A real-time control method and system for short circuit current duration

Abstract

The application provides a short-circuit current duration real-time control method and system, and belongs to the technical field of current resistance test, and comprises the following steps: collecting short-circuit current data and obtaining inherent breaking time of an auxiliary switch; adopting an attenuation factor to simulate short-circuit current attenuation of resistivity with temperature increase of the short-circuit current data, so as to obtain a current expression; calculating a parameter-determined current expression based on a plurality of key maximum points of the current expression; performing Joule integral on the parameter-determined current expression to obtain a breaking time of the auxiliary switch in combination with the inherent breaking time of the auxiliary switch, and controlling the short-circuit current duration according to the breaking time. The application realizes accurate control of the short-circuit current duration of a resistance change test product.

Description

A real-time control method and system for short-circuit current duration Technical Field

[0001] This invention belongs to the field of withstand current testing technology, and particularly relates to a real-time control method and system for the duration of short-circuit current. Background Technology

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

[0003] Short-time withstand current and peak withstand current tests are used to evaluate the ability of electrical equipment to withstand transient peak currents and steady-state short-time currents under fault conditions. Traditional short-time withstand current and peak withstand current tests are based on ignoring changes in the impedance of the test object. This is because the resistance of the main circuit, grounding switch, and grounding circuit connection wire of the test object is very small, reaching the micro-ohm level, resulting in minimal heat generation and a relatively insignificant temperature rise, thus keeping the steady-state current amplitude essentially constant.

[0004] However, some special situations often occur in actual tests. For example, when conducting short-time withstand current and peak withstand current tests on high-voltage connecting lines (cables), the short-circuit current causes the test object (cable) to heat up severely, and the temperature rises. Then its corresponding resistance will increase accordingly, and thus a decaying short-circuit current will be generated under the excitation of the voltage source (constant voltage).

[0005] For test specimens with insignificant resistance changes, traditional testing methods can be applied: the required current-limiting reactance and resistance values ​​for the test circuit can be calculated based on the power supply voltage and the short-circuit current of the test specimen. The closing and opening times of the auxiliary switch are preset based on the short-circuit current duration t, and finally, the Joule integral is obtained. .

[0006] However, for samples exhibiting resistance changes, traditional testing methods cannot meet the Joule integral value requirement, meaning the final test result is lower than the standard requirement. This renders the test invalid, and the test is extremely destructive to the sample, making it impossible to repeat. Ultimately, a new sample is needed to successfully complete the test, resulting in a certain degree of economic loss. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, this invention proposes a real-time control method and system for the duration of short-circuit current. It considers the current decay caused by the temperature change of the test sample to calculate the accurate opening time of the auxiliary switch, and finally successfully meets the Joule integral value specified in the standard.

[0008] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0009] In a first aspect, the present invention discloses a real-time control method for the duration of a short-circuit current, comprising:

[0010] Collect short-circuit current data and obtain the inherent opening time of the auxiliary switch;

[0011] An attenuation factor is used to simulate the attenuation of short-circuit current as resistivity increases with temperature, resulting in a current expression containing several unknown parameters. An exponential function is used as the attenuation factor to simulate the attenuation of short-circuit current caused by increasing resistivity with temperature.

[0012] Based on several key maxima points of the current expression, several unknown parameters are solved to obtain a current expression with determined parameters.

[0013] The opening time of the auxiliary switch is obtained by performing Joule integration on the current expression determined by the parameters and combining it with the inherent opening time of the auxiliary switch. The duration of the short-circuit current is controlled according to the opening time.

[0014] Secondly, the present invention discloses a real-time control system for the duration of a short-circuit current, comprising:

[0015] The data acquisition module is configured to: collect short-circuit current data and acquire the inherent opening time of the auxiliary switch;

[0016] The attenuation simulation module is configured to: use an attenuation factor to simulate the attenuation of short-circuit current as resistivity increases with temperature on the short-circuit current data, and obtain a current expression, wherein the current expression contains several unknown parameters;

[0017] The current expression module is configured to: solve for several unknown parameters based on several key maximum points of the current expression to obtain a current expression with determined parameters;

[0018] The tripping control module is configured to: perform Joule integration on the current expression determined by the parameters and combine it with the inherent tripping time of the auxiliary switch to obtain the tripping time of the auxiliary switch, and control the duration of the short-circuit current according to the tripping time.

[0019] Thirdly, the present invention discloses an electronic device, including a memory and a processor, and computer instructions stored in the memory and running on the processor, wherein the computer instructions, when run by the processor, complete the steps of the above-mentioned real-time control method for the duration of short-circuit current.

