A method for detecting the impedance of a connection in a metering box

Abstract

The application provides a metering box internal wiring impedance detection method, comprising the following steps: step 1, obtaining current and voltage data of each phase line at the metering box inlet and current and voltage data of each electric energy meter in the metering box; step 2, obtaining the connection relationship between each electric energy meter and each phase line at the metering box inlet; step 3, obtaining the line topology relationship between the transformer, the branch box, the metering box and the electric energy meter; and step 4, calculating the metering box internal wiring impedance of each electric energy meter. The application can obtain the metering box internal wiring impedance of each electric energy meter, that is, the line impedance between the electric energy meter and the metering box inlet, can accurately locate the line with line aging or device loosening in the metering box, thereby reducing the detection difficulty of the line impedance in the metering box and improving the accuracy.

Description

Technical Field

[0001] This invention belongs to the field of low-voltage power distribution networks, and specifically relates to a method for detecting the wiring impedance inside a metering box. Background Technology

[0002] In current low-voltage distribution network systems, the power transmission path is generally from the transformer substation, through branch boxes, to metering boxes, and finally to each user, with each user corresponding to an electricity meter. The physical wiring of the transformer substation, branch boxes, metering boxes, and electricity meters forms a tree-like branch topology, as shown in the attached instruction manual. Figure 1 As shown, the metering box, as the end of the distribution area's wiring structure, is directly connected to the user's electricity meter. Its environment is enclosed and the space is small, with a relatively large variety and number of devices installed inside. The existing metering box mainly includes electricity meters, incoming line switches, miniature circuit breakers, and data collectors. The number of electricity meters and miniature circuit breakers is related to the number of users; the more users, the more corresponding equipment. The dispersed installation of various devices also leads to numerous wiring fault points in the entire system operation. Therefore, aging of the lines and loosening of components are inevitable. This may result in excessive line loss, severe localized overheating of lines or equipment, and in more serious cases, equipment damage and fires in the surrounding area, posing a serious safety threat to residents' lives and property. To prevent these situations, the line impedance is generally detected to determine the transmission condition of the line. When the circuit impedance from a certain device to the metering box inlet is detected to be greater than a set value, it is considered that the line between that device and the metering box inlet has aging or loose components, requiring timely maintenance and repair to ensure the safety of residents' lives and property. However, due to the large number of devices and complex wiring in the metering box, and the parallel connection of various metering boxes in the same area, it is difficult to actually test the circuit impedance in each metering box, the calculation accuracy is low, and it is difficult to characterize the actual wiring situation. Summary of the Invention

