Switch cabinet conductor temperature rise budgeting system and method thereof

Abstract

The invention discloses a switch cabinet conductor temperature rise budgeting system and a switch cabinet conductor temperature rise budgeting method, belongs to the technical field of switch equipment conductor temperature rise state evaluation, is suitable for 3.6-40.5 kV alternating current metal closed switch equipment, and is composed of a data acquisition module, a data processing module, a model operation module and an output module. The method comprises the following steps: collecting data; preprocessing the data; building a temperature rise budget model; and outputting a temperature rise budget result. The invention provides a high-precision switch cabinet conductor temperature rise budgeting system and a high-precision switch cabinet conductor temperature rise budgeting method which can comprehensively consider fusion of multiple parameters such as load current, operation time, environment temperature and humidity, tulip contact temperature, tulip contact insertion depth and spring holding force, and solves the problem of inaccurate early warning caused by incomplete parameter coverage of a traditional system.

Description

Technical Field

[0001] This invention relates to the field of conductor temperature rise condition assessment technology for switchgear, specifically a switchgear conductor temperature rise estimation system and method, which is particularly applicable to 3.6-40.5kV AC metal-enclosed switchgear, providing core technical support for condition-based maintenance of intelligent substations. Background Technology

[0002] High-voltage switchgear, as widely used switching and control equipment in power systems, directly affects the safety and stability of the power grid in terms of operational reliability. Conductor temperature rise is one of the core indicators for measuring the operating status of high-voltage switchgear. When the conductor temperature rise exceeds the allowable threshold, it can lead to a decrease in conductor insulation performance, an increase in contact resistance, and even serious faults such as arc discharge and equipment burnout. Existing systems and methods for calculating conductor temperature rise in high-voltage switchgear generally suffer from the following problems: Temperature rise warning is not possible: It relies solely on two parameters, the measuring point temperature and the ambient temperature, for over-temperature alarms, completely ignoring key factors such as load current, running time, ambient humidity, insertion depth of the plum blossom contact, and spring clamping force, thus failing to provide temperature rise warning. The contact state is not quantified: As the core component of conductive connection, insufficient insertion depth of the plum blossom contact will reduce the contact area, and the weakening of the spring clamping force will reduce the contact pressure. Both of these factors will increase the contact resistance, but the existing algorithm model does not take this factor into account. The influence of ambient humidity is missing: Increased humidity will reduce the heat dissipation efficiency of the conductor surface, and long-term heat accumulation will lead to non-linear temperature rise. The existing algorithm model does not consider the influence of this factor. Inaccurate early warnings: Due to incomplete coverage of monitoring parameters, the existing algorithm model usually has an error of more than 15%, which cannot provide early warning guidance for temperature rise in operation and maintenance. Summary of the Invention

[0003] The first technical problem this invention aims to solve is to provide a highly accurate method for estimating the temperature rise of switchgear conductors by comprehensively considering multiple parameters such as load current, operating time, ambient temperature and humidity, stud contact temperature, stud contact insertion depth, and spring clamping force. This solves the problem of inaccurate temperature rise warnings caused by incomplete monitoring parameter coverage in traditional methods.

[0004] To achieve the above objectives, this invention discloses a method for estimating conductor temperature rise in switchgear, applicable to 3.6-40.5kV AC metal-enclosed switchgear, comprising the following steps: Step 1: Data Collection; Key parameters for the operation of conductors in high-voltage switchgear are collected, specifically including: Electrical parameters: The real-time load current I(t) of the conductor is collected through a current transformer, and the continuous running time t of the current is recorded at the same time; Environmental parameters: The real-time ambient temperature T1(t) and relative humidity RH(t) inside the switch cabinet are collected by temperature and humidity sensors. The temperature and humidity sensors are deployed at the top of the switch cabinet away from the heat source. Contact parameters: The real-time insertion depth h(t) of the plum blossom contact is acquired by a distance sensor, which is fixed to the side of the contact mounting base. The measurement accuracy is ±1mm and the resolution is 0.1mm. The real-time clamping force F(t) of the plum blossom contact spring is acquired by a pressure sensor, which is embedded in the fixed end of the spring. The measurement range is 0-500N. The real-time temperature T2(t) of the plum blossom contact is acquired by a temperature sensor. The measurement accuracy is ±2℃. Basic parameters: Obtain the material properties of the conductor in advance (resistivity of copper conductor ρ = 1.72 × 10⁻⁶). -8 Ω·m, temperature coefficient α=0.00393 / ℃), structural parameters (conductor cross-sectional area S, length L) and heat dissipation characteristic parameters (surface heat dissipation coefficient h).

