific conditions in the single determination process by the obtained value.

[0047] The preferred embodiments of the present application will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present application, and do not limit the protection scope of the present application.

[0048] It should be noted that in the description of the present application, the terms indicating the direction or positional relationship of "upper", "lower", "left", "right", "inner", "outer" and the like are based on the direction or positional relationship shown in the drawings, which is only for the convenience of description, and does not indicate or imply that the device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0049] In addition, it should be noted that in the description of the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0050] Please refer to Figure 1 The flow chart of the intelligent monitoring method for contact resistance fault of the ring main unit is shown.

[0051] The intelligent monitoring method for contact resistance fault of the ring main unit provided in the embodiment comprises:

[0052] Step S1, periodically collecting current data information at each wiring end in the cable chamber, calculating the average current value of each period, and drawing a period-average current curve;

[0053] Step S2, calculating the curve slope of the curve in the current detection period, and determining the operation fault tendency type of the ring main unit based on the absolute value of the curve slope;

[0054] Step S3, determining the analysis mode for the ring main unit based on the operation fault tendency type of the ring main unit, comprising:

[0055] determining that the operation condition of the ring main unit is unqualified and the unqualified reason is that there is a poor contact wiring end, and adjusting the contact pressure based on the curve slope, and analyzing whether to correct the contact pressure based on the proportion of the number of abnormal wiring ends,

[0056] or, determining that the operation condition of the ring main unit is qualified;

[0057] Step S4, outputting the analysis result.

[0058] In the present application, by periodically collecting current data, calculating the average current, and drawing the period-average current curve, the discrete current data is converted into a continuous trend curve, which intuitively reflects the dynamic change of the contact resistance. For example, when the contact resistance increases, the current will show a downward trend with the period, and the absolute value of the curve slope will change accordingly. This change can be captured in real time through the curve. Compared with static data collection, this method can accurately depict the process of resistance change and provide a more comprehensive trend basis for subsequent analysis, solving the problem of insufficient application of current data in the existing method. In the present application, by calculating the absolute value of the curve slope and comparing it with the preset absolute value, the strong running fault tendency or weak running fault tendency can be determined at the initial stage of the poor contact problem. When the absolute value of the slope is greater than or equal to the preset value, the strong tendency that may cause serious failure is locked in advance. At this time, although the contact resistance has not reached the failure threshold, the change rate is already abnormal. By intervening in advance, the failure can be avoided. This trend prediction mode moves the failure judgment node from after the failure occurs to the failure brewing period, solving the core pain point of the existing method of response lag.

[0059] Please refer to Figure 2 Fig. 2 is a flow chart for determining the running fault tendency type of the ring network cabinet.

[0060] Specifically, in step S2, the running fault tendency type of the ring network cabinet is determined based on the absolute value of the curve slope, comprising:

[0061] If the absolute value of the curve slope is greater than or equal to the preset absolute value, it is determined that the running fault tendency type of the ring network cabinet is a strong running fault tendency.

[0062] If the absolute value of the curve slope is less than the preset absolute value, it is determined that the running fault tendency type of the ring network cabinet is a weak running fault tendency.

[0063] Specifically, in the present embodiment, the preset absolute value can be determined by the following method: extracting the period-average current curve slope data set of the same type and same working condition ring network cabinet under normal operating state (no poor contact failure) within a preset time window (such as 6 months), calculating its statistical characteristics (such as mean, 95% quantile), and taking the 95% quantile as the initial reference benchmark (reflecting the maximum slope fluctuation in most normal scenarios); adjust according to the running load (such as peak / flat peak) and environmental temperature (high temperature easily aggravates the change of contact resistance) of the ring network cabinet: when the load is at the peak or the environmental temperature exceeds 35℃, the initial benchmark value is increased by 10%-15%; under low load or normal temperature environment, the benchmark value is decreased by 5%-10%; set a minimum threshold (such as a certain fixed value) to ensure that even in a low fluctuation scenario, significant abnormalities can be effectively identified; at the same time, set a maximum threshold (such as no more than 2 times the initial benchmark) to avoid excessive sensitivity leading to misjudgment.

