Power distribution terminal current two-channel sampling circuit

Abstract

The utility model belongs to the technical field of power distribution terminals, and relates to a power distribution terminal current dual-channel sampling circuit comprising a precision sampling module which is electrically connected with a protection signal conditioning module and a measurement signal conditioning module. The protection signal conditioning module and the measurement signal conditioning module are electrically connected with the double-channel selection acquisition module, the double-channel selection acquisition module is electrically connected with the single-chip microcomputer and the AD acquisition module, and the AD acquisition module is electrically connected with the single-chip microcomputer. The protection signal conditioning module comprises an operational amplifier U1, resistors R2-R5 and capacitors C2 and C3. The measurement signal conditioning module comprises an operational amplifier U2, resistors R6-R9, capacitors C4 and C5, a bidirectional voltage-regulator tube Z1 and a bidirectional TVS D2. According to the utility model, the current dual-channel sampling function is realized, only one precision mutual inductor and one AD acquisition channel are used during conversion, the precision of current measurement is ensured, and the maximum amplitude of current protection is also ensured.

Description

Technical Field

[0001] The utility model belongs to the technical field of power distribution terminals, and more specifically, relates to a current dual-channel sampling circuit for a power distribution terminal, which can realize dual-channel collection of current signals. Background Art

[0002] Distribution terminals play a vital role in the construction of distribution automation in my country's distribution network. As the national electricity consumption requirements for distribution networks become higher and higher, the role played by distribution terminals is becoming more and more important.

[0003] Distribution terminals are increasingly used in urban and rural distribution networks. In actual applications, in order to save the cost of primary equipment and reduce the size, the current transformers of distribution terminals often adopt an integrated design of protection signal and measurement signal output, that is, the protection signal and the measurement signal share a collection circuit. The measurement signal refers to the signal collected by the distribution terminal during rated normal operation, and the protection signal refers to the signal collected by the distribution terminal when a fault occurs, so the protection signal is much larger than the measurement signal amplitude. This design has a technical disadvantage, which will lose the accuracy of collecting the measurement signal, because the acquisition circuit is configured according to the high amplitude of the protection signal. For example, the maximum value of the precision transformer built into the distribution terminal is often designed according to the secondary rated value of the protection signal of 50A, while the optimal secondary rated value of the measurement signal is 5A, resulting in a loss of 10 times the measurement accuracy in order to take into account the protection performance. Utility Model Content

[0004] The utility model designs a dual-channel current sampling circuit for a power distribution terminal. The circuit board is installed inside the power distribution terminal to realize dual-channel collection of current protection signals and current measurement signals. The technical solution adopted by the utility model is as follows:

[0005] The distribution terminal current dual-channel sampling circuit includes a precision sampling module, the precision sampling module is electrically connected to the protection signal conditioning module and the measurement signal conditioning module, the protection signal conditioning module and the measurement signal conditioning module are electrically connected to the dual-channel channel selection acquisition module, the dual-channel channel selection acquisition module is electrically connected to the single-chip microcomputer and the AD acquisition module, and the AD acquisition module is electrically connected to the single-chip microcomputer;

[0006] The protection signal conditioning module includes an operational amplifier U1, resistors R2-R5, capacitors C2 and C3, a precision sampling module connected to the positive input terminal of U1 via R3, one end of R5 connected to the positive input terminal of U1, the other end of R5 connected to GND, one end of R2 connected to the reverse input terminal of U1, the other end of R2 connected to GND, the reverse input terminal of U1 connected to the output terminal via R4, one end of C2 connected to GND, the other end of C2 respectively connected to the positive power supply terminal of U1 and +AVCC, one end of C3 connected to GND, the other end of C3 respectively connected to the negative power supply terminal of U1 and -AVCC;

[0007] The measurement signal conditioning module includes an operational amplifier U2, resistors R6~R9, capacitors C4 and C5, a bidirectional voltage regulator Z1 and a bidirectional TVS D2. The precision sampling module is connected to the positive input end of U2 via R8, one end of R9 is connected to the positive input end of U2, the other end of R9 is connected to GND, one end of R7 is connected to the reverse input end of U2, the other end of R7 is connected to GND, the reverse input end of U2 is connected to the output end via R6, one end of C4 is connected to GND, the other end of C4 is respectively connected to the positive power supply end of U2 and +AVCC, one end of C5 is connected to GND, the other end of C5 is respectively connected to the negative power supply end of U2 and -AVCC, the output end of U2 is connected to D2 and one end of Z1, and the other end of D2 and Z1 is connected to GND.