[0005] Step 2: Data preprocessing; Preprocessing of the collected multi-dimensional data includes: Outlier removal: The 3σ criterion is used to remove outlier data in load current, ambient temperature and humidity, contact temperature, insertion depth and spring clamping force, where σ is the standard deviation of the parameter sample. Data standardization: The preprocessed parameters are normalized and mapped to the [0,1] interval to eliminate the influence of dimensions. The standardization formula is: X = (X - Xmin) / (Xmax - Xmin) Where X is the original parameter value, and Xmin and Xmax are the minimum and maximum values ​​of the parameter, respectively; Contact resistance calculation: Based on the insertion depth h(t) of the plum blossom contact and the spring clamping force F(t), the real-time contact resistance R(t) is calculated using a theoretical model of contact resistance. The empirical formula is as follows: R1(t) = K / [n*F(t)*h(t) / h] Wherein, K is the contact material coefficient (K=8*10Ω·m² / N for copper contacts), h is the standard insertion depth of the plum blossom contact (design value, usually 15mm), and n is the contact form coefficient. The research object of this invention is the plum blossom contact, n=1. Conductor resistance correction: Considering the effect of temperature on conductor resistance, the conductor's bulk resistance R(t) is corrected based on the ambient temperature T(t), using the following formula: R2(t) = ρ * L * [1 + α(T2(t) - 20)] / S Heat dissipation coefficient correction: Considering the influence of ambient humidity on heat dissipation, the heat dissipation coefficient h(t) of the conductor surface is corrected, and the formula is as follows: h(t) = h * [1 - 0.01 * (RH(t) - 50)] Where h is the heat dissipation coefficient under standard humidity (RH=50%), with a value of 10W / (m²·℃).

[0006] Step 3: Constructing the temperature rise budget model; Based on the thermal balance theory and combined with multi-dimensional correction parameters, a temperature rise budget model for switchgear conductors is constructed, specifically including: Calculation of heating power: The total heating power P(t) of the conductor consists of the Joule heating power P1(t) of the conductor body and the heating power P2(t) of the contact resistance, and the formula is: P(t)=P1(t)+P2(t)=I(t)²*R1(t)+I(t)²*R2(t)=I(t)²*[R1(t)+R2(t)] Heat dissipation power calculation: The heat dissipation power Q(t) of a conductor includes convective heat dissipation and radiative heat dissipation. The empirical formula is: Q(t)=h(t)*A*[T2 end (t)-T2 beginning (0)]+ε*σ*A*[T2 end (t)-T2 beginning (0)] Where A is the heat dissipation area of ​​the conductor, ε is the emissivity of the conductor surface, σ is the blackbody radiation constant, T2initial(0) is the temperature of the conductor at the initial moment, and T2final(t) is the temperature of the conductor after time t.

[0007] The thermal balance equation is established as follows: According to the principle of thermal balance, the rate of change of conductor temperature is directly proportional to the difference between the heating power and the heat dissipation power, as shown in the formula: C*m*dT2(t) / dt=P(t)-Q(t) Where C is the specific heat capacity of the conductor (C = 385 J / (kg·℃) for copper), and m is the mass of the conductor; Solution of the temperature rise budget model: The heat balance equation is discretized, and the real-time temperature T(t) of the conductor is solved using the Euler iteration method. The formula is as follows: T(t+Δt)=T2(t)+[P(t)-Q(t)]*Δt / (C*m) Where Δt is the iteration step size, which takes the value 0.1, and the initial condition is T(0) = T2(0).

[0008] Therefore, the conductor temperature rise ΔT2(t) = T(t) - T2(t) is obtained.

[0009] Step 4: Output the temperature rise budget results; The calculated conductor temperature rise ΔT2(t) is compared with the allowable temperature rise threshold ΔT1(t) = T2(t) - T1(t) of the high-voltage switchgear conductor. The calculated results are output, including the real-time temperature rise curve, the maximum temperature rise prediction value, and the over-temperature warning signal. Based on experience, if the difference is less than or equal to 5K, no alarm is output.