[0064] The present application considers that the existing method is often lack of clear risk grading standard, or over-treats slight current fluctuation (leading to increased equipment loss), or reacts slowly to significant abnormal signals (missing the best intervention opportunity), so step S2 clearly divides the fault tendency into two categories of "strong running fault tendency" and "weak running fault tendency" by comparing the absolute value of the curve slope with the preset absolute value: when the absolute value of the slope is greater than or equal to the preset value, the high-risk state (such as rapid increase of contact resistance) is directly locked; when the absolute value of the slope is less than the preset value, the low-risk state (such as normal fluctuation) is determined. This clear definition of "this or that" avoids ambiguous risk judgment, prevents over-intervention on slight abnormalities, ensures that serious risks are identified in time, and realizes precise grading control of fault risks.

[0065] Please refer to Figure 3 As shown in the determination flow chart of the analysis mode for the ring net cabinet.

[0066] Specifically, in step S3, the analysis mode for the ring net cabinet is determined based on the running fault tendency type of the ring net cabinet, including:

[0067] If the running fault tendency type of the ring net cabinet is a strong running fault tendency, it is determined that the running condition of the ring net cabinet is unqualified and the unqualified reason is that there is a poor contact connection terminal, and the contact pressure is adjusted based on the curve slope, and whether the contact pressure is corrected is analyzed based on the proportion of the number of abnormal connection terminals.

[0068] If the running fault tendency type of the ring net cabinet is a weak running fault tendency, it is determined that the running condition of the ring net cabinet is qualified.

[0069] Specifically, the contact pressure is adjusted based on the curve slope, including:

[0070] The absolute difference value is obtained by calculating the difference between the absolute value of the curve slope and the preset absolute value, wherein the increase amplitude of the contact pressure is positively correlated with the absolute difference value.

[0071] Specifically, in this embodiment, it is assumed that the preset absolute value of a certain ring net cabinet determined by calculation is 0.33 A / cycle, and the absolute value of the curve slope in the current detection cycle is 0.5 A / cycle. First, the absolute difference is calculated: 0.5 A / cycle-0.33 A / cycle=0.17 A / cycle. The basic contact pressure of the ring net cabinet is set to 500 N, and the preset adjustment rule of "increasing 50 N of contact pressure for every 0.1 A / cycle of absolute difference value" (reflecting a positive correlation) is set. According to the calculation of the absolute difference value 0.17 A / cycle, the increase of the contact pressure is: (0.17 / 0.1) x 50 N=85 N. Therefore, the adjusted contact pressure is: 500 N+85 N=585 N. Through this adjustment method, the contact pressure is dynamically increased with the abnormality degree of the current curve slope, and the contact problem is improved.

[0072] In the present application, it is considered that the essence of poor contact is the increase of contact resistance, and the contact pressure is the key factor affecting the resistance. Insufficient pressure will cause the resistance to rise, and excessive pressure may cause the deformation of the wiring terminal. In step S3, the logic of adjusting the contact pressure based on the curve slope is to calculate the absolute difference value (the difference between the absolute value of the curve slope and the preset absolute value), so that the increase of the pressure is positively correlated with the abnormality degree. This dynamic adjustment mechanism avoids the limitations of "fixed value adjustment": when the abnormality is slight (small difference), a small increase in pressure can improve the contact; when the abnormality is significant (large difference), the resistance is quickly reduced by a larger increase in pressure. Compared with the traditional "uniformly increasing fixed pressure" method, this method not only ensures the repair effect, but also prevents secondary damage to the equipment caused by excessive adjustment, and realizes the precise repair of "on-demand adjustment".

[0073] Specifically, when the adjustment to the contact pressure is completed, it is analyzed whether to correct the contact pressure based on the proportion of the number of abnormal wiring terminals, including:

[0074] screening the abnormal wiring terminals and counting the number of abnormal wiring terminals,

[0075] calculating the ratio of the number of abnormal wiring terminals to the total number of wiring terminals to obtain an abnormality proportion,

[0076] if the abnormality proportion is greater than or equal to a preset abnormality proportion, it is determined that the contact pressure is not corrected;

[0077] if the abnormality proportion is less than the preset abnormality proportion, it is determined that the contact pressure is corrected, and the decrease of the contact pressure in the correction process is negatively correlated with the abnormality proportion.

