A DC circuit breaker electrical life analysis technology

Abstract

The invention discloses a DC circuit breaker electrical life analysis technology. The invention adopts a deduction estimation method to calculate the maximum value of short-circuit breaking current I=di / dt(max)×1 / 2T+I(max) according to collected data, input data and judgment data. The invention adopts an approximate ratio to deduce the maximum allowable breaking times of any short-circuit breaking current according to the experimental data provided by the product. The invention adopts a percentage method to unify the influence of different short-circuit breaking currents and times on the electrical life of the circuit breaker, and obtains the service life of the circuit breaker. The direct difference method is adopted to obtain the remaining life percentage. When the remaining life percentage reaches a minimum limit, the equipment is overhauled or replaced. The invention calculates the remaining life, timely finds the time when the remaining life percentage reaches the minimum limit, and performs equipment overhaul or replacement, thereby reducing the accident rate, reducing the loss and improving the reliability of the equipment.

Description

Technical Field

[0001] The present invention relates to the field of urban rail transit DC traction power supply systems, and in particular to a DC circuit breaker electrical life analysis technology. Background Art

[0002] The DC switchgear in the DC traction power supply system of urban rail transit is an important electrical equipment in the traction substation. During the long-term operation of the equipment, the service life of the circuit breaker, the most important component in the switchgear, affects the maintenance cycle of the entire equipment operation. In recent years, the rapid development of my country's urban rail transit industry has brought huge challenges to the operation and maintenance capabilities of urban rail companies. Due to the low visibility of the actual status of the equipment and the unclear health status, the different breaking currents of the circuit breaker each time, the corresponding losses of the circuit breaker contacts and arc extinguishing chambers are also different, and the impact on the life of the entire circuit breaker is also different. It is impossible to reliably judge the electrical life of the circuit breaker solely by relying on human experience and ability. For this reason, a technical means is needed to conduct accurate data collection, calculation and analysis.

[0003] In order to solve the above problems, a Chinese patent with publication number CN114626312A discloses a method for comprehensively evaluating the electrical life of a circuit breaker, which is specifically carried out in the following steps: Step 1: Establish a magnetohydrodynamic simulation model based on the designed circuit breaker arc extinguishing chamber structure; Step 2: Obtain the temporal and spatial evolution characteristics of the arc under different voltages and currents, arc current, arc voltage and let-through energy through simulation calculation, and establish a database of circuit breaker simulation results; Step 3: Calculate the electrical life of a new circuit breaker product: Calculate the remaining electrical life of the circuit breaker in online operation. Thereby achieving a comprehensive evaluation of the electrical life of different circuit breakers. The present invention not only theoretically evaluates the electrical life parameters of new circuit breaker products, but also can evaluate the number of remaining electrical life according to the real-time status of the circuit breaker, which saves costs while improving the accuracy of electrical life evaluation. This method can be applied to low-voltage circuit breakers and high-voltage gas circuit breakers.

[0004] Another example is a Chinese patent with publication number CN112084662A, which discloses a method and device for detecting the electrical life of a circuit breaker. Specifically, the method includes receiving the model and disconnection status of the circuit breaker to be detected input by the user; performing offline dynamic resistance measurement on the circuit breaker to be detected to obtain the dynamic resistance at the disconnection point of the circuit breaker to be detected; comparing the dynamic resistance with the evaluation curve in the pre-established comparison database to obtain the reliability and electrical life of the circuit breaker for the next disconnection; responding to the user's query request, outputting the model, relevant parameters, reliability and electrical life of the circuit breaker to be detected; and classifying the obtained reliability and electrical life into the comparison database. In this way, there is no need to use a large number of tests, and only the dynamic resistance needs to be measured to calculate the electrical life of the circuit breaker, thereby improving the detection efficiency, and the reliability can also be obtained, thereby improving the detection effect.