[0008] Preferably, the precision sampling module includes an input terminal J1, a precision sampling transformer CT1, an output resistor R1, a TVS D1 and a capacitor C1, the input terminal J1 is connected to the secondary side output of the current transformer, the primary side of CT1 is connected to the input terminal J1, the secondary side of CT1 is connected to R1, D1 and C1 in parallel in sequence, one end of C1 is respectively connected to the protection signal conditioning module and the measurement signal conditioning module, and the other end of C1 is connected to GND.

[0009] Preferably, the dual-channel channel selection acquisition module includes an analog channel selection chip U3 and a capacitor C6, the SELECT pin of U3 is connected to the IO1 pin of the microcontroller, the A pin of U3 is connected to the AD acquisition module, one end of C6 is connected to GND, and the other end of C6 is respectively connected to the power supply pin of U3 and the power supply.

[0010] Preferably, the AD acquisition module is connected to the single-chip microcomputer using an SPI bus, and the IO2 pin of the single-chip microcomputer is connected to the conversion control pin of the AD acquisition chip.

[0011] Beneficial effects of the utility model:

[0012] Compared with the existing devices, the utility model has a dual-channel current sampling function. Only one precision mutual inductor and one AD acquisition channel are used during conversion, which saves space and cost while meeting the performance requirements of relay protection and the high-precision acquisition requirements of protection signals and measurement signals. It ensures the accuracy of current measurement and the maximum amplitude of current protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0014] Figure 1 It is a framework diagram of a dual-channel sampling circuit of an embodiment of the utility model;

[0015] Figure 2 It is a schematic diagram of the overall circuit structure of the dual-channel sampling circuit of an embodiment of the utility model;

[0016] Figure 3 yes Figure 2 A schematic diagram of the circuit structure of the precision sampling module in FIG.

[0017] Figure 4 yes Figure 2 A schematic diagram of the circuit structure of the protection signal conditioning module;

[0018] Figure 5 yes Figure 2 A schematic diagram of the circuit structure of the measurement signal conditioning module;

[0019] Figure 6 yes Figure 2 A schematic diagram of the circuit structure of the dual-channel channel selection acquisition module;

[0020] Figure 7 yes Figure 2 The connection framework diagram of the microcontroller and AD acquisition module. DETAILED DESCRIPTION

[0021] The technical solution of the present utility model will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present utility model, rather than all of the embodiments.

[0022] like Figure 1 , 2As shown, the distribution terminal current dual-channel sampling circuit includes a precision sampling module, which is electrically connected to the protection signal conditioning module and the measurement signal conditioning module respectively, and the protection signal conditioning module and the measurement signal conditioning module are electrically connected to the dual-channel channel selection acquisition module respectively, and the dual-channel channel selection acquisition module is electrically connected to the single-chip computer and the AD acquisition module respectively. The current signal is input to the precision sampling module from the current transformer, and the final processed signal is output through the dual-channel channel selection acquisition module, and the time-sharing output of the measurement signal and the protection signal is realized according to the single-chip computer channel control.

[0023] like Figure 3 As shown, the precision sampling module includes an input terminal J1, a precision sampling transformer CT1, an output resistor R1, a TVS D1 and a capacitor C1. The input terminal J1 is connected to the secondary output of the current transformer. The primary side (primary side) of the precision sampling transformer CT1 is connected to the input terminal J1. The secondary side (secondary side) of the precision sampling transformer CT1 is connected in parallel with the output resistor R1, TVSD1 and capacitor C1 in sequence. One end of the capacitor C1 is connected to the protection signal conditioning module and the measurement signal conditioning module respectively, and the other end of the capacitor C1 is connected to GND. The precision sampling transformer CT1 realizes the transformation of the secondary current signal to the weak current signal. The output resistor R1 is connected to the secondary side of the precision sampling transformer CT1 to convert the weak current signal into a voltage signal. The bidirectional TVS D1 connected to the voltage signal is used to realize overvoltage protection. The function of D1 is to prevent the excessively high induced voltage from burning the subsequent circuit. The capacitor C1 is mainly used for filtering, which can filter the high-frequency interference part in the signal.