[0020] Fourthly, the present invention discloses a computer-readable storage medium for storing computer instructions, which, when executed by a processor, complete the steps of the above-mentioned real-time control method for the duration of short-circuit current.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention employs an exponential function as an attenuation factor to simulate the decay of short-circuit current caused by increasing resistivity with temperature. This allows for the calculation of the Joule integral value of the sample with changing resistance, improving experimental accuracy and avoiding the waste of samples due to invalid experiments. On one hand, the short-circuit current expression based on the exponential function as an attenuation factor has advantages such as convergence and versatility compared to other functions, making it the best choice for predicting the Joule integral of the short-circuit current of a sample in engineering. On the other hand, considering the heat transfer between the sample and the external environment during the experiment, the relationship between the change in resistivity of the sample and the Joule heat generated by the short-circuit current becomes complicated. This invention does not consider the complex intermediate process of the coupling between electricity and temperature, and directly uses the exponential function as an attenuation factor to fit the short-circuit current, which has the advantage of smaller error compared to other functions. In summary, this invention uses an exponential function to fit the short-circuit current with AC component attenuation.

[0023] Specifically, this invention has the advantage of real-time, closed-loop control of the Joule integral value: First, input the given Joule integral value (standard requirement value). The second step is to use the attenuation current model proposed in this invention, combined with several maxima points, to deduce the analytical expression for the attenuation current (the final expression); the third step is to perform a Joule integral on the solved analytical expression for the current and set it equal to the standard required value, i.e. ,in The (current initiation time) can be read from the acquired data and calculated. (Current termination time); Fourth step, determine the tripping time of the auxiliary switch ( )in The fifth step is to finally achieve a Joule integral value equal to the standard value. This is the inherent opening time of the auxiliary switch, and at this time, a opening command is sent to the auxiliary switch to execute the opening.

[0024] The short-circuit current duration calculated in this invention is based on the standard value of Joule integral. It assesses the ability of power equipment to withstand the thermal effects of short-circuit current. When the current decays and the Joule integral still meets the standard, it is necessary to determine the function of Joule integral in order to predict the duration of short-circuit current in advance. Therefore, the Joule integral value is used as the final basis for rationality verification.

[0025] This invention has the advantage of wide applicability: it is not only applicable to the Joule integral calculation of short-circuit current models with attenuation caused by changes in the resistance of the sample, but also applicable to the calculation of constant (no attenuation) short-circuit current models.

[0026] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0028] Figure 1 is a waveform diagram of the short-circuit current of the constant AC component described in Embodiment 1 of the present invention.

[0029] Figure 2 is a short-circuit current waveform diagram of the attenuated AC component described in Embodiment 1 of the present invention.

[0030] Figure 3 is a flowchart of the closed-loop control method of the real-time control method described in Embodiment 1 of the present invention.

[0031] Figure 4 is a test circuit diagram of the constant AC component short-circuit current as described in Embodiment 1 of the present invention.

[0032] Figure 5 is a simulation waveform of the short-circuit current described in Embodiment 1 of the present invention.

[0033] Figure 6 is a diagram of the experimental waveform results described in Embodiment 1 of the present invention.

[0034] Figure 7 is a graph of the test data results described in Embodiment 1 of the present invention. Detailed Implementation

[0035] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0037] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0038] Example 1

[0039] Short-time withstand current and peak withstand current tests involve applying a large current close to the rated short-circuit current to the test specimen and maintaining it for a period of time to observe whether the equipment can maintain normal function during this period. In traditional short-time withstand current and peak withstand current tests, the impedance change of the test specimen is ignored, so the AC component of the resulting steady-state current remains basically unchanged, and the waveform of the short-circuit current with constant AC component is shown in Figure 1. However, in actual tests, the test specimen will heat up due to the short-circuit current, causing an increase in resistance, which will generate a short-circuit current with attenuated AC component, and its waveform is shown in Figure 2.

[0040] In one or more embodiments, a real-time control method for the duration of a short-circuit current is disclosed. As shown in Figure 3, the method considers the current decay caused by temperature changes in the test sample to calculate the accurate opening time of the auxiliary switch, thereby precisely controlling the current duration in a closed loop. The method includes the following steps:

[0041] Step S1: Collect short-circuit current data in real time and obtain the inherent opening time of the auxiliary switch.

[0042] Step S2: Use the attenuation factor to simulate the attenuation of short-circuit current as resistivity increases with temperature on the short-circuit current data to obtain the current expression.