[0005] At present, the existing circuit breaker electrical life analysis technology still has shortcomings: the first patent establishes a magnetohydrodynamic simulation model, establishes a database of circuit breaker simulation results through simulation calculation, and calculates the remaining electrical life of the circuit breaker in online operation. The second patent measures the dynamic resistance and compares the measured value with the pre-established comparison database to obtain the electrical life of the circuit breaker. Both patents are implemented by establishing a database. The solution is relatively complex, the cost is high, and the accuracy needs to be improved. The existing technology still needs to be improved. Summary of the invention

[0006] In view of the deficiencies of the prior art, the present invention provides a DC circuit breaker electrical life analysis technology to solve the above problems.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] A DC circuit breaker electrical life analysis technology includes the following steps:

[0009] S1 Acquisition of collected data: Using the estimation method, there is no need to add additional measuring equipment. The protection device of the existing DC switch cabinet is used to provide the necessary collected data for the circuit breaker electrical life analysis device;

[0010] S2 calculates the circuit-breaking current and input data: using the data provided by the protection device of the DC switch cabinet, the circuit breaker electrical life analysis device calculates the short-circuit breaking current, which is the difficulty of the entire data calculation and analysis, and is used as the measurement data for electrical life judgment, i.e., input data;

[0011] S3 obtains judgment data: utilizes the electrical life characteristic parameters of the circuit breaker before leaving the factory and inputs them into the circuit breaker electrical life analysis device as reference data for electrical life judgment, i.e., judgment data;

[0012] S4 Calculate the remaining electrical life: Calculate the used electrical life and remaining electrical life of the circuit breaker by using the above-mentioned collected data, input data and judgment data, which is divided into the following steps:

[0013] ①Measurement records of protection devices and provide them;

[0014] ②Calculate the breaking current

[0015] ③N number of breaking times corresponding to the breaking current;

[0016] ④The electrical life value S used this time 本 =1 / (number of breaking times corresponding to breaking current);

[0017] ⑤ Used electrical life value S 已 = The electrical life value of this use S本 + Last used electrical life value S 上 (The initial value is 0);

[0018] ⑥Total electrical life value S 总 = Used electrical life value S 已 + Remaining electrical life value S 剩 .

[0019] Furthermore, in step S1 of acquiring collected data, each DC switch cabinet is provided with a protection device to collect corresponding current and voltage data on the DC traction power supply system, that is, current and voltage data corresponding to the DC circuit breaker in real time.

[0020] Furthermore, in the step S1 of acquiring the collected data, the main current data is stored and calculated in real time by a device specifically used for circuit breaker electrical life analysis.

[0021] Furthermore, in step S2, the short-circuit breaking current and the input data are calculated. When the short-circuit breaking current is calculated, if the short-circuit current is within the measurable recorded maximum value, the recorded maximum value can be directly used as the maximum short-circuit current.

[0022] Furthermore, in step S2, the short-circuit breaking current is calculated and inputted into the data. When the short-circuit breaking current is calculated, when the short-circuit current exceeds the maximum value recorded in the data, the duration of the maximum value recorded is calculated, the maximum current change rate is screened out, and the maximum value of the short-circuit current is calculated.

[0023] Furthermore, in step S2, the short-circuit breaking current and the input data are calculated, and according to the data, the maximum value of the short-circuit current is calculated as I=di / dt(max)x 1 / 2T+I(max).

[0024] Furthermore, in step S3, in obtaining the judgment data, the test data of the electrical life in the type test report of the circuit breaker directly adopts the electrical life data of the circuit breaker, that is, the service life of the product.

[0025] Furthermore, in step S4, in calculating the remaining electrical life, different breaking currents and breaking times are converted into a uniform electrical life percentage in a percentage manner.

[0026] Furthermore, in step S4, in calculating the remaining electrical life, the calculated percentage of the input data is used as the used electrical life, the test data is used as the judgment data, and the result of subtracting the input data is the remaining electrical life.

[0027] Furthermore, in step S4, the remaining electrical life is calculated by using a direct difference method, which is to subtract the percentage of service life from the 100% electrical life of a new product to obtain the remaining life percentage.