[0003] To address the challenges and low accuracy of impedance detection within metering boxes in existing technologies, this invention provides a method for detecting wiring impedance within metering boxes. This method can obtain the wiring impedance of each energy meter within the metering box, specifically the impedance between the energy meter and the metering box's inlet line. It can accurately locate lines within the metering box that are aging or have loose components, thereby reducing the difficulty of impedance detection and improving accuracy.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for detecting the wiring impedance inside a metering box includes the following steps: Step 1: Obtain the current and voltage data of each phase line at the metering box inlet and the current and voltage data of each energy meter inside the metering box. The current and voltage data of each phase line at the metering box in the transformer substation are collected at high frequency. According to the set collection time, the current and voltage data of each phase line at the metering box inlet and the current and voltage data of each energy meter in the metering box are acquired in different time periods. All data in each time period are treated as a set of data to be processed. During acquisition, the current and voltage data of each phase line at the metering box inlet are converted from analog signals to digital signals. Step 2: Obtain the connection relationship between each energy meter and the phase line at the inlet of the metering box; Step 2.1: Process the multiple sets of data to be processed separately. If the current of each phase line at the inlet of each energy meter and metering box remains stable in a set of data to be processed, then the data in this set is steady-state data; otherwise, discard the data in this set. Step 2.2: If, when comparing the two sets of steady-state data, only one energy meter shows a current fluctuation while the current of the other energy meters does not fluctuate, proceed to step 2.3. Step 2.3: If only one phase line at the metering box inlet experiences current fluctuation, while the other phase lines do not, and the time of current fluctuation in the fluctuating phase line is the same as the time of current fluctuation in the fluctuating energy meter, then the energy meter experiencing current fluctuation is connected to the phase line experiencing current fluctuation, and the two sets of steady-state data are retained. Step 2.4: Using steps 2.2 and 2.3, process the multi-steady-state data to obtain the connection relationship between each energy meter and each phase line at the inlet of the metering box, and retain the two sets of steady-state data corresponding to each energy meter. Step 3: Obtain the line topology between the transformer, branch box, metering box and energy meter in the distribution area; The transformer, branch box, metering box and electricity meter in the distribution area are divided into four levels to form a tree topology. Based on the tree topology and the connection relationship between each electricity meter and the phase line at the inlet of the metering box, a line topology relationship is formed. Step 4: Calculate the wiring impedance inside the metering box of each electricity meter; Step 4.1: Based on the line topology, and according to the voltage change relationship of the current fluctuation of the energy meter, obtain the calculation formula for the voltage change value of the energy meter and the calculation formula for the voltage change value of the phase line connected to the energy meter. Step 4.2: The line impedance between the energy meter and the connected phase line is recorded as the wiring impedance inside the meter box of the energy meter. The calculation formula for the voltage change value on the wiring impedance inside the meter box of the energy meter is obtained by using the two calculation formulas in Step 4.1. Step 4.3: Based on the fact that the voltage change on the wiring impedance inside the meter box of the energy meter is equal to the current change on the wiring impedance inside the meter box of the energy meter multiplied by the wiring impedance inside the meter box of the energy meter, the calculation formula obtained in 4.2 is used to construct the calculation formula for the wiring impedance inside the meter box of the energy meter. Step 4.4: Process the two sets of steady-state data corresponding to each energy meter to obtain the calculation formula for the wiring impedance inside the metering box of each energy meter, calculate the required parameters, and then calculate the wiring impedance inside the metering box of each energy meter.

[0005] In a further improvement to the technical solution of the present invention, in step 2.1, if the change in current of the phase line at the inlet of the energy meter and the metering box is less than the stability threshold, then the current of the phase line at the inlet of the energy meter and the metering box remains stable.

[0006] The wiring impedance inside the metering box of each energy meter obtained in this invention is the line impedance between the energy meter and the metering box inlet. When the wiring impedance inside the metering box of a certain energy meter is greater than a set value, there is aging of the line or loosening of the components in the line between the energy meter and the metering box inlet. This allows for accurate location of the line with aging or loose components inside the metering box. Only the equipment on this line needs to be maintained and repaired, eliminating the need to test the line impedance of each device. This reduces the difficulty of testing the line impedance inside the metering box and improves the accuracy.

[0007] In a further improvement to the technical solution of the present invention, in step 2.2, if the change value of the current of the electricity meter is greater than the fluctuation threshold, then the electricity meter experiences current fluctuation.

[0008] In a further improvement to the technical solution of the present invention, in step 2.3, if the difference between the current change value of a phase line at the metering box inlet and the current change value of the energy meter that is experiencing current fluctuation is less than the difference threshold, then current fluctuation occurs in this phase line.

[0009] In a further improvement to the technical solution of the present invention, in step 3, the line impedance between the electricity meter and the transformer of the entire distribution area, and between the transformer of the distribution area and the branch box, is recorded as the common impedance of the entire distribution area, and the line impedance between the branch box and the metering box inlet is recorded as the private wiring impedance of the metering box; in step 4.1, the voltage change value of the electricity meter is equal to the sum of the voltage change value on the common impedance of the entire distribution area, the voltage change value on the private wiring impedance of the metering box, and the voltage change value on the wiring impedance inside the metering box; the voltage change value of the phase line connected to the electricity meter is equal to the sum of the voltage change value on the common impedance of the entire distribution area and the voltage change value on the private wiring impedance of the metering box.

[0010] In a further improvement to the technical solution of the present invention, in step 4.2, the voltage change value on the wiring impedance inside the metering box of the energy meter is equal to the difference between the voltage change value of the energy meter and the voltage change value of the phase line connected to the energy meter.