[0024] like Figure 4 As shown, the protection signal conditioning module includes an operational amplifier U1, resistors R2~R5, capacitors C2 and C3, one end of capacitor C1 is connected to the positive input end of U1 through R3, one end of R5 is connected to the positive input end of U1, the other end of R5 is connected to GND, one end of R2 is connected to the reverse input end of U1, the other end of R2 is connected to GND, the reverse input end of U1 is connected to the output end through R4, one end of C2 is connected to GND, the other end of C2 is connected to the positive power supply end and +AVCC of U1 respectively, one end of C3 is connected to GND, and the other end of C3 is connected to the negative power supply end and -AVCC of U1 respectively. The signal is adjusted to ±10V by resistors R2~R5 when the current input of the precision mutual inductor is 50A, so as to adapt to the peak value input by the AD acquisition chip. Capacitors C2 and C3 are mainly used to filter out the high-frequency noise of the power supply, reduce the fluctuations generated by the power supply, and improve the acquisition accuracy. The input of the protection signal conditioning module is connected to the voltage output signal of the precision sampling module.

[0025] like Figure 5As shown, the measurement signal conditioning module includes an operational amplifier U2, resistors R6~R9, capacitors C4 and C5, a bidirectional voltage regulator Z1 and a bidirectional TVS D2, one end of the capacitor C1 is connected to the positive input end of U2 via R8, one end of R9 is connected to the positive input end of U2, the other end of R9 is connected to GND, one end of R7 is connected to the reverse input end of U2, the other end of R7 is connected to GND, the reverse input end of U2 is connected to the output end via R6, one end of C4 is connected to GND, the other end of C4 is respectively connected to the positive power supply end of U2 and +AVCC, one end of C5 is connected to GND, the other end of C5 is respectively connected to the negative power supply end of U2 and -AVCC, the output end of U2 is connected to D2 and one end of Z1, and the other end of D2 and Z1 is connected to GND. Through the combination of resistors R6~R9, the signal is adjusted to when the current input of the precision transformer is 5A, the peak value of the voltage signal output by the measurement signal conditioning module is ±10V, so as to adapt to the peak value input by the AD acquisition chip. Since the input rated current of the precision transformer can reach up to 50A, the peak value of the voltage signal output by the measurement signal conditioning module may reach the limit of the operational amplifier, which will exceed the range that the AD acquisition chip can withstand, and even burn out the AD acquisition chip in extreme cases. Therefore, a bidirectional voltage regulator Z1 and a bidirectional TVS D2 are used on the output side for overvoltage protection. The input of the measurement signal conditioning module is connected to the voltage output signal of the precision sampling module.

[0026] Since the collected protection signals and measurement signals have positive and negative signals relative to GND, the power supply parts of U1 and U2 need to have positive and negative power supplies, namely +AVCC and -AVCC.

[0027] like Figure 6 As shown, the dual-channel channel selection acquisition module includes an analog channel selection chip U3 and a capacitor C6, the SELECT pin of U3 is connected to the IO1 pin of the single-chip microcomputer, the A pin of U3 is connected to the AD acquisition module, one end of C6 is connected to GND, and the other end of C6 is respectively connected to the 5 pin of U3 and VCC. The input signal of the dual-channel channel selection acquisition module includes two paths: one is connected to the output signal of the protection signal conditioning module, that is, the protection signal corresponding to the rated value of 50A; the other is connected to the output signal of the measurement signal conditioning module, that is, the measurement signal corresponding to the rated value of 5A. The channel selection control input SELECT pin of the analog channel selection chip U3 is connected to the IO1 pin output of the single-chip microcomputer, which is used to realize that the dual-channel channel selection acquisition module outputs a protection signal rated at 50A or a measurement signal rated at 5A.

[0028] U3 is a two-choice analog switch chip. Pin 5 is used to power the U3 chip. C6 is used to reduce the noise and interference of the power supply to pin 5. VCC refers to the power supply for U3.

[0029] like Figure 7As shown, the AD acquisition module mainly realizes the conversion of analog signals to digital signals. The AD acquisition module is connected to the single-chip microcomputer using the SPI bus to realize the reading of the signal collected by the AD acquisition module. A signal for sampling control is also connected between the AD acquisition module and the single-chip microcomputer, and its function is to control the start of AD conversion. The single-chip microcomputer module is used to collect, control and process digital signals. The IO1 pin output of the single-chip microcomputer is connected to the analog channel selection chip U3, which is used to control the signal source of the dual-channel channel selection acquisition module; the IO2 pin output of the single-chip microcomputer is connected to the conversion control pin of the AD acquisition chip, which is used for sampling start control.

[0030] In order to realize dual-channel sampling of the protection signal with a rated value of 50A and the measurement signal with a rated value of 5A, it is necessary to stipulate the control and reading sequence of the microcontroller.

[0031] Taking the sampling rate of the current signal as 6.4kHz as an example, a 12.8kHz PWM output signal is designed for the microcontroller through software driver. The frequency of this signal is twice the sampling rate and is output through the IO2 pin of the microcontroller.