[0010] The second technical problem to be solved by the present invention is to provide a high-precision switchgear conductor temperature rise estimation system that can comprehensively consider multiple parameters such as load current, running time, ambient temperature and humidity, plum blossom contact insertion depth and spring clamping force, so as to solve the problem of low accuracy and inaccurate early warning caused by parameter omission in traditional systems.

[0011] The data acquisition module consists of a multi-functional sensor (integrating the functions of a through-hole current transformer, pressure sensor, and temperature sensor), a temperature and humidity sensor, a distance sensor, and an intelligent unit (data acquisition unit). It is used to collect load current I(t), running time t, ambient temperature T1(t), relative humidity RH(t), plum blossom contact temperature T2(t), plum blossom contact insertion depth h(t), and spring clamping force F(t), and transmit the collected data to the data processing module. Data processing module: The intelligent unit uses an MCU microcontroller to remove outliers and standardize the collected data, and calculate the contact resistance R(t), correct the conductor body resistance R(t), and the heat dissipation coefficient h(t). Model calculation module: The intelligent unit uses an FPGA chip to build a temperature rise budget model and solves for the real-time temperature and temperature rise of the conductor using the Euler iteration method; Output module: Composed of touch screen, alarm and communication interface, used to display real-time temperature rise curve, maximum temperature rise prediction value, trigger early warning when temperature rise approaches threshold, and upload relevant results and signals to background monitoring system in real time; Compared to traditional simple temperature measurement solutions, the advantages of this invention are: 1. High Prediction Accuracy: This solution comprehensively considers multiple influencing factors such as load current, running time, ambient temperature and humidity, insertion depth of the plum blossom contact, and spring clamping force. Through contact resistance model and heat dissipation coefficient correction, it effectively makes up for the shortcomings of existing technologies that only consider a single parameter. Through simulation and experimental verification, the temperature rise prediction error of this invention is ≤5%, which is far lower than the 15% or more of the existing technology, providing accurate data support for equipment fault early warning. 2. High practicality: This invention is designed for the structural characteristics of high-voltage switchgear (such as the structure and connection form of the plum blossom contact, and the heat dissipation conditions of the switchgear) and the characteristics of the operating environment, and has good compatibility with the original structure of the switchgear; the information output module provides real-time curve display and alarm signals, which meets the needs of on-site operation and maintenance, and can be directly applied to the upgrading and transformation of new switchgear and existing switchgear. 3. Extend equipment life: By accurately predicting conductor temperature rise, potential faults such as insufficient insertion depth of the plum blossom contact and weakening of spring clamping force can be detected in advance, guiding maintenance personnel to carry out targeted repairs (such as adjusting the contact insertion depth and replacing the spring), avoiding conductor insulation aging and contact burnout caused by excessive temperature rise, and extending the service life of the switchgear by more than 30%. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram showing the sensor installation location; Figure 2 This is a system flowchart.

[0014] Attached diagram descriptions: 1-Switch cabinet; 2-Instrument room; 3-Circuit breaker room; 4-Intelligent unit; 5-Information output module; 6-Circuit breaker; 7, 8-Multi-function sensor; 9-Distance sensor; 10-Temperature and humidity sensor; 11-Switch cabinet heat dissipation hole. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] like Figures 1 to 2 As shown, a method for estimating conductor temperature rise in switchgear is provided, taking the KYN28A-12(Z) type switchgear (rated current 1250A, conductor material T2 copper, cross-sectional area 1200mm², length 1.2m, standard insertion depth of plum blossom contact 15mm, standard spring clamping force 300N) as an example. Figure 1 As shown, it is implemented in conjunction with the switchgear conductor temperature rise budgeting system, such as... Figure 2 As shown, the steps are as follows: Step 1: Data Collection; The load current I(t) is collected by a current transformer, and its variation range within 10 minutes is 800-1200A. The running time t is started from 0. The ambient temperature T1(t) = 30℃ and the relative humidity RH(t) = 60% are collected by a temperature and humidity sensor. The current conductor surface temperature T2(t) = 55℃ is measured by a temperature sensor, and the conductor surface temperature is T2(t) = 52℃ after 10 minutes. It is calculated that the temperature changes by 4℃ after 10 minutes of operation, and the temperature rise = T2(t) - T1(t) = 29K. The insertion depth h(t) of the plum blossom contact is collected by a distance sensor, which is 14.5mm. The spring clamping force F(t) is collected by a pressure sensor, which is 280N. Pre-obtain basic parameters: ρ=1.72*10 -8 Ω·m, α=0.00393 / ℃, S=1200mm², L=1.2m, h=10W / (m²·℃), A = 0.048 m² (conductor surface area), ε = 0.85, C = 385 J / (kg·℃), m = 1.28 kg.

