Plug-in distribution network ring main unit alternating current measuring device and measuring error correction method

Abstract

The invention discloses a plug-in distribution network ring main unit alternating current measurement device and a measurement error correction method. The plug-in distribution network ring main unit alternating current measurement device comprises a front inner cone sleeve, a mounting plate, a bus connector, a conducting rod, epoxy resin, a primary coil, a secondary coil, a secondary binding post and a current measurement software and hardware system. The alternating current measuring device is connected with a distribution network ring main unit in a pluggable mode through the inner cone sleeve, the mounting plate and the bus connector, the conducting rod is made of a large-diameter T2-level copper material and can achieve full coverage of a primary coil from 5A to 600A, and the epoxy resin improves the insulating strength and the antifouling and waterproof capacity of a primary high-voltage part. And a high magnetic flux exchange law exists between the primary coil and the secondary coil. On the basis of current conversion and measurement of the hardware circuit and software program algorithm analysis, the accuracy of alternating current measurement of the plug-in distribution network ring main unit is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, in particular to a plug-in type distribution network ring main unit AC current measuring device and a measurement error correction method. Background Art

[0002] As a high-voltage switchgear, the primary current data of the distribution network ring main unit is crucial to the safe operation of the distribution network. In the existing technology, the distribution network ring main unit has the following shortcomings when measuring AC current:

[0003] Insufficient measurement accuracy: Traditional current measurement devices are affected by hardware circuit noise, coil coupling efficiency, and other factors, which can easily lead to measurement deviations and lack real-time error correction mechanisms.

[0004] Poor environmental adaptability: Insufficient insulation strength, anti-fouling and waterproof performance on the high-voltage side leads to reduced device reliability;

[0005] Low installation convenience: The connection method with the ring network cabinet is complicated, and the plug-in alignment performance is poor, which affects operation and maintenance efficiency. Summary of the Invention

[0006] The purpose of the present invention is to provide a plug-in distribution network ring main cabinet AC current measuring device and a measurement error correction method to solve the problems of low measurement accuracy, poor environmental adaptability and inconvenient installation in the prior art.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A plug-in type AC current measuring device for a distribution network ring main unit comprises a front inner cone bushing, a mounting plate, a busbar connector, a conductive rod, epoxy resin, a primary coil, a secondary coil and a secondary terminal. The inner cone bushing is fixed to the ring main unit via the mounting plate and the busbar connector to form a plug-in interface. The conductive rod passes through the inner cone bushing, with both ends connected to external conductive components via busbar connectors. The primary coil and the secondary coil are arranged in parallel around the conductive rod and are encapsulated in the inner cone bushing with epoxy resin. The secondary terminal is led out from the bottom of the device to connect to the secondary coil.

[0009] As a further technical solution of the present invention: the connection between the inner cone sleeve and the cable connector adopts a ball head structure to improve the centering performance and the convenience of plugging and unplugging.

[0010] As a further technical solution of the present invention: the conductive rod is made of T2 grade copper material.

[0011] As a further technical solution of the present invention: the gap between the primary coil and the secondary coil is set based on the maximum magnetic flux exchange amount.

[0012] A method for real-time correction of measurement errors based on the above device comprises the following steps:

[0013] Step 1: The secondary side current signal is converted into a voltage signal through the hardware circuit of the secondary terminal and transmitted to the controller;

[0014] Step 2: The controller calculates the primary high-voltage side current value based on the secondary side current value and the coil turns ratio;

[0015] Step 3: Collect the real-time current value of the high-voltage side and compare it with the calculated value to obtain the measurement error;

[0016] Step 4: Use software to perform parameter compensation for errors and improve measurement accuracy.

[0017] As a further technical solution of the present invention: in the step 1, the hardware circuit includes an LM324 chip, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a capacitor C, a diode D1 and a diode D2, the forward input end of the LM324 chip is connected to the resistor R1 and the signal input end, the other end of the resistor R1 is connected to the resistor R2 and the ground end, the output end of the LM324 chip is connected to the resistor R3, the resistor R4, the positive electrode of the diode D1 and the signal output end, the other end of the resistor R3 is connected to the other end of the resistor R2 and the reverse input end of the LM324 chip, the cathode of the diode D1 is connected to the cathode of the diode D2, and the positive electrode of the diode D2 is grounded.

[0018] As a further technical solution of the present invention: the differential operation formula for converting the secondary side current signal into a voltage signal is:

[0019] Output voltage = input current × R1 × (1 + R3 / R2)

[0020] Among them, input current × R1 is the AC current signal 0A~10A converted into a preliminary AC voltage signal, and (1+R3 / R2) is the amplification factor of LM324.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) Improve measurement accuracy: Through the combination of software and hardware, real-time correction of measurement errors can be achieved to improve measurement accuracy.

[0023] (2) Enhanced insulation and anti-fouling and waterproof performance: The interior of the device is filled with epoxy resin to improve the insulation strength and anti-fouling and waterproof performance, ensuring the stable operation of the equipment in harsh environments.