[0078] Specifically, in this embodiment, the preset abnormal proportion can be determined by the following method: collecting the operation data of the same type and same working condition ring network cabinet in the past 3-5 years, screening the abnormal connection end quantity proportion when the fault is caused by poor contact, calculating the statistical distribution (such as mean, 75% quantile, etc.), if the abnormal proportion in most fault cases is concentrated in 20%-30%, the initial reference range is taken as the interval; for the ring network cabinet with less total number of connection ends (such as ≤10), the preset abnormal proportion can be reduced by 5%-10% because a single abnormal connection end has more significant impact on the whole; for the ring network cabinet with more total number of connection ends (such as ≥30), the preset abnormal proportion can be appropriately increased by 5%-10% to avoid excessive sensitivity; in the key load scene (such as hospital, data center), the ring network cabinet needs higher stability, and the preset abnormal proportion can be set to a lower value (such as 15%); in the ordinary industrial scene, it can be set to a higher value (such as 25%); the finally determined preset abnormal proportion needs to meet the minimum threshold ≥5% (to avoid misjudgment due to a small number of abnormalities) and the maximum threshold ≤40% (to prevent blind correction when there are a large number of abnormalities).

[0079] Specifically, in this embodiment, assuming that the ring network cabinet of a certain ordinary industrial scene has a total number of connection ends of 20 and a preset abnormal proportion of 20%, the contact pressure after the basic adjustment is 585N, and the preset correction rule is that the contact pressure decreases by 20N for each 5% reduction in abnormal proportion. The number of abnormal connection ends is 3 (3 / 20=15%), the difference from the preset abnormal proportion is 20%-15%=5%, the contact pressure reduction amount is calculated as follows: since the difference is 5%, according to the rule, the reduction amount is 20N, and the corrected contact pressure is 585N-20N=565N. At this time, the abnormal proportion is 5% lower than the preset value, and the contact pressure is moderately reduced, which can ensure the contact effect of the abnormal connection end and avoid damage to the normal connection end due to excessive pressure.

[0080] In the present application, when the number of abnormal connection ends is greater than or equal to the preset abnormal proportion, it means that there may be a systemic problem, such as overall failure of the pressure device or general aging of the connection ends. At this time, if the contact pressure is still corrected, it cannot solve the root problem and may exacerbate equipment wear and tear due to repeated adjustment. The determination of not correcting in the step can timely terminate invalid pressure adjustment and guide the maintenance personnel to investigate the systemic reasons (such as checking whether the pressure device is malfunctioning), thereby avoiding wasting resources on surface adjustment and improving the directionality and efficiency of fault handling.

[0081] Specifically, when the adjustment to the contact pressure is completed, the preset current and the actual current at each connection end are calculated, and the contact pressure of a single connection end is corrected based on the current difference, wherein the increase of the contact pressure is positively correlated with the current difference.

[0082] Specifically, in this embodiment, if the above determination does not need to be corrected, the adjusted contact pressure parameter is used as the initial value, and if the above determination needs to be corrected, the corrected contact pressure parameter is used as the initial value, and then it is analyzed whether the correction is based on the current difference.

[0083] Specifically, in this embodiment, assuming that the ring main unit of a certain general industrial scene has a total of 20 connection ends, after adjustment and abnormal proportion correction in step S3, the overall contact pressure is 565N (reference the correction result of 15% abnormal proportion in the foregoing), the preset current (standard current value during normal operation) of each connection end is 100A, and the preset correction rule is "5N contact pressure is increased for every 1A current difference"; the actual current of a certain connection end is 97A; the current difference is calculated as: preset current-actual current=100A-97A=3A (the actual current is lower than the preset value, and there is a tendency of poor contact); the contact pressure increase is: 3A x 5N / A=15N; the contact pressure of the single connection end after correction is: 565N+15N=580N; the current of the connection end is slightly lower than the preset value, and a small increase in the contact pressure can improve the contact state and avoid further reduction of the current due to excessive contact resistance.

[0084] In the present application, it is considered that in the ring main unit, most connection ends are usually in a normal operating state (the current difference is close to 0), and if the pressure is uniformly adjusted for all connection ends (such as increasing 85N overall), it will cause the normal connection end to bear unnecessary high pressure, accelerate its aging and deformation (such as plastic deformation of the copper connection end for a long time under excessive pressure), and only the connection end with a current difference is adjusted in the step, and the normal connection end maintains the original pressure (such as 565N), thereby avoiding the waste of normal components caused by "non-discriminatory adjustment".

[0085] Specifically, when the adjustment of the contact pressure is completed, steps S1-S3 are repeated, if it is determined that the operating condition of the ring main unit is unqualified, it is determined that the contact pressure is repeatedly adjusted based on the reacquired curve slope, and the reason why the operating condition of the ring main unit is unqualified is that the surface of the connection end is unqualified.