[0032] Before the first PWM output, the IO1 pin of the microcontroller is pulled high. At this time, the protection signal with a rated value of 50A is selected to enter the AD acquisition chip.

[0033] After the first PWM output, the IO1 pin of the microcontroller is pulled low again. At this time, the measurement signal with a selected rated value of 5A enters the AD acquisition chip.

[0034] By analogy, each subsequent PWM flip will swap the IO1 pin state. The microcontroller reads the sampled values ​​of the AD acquisition chip and distributes them at intervals to obtain two sets of values. The first set is the sampled values ​​of the protection signal with a rated value of 50A, and the second set is the sampled values ​​of the measurement signal with a rated value of 5A.

[0035] The GND in the figure represents the common terminal, which can also be said to be the ground. GND provides a potential reference for other nodes.

[0036] In the embodiments of the utility model, the technical features not described in detail are all existing technologies or conventional technical means and will not be described in detail here.

[0037] Finally, it should be noted that the above embodiments are only specific implementation methods of the present utility model, which are used to illustrate the technical solution of the present utility model, rather than to limit it, and the protection scope of the present utility model is not limited thereto. Those skilled in the art should understand that any technician familiar with the technical field can modify the technical solution recorded in the above embodiments within the technical scope disclosed by the present utility model, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solution deviate from the spirit and scope of the technical solution of the embodiment of the present utility model, and should be covered within the protection scope of the present utility model.

Claims

1. The dual-channel sampling circuit of the power distribution terminal current is characterized by: It includes a precision sampling module, the precision sampling module is electrically connected to a protection signal conditioning module and a measurement signal conditioning module respectively, the protection signal conditioning module and the measurement signal conditioning module are electrically connected to a dual-channel channel selection acquisition module respectively, the dual-channel channel selection acquisition module is electrically connected to a single-chip microcomputer and an AD acquisition module respectively, and the AD acquisition module is electrically connected to the single-chip microcomputer; The protection signal conditioning module includes an operational amplifier U1, resistors R2-R5, capacitors C2 and C3, a precision sampling module connected to the positive input terminal of U1 via R3, one end of R5 connected to the positive input terminal of U1, the other end of R5 connected to GND, one end of R2 connected to the reverse input terminal of U1, the other end of R2 connected to GND, the reverse input terminal of U1 connected to the output terminal via R4, one end of C2 connected to GND, the other end of C2 respectively connected to the positive power supply terminal of U1 and +AVCC, one end of C3 connected to GND, the other end of C3 respectively connected to the negative power supply terminal of U1 and -AVCC; The measurement signal conditioning module includes an operational amplifier U2, resistors R6~R9, capacitors C4 and C5, a bidirectional voltage regulator Z1 and a bidirectional TVS D2. The precision sampling module is connected to the positive input end of U2 via R8, one end of R9 is connected to the positive input end of U2, the other end of R9 is connected to GND, one end of R7 is connected to the reverse input end of U2, the other end of R7 is connected to GND, the reverse input end of U2 is connected to the output end via R6, one end of C4 is connected to GND, the other end of C4 is respectively connected to the positive power supply end of U2 and +AVCC, one end of C5 is connected to GND, the other end of C5 is respectively connected to the negative power supply end of U2 and -AVCC, the output end of U2 is connected to D2 and one end of Z1, and the other end of D2 and Z1 is connected to GND.

2. The dual-channel current sampling circuit for distribution terminals according to claim 1, characterized in that: The precision sampling module includes an input terminal J1, a precision sampling transformer CT1, an output resistor R1, a TVS D1 and a capacitor C1. The input terminal J1 is connected to the secondary side output of the current transformer, the primary side of CT1 is connected to the input terminal J1, the secondary side of CT1 is connected to R1, D1 and C1 in parallel in sequence, one end of C1 is respectively connected to the protection signal conditioning module and the measurement signal conditioning module, and the other end of C1 is connected to GND.

3. The dual-channel sampling circuit for power distribution terminal current according to claim 1, characterized in that: The dual-channel channel selection acquisition module includes an analog channel selection chip U3 and a capacitor C6, the SELECT pin of U3 is connected to the IO1 pin of the microcontroller, the A pin of U3 is connected to the AD acquisition module, one end of C6 is connected to GND, and the other end of C6 is respectively connected to the power supply pin of U3 and the power supply.

4. The dual-channel current sampling circuit for distribution terminals according to claim 1, characterized in that: The AD acquisition module is connected to the single-chip microcomputer by using the SPI bus, and the IO2 pin of the single-chip microcomputer is connected to the conversion control pin of the AD acquisition chip.

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