[0043] The test circuit for the constant AC component short-circuit current is shown in Figure 4. The analytical expression for the waveform of the constant AC component short-circuit current is:

[0044] (1)

[0045] In the formula, The short-circuit current is a constant alternating component. The amplitude of the constant AC component, The magnitude of the DC component of the short-circuit current is a constant AC component. Angular frequency, For time, For the initial phase, The time constant of the short-circuit current with a constant AC component.

[0046] The Joule integral is:

[0047] (2)

[0048] In the formula, This is the moment when the short-circuit current begins. This is the moment when the short-circuit current terminates.

[0049] This embodiment uses an exponential function as the attenuation factor to simulate the attenuation of short-circuit current caused by the increase of resistivity ρ with temperature, expressed as:

[0050] (3)

[0051] In the formula, To attenuate the AC component of the short-circuit current, The magnitude of the attenuation factor. The time constant is the decay factor.

[0052] From formula (3), we get:

[0053] (4)

[0054] Further simplifying formula (4), let , , , Therefore, we obtain the expression for the current:

[0055] (5)

[0056] In the formula, To attenuate the amplitude of the AC component, The attenuation coefficient is the attenuation factor for the AC component. To attenuate the amplitude of the DC component of the short-circuit current in the AC component, This is the attenuation coefficient of the DC component of the short-circuit current that attenuates the AC component. At this point, the current expression contains unknown parameters: the amplitude and attenuation coefficient of the AC component, the amplitude and attenuation coefficient of the DC component of the short-circuit current that attenuates the AC component, and the initial phase.

[0057] Step S3: Based on several key maximum points of the current expression, calculate several unknown parameters to obtain a current expression with determined parameters.

[0058] Considering the inherent opening time of auxiliary switch FK It must be in ( The tripping signal is sent to the auxiliary switch FK at all times, therefore the first maximum value of the short-circuit current is used. The 5th maximum point [ The 9th maximum point [ The 13th maximum point [ Given that the power supply frequency f is known, we can deduce the analytical expression for the short-circuit current. .

[0059] The expression for the maximum point is formula (6), and the condition for the maximum point is... Therefore, formula (6) gives formula (7), which is expressed as formula (7):

[0060] (6)

[0061] (7)

[0062] In the formula, This is the time corresponding to the (n+1)th maximum point.

[0063] Based on the given conditions, we know that:

[0064] (8)

[0065] (9)

[0066] (10)

[0067] In the formula, T is the period of the voltage source, T = 1 / f. This is the time corresponding to the first maximum point.

[0068] Substituting the above formulas (8)-(10) into formula (7), we obtain the current expressions for the first, fifth, ninth, and thirteenth maximum values ​​of the short-circuit current:

[0069] (11)

[0070] (12)

[0071] (13)

[0072] (14)

[0073] Furthermore, let , , , ,but:

[0074] (15)

[0075] (16)

[0076] (17)

[0077] (18)

[0078] Through derivation, we have:

[0079] (19)

[0080] (20)

[0081] make , ,but:

[0082] (twenty one)

[0083] (twenty two)

[0084] Solving the above two equations yields:

[0085] (twenty three)

[0086] (twenty four)

[0087] Depend on , Know and It is an equation The two roots, therefore:

[0088] (25)

[0089] because , ,and and It is the attenuation coefficient, usually and It is a positive number, so and Between 0 and 1. Theoretically. and It is symmetrical, so it can be allocated arbitrarily, that is... , Let the parameter be any positive number between 0 and 1. ; .

[0090] and Since X and Y have been calculated, they conform to formulas (26)-(27).

[0091] (26)

[0092] (27)

[0093] It can be found that:

[0094] (28)

[0095] (29)

[0096] because , ,and Given that, we can therefore find , .

[0097] The initial phase φ can be obtained through the maximum condition. If confirmed, then For n=0,1,2……, setting n=0 yields the following results. .

[0098] At this point, all the unknown parameters of the short-circuit current expression for the attenuated AC component have been determined, and the expression is as follows:

[0099] (30)

[0100] The parameters are all analyzed through the above process.

[0101] Step S4: Perform Joule integration on the current expression with the determined parameters and combine it with the inherent opening time of the auxiliary switch to obtain the opening time of the auxiliary switch, and control the duration of the short-circuit current according to the opening time.

[0102] Let Joule integral (in It is a real-time calculation of the Joule integral, thereby determining the termination time of the short-circuit current. .

