CN204287268U - Anti-error intelligent electric meter of checking meter - Google Patents

Abstract

The utility model provides an intelligent electric meter for preventing misreading of meters, which includes a casing, an isolation transformer T1 and a circuit board arranged in the casing; the input terminal of the isolation transformer T1 is connected to the incoming line terminal, and the output terminal is connected to the circuit board; the casing adopts magnetic conduction materials, and the inner wall of the shell is coated with a conductive film; the conductive film on the inner wall of the shell is used to connect the field ground wire; the ground terminals of the digital chips on the circuit board are connected to the digital ground GND2 of the circuit board, and the digital chips are all located in the electrostatic shielding cover. The electrostatic shield is connected to the digital ground GND2 of the circuit board; the circuit on the circuit board also includes a power supply decoupling filter circuit and a power supply unit for supplying power to the circuit board; the output terminal of the isolation transformer T1 is connected to the input of the power supply unit through the power supply decoupling filter circuit The ground terminal of the power supply unit is connected to the analog ground GND1 of the circuit board; the analog ground GND1 of the circuit board is connected to the digital ground GND2 of the circuit board with magnetic beads; the incoming line of the smart meter adopts a floating shield structure. The readings fed back by the smart meter are stable and accurate.

Description

Smart Meters Against Misreading Meters

technical field

The utility model relates to an electric power system, in particular to an intelligent electric meter capable of preventing interference.

Background technique

The smart meter is a special instrument for the power marketing department. In the past, when the concentrator in the station area reads the meter, it can often read the information of the meter in other station areas, causing confusion in the data statistics. The stations in the same power distribution room are relatively close to each other, and the carrier signal of the same frequency crosstalks between stations through transformers and high-voltage power lines, resulting in a very low success rate of meter reading in the stations. At the same time, there is a carrier island phenomenon in some stations, that is, the concentrator cannot Meter reading, therefore need to pass the signal through the repeater.

The transformation of smart meters is in full swing, and the "full coverage and full collection" of low-voltage users will be fully realized within 4-5 years. With the gradual realization of low-voltage automatic collection, the investment in manpower and material resources for meter reading in the power supply department will be greatly reduced. However, in actual use, it is found that due to the 24-hour operation of some three-phase equipment in the low-voltage station area, such as: high-frequency water pumps, etc., the meter reading efficiency will decrease. In order to deal with interference, the concentrator will continue to make up and change the route. , that is, using different smart meters to relay meter reading, there will be a certain improvement. However, due to the high interference intensity of high-frequency water pumps and other strong interference equipment, and 24-hour hot standby, it will have a fatal impact on carrier communication. In the existing meter reading system, the zero-point concentrator transmits all the intelligence under the concentrator through a low-voltage power supply cable every night. Electricity meters, generally around 300 smart electric meters, the concentrator will read the meter continuously, and the concentrator will regularly send the read data to the master station through the GPRS channel at 4 o'clock in the morning every day, or send it to the master station through a cable. The master station stores the data, and you can log in to the master station through the LAN to log in to browse relevant data and perform operations. In uploading data, due to the interference of the equipment in the line, the supplementary recruiting and relay mechanism of the concentrator cannot play a very good effect, and the copying rate will be greatly reduced, generally only about 60%. After consulting the data, it is found that such The problem is common in the low-voltage carrier field. The traditional treatment method is mainly to increase the concentrator and repeater, which not only increases the follow-up capital investment, but also has a certain effect on the station area with light interference source, and is powerless to the station area with heavy interference source. , there is currently no effective solution in the country.

Traditional electric meter anti-interference design, such as Chinese patent document CN201120473990 has an automatic meter reading system for smart electric meters with anti-carrier interference. The phase-to-phase AC contactor is connected to the three-phase smart meter through a time-space switch. When using it, it is necessary to sign a time-sharing power supply agreement with the power user terminal. This technology is used to stop power supply regularly for key interference equipment. Eliminate the interference of the meter reading time period, thereby improving the copying rate in the station area. The patent does not analyze the cause of the interference and take targeted measures. During the implementation, it is difficult to sign the customer power outage agreement, because the power company implements the peak and valley electricity price, and the electricity price at night is lower than that during the day, so large-scale power equipment is in operation. Work at night, which can save a lot on electricity bills. The user's power outage at night will also interfere with the normal operation of the user.