[0028] Further, the subdivision steps in calculating the remaining electrical life in step S4 are as follows: ① The protection device measures and records and provides: the maximum value of the current change rate di / dt(max), the duration T, the maximum current of the protection device

[0029] Value I(max);

[0030] ②Calculate the breaking current:

[0031] Breaking current I≤maximum current value of protection device I(max), breaking current value I=current value of protection device I(max);

[0032] That is: I = I (max); - (Formula 1)

[0033] Breaking current value I> maximum current value I(max) of protection device, breaking current value I=maximum value of current change rate di / dt(max)x1 / 2x duration T+maximum current value I(max) of protection device;

[0034] That is: I = di / dt(max) x 1 / 2T + I(max) - (Formula 2)

[0035] ③ The number of breaking times N corresponding to the breaking current is based on the circuit breaker characteristic curve or test report data; for example, the number of breaking times N corresponding to the breaking current of 90kA 90 ; However, if the characteristic curve or test report data does not directly list the corresponding data, an approximate ratio can be used for calculation;

[0036] ④The electrical life value S used this time 本 =1 / (number of breaking times corresponding to breaking current);

[0037] That is: S 本 =1 / N;——(Formula 3)

[0038] ⑤ Used electrical life value S 已 = The electrical life value of this use S 本 + Last used electrical life value S 上 (The initial value is 0);

[0039] S 已 =S 本 +S 上 ——(Formula 4)

[0040] ⑥Total electrical life value S 总 = Used electrical life value S 已 + Remaining electrical life value S 剩

[0041] The electrical life value is expressed as a percentage, and the total electrical life value S 总 =1

[0042] S 总 =S 已 +S 剩 ——(Formula 5).

[0043] Compared with the prior art, the beneficial effects of the device of the present invention are: a DC circuit breaker electrical life analysis technology, using a deduction estimation method, according to the collected data, input data and judgment data, calculates the maximum value of the short-circuit current I=di / dt(max)x 1 / 2T+I(max), according to the experimental data provided by the product, uses an approximate ratio to deduce the maximum allowable number of interruptions of any short-circuit current; uses a percentage method to unify the influence of different interruption currents and times on the electrical life of the circuit breaker, and combines formulas 1 to 5 to obtain the service life of the circuit breaker; uses a direct difference method to obtain the remaining life percentage, and when the remaining life percentage reaches the minimum limit, the equipment is overhauled or replaced. The present invention calculates the remaining life, promptly finds the time when the remaining life percentage reaches the minimum limit, and overhauls or replaces the equipment, thereby reducing the accident rate, reducing losses, and improving the reliability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic diagram of the structure of a DC circuit breaker electrical life analysis technology of the present invention;

[0045] Figure 2 This is a data collection diagram of a DC circuit breaker electrical life analysis technology protection device of the present invention (if the data cannot be read, it is recorded as the maximum value);

[0046] Figure 3 A data collection diagram of a DC circuit breaker electrical life analysis technology protection device of the present invention (calculating the maximum current value that cannot be read);

[0047] Figure 4 A current change rate data diagram obtained by a DC circuit breaker electrical life analysis technology according to data provided by a protection device;

[0048] Figure 5 A circuit breaker characteristic curve diagram is provided as the basis for the DC circuit breaker electrical life analysis technology of the present invention, and the number of electrical life operations corresponding to different breaking currents is used as the basis for judgment. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0050] The present invention provides a technical solution:

[0051] S1 Acquisition of collected data: The estimation method is adopted, and no additional measuring equipment is required. The protection device of the existing DC switch cabinet is mainly used to provide the necessary collected data for the circuit breaker electrical life analysis device. Usually, a DC switch cabinet is equipped with a protection device to collect the corresponding current and voltage data on the DC traction power supply system in real time, that is, the current and voltage data corresponding to the DC circuit breaker. The main current data is specifically used for real-time storage and calculation of the circuit breaker electrical life analysis device. The steps are:

[0052] S2 calculates the circuit-breaking current and input data: In the DC traction power supply system of urban rail transit, the general short-circuit breaking current is more than 10,000A, while the data recorded by the protection device is only around 10,000A to 20,000A. The calculation of the short-circuit breaking current includes two cases: when the short-circuit current is within the measurable recorded maximum value, the recorded maximum value can be directly used as the maximum short-circuit current; when the short-circuit current exceeds the maximum value recorded in the data, the duration of the recorded maximum value is calculated, the maximum current change rate is screened out, and the maximum short-circuit current is calculated. Using the data provided by the protection device of the DC switch cabinet, the circuit breaker electrical life analysis device calculates the short-circuit breaking current, which is the difficulty of the entire data calculation and analysis, as the measurement data for electrical life judgment, that is, the input data.