[0017] Step 2: Data preprocessing; Outlier removal: No outliers were found in the collected current, temperature and humidity, insertion depth and clamping force data; Contact resistance calculation: R1 = 100 * 10 -6 / [280*(14.5 / 15)]≈3.69*10 -7 Ω; Correction for conductor bulk resistance: R2 = 1.72 * 10 -8 *1.2*[1+0.00393*(55-20)] / (1200*10 -6 )≈1.957*10 -5 Ω; Heat dissipation coefficient correction: h(t)=10*[1-0.01*(60-50)]=9W / (m²·℃).

[0018] Step 3: Solve the temperature rise budget model; Heating power calculation: Take I = 1200A, P = 1200² * (3.69 * 10⁻⁶) -7 +1.957*10 -5 )≈28.7W; Heat dissipation calculation: Initial temperature T2init(0) = 55℃ = T2(t), Q(0)=9*0.048*(59-55)+0.85*5.67*10 -8 *0.048*(59-55)=4.32W; Iterative solution: Δt=0.1, T(0.1)=55+(28.7-4.32)*0.1 / (385*1.28)≈55.005℃, ΔT(0.1)=0.005K; after 10 minutes of continuous iteration, T(60)=64.6℃, ΔT(60)=34.6K, which did not exceed the allowable threshold of 55K, and there was no temperature rise alarm signal.

[0019] Step 4, Output Results: The touchscreen displays the temperature rise curve over 10 minutes. The maximum predicted temperature rise is 34.6K. The temperature rise threshold is T2 (t) - T1 (t) = 59 - 30 = 29K. The difference is 34.6 - 29 = 5.6K < 8K. Therefore, there is no over-temperature warning signal.

[0020] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A switchgear conductor temperature rise estimation system, characterized in that, Includes the following modules: Data acquisition module: used to collect load current I(t), running time t, ambient temperature T1(t), relative humidity RH(t), plum blossom contact temperature T2(t), plum blossom contact insertion depth h(t) and spring clamping force F(t); Data processing module: used to remove outliers and standardize the collected data, and calculate the contact resistance R(t), correct the conductor body resistance R(t), and the heat dissipation coefficient h(t); Model calculation module: used to construct the temperature rise budget model and solve for the conductor temperature rise; Output module: Used to output budget results and over-temperature warning signals, and integrates a communication interface to upload relevant results and signals to the background monitoring system.

2. The switchgear conductor temperature rise estimation system according to claim 1, characterized in that: The data processing module uses an MCU microcontroller, the model calculation module uses an FPGA chip, the output module uses a human-computer interaction touch screen and an alarm, and the communication interface uses a LoRa module, a Wi-Fi module, or a BCNet module.

3. A method for estimating the temperature rise of conductors in a switchgear, characterized in that, It is implemented using the switchgear conductor temperature rise estimation system according to claim 1, and includes the following steps: Step 1: Data Collection; The load current I(t), running time t, ambient temperature T1(t), relative humidity RH(t), plum blossom contact temperature T2(t), plum blossom contact insertion depth h(t), and spring clamping force F(t) of the conductor of the high voltage switchgear are collected, and the material characteristics, structural parameters, and heat dissipation characteristics of the conductor are obtained. Step 2: Data preprocessing; Outlier removal and standardization are performed on the collected data. The contact resistance R(t) is calculated based on the insertion depth h(t) of the plum blossom contact and the spring clamping force F(t). The conductor body resistance R(t) is corrected by combining the ambient temperature T1(t). The conductor surface heat dissipation coefficient h(t) is corrected by combining the relative humidity RH(t). The actual temperature rise ΔT1(t) is calculated by combining the ambient temperature T1(t) and the plum blossom contact temperature T2(t). This temperature rise is the allowable temperature rise threshold. Step 3: Constructing the temperature rise budget model; Based on the thermal balance theory, a thermal balance equation is established by combining the heat generation power P(t) and the heat dissipation power Q(t). The real-time temperature T(t) of the conductor is solved by the Euler iteration method, and then the conductor temperature rise ΔT2(t) = T(t) - T2(t) is obtained. Step 4: Output the temperature rise budget results; The estimated conductor temperature rise ΔT2(t) is compared with the actual conductor temperature rise ΔT1(t), and the estimated result and over-temperature warning signal are output.