[0011] In a further improvement to the technical solution of the present invention, in step 4.3, the wiring impedance inside the metering box of the energy meter is equal to the ratio of the difference between the voltage change value of the energy meter and the voltage change value of the phase line connected to the energy meter to the current change value on the wiring impedance inside the metering box of the energy meter.

[0012] In a further improvement to the technical solution of the present invention, in step 4.4, the required parameters are the voltage change value of the energy meter, the voltage change value of the phase line connected to the energy meter, and the current change value of the wiring impedance in the metering box of the energy meter.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention can obtain the wiring impedance inside the metering box of each electricity meter, and can accurately locate the wiring inside the metering box that is aging or has loose components, thereby reducing the difficulty of detecting the wiring impedance inside the metering box and improving the accuracy.

[0014] 2. In this invention, the connection relationship between each energy meter and each phase line at the inlet of the metering box is obtained by using the selected steady-state data. Then, the wiring impedance inside the metering box is calculated using the two sets of steady-state data corresponding to each energy meter. The result is stable and reliable.

[0015] 3. The Type I data acquisition unit supports high-frequency acquisition of current and voltage data of each phase line at the metering box inlet. It can also acquire current and voltage data of each energy meter inside the metering box. In the implementation of this invention, for metering boxes that have a Type I data acquisition unit installed at the inlet, the aforementioned method for detecting the wiring impedance inside the metering box can be configured in the Type I data acquisition unit to realize the detection of the wiring impedance inside the metering box. The implementation method is simple and low cost. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a typical power line structure across the entire Taiwan region.

[0017] Figure 2 This is a schematic diagram of the system structure of the present invention. Figure 3 This is a schematic diagram of the system structure in Embodiment 2 of the present invention. Detailed Implementation

[0018] The present invention will be further described below. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be construed as limiting the scope of protection of this application.

[0019] Example 1 A method for monitoring wiring impedance inside a metering box includes the following steps: Step 1: Obtain the current and voltage data of each phase line at the metering box inlet and the current and voltage data of each energy meter inside the metering box. The current and voltage data of each phase line at the metering box in the transformer substation are collected at high frequency. According to the set collection time, the current and voltage data of each phase line at the metering box inlet and the current and voltage data of each energy meter in the metering box are acquired in different time periods. All data in each time period are treated as a set of data to be processed. During acquisition, the current and voltage data of each phase line at the metering box inlet are converted from analog signals to digital signals. Step 2: Obtain the connection relationship between each energy meter and the phase line at the inlet of the metering box; Step 2.1: Process the multiple sets of data to be processed separately. If the current of each phase line at the inlet of each energy meter and metering box remains stable in a set of data to be processed, then the data in this set is steady-state data; otherwise, discard the data in this set. Step 2.2: If, when comparing the two sets of steady-state data, only one energy meter shows a current fluctuation while the current of the other energy meters does not fluctuate, proceed to step 2.3. Step 2.3: If only one phase line at the metering box inlet experiences current fluctuation, while the other phase lines do not, and the time of current fluctuation in the fluctuating phase line is the same as the time of current fluctuation in the fluctuating energy meter, then the energy meter experiencing current fluctuation is connected to the phase line experiencing current fluctuation, and the two sets of steady-state data are retained. Step 2.4: Using steps 2.2 and 2.3, process the multi-steady-state data to obtain the connection relationship between each energy meter and each phase line at the inlet of the metering box, and retain the two sets of steady-state data corresponding to each energy meter. Step 3: Obtain the line topology between the transformer, branch box, metering box and energy meter in the distribution area; The transformer, branch box, metering box and electricity meter in the distribution area are divided into four levels to form a tree topology. Based on the tree topology and the connection relationship between each electricity meter and the phase line at the inlet of the metering box, a line topology relationship is formed. Step 4: Calculate the wiring impedance inside the metering box of each electricity meter; Step 4.1: Based on the line topology, and according to the voltage change relationship of the current fluctuation of the energy meter, obtain the calculation formula for the voltage change value of the energy meter and the calculation formula for the voltage change value of the phase line connected to the energy meter. Step 4.2: The line impedance between the energy meter and the connected phase line is recorded as the wiring impedance inside the meter box of the energy meter. The calculation formula for the voltage change value on the wiring impedance inside the meter box of the energy meter is obtained by using the two calculation formulas in Step 4.1. Step 4.3: Based on the fact that the voltage change on the wiring impedance inside the meter box of the energy meter is equal to the current change on the wiring impedance inside the meter box of the energy meter multiplied by the wiring impedance inside the meter box of the energy meter, the calculation formula obtained in 4.2 is used to construct the calculation formula for the wiring impedance inside the meter box of the energy meter. Step 4.4: Process the two sets of steady-state data corresponding to each energy meter to obtain the calculation formula for the wiring impedance inside the metering box of each energy meter, calculate the required parameters, and then calculate the wiring impedance inside the metering box of each energy meter.