[0086] Specifically, in this embodiment, if it is determined that the contact pressure needs to be repeatedly adjusted, the contact pressure is repeatedly adjusted to a critical value or the number of adjustments reaches a critical value to stop.

[0087] Specifically, in this embodiment, if the above determination does not need to be corrected, the adjusted contact pressure parameter is used as the initial value, and if the above determination needs to be corrected, the corrected contact pressure parameter is used as the initial value, and then steps S1-S3 are repeated.

[0088] Specifically, in this embodiment, the critical value of the contact pressure can be determined as follows: according to the material of the terminal (such as copper, aluminum or alloy), referring to the compressive strength parameters of the material, for example, the compressive strength of a copper terminal is usually 300-400 MPa, combined with the calculation of the maximum bearing pressure (pressure = compressive strength x contact area) of the contact area; obtain the fatigue damage data of the terminal after repeated compression through simulation experiment, take 80% of the maximum pressure value before fatigue damage as the safety critical reference; count the cases of deformation and cracking of the terminals of the same type of ring network cabinet caused by excessive pressure, and take the pressure value at the time of failure as the upper limit of the critical value; in the scene of frequent vibration (such as industrial workshop), the critical value is reduced by 10%-15%; in the stable environment (such as transformer substation), the basic critical value can be maintained; taking a copper terminal ring network cabinet (20 terminals) in a certain ordinary industrial scene as an example: the contact area of the copper terminal is 100 mm² (0.0001 m²), and the compressive strength is taken as 350 MPa, so the theoretical maximum bearing pressure is ; according to the historical data, the terminals of this type of ring network cabinet are prone to slight deformation when the pressure exceeds 800 N, and the specific process of fatigue limit correction is as follows: through fatigue experiment, the fatigue limit pressure of this type of terminal is obtained as 850 N (i.e. the critical value of long-term bearing pressure without plastic deformation); considering the engineering safety margin (usually taking 90% of the fatigue limit), 850 N x 90% = 765 N is calculated; combined with the boundary condition of “slight deformation at 800 N” in the historical failure data, the final critical value of the contact pressure is determined as 750 N (which is lower than the failure critical value of 800 N and meets the safety requirements after fatigue limit correction).

[0089] Specifically, in this embodiment, the critical value of the adjustment frequency can be determined as follows: count the maximum adjustment frequency required for the cases that can be repaired by pressure adjustment in the same type of poor contact failure, which is usually 3-5 times (more than that, the effect of pressure adjustment on improving the contact is significantly reduced); considering the mechanical life of the pressure adjustment device of the ring network cabinet, if the design life of the device is 200 adjustments, take 1 / 50 (i.e. 4 times) as the critical value to avoid excessive wear of the device; combined with the operation and maintenance cost, when the adjustment frequency exceeds a certain value (such as 5 times), the cost of continuing adjustment is higher than the cost of directly repairing the terminal, at which time the value is the critical value; taking a copper terminal ring network cabinet (20 terminals) in a certain ordinary industrial scene as an example: in the same type of ring network cabinet, 90% of the repairable cases are solved by adjusting within 3 times, and the repair rate is reduced to less than 10% after more than 4 times of adjustment; the mechanical life of the pressure adjustment device is 200 times, and 1 / 50 of it is 4 times; the critical value of the adjustment frequency is determined as 4 times.

[0090] ​The present application considers that the contact pressure is not the greater the better: exceeding the pressure limit of the terminal material (such as copper terminal exceeding 750N) will cause deformation and cracking, and excessive frequent adjustment (such as exceeding 4 times) will accelerate the mechanical wear of the pressure device. The rule of "adjusting to reach the critical value or stopping when the number of adjustments reaches the critical value" in the step limits the adjustment behavior from two aspects of physical limit and mechanical life through the double constraints of "pressure critical value" and "number of times critical value".

[0091] Specifically, when determining that the terminal surface is unqualified, the curve data in the current detection period is extracted, the curve integral value is calculated, and the processing mode is determined based on the curve integral value, including:

[0092] If the curve integral is less than or equal to the preset curve integral, it is determined to issue a replacement joint notification signal;

[0093] If the curve integral is greater than the preset curve integral, it is determined to adjust the heat dissipation operating power.