Chinese patent document CN201310008166 anti-jamming smart meter and anti-jamming method of smart meter, including relay, shunt and meter circuit board, shunt includes conductive sheet on both sides and manganin sampling sheet, conductive sheet on one side is connected to relay, manganese The two ends of the copper sampling piece are respectively connected with the conductive strips on both sides, and the two ends of the manganese copper sampling piece are respectively provided with binding posts, and the binding posts at both ends are respectively connected to the electric meter circuit board through two stranded sampling lines, and the manganese copper sampling piece It has three reference planes that are perpendicular to each other in space, and the two ends of the manganin sampling sheet are symmetrically distributed on both sides with one reference plane as the center, and the projected area of the manganin sampling sheet on the central reference plane is larger than that of manganese copper. The projected area of the sampling piece on the other two reference planes. This invention provides a technical idea for reducing magnetic field interference. The three reference planes in space are virtual concepts, which are intended to express three virtual planes that are perpendicular to each other in space, and these three planes are respectively It is perpendicular to the changing magnetic field from three directions, so by setting a reference plane perpendicular to it in the direction of the largest changing magnetic field, and setting the manganese-copper sampling piece at its symmetrical ends with the reference plane as the center , and each end of the symmetrical two ends has the largest extension area in space relative to the manganese-copper sampling piece, then the induced electromotive force generated at the two ends of the maximum changing magnetic field can cancel each other, thereby reducing the maximum changing magnetic field. Compared with the existing smart meters, under the premise that the basic parameters such as cross-sectional area, volume and resistance value remain unchanged, only the overall shape of the manganese-copper sampling piece is tested. Changes can reduce the interference to the manganese copper shunt, so that the smart meter can obtain accurate measurement values. This invention only solves a method of anti-interference, but it cannot suppress the crosstalk signal generated by the meter itself, and cannot solve the problem of signal crosstalk; at the same time, the direction of the maximum changing magnetic field is also constantly changing, which depends on the site installation environment. Adjust the device reference face is more difficult.

In the past, the electromagnetic compatibility design of smart meters was only designed for common electromagnetic compatibility indicators such as fast transient burst immunity, thinking that it was enough to solve these common electromagnetic compatibility test indicators to pass the type test. , did not consider analyzing and solving problems from the perspective of electromagnetic compatibility. The electromagnetic interference encountered by smart meters is of various types, including external radiation, pulse interference from the power supply, and interference signals generated by the meter itself. Different types of interference require different targeted measures to completely solve the problem of electromagnetic interference encountered by smart meters. The problem of signal crosstalk has long existed in electric power marketing instruments, such as smart meters, meter reading collectors, concentrators, etc. In the field, there is serious crosstalk in the station area, and a concentrator may report several times the number of meters in the area, causing data confusion. It can be seen that signal crosstalk is a long-standing unresolved technical problem. Therefore, anti-external strong electromagnetic interference and signal crosstalk are also problems that need to be solved.

Contents of the invention

The purpose of the utility model is to overcome the deficiencies in the prior art, and provide a smart meter capable of suppressing external strong electromagnetic interference, thereby avoiding the influence of external interference and signal crosstalk on the meter, and making the smart meter reading more accurate. The technical scheme that the utility model adopts is:

An intelligent electric meter for preventing false meter reading, comprising a casing, an isolation transformer T1 and a circuit board arranged in the casing; the input terminal of the isolation transformer T1 is connected to the incoming line terminal, and the output terminal is connected to the circuit board;

The shell is made of magnetic material, and the inner wall of the shell is coated with a conductive film; the conductive film on the inner wall of the shell is used to connect the field ground wire;

The ground terminals of the digital chips on the circuit board are all connected to the digital ground GND2 of the circuit board, and the digital chips are all arranged in an electrostatic shielding cover, and the electrostatic shielding cover is connected to the digital ground GND2 of the circuit board;

The circuit on the circuit board also includes a power supply decoupling filter circuit and a power supply unit for supplying power to the circuit board; the output terminal of the isolation transformer T1 is connected to the input terminal of the power supply unit through the power supply decoupling filter circuit, and the ground terminal of the power supply unit is connected to the analog ground of the circuit board GND1;

The analog ground GND1 of the circuit board and the digital ground GND2 of the circuit board are connected with magnetic beads;

The incoming line of the smart meter adopts a floating shield structure.