[0020] In step 2.1 of this embodiment, if the change in current of the phase line at the inlet of the energy meter and the metering box is less than the stable threshold, the current of the phase line at the inlet of the energy meter and the metering box remains stable; the stable threshold is set to 0.2A.

[0021] In step 2.2 of this embodiment, if the change in current of the electricity meter is greater than the fluctuation threshold, the electricity meter will experience current fluctuation; the fluctuation threshold is set to 2A.

[0022] In step 2.3 of this embodiment, if the difference between the current change value of a phase line at the metering box inlet and the current change value of the energy meter that is experiencing current fluctuation is less than the difference threshold, then the current of this phase line is experiencing current fluctuation; the difference threshold is set to ±0.1A.

[0023] In step 3 of this embodiment, the line impedance between the electricity meter and the transformer of the entire distribution area, and between the transformer of the distribution area and the branch box, is recorded as the common impedance of the entire distribution area, and the line impedance between the branch box and the metering box inlet is recorded as the private wiring impedance of the metering box; in step 4.1, the voltage change value of the electricity meter is equal to the sum of the voltage change value on the common impedance of the entire distribution area, the voltage change value on the private wiring impedance of the metering box, and the voltage change value on the wiring impedance inside the metering box; the voltage change value of the phase line connected to the electricity meter is equal to the sum of the voltage change value on the common impedance of the entire distribution area and the voltage change value on the private wiring impedance of the metering box.

[0024] In step 4.2 of this embodiment, the voltage change value on the wiring impedance inside the metering box of the energy meter is equal to the difference between the voltage change value of the energy meter and the voltage change value of the phase line connected to the energy meter.

[0025] In step 4.3 of this embodiment, the wiring impedance inside the metering box of the energy meter is equal to the ratio of the difference between the voltage change value of the energy meter and the voltage change value of the phase line connected to the energy meter to the current change value on the wiring impedance inside the metering box of the energy meter.

[0026] In step 4.4 of this embodiment, the required parameters are the voltage change value of the electricity meter, the voltage change value of the phase line connected to the electricity meter, and the current change value of the wiring impedance inside the metering box of the electricity meter.

[0027] Figure 1 This is a schematic diagram of a typical full-area power distribution line structure. The transformer, branch box, metering box and energy meter in the distribution area are connected by phase A, phase B and phase C lines.