[0024] (3) Improve the convenience of plugging and unplugging: The connection method between the inner cone sleeve and the cable connector adopts a ball head structure design, which is convenient for installation and disassembly, and improves operation and maintenance efficiency.

[0025] (4) Wide scope of application: The present invention can be applied to ring main units of different voltage levels, as well as AC current measurement system devices of different power conversion equipment such as ring main units, substations, and switchgear. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a structural diagram of the primary-side AC current measuring device of a pluggable distribution network ring main unit.

[0027] Figure 2 This is the hardware circuit diagram of the secondary side AC current measurement system of the distribution network ring main unit.

[0028] Figure 3 This is a flowchart for real-time correction of AC current measurement errors in plug-in distribution network ring main unit.

[0029] Figure 1 Middle: 1-front inner cone bushing, 2-mounting plate, 3-busbar connector, 4-conductive rod, 5-epoxy resin, 6-primary coil, 7-secondary coil, 8-secondary terminal. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] See also Figure 1-3 A plug-in distribution network ring network cabinet AC current measuring device consists of a front inner cone bushing 1, a mounting plate 2, a busbar connector 3, a conductive rod 4, epoxy resin 5, a primary coil 6, a secondary coil 7 and a secondary terminal 8.

[0032] The inner cone bushing 1 is installed inside the distribution network ring main unit, and its connection with the cable connector adopts a ball head structure design, the purpose of which is to improve the centering performance and plug-in convenience between the cable connector and the AC current measuring device.

[0033] In order to improve the full coverage of the primary side AC current measurement of the distribution network ring main unit, the conductive rod 4 is made of large-diameter T2 grade copper material, which can achieve full coverage of the primary side AC current measurement range of 5A to 600A.

[0034] In order to improve the insulation strength and anti-fouling and waterproof performance of the primary side AC current of the distribution network ring network cabinet under high amplitude operation state, the internal space of the AC current measuring device of the distribution network ring network cabinet is filled with epoxy resin 5.

[0035] Specifically, in order to improve the AC magnetic flux inductance between the primary side and the secondary side, the primary coil 6 and the secondary coil 7 in the device are installed in parallel with each other, and the gap between them is set based on the maximum magnetic flux exchange amount.

[0036] like Figure 2 The figure shows the hardware circuit of the secondary side AC current measurement system of the distribution network ring main cabinet. Its main function is to convert the secondary side 0A~10A AC current signal into an AC voltage signal of 0V~3.3V, which is conducive to the controller's reception and processing of the signal.

[0037] Typically, the hardware circuit that converts a 0A to 10A AC current signal into a 0V to 3.3V AC voltage signal consists of a four-bit operational amplifier, the LM324, resistors, capacitors, and diodes. The LM324 has a differential function and can operate over a wide range of DC voltages, from 3V to 32V.

[0038] The function of resistor R1 is to convert the input 0A~10A AC current signal into a preliminary AC voltage signal; the function of resistor R2 is to eliminate zero drift, that is, to make the input 0A AC current signal and the output 0V AC voltage signal absolutely consistent; the function of resistor R3 is to maintain a geometric conversion between the input 0A~10A AC current signal and the output 0V~3V voltage signal.

[0039] The reason for converting the above 0A-10A AC current signal into a 0V-3.3V AC voltage signal is to facilitate the acquisition of the AC voltage signal by the controller (the range of the controller's analog voltage acquisition is 0V-3.3V).

[0040] Figure 2 The differential operation formula for the AC current signal to AC voltage signal circuit shown is:

[0041] Output voltage = input current × R1 × (1 + R3 / R2)

[0042] Among them, the AC current signal 0A~10A is converted into a preliminary AC voltage signal, which is the amplification factor of LM324.

[0043] Figure 2 The series-parallel connection between resistor R4, capacitor C, and diodes D1 and D2 forms a high-pass filter. Diodes D1 and D2 store charge on capacitor C, filtering low-frequency signals as the 0V to 3.3V AC voltage signal changes. Furthermore, capacitor C and diodes D1 and D2 provide voltage stabilization, while resistor R4 limits current and reduces temperature rise in the circuit.

[0044] like Figure 3The figure shows the real-time correction process for the AC current measurement error of the plug-in distribution network ring main unit. This real-time correction process is completed by the software program running in the controller. The specific execution steps are as follows:

[0045] Step 1: The controller receives Figure 2 The secondary side AC current measurement value of 0V to 3.3V uploaded by the measurement circuit shown ( Figure 2 The AC current value has been converted into a voltage value of 0V to 3.3V);

[0046] Step 2: Controller according to Figure 2 The secondary side AC current value uploaded by the measurement circuit shown, as well as the turns ratio between the primary coil 6 and the secondary coil 7, are used to obtain the calculated AC current value on the primary high voltage side through a program algorithm;

[0047] Step 3: The controller collects the AC current measurement value on the primary high-voltage side and compares and analyzes it with the AC current calculation value on the primary high-voltage side in step 2 to obtain the measurement error of the AC current measurement device of the plug-in distribution network ring main unit;

[0048] Step 4: Based on the above steps 2 and 3, software program calculation and parameter compensation are used to improve the accuracy of AC current measurement of the plug-in distribution network ring main unit involved in the present invention.