[0053] S3 calculates judgment data: uses the electrical life characteristic parameters of the circuit breaker at the factory and inputs them into the circuit breaker electrical life analysis device as reference data for electrical life judgment, i.e., judgment data;

[0054] S4 Calculate the remaining electrical life: Calculate the used electrical life and remaining electrical life of the circuit breaker by using the above-mentioned collected data, input data and judgment data, which is divided into the following steps:

[0055] ① The protection device measures, records and provides: the maximum value of the current change rate di / dt(max), the duration T, and the maximum current value I(max) of the protection device: Figure 2 and 4 , given that di / dt(max)=548A / ms, T=6ms, I(max)=11000A;

[0056] ②Calculate the breaking current:

[0057] Breaking current I≤maximum current value of protection device I(max), breaking current value I=current value of protection device I(max);

[0058] That is: I = I (max); - (Formula 1)

[0059] The breaking current value I > the maximum current value I(max) of the protection device. The breaking current value I = the maximum value of the current change rate di / dt(max) × 1 / 2 × the duration T + the maximum current value I(max) of the protection device.

[0060] That is: I = di / dt(max) × 1 / 2T + I(max) —— (Formula 2), for example Figure 2 , it can be known that I > I(max), then substitute the above values into Formula 2;

[0061] I = di / dt(max) × 1 / 2T + I(max) = 548 × 1 / 2 × 6 + 11000 = 12644A = 12.644kA, then for example Figure 3 the peak value;

[0062] ③ The number of breakings N corresponding to the breaking current is based on the breaker characteristic curve or test report data; for example, the number of breakings N corresponding to a 90kA breaking current 90 ; however, if the corresponding data is not directly listed in the characteristic curve or test report data, approximate proportion calculation can be used. For example Figure 5 , 10kA < I < 18kA, then the number of breakings N at this time is between 300 and 1000 times. Using approximate proportion calculation, (18 - 12.644) / (N - 300) = (12.644 - 10) / (1000 - N), and N = 769 times is obtained;

[0063] ④ The electrical life value S used this time 本 = 1 / (the number of breakings corresponding to the breaking current),

[0064] That is: S 本 = 1 / N; —— (Formula 3). For example, substituting N = 769 times into Formula 3, S 本 = 1 / 769 = 0.13%;

[0065] ⑤ The used electrical life value S 已 = the electrical life value S used this time 本 + the used electrical life value S of the previous time 上 (the initial value is 0),

[0066] S 已 = S 本 + S 上 —— (Formula 4). For example, substituting S 本 = 0.13% into Formula 4, S 已 = 0.13%;

[0067] ⑥ The total electrical life value S 总 = the used electrical life value S 已 + the remaining electrical life value S 剩,

[0068] The electrical life value is expressed as a percentage, and the total electrical life value S 总 =1,

[0069] S 总 =S 已 +S 剩 ——(Formula 5), ​​if S 已 =0.13% Substituting into formula 5, S 总 =S 已 +S 剩 , S 剩 =1-0.13%=99.87%.

[0070] The test data of electrical life in the type test report of the circuit breaker: The electrical life test of the circuit breaker is a damaging test for the circuit breaker, so it is impossible to conduct a variety of machine tests, otherwise it will accelerate the reduction of the service life of the circuit breaker. Even if such tests are done, due to production process and other reasons, the electrical life results of each circuit breaker are basically the same. The present invention directly uses the electrical life data of the circuit breaker, that is, the service life of the product. Usually, the experimental data of DC circuit breakers come from the most authoritative experimental institutions in the world, and the test standards are generally European standards or the latest national standards.