[0103]

[0104]

[0105]

[0106]

[0107]

[0108]

[0109] in:

[0110]

[0111]

[0112]

[0113]

[0114]

[0115] The test will provide the following test parameters: effective value of short-circuit current I, Joule integral value Q (standard requirement value), and duration of short-circuit current t. k (Standard requirement value). Therefore, the algorithm first presets the short-circuit current termination time as 2t. k ,like If ≤0, then in the interval [ ]function If there is a root, it can be determined. ;like If the value is greater than 0, then there is no root, and the termination time of the short-circuit current can be changed to 3t. k The same method is used to determine the function. In the interval [ [The interval contains no roots; after determining the final interval, use the bisection method to find the one that contains roots.] =0 Numerical solutions should satisfy the relative error requirement. .

[0116] The opening time of the auxiliary switch is obtained from the above process. The tripping command (pulse) is then fed back to the auxiliary switch to accurately execute the tripping command, thus completing a valid test.

[0117] As an example, a simulation experiment was conducted. The short-circuit current expression of the attenuated AC component was obtained using the four maximum points 1, 5, 9 and 13 in Figure 7, and its waveform was plotted as shown in Figure 5. The first 14 maximum points corresponding to the short-circuit current expression of the attenuated AC component obtained from the simulation experiment are shown in Table 1.

[0118] Table 1. Examples of Maximum Points

[0119]

[0120] Based on the above algorithm, four effective maxima are extracted, and the analytical expression for the short-circuit current of the attenuated AC component is derived. Then, through integration, that is... It can be found that in By calculating the Joule integral that always meets the experimental requirements, the opening time of the auxiliary switch can be deduced. The tripping command (pulse) is fed back to the auxiliary switch to accurately execute the tripping command. As shown in Figure 6, using several maximum points and the time of the first maximum point in the actual test data, the test waveform is obtained in the test using the above algorithm according to the Joule integral required by the test sample. As shown in Figure 7, the test waveform results in Figure 6 show several maximum points, current duration, and Joule integral data. Combining Figures 5-7 and Table 1, the simulated Joule integral value is 1073.44 (kA)²s, and the experimental Joule integral value is 1031.07 (kA)²s. This shows the test waveform and its data, the simulated waveform and its data, and verifies the accuracy, reliability, and stability of this scheme.

[0121] resistivity of materials such as copper and aluminum With temperature The relationship is:

[0122]

[0123] in, Temperature coefficient of resistance To be at the reference temperature The resistivity at that time. The continuous current test (temperature rise test) for electrical equipment (such as transformers, switchgear, and circuit breakers) is a mandatory type test specified in the standard, and the temperature rise curve of the relevant test specimen is similar to the function:

[0124]

[0125] in, Let be a constant. ,but ;resistance Where L is the length of the wire and S is the cross-sectional area of ​​the wire, the change in resistance with temperature can be fitted by a suitable exponential function, i.e. Therefore, this embodiment selects an exponential function as the attenuation factor to obtain the accurate AC component attenuation of the short-circuit current, thus providing a theoretical basis for the Joule integral calculation process.

[0126] Example 2

[0127] In one or more embodiments, a real-time control system for the duration of a short-circuit current is disclosed, specifically including:

[0128] The data acquisition module is configured to: collect short-circuit current data and acquire the inherent opening time of the auxiliary switch;

[0129] The attenuation simulation module is configured to: use an attenuation factor to simulate the attenuation of short-circuit current as resistivity increases with temperature on the short-circuit current data, and obtain a current expression, wherein the current expression contains several unknown parameters;

[0130] The current expression module is configured to: solve for several unknown parameters based on several key maximum points of the current expression to obtain a current expression with determined parameters;

[0131] The tripping control module is configured to: perform Joule integration on the current expression determined by the parameters and combine it with the inherent tripping time of the auxiliary switch to obtain the tripping time of the auxiliary switch, and control the duration of the short-circuit current according to the tripping time.

[0132] Example 3

[0133] This embodiment provides an electronic device, including a memory and a processor, as well as computer instructions stored in the memory and running on the processor. When the computer instructions are executed by the processor, they complete the steps of the real-time control method for the duration of the short-circuit current described above.

[0134] Example 4

[0135] This embodiment provides a computer-readable storage medium for storing computer instructions, which, when executed by a processor, complete the steps of the above-described real-time control method for the duration of short-circuit current.

[0136] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in one or more blocks of the flowchart illustrations and / or one or more blocks of the block diagrams.

[0137] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means that implement the functions specified in one or more flowcharts and / or one or more block diagrams.

[0138] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to perform a series of operational steps on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide steps for implementing the functions specified in one or more flowcharts and / or one or more block diagrams.