[0049] In particular, the controller for real-time correction of AC current measurement errors adopts a data processing chip with high computing performance, the purpose of which is to improve the timeliness of the entire measurement data analysis and comparison, thereby embodying the real-time measurement error correction function of the present invention.

[0050] In particular, since there is a fixed deviation problem of hardware measurement parameters in the process of converting the secondary low-voltage side AC current 0A-10A into the AC voltage of 0V-3.3V, the present invention adopts the following method to eliminate the fixed deviation and further improve the accuracy of the entire AC current measurement system. Specific examples are as follows:

[0051] First, the controller and Figure 2 The AC current signal to AC voltage signal circuit shown is powered on, but no Figure 1 The plug-in type distribution network ring main unit primary side AC current measuring device is powered on and the controller reads Figure 2 The value of the 0V to 3.3V AC voltage shown is the fixed deviation value X;

[0052] Secondly, by assigning parameters and performing calculations in the software program, the fixed deviation value X is subtracted from the 0V to 3.3V AC voltage measurement value (which is 0 at this time), thereby eliminating the fixed deviation during operation of the entire AC current measurement system.

[0053] Finally, based on the ratio of the secondary low-voltage side AC current 0A to 10A converted to 0V to 3.3V AC voltage, and the ratio between the primary coil 6 and the secondary coil 7, the value of the primary high-voltage side AC current is calculated through a software program.

[0054] The above-mentioned method for measuring the primary side AC current of a distribution network ring main unit and correcting the measurement error can be applied to ring main units of different voltage levels (10kV, 20kV, 35kV, etc.), and can also be applied to the AC current measurement system devices of different power conversion equipment such as ring main units, substations, and switchgear.

[0055] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0056] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A plug-in type distribution network ring network cabinet AC current measuring device, comprising a front inner cone bushing (1), a mounting plate (2), a busbar connector (3), a conductive rod (4), epoxy resin (5), a primary coil (6), a secondary coil (7) and a secondary terminal (8); characterized in that: The inner cone sleeve (1) is fixed to the ring network cabinet via a mounting plate (2) and a busbar connector (3) to form a plug-in interface; a conductive rod (4) passes through the inner cone sleeve (1), and both ends are connected to external conductive components via the busbar connector (3); a primary coil (6) and a secondary coil (7) are arranged in parallel around the conductive rod (4) and are encapsulated in the inner cone sleeve (1) with epoxy resin (5); a secondary terminal (8) is led out from the bottom of the device and connected to the secondary coil (7).

2. The plug-in type distribution network ring main unit AC current measuring device according to claim 1, characterized in that: The connection between the inner cone sleeve (1) and the cable connector adopts a ball head structure.

3. The plug-in type distribution network ring main unit AC current measuring device according to claim 1, characterized in that: The conductive rod (4) is made of T2 grade copper material.

4. The plug-in type distribution network ring main unit AC current measuring device according to claim 1, characterized in that: The gap between the primary coil (6) and the secondary coil (7) is set based on the maximum magnetic flux exchange amount.

5. A method for real-time correction of measurement errors based on the device according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: The secondary side current signal is converted into a voltage signal through the hardware circuit of the secondary terminal and transmitted to the controller; Step 2: The controller calculates the primary high-voltage side current value based on the secondary side current value and the coil turns ratio; Step 3: Collect the real-time current value of the high-voltage side and compare it with the calculated value to obtain the measurement error; Step 4: Use software to perform parameter compensation for errors and improve measurement accuracy.

6. A real-time correction method for measurement error according to claim 5, characterized in that: In the step 1, the hardware circuit includes an LM324 chip, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a capacitor C, a diode D1 and a diode D2, the forward input end of the LM324 chip is connected to the resistor R1 and the signal input end, the other end of the resistor R1 is connected to the resistor R2 and the ground end, the output end of the LM324 chip is connected to the resistor R3, the resistor R4, the positive electrode of the diode D1 and the signal output end, the other end of the resistor R3 is connected to the other end of the resistor R2 and the reverse input end of the LM324 chip, the cathode of the diode D1 is connected to the cathode of the diode D2, and the positive electrode of the diode D2 is grounded.

7. A real-time correction method for measurement errors according to claim 6, characterized in that: The differential operation formula for converting the secondary side current signal into a voltage signal is: Output voltage = input current × R1 × (1 + R3 / R2) Among them, input current × R1 is the AC current signal 0A~10A converted into a preliminary AC voltage signal, and (1+R3 / R2) is the amplification factor of the LM324 chip.

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