[0071] The number of times a circuit breaker can withstand different short-circuit currents is different, so it is necessary to convert it into consistent data for intuitive quantification. For this purpose, the percentage method is used, that is, different breaking currents and breaking times are converted into a unified percentage of electrical life. The calculated percentage of the input data is used as the used electrical life, and the test data is used as the judgment data. The result of subtracting the input data is the remaining electrical life. The specific working principle is as follows:

[0072] Data collection of protection devices of DC switch cabinet: After the data collected by the protection device reaches the maximum value of the full range, it is continuously recorded at the maximum value, such as Figure 2 shown.

[0073] Calculation of short-circuit breaking current: Take the maximum value recorded by the protection device as 11000A as an example (the maximum value is set according to different projects). When the short-circuit current is lower than 11000A, the maximum current value is directly read, and the maximum value recorded can be directly used as the maximum short-circuit current; when the short-circuit current is greater than 11000A, the corresponding maximum current value cannot be read. Figure 3 The curve part above the rectangular area cannot be read and needs to be inferred based on the waveform record of the protection device: filter the data provided by the protection device and select the maximum value of the current change rate di / dt, such as Figure 4, and calculate the maximum recorded current duration T, and deduce the maximum short-circuit current: I = di / dt(max) x 1 / 2T + I(max). Figure 3 The remaining part after eliminating the peak is the actual recorded value, the curve part above the rectangular area is the deduced estimated value, and the peak is the maximum short-circuit current. In this process, the current changes in a process of rising and falling by half, and the duration is 31 - 25 = 6 ms, that is, the time from the recorded maximum value rising to the short-circuit maximum value is about 1 / 2 of the duration, that is, 3 ms; through Figure 4 Select the maximum current change rate di / dt(max), that is, 548 kA / S or 548 A / ms, and the maximum recorded current duration T is Figure 3 In, it can also be in Figure 4 Such waveform recording data can be obtained, T is 31 - 25 = 6 ms; I(max) is Figure 3 The maximum value after eliminating the peak, and can be obtained in Figure 4 Such waveform recording data, I(max) is 11000 A, and I is Figure 3 The peak maximum value in the middle wave, that is, the deduced short-circuit current, then calculate the maximum short-circuit current I = 548 x 6 x 1 / 2 + 11000 A = 12644 A.

[0074] The test data of the electrical life in the type test report of the circuit breaker: the number of opening times of the circuit breaker's factory characteristic parameters at 90 kA is 20 times, at 50 kA is 40 times, at 18 kA is 300 times, and at 10 kA (and below) is 1000 times. The above data are the factory characteristic parameters of the circuit breaker, which have been verified by laboratory tests and many years of verification of similar products on site, so there is no need to repeat the verification again, that is, the service life. Using the above calculation of the maximum short-circuit current I = 12644 A, that is, 12.644 kA, 10 kA < I < 18 kA, then the number of opening times n at this time is between 300 and 1000 times. By adopting approximate proportional deduction, (18 - 12.644) / (n - 300) = (12.644 - 10) / (1000 - n), and n = 769 times is obtained.

[0075] Since the short-circuit current is different each time, the impact on the DC circuit breaker is different, that is, the response to the electrical life is different, so it needs to be converted into unified and intuitive quantitative data, so the percentage form is used. For example, when the short-circuit current is 18kA, the percentage of electrical life used is 1 / 300, that is, 0.3%. If the short-circuit current is 90kA again, the percentage of electrical life used is 1 / 20+0.3%, that is, 5.3%, and the remaining electrical life percentage is 100%-5.3%=94.7%; the percentage of the short-circuit current on the electrical life calculated above is 1 / 769, that is, 1.3%. If there has been an 18kA and a 90kA short-circuit current before, the cumulative percentage of electrical life used is 5.3%+1.3%=6.6%, and the remaining electrical life percentage is 93.4%. When the percentage of the remaining electrical life of the circuit breaker reaches the minimum limit of the actual service life of the product (the service life marked on the instruction manual when the product leaves the factory), it should be overhauled or replaced in time.