[0139] The descriptions of each embodiment in the above embodiments have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0140] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A real-time control method for the duration of short-circuit current, characterized in that, include: Collect short-circuit current data and obtain the inherent opening time of the auxiliary switch; An attenuation factor is used to simulate the attenuation of short-circuit current as resistivity increases with temperature, resulting in a current expression containing several unknown parameters. An exponential function is used as the attenuation factor to simulate the attenuation of short-circuit current due to increasing resistivity with temperature. Based on several key maxima points of the current expression, the unknown parameters are solved to obtain a parameter-determined current expression. Joule integration is performed on the parameter-determined current expression, combined with the inherent opening time of the auxiliary switch, to obtain the opening time of the auxiliary switch. The duration of the short-circuit current is controlled according to the opening time. The use of an exponential function as the attenuation factor to simulate the attenuation of short-circuit current due to increasing resistivity with temperature is expressed as: In the formula, To attenuate the amplitude of the AC component, The attenuation coefficient for the AC component is used to attenuate the signal. To attenuate the amplitude of the DC component of the short-circuit current in the AC component, The attenuation coefficient for the DC component of the short-circuit current that attenuates the AC component. The magnitude of the attenuation factor. The time constant of the decay factor The amplitude of the constant AC component, The magnitude of the DC component of the short-circuit current is a constant AC component. Angular frequency, For time, For the initial phase, Let be the time constant of the short-circuit current with a constant AC component; the termination time of the short-circuit current is obtained by performing a Joule integral on the current expression according to the following formula: In the formula, Q is the known standard requirement for the Joule integral value. This is the moment when the short-circuit current terminates. This is the starting moment of the short-circuit current.

2. The real-time control method for the duration of short-circuit current as described in claim 1, characterized in that, The current expression for the critical maximum point includes: In the formula, To attenuate the amplitude of the AC component, The attenuation coefficient for the AC component is used to attenuate the signal. To attenuate the amplitude of the DC component of the short-circuit current in the AC component, The attenuation coefficient for the DC component of the short-circuit current that attenuates the AC component. The time corresponding to the first maximum point, ， ， T is the period of the voltage source.

3. The real-time control method for the duration of short-circuit current as described in claim 2, characterized in that, make ， ， ， Through derivation: in, 、 The parameter is any positive number between 0 and 1.

4. The real-time control method for the duration of short-circuit current as described in claim 1, characterized in that, The duration of the short-circuit current is controlled according to the opening time, specifically based on the inherent opening time of the auxiliary switch itself. and the calculated termination time of the short-circuit current The tripping time is obtained; the tripping time is... At the moment of tripping, a tripping signal is sent to the auxiliary switch to execute the tripping command.

5. A real-time control system for the duration of short-circuit current, characterized in that, include: The data acquisition module is configured to: collect short-circuit current data and acquire the inherent opening time of the auxiliary switch; The attenuation simulation module is configured to: use an attenuation factor to simulate the attenuation of short-circuit current as resistivity increases with temperature using the short-circuit current data, and obtain a current expression, which contains several unknown parameters; the current expression module is configured to: solve for several unknown parameters based on several key maximum points of the current expression, and obtain a current expression with determined parameters. The tripping control module is configured to: perform Joule integration on the current expression determined by the parameters and combine it with the inherent tripping time of the auxiliary switch to obtain the tripping time of the auxiliary switch, and control the duration of the short-circuit current according to the tripping time. An exponential function is used as the attenuation factor to simulate the decrease in short-circuit current caused by increasing resistivity with temperature, expressed as: In the formula, To attenuate the amplitude of the AC component, The attenuation coefficient for the AC component is used to attenuate the signal. To attenuate the amplitude of the DC component of the short-circuit current in the AC component, The attenuation coefficient for the DC component of the short-circuit current that attenuates the AC component. The magnitude of the attenuation factor. The time constant of the decay factor The amplitude of the constant AC component, The magnitude of the DC component of the short-circuit current is a constant AC component. Angular frequency, For time, For the initial phase, The time constant of the short-circuit current with a constant AC component; The termination time of the short-circuit current can be obtained by performing Joule integration on the current expression according to the following formula: In the formula, Q is the known standard requirement for the Joule integral value. This is the moment when the short-circuit current terminates. This is the starting moment of the short-circuit current.

6. An electronic device, characterized in that, The method includes a memory and a processor, as well as computer instructions stored in the memory and running on the processor, which, when executed by the processor, perform the real-time control method for the duration of the short-circuit current as described in any one of claims 1-4.

7. A computer-readable storage medium, characterized in that, Used to store computer instructions, which, when executed by a processor, complete the real-time control method for the duration of short-circuit current as described in any one of claims 1-4.

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