[0028] The method of the present invention is in Figure 1 When implementing this on the structure of the transformer substation: In step 1, the current and voltage data of each phase line at the metering box inlet are collected at a high frequency of seconds, and the collection time is set to one minute. In step 2, the connection relationship of each phase line at the inlet of the electricity meter and the metering box is determined. Electricity meter 1 and electricity meter 2 are connected to the A phase line at the inlet of metering box 1, electricity meter 3 is connected to the B phase line at the inlet of metering box 1, electricity meter 4 and electricity meter 5 are connected to the C phase line at the inlet of metering box 1, electricity meter 6 is connected to the A phase line at the inlet of metering box 2, electricity meter 7 is connected to the B phase line at the inlet of metering box 2, and electricity meter 8 is connected to the C phase line at the inlet of metering box 2. Step 4 calculates the wiring impedance within the metering box of each electricity meter. Taking electricity meter 1 as an example, the wiring impedance between electricity meter 1 and the transformer in the entire distribution area is as follows: Figure 2 As shown, the common impedance of the entire Taiwan region is denoted as... The impedance of the metering box's private wiring is recorded as The wiring impedance inside the metering box of electricity meter 1 is denoted as... Then, in step 4.1, the voltage change value of electricity meter 1... for The voltage change of phase line A connected to energy meter 1 for ,in, This represents the voltage change across the common impedance of the entire distribution area. This represents the voltage change value across the private wiring impedance of the metering box. This represents the voltage change across the wiring impedance inside the metering box. In step 4.2, In step 4.3, ,in, Let be the change in current across the wiring impedance inside the metering box of electricity meter 1. In step 4.4, , , ,in , and To compare with the voltage of energy meter 1, the current of energy meter 1, and the voltage of phase A line at the inlet of metering box 1 in one set of steady-state data, , and This is compared with the voltage of energy meter 1, the current of energy meter 1, and the voltage of phase A line at the inlet of meter box 1 in another set of steady-state data.

[0029] Example 2 This embodiment is for metering boxes that have already been equipped with Type I data loggers, such as... Figure 3 As shown, Type I data acquisition unit 1 and Type I data acquisition unit 2 are respectively installed at the inlet of metering box 1 and metering box 2. The Type I data acquisition unit supports high-frequency acquisition of current and voltage data of each phase line at the inlet of the metering box, and can also acquire current and voltage data of each energy meter inside the metering box. In this embodiment, the wiring impedance detection method described in Embodiment 1 is configured in the Type I data acquisition unit, thus realizing the detection of wiring impedance inside the metering box. The implementation method is simple and low-cost.

[0030] Example 3 Compared to Example 2, this example uses a 24-bit AD converter and a DSP chip to achieve high-frequency acquisition of current and voltage data of each phase line at the metering box inlet. Simultaneously, the DSP chip and RS485 communication technology are used to acquire current and voltage data of each energy meter inside the metering box. In this example, the wiring impedance detection method described in Example 1 is configured in the DSP chip, thus enabling the detection of wiring impedance within the metering box. This method is simple and low-cost. The acquisition of current and voltage data of each energy meter inside the metering box follows the "DL / T645-2007 Multifunctional Energy Meter Communication Protocol" or the "Q / GDW 11778—2017 Object-Oriented Electricity Information Data Exchange Protocol".

Claims

1. A method for detecting the wiring impedance inside a metering box, characterized in that, Includes the following steps: Step 1: Obtain the current and voltage data of each phase line at the metering box inlet and the current and voltage data of each energy meter inside the metering box. The current and voltage data of each phase line at the metering box in the transformer substation are collected at high frequency. According to the set collection time, the current and voltage data of each phase line at the metering box inlet and the current and voltage data of each energy meter in the metering box are acquired in different time periods. All data in each time period are treated as a set of data to be processed. During acquisition, the current and voltage data of each phase line at the metering box inlet are converted from analog signals to digital signals. Step 2: Obtain the connection relationship between each energy meter and the phase line at the inlet of the metering box; Step 2.1: Process the multiple sets of data to be processed separately. If the current of each phase line at the inlet of each energy meter and metering box remains stable in a set of data to be processed, then the data in this set is steady-state data; otherwise, discard the data in this set. Step 2.2: If, when comparing the two sets of steady-state data, only one energy meter shows a current fluctuation while the current of the other energy meters does not fluctuate, proceed to step 2.