[0076] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A DC circuit breaker electrical life analysis technology, characterized in that: The following steps are involved: S1 Acquisition of collected data: Using the estimation method and the protection device of the existing DC switch cabinet, the necessary collected data is provided to the circuit breaker electrical life analysis device; S2 calculates the short-circuit breaking current and input data: using the data provided by the protection device of the DC switch cabinet, the circuit breaker electrical life analysis device calculates the short-circuit breaking current as the measurement data for electrical life judgment, that is, the input data. When calculating the short-circuit breaking current, when the short-circuit current exceeds the maximum value of the data record, calculate the duration of the maximum value, screen out the maximum current change rate, and calculate the maximum value of the short-circuit breaking current; When calculating the short-circuit breaking current and input data, the protection device measures, records and provides: the maximum value of the current change rate di / dt(max), the duration T, and the maximum current value I(max) of the protection device; According to the data, calculate the short-circuit breaking current: When the short-circuit breaking current I≤the maximum current value I(max) of the protection device, take the short-circuit breaking current I=the maximum current value I(max) of the protection device; That is: I = I(max); —— (Formula 1) When the short-circuit breaking current I> the maximum current value I(max) of the protection device, take the short-circuit breaking current I=the maximum value of the current change rate di / dt(max)×1 / 2×the duration T+the maximum current value I(max) of the protection device, That is: I = di / dt(max) × 1 / 2T + I(max) —— (Formula 2); S3 obtains judgment data: the electrical life characteristic parameters of the circuit breaker are input into the circuit breaker electrical life analysis device as reference data for electrical life judgment, i.e., judgment data; the electrical life test data in the circuit breaker type test report directly uses the electrical life data of the circuit breaker, i.e., the service life of the product; S4 calculates the remaining electrical life: using percentages to convert different short-circuit breaking currents and breaking times into a unified electrical life percentage, using the above-mentioned collected data, input data and judgment data to analyze the used electrical life and remaining electrical life of the circuit breaker. In calculating the remaining electrical life, the calculated percentage of the input data is used as the used electrical life, and the test data is used as the judgment data. The result of subtracting the input data is the remaining electrical life. Using the direct difference method, the product's 100% electrical life is subtracted from the percentage of the used life to obtain the remaining life percentage. It is divided into the following steps: ① The protection device measures, records and provides: the maximum value of the current change rate di / dt(max), the duration T, and the maximum current value I(max) of the protection device; ②Calculate the short-circuit breaking current; ③N number of breaking times corresponding to the short-circuit breaking current: N number of breaking times corresponding to the breaking current is based on the circuit breaker characteristic curve or test report data, such as N number of breaking times corresponding to 90kA breaking current 90 , if the characteristic curve or test report data does not directly list the corresponding data, the approximate proportion shall be used for calculation; ④The electrical life value S used this time 本 =1 / (number of breaking times corresponding to breaking current), That is: S 本 =1 / N;——(Formula 3); ⑤ Used electrical life value S 已 = The electrical life value of this use S 本 + Last used electrical life value S 上 , That is S 已 =S 本 + S 上 ——(Formula 4); ⑥Total electrical life value S 总 = Used electrical life value S 已 + Remaining electrical life value S 剩 The electrical life value is expressed in percentage, and the total electrical life value is S 总 =1, S 总 =S 已 + S 剩 ——(Formula 5).

2. The DC circuit breaker electrical life analysis technology according to claim 1 is characterized by: In step S1 of acquiring collected data, each DC switch cabinet is provided with a protection device to collect corresponding current and voltage data on the DC traction power supply system, that is, current and voltage data corresponding to the DC circuit breaker in real time.

3. The DC circuit breaker electrical life analysis technology according to claim 2 is characterized by: In step S1 of acquiring collected data, main current data is stored and calculated in real time by a device specifically used for circuit breaker electrical life analysis.

4. The DC circuit breaker electrical life analysis technology according to claim 3 is characterized by: In step S2, the short-circuit breaking current is calculated and the input data is input. When the short-circuit breaking current is calculated, if the short-circuit current is within the measurable recorded maximum value, the recorded maximum value is directly used as the maximum short-circuit current.

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