4. The method for estimating the temperature rise of switchgear conductors according to claim 3, characterized in that: In the data acquisition step, a current transformer is used to acquire the load current I(t). This current transformer can be integrated into a multi-in-one sensor or can be an independent primary current transformer on the switch cabinet, or it can be a Hall current sensor used to monitor the secondary current of the current transformer. A temperature and humidity sensor is used to collect the ambient temperature T1(t) and relative humidity RH(t), and a multi-functional sensor is used to collect the temperature T2(t) of the plum blossom contact. The sensor is deployed at the top of the switch cabinet away from the heat source. The insertion depth h(t) of the plum blossom contact was collected using a distance measuring sensor, with a measurement accuracy of ±1mm and a resolution of 0.1mm. A pressure sensor is used to collect the clamping force F(t) of the plum blossom contact spring, with a measurement range of 0~500N.

5. The method for estimating the temperature rise of switchgear conductors according to claim 3, characterized in that: In the data preprocessing step, the empirical formula for contact resistance R(t) is: R1(t) = K / [n*F(t)*h(t) / h] Where K is the contact material coefficient, h is the standard insertion depth of the plum blossom contact, and n is the contact form coefficient, where n=1 for the plum blossom contact.

6. The method for estimating the temperature rise of switchgear conductors according to claim 3, characterized in that: In the data preprocessing step, the corrected formula for the conductor bulk resistance R(t) is: R2(t) = ρ * L * [1 + α(T2(t) - 20)] / S Where ρ is the resistivity of the conductor at 20℃, L is the length of the conductor, α is the temperature coefficient of the conductor, and S is the cross-sectional area of ​​the conductor.

7. The method for estimating the temperature rise of switchgear conductors according to claim 3, characterized in that: In the data preprocessing step, the empirical correction formula for the heat dissipation coefficient h(t) of the conductor surface is: h(t) = h * [1 - 0.01 * (RH(t) - 50)] Where h is the heat dissipation coefficient when the standard humidity RH=50%.

8. The method for estimating the temperature rise of switchgear conductors according to claim 3, characterized in that: In the steps of constructing the temperature rise budget model, the formula for calculating the heating power P(t) is: P(t) = I(t)² * [R1(t) + R2(t)] The empirical formula for calculating the heat dissipation power Q(t) is: Q(t)=h(t)*A*[T2 end (t)-T2 beginning (0)]+ε*σ*A*[T2 end (t)-T2 beginning (0)] Where A is the heat dissipation area of ​​the conductor, ε is the emissivity of the conductor surface, σ is the blackbody radiation constant, T2initial(0) is the temperature of the conductor at the initial moment, and T2final(t) is the temperature of the conductor after time t.

9. The method for estimating the temperature rise of switchgear conductors according to claim 3, characterized in that: In the steps of constructing the temperature rise budget model, the heat balance equation is: C*m*dT2(t) / dt =P(t)-Q(t) The Euler iteration method is used to solve this problem, and the iteration formula is as follows: T(t+Δt)=T2(t)+[P(t)-Q(t)]*Δt / (C*m) Where C is the specific heat capacity of the conductor, m is the mass of the conductor, Δt is the iteration step size, which is 0.1, and the initial condition is T(0) = T2(0); This leads to the conductor temperature rise ΔT2(t) = T(t) - T2(t); The actual temperature rise ΔT1(t) is calculated by combining the ambient temperature T1(t) and the temperature of the plum blossom contact T2(t). This temperature rise is the allowable temperature rise threshold, i.e., ΔT1(t) = T2(t) - T1(t). The estimated conductor temperature rise ΔT2(t) is compared with the actual conductor temperature rise ΔT1(t), and the estimated result and over-temperature warning signal are output. Based on experience, if the difference is less than or equal to 8K, no alarm is output.

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