3. Step 2.3: If only one phase line at the metering box inlet experiences current fluctuation, while the other phase lines do not, and the time of current fluctuation in the fluctuating phase line is the same as the time of current fluctuation in the fluctuating energy meter, then the energy meter experiencing current fluctuation is connected to the phase line experiencing current fluctuation, and the two sets of steady-state data are retained. Step 2.4: Using steps 2.2 and 2.3, process the multi-steady-state data to obtain the connection relationship between each energy meter and each phase line at the inlet of the metering box, and retain the two sets of steady-state data corresponding to each energy meter. Step 3: Obtain the line topology between the transformer, branch box, metering box and energy meter in the distribution area; The transformer, branch box, metering box and electricity meter in the distribution area are divided into four levels to form a tree topology. Based on the tree topology and the connection relationship between each electricity meter and the phase line at the inlet of the metering box, a line topology relationship is formed. Step 4: Calculate the wiring impedance inside the metering box of each electricity meter; Step 4.1: Based on the line topology, and according to the voltage change relationship caused by the current fluctuation of the electricity meter, obtain the calculation formulas for the voltage change value of the electricity meter and the voltage change value of the phase line connected to the electricity meter; In Step 4.1, the voltage change value of the electricity meter is equal to the sum of the voltage change value on the common impedance of the entire distribution area, the voltage change value on the private wiring impedance of the metering box, and the voltage change value on the wiring impedance within the metering box; the voltage change value of the phase line connected to the electricity meter is equal to the sum of the voltage change value on the common impedance of the entire distribution area and the voltage change value on the private wiring impedance of the metering box; Step 4.2: The line impedance between the energy meter and the connected phase line is recorded as the wiring impedance inside the meter box of the energy meter. The calculation formula for the voltage change value on the wiring impedance inside the meter box of the energy meter is obtained by using the two calculation formulas in Step 4.

1. Step 4.3: Based on the fact that the voltage change on the wiring impedance inside the meter box of the energy meter is equal to the current change on the wiring impedance inside the meter box of the energy meter multiplied by the wiring impedance inside the meter box of the energy meter, the calculation formula obtained in 4.2 is used to construct the calculation formula for the wiring impedance inside the meter box of the energy meter. Step 4.4: Process the two sets of steady-state data corresponding to each energy meter to obtain the calculation formula for the wiring impedance inside the metering box of each energy meter, calculate the required parameters, and then calculate the wiring impedance inside the metering box of each energy meter.

2. The method for detecting wiring impedance inside a metering box according to claim 1, characterized in that, In step 2.1, if the change in current of the phase line at the inlet of the electricity meter and the metering box is less than the stability threshold, then the current of the phase line at the inlet of the electricity meter and the metering box remains stable.

3. The method for detecting wiring impedance inside a metering box according to claim 1, characterized in that, In step 2.2, if the electricity If the change in current of the energy meter exceeds the fluctuation threshold, the energy meter will experience current fluctuation.

4. The method for detecting wiring impedance inside a metering box according to claim 1, characterized in that, In step 2.3, if the difference between the current change value of a phase line at the meter box inlet and the current change value of the energy meter that is experiencing current fluctuation is less than the difference threshold, then current fluctuation occurs in this phase line.

5. The method for detecting wiring impedance inside a metering box according to claim 1, characterized in that, In step 3, the line impedance between the electricity meter and the transformer in the whole area, and between the transformer in the whole area and the branch box, is recorded as the common impedance of the whole area, and the line impedance between the branch box and the meter box inlet is recorded as the private wiring impedance of the meter box.

6. The method for detecting wiring impedance inside a metering box according to claim 5, characterized in that, In step 4.2, the voltage change value on the wiring impedance inside the metering box of the energy meter is equal to the difference between the voltage change value of the energy meter and the voltage change value of the phase line connected to the energy meter.

7. The method for detecting wiring impedance inside a metering box according to claim 6, characterized in that, In step 4.3, the wiring impedance inside the metering box of the energy meter is equal to the ratio of the difference between the voltage change value of the energy meter and the voltage change value of the phase line connected to the energy meter to the current change value on the wiring impedance inside the metering box of the energy meter.

8. The method for detecting wiring impedance inside a metering box according to claim 7, characterized in that, In step 4.4, the required parameters are the voltage change value of the electricity meter, the voltage change value of the phase line connected to the electricity meter, and the current change value of the wiring impedance inside the metering box of the electricity meter.

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