[0094] Specifically, in the embodiment, the preset curve integral can be determined by the following method: the curve integral value reflects the cumulative effect of the current in a certain period (positively correlated with the heat generation), the "curve integral value-terminal temperature" corresponding relationship is established through experiments, for example, the integral value increases by 100A period, and the terminal temperature rises by 5℃; according to the heat resistance parameters of the terminal surface insulating layer and metal material (such as the maximum heat resistance of the insulating layer is 105℃), combined with the temperature correlation, the critical curve integral value is deduced; collect the curve integral data when the same type of ring network cabinet fails due to terminal surface problems (such as oxidation, ablation), take 90% of the integral value before failure as the initial reference threshold; in high temperature environment (such as outdoor cabinet in summer), the preset curve integral is reduced by 10%-20%; in low temperature environment (such as air-conditioned machine room), it can be increased by 5%-10%; the calculation method of the curve integral value is: the periodic-average current curve in the current detection period is definite integral, the integral interval is the starting time to the end time of the current detection period (assuming the number of periods is t, and the average current is I(t)), and the integral formula is: curve integral value = ∑t=1t=0I(t)dt; wherein, is the starting period of the current detection period, is the end period of the current detection period, and I(t) is the average current value of the t period. The unit of the integral result is 'A·h' (i.e. the product of average current and period number accumulation).

[0095] Specifically, in the embodiment, the specific calculation method of deducing the critical curve integral value combined with the temperature correlation is: the functional relationship between temperature T and curve integral value S is established through experiments: ​​(wherein k, b are experimental fitting constants, obtained by fitting the temperature measured data of the same type of ring main unit at different integral values); according to the highest tolerance temperature T_max (such as 105℃) of the insulating layer of the terminal, the critical curve integral value S_critical is obtained by substituting the above function, that is, S_critical=(T_max-b) / k; for example, if k=0.05℃ / ( ), b=30℃, T_max=105℃, then period.

[0096] In the present application, the harm degree of the unqualified surface of the terminal is not completely consistent, slight oxidation may only cause the contact resistance to slowly rise, and serious ablation may cause local overheating in a short time. In the step, the curve integral value (reflecting the cumulative effect of current in a certain period, which is positively correlated with the heat generation) is calculated, and compared with the preset curve integral, the surface fault is divided into two categories of "low emergency degree" and "high emergency degree". For the surface fault with integral ≤ preset value (such as slight oxidation), it will not cause serious risk in a short time, at this time, the replacement notice is issued instead of immediate shutdown for maintenance, which can avoid the production interruption (such as factory production line shutdown, data center downtime) caused by emergency shutdown.

[0097] Specifically, when determining the adjustment of the heat dissipation operating power, the integral difference value of the curve integral and the preset curve integral is calculated, wherein the increase of the heat dissipation operating power is positively correlated with the integral difference value.

[0098] Specifically, in the embodiment, for example, the copper terminal ring main unit (20 terminals) of a certain ordinary industrial scene, the preset curve integral is period (referring to the determination result in the foregoing text), the basic heat dissipation operating power of the ring main unit is 1000W, and the preset adjustment rule is "10% of the heat dissipation power is increased every period corresponding to the integral difference value"; the implementation is as follows: the integral difference value is period; the curve integral value in the current detection period is: period; the integral difference value is calculated as: period- period= period; the increase of the heat dissipation operating power is: according to the rule, period, 10% is increased, that is, 1000W*10%=100W; the adjusted heat dissipation operating power is: 1000W+100W=1100W; at this time, the integral difference value is small, the heat generation slightly exceeds the safe range, and the heat dissipation power is slightly improved to control the temperature in the tolerance range of the insulating layer (such as from 86℃ to 82℃).

[0099] Specifically, when the adjustment for the heat dissipation operating power is completed, the steps S1-S3 are re-executed, and if it is determined that the operating condition of the ring main unit is unqualified, it is determined to issue a replacement joint notification signal.

[0100] The technical scheme of the present application has been described in combination with the preferred embodiments shown in the drawings, but it is easy for those skilled in the art to understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the present application, and the technical schemes after the changes or replacements will fall within the protection scope of the present application.

[0101] The above description is only the preferred embodiments of the present application and is not intended to limit the present application; for those skilled in the art, the present application can have various changes and variations, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An intelligent monitoring method for contact resistance fault of a ring main unit, characterized in that, The method comprises the following steps: Step S1, periodically collecting current data information at each terminal in the cable chamber, calculating the average current value of each period, and drawing a period-average current curve; Step S2, calculating the curve slope of the curve in the current detection period, and determining the operation fault tendency type of the ring net cabinet based on the absolute value of the curve slope; Step S3, determining the analysis mode for the ring net cabinet based on the operation fault tendency type of the ring net cabinet, comprising: determining that the operation condition of the ring net cabinet is unqualified and that the unqualified reason is that there is a poorly contacted terminal, and adjusting the contact pressure based on the curve slope, and analyzing whether to correct the contact pressure based on the proportion of the number of abnormal terminals, or, determining that the operation condition of the ring net cabinet is qualified; Step S4, outputting the analysis result; When the adjustment to the contact pressure is completed, whether to correct the contact pressure based on the proportion of the number of abnormal terminals, comprising: screening abnormal terminals and counting the number of abnormal terminals, calculating the ratio of the number of abnormal terminals to the total number of terminals to obtain an abnormal proportion, if the abnormal proportion is greater than or equal to a preset abnormal proportion, it is determined that the contact pressure is not corrected; if the abnormal proportion is less than the preset abnormal proportion, it is determined that the contact pressure is corrected, wherein the decrease of the contact pressure in the correction process is negatively correlated with the abnormal proportion.

2. The method for intelligent monitoring of contact resistance fault of ring main unit according to claim 1, characterized in that, In the step S2, the operation fault tendency type of the ring net cabinet is determined based on the absolute value of the curve slope, comprising: if the absolute value of the curve slope is greater than or equal to a preset absolute value, it is determined that the operation fault tendency type of the ring net cabinet is strong operation fault tendency; if the absolute value of the curve slope is less than the preset absolute value, it is determined that the operation fault tendency type of the ring net cabinet is weak operation fault tendency.

3. The method for intelligent monitoring of contact resistance fault of ring main unit according to claim 2, characterized in that, In the step S3, the analysis mode for the ring net cabinet is determined based on the operation fault tendency type of the ring net cabinet, comprising: if the operation fault tendency type of the ring net cabinet is strong operation fault tendency, it is determined that the operation condition of the ring net cabinet is unqualified and that the unqualified reason is that there is a poorly contacted terminal, and the contact pressure is adjusted based on the curve slope, and whether to correct the contact pressure is analyzed based on the proportion of the number of abnormal terminals; if the operation fault tendency type of the ring net cabinet is weak operation fault tendency, it is determined that the operation condition of the ring net cabinet is qualified.

4. The method for intelligent monitoring of contact resistance fault of ring main unit according to claim 3, characterized in that, The contact pressure is adjusted based on the curve slope, comprising: calculating the absolute value of the curve slope and the difference between the preset absolute value to obtain an absolute difference value, wherein the increase amplitude of the contact pressure is positively correlated with the absolute difference value.

5. The method for intelligent monitoring of contact resistance fault of ring main unit according to claim 1, characterized in that, When the adjustment to the contact pressure is completed, the current difference between the preset current and the actual current at each terminal is calculated, and the contact pressure for a single terminal is corrected based on the current difference, wherein the increase of the contact pressure is positively correlated with the current difference.

6. The method for intelligent monitoring of contact resistance fault of ring main unit according to claim 1, characterized in that, When the adjustment to the contact pressure is completed, steps S1-S3 are repeated, if it is determined that the operation condition of the ring net cabinet is unqualified, it is determined that the contact pressure is repeatedly adjusted based on the reacquired curve slope, and it is determined that the unqualified reason for the operation condition of the ring net cabinet is that the surface of the terminal is unqualified.

7. The method for intelligent monitoring of contact resistance fault of ring main unit according to claim 6, characterized in that, When determining that the terminal surface is unqualified, curve data in the current detection period is extracted, a curve integral value is calculated, and a processing mode is determined based on the curve integral value, including: If the curve integral is less than or equal to a preset curve integral, it is determined to issue a joint replacement notification signal; If the curve integral is greater than the preset curve integral, it is determined to adjust the heat dissipation operating power.

8. The method for intelligent monitoring of contact resistance fault of ring main unit according to claim 7, characterized in that, When determining to adjust the heat dissipation operating power, an integral difference value between the curve integral and the preset curve integral is calculated, wherein the increase amount of the heat dissipation operating power is positively correlated with the integral difference value.

9. The method for intelligent monitoring of contact resistance fault of ring main unit according to claim 8, characterized in that, When the adjustment to the heat dissipation operating power is completed, steps S1-S3 are restarted, and if it is determined that the operating condition of the ring network cabinet is unqualified, a joint replacement notification signal is issued.

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