Further, conductive rubber mud is filled in the opening gaps of the outer casing and the peripheral gaps of the incoming wire terminals.

Further, the magnetically permeable material of the shell is iron-nickel alloy 1J76.

Further, the primary coil of the isolation transformer T1 is surrounded by an electrostatic shielding layer that is connected to the simulated ground GND1 of the circuit board.

The power supply decoupling filter circuit includes resistors R1, R2, R3, R4, capacitors C1 and C2; resistors R1 and R2 are connected in series to form the first branch, resistors R3 and R4 are connected in series to form the second branch, the first branch and the second branch One end of the circuit is respectively connected to the two output terminals of the isolation transformer T1, and the other ends of the first branch and the second branch are respectively connected to the power supply unit; the capacitor C1 is connected between the connection node of the resistors R1 and R2 and the connection node of the resistors R3 and R4; Capacitor C2 is connected between the other end of the first branch and the other end of the second branch.

The floating shielding structure of the incoming line includes: the signal ground of the signal source is connected to the shielding layer of the incoming cable, and the shielding layer of the incoming cable is connected to the digital ground GND2 of the circuit board; the electrostatic shield is connected to the digital ground GND2 of the circuit board as the inner shielding layer of the smart meter. The conductive film on the inner wall of the casing is connected to the ground wire as the outer shielding layer of the smart meter.

The utility model has the advantages of adopting multiple anti-interference measures, the smart meter has strong anti-interference ability, the feedback reading is stable and accurate, and the occurrence of mistaken meter reading is effectively avoided.

Description of drawings

Fig. 1 is the external schematic view of the utility model.

Fig. 2 is the internal electrical schematic diagram of the utility model.

FIG. 3 is a schematic structural diagram of the power decoupling filter circuit of the present invention.

Fig. 4 is a schematic diagram of the floating shielding structure of the incoming line of the present invention.

Detailed ways

Below in conjunction with specific accompanying drawing and embodiment the utility model is further described.

The intelligent electric meter for preventing mistaken meter reading proposed by the utility model firstly performs good electromagnetic shielding treatment on the shell of the intelligent electric meter. As shown in Figure 1, the smart meter for preventing false meter reading includes a housing 1, a display screen 2, an incoming line terminal 3, various function keys 4, LED lights 5, etc.;

Shell 1 uses high-permeability materials to form a low-reluctance path, allowing low-frequency interference magnetic force lines to pass through the magnetic shielding layer with small reluctance, so that the internal circuit of the meter is free from the influence of low-frequency magnetic field coupling interference, and the high-permeability material closes the magnetic circuit. It can reduce electromagnetic interference from magnetic field interference sources such as large motors, reactors, magnetic switches, and high-current current-carrying wires. The magnetically permeable material of the shell 1 is an iron-nickel alloy 1J76 with high nickel content.

The inner wall of the housing 1 is coated with a conductive film, so that the circuit components inside the meter are in a closed and fully shielded space. The double shielding design of the housing 1 makes it difficult for external electromagnetic interference to enter it.

In order to further increase the electromagnetic shielding effect of the shell 1, it is also possible to further fill the gap 101 of the outer cover of the shell 1 and the gap 301 around the incoming terminal 3 with conductive rubber clay; the conductive rubber clay is based on high elastomer rubber. It is a lifetime non-curing self-adhesive conductive mastic made of polymer material, and the conductive particles are evenly distributed in the resin adhesive.

The internal circuit of the smart meter is shown in Figure 2, including the isolation transformer T1 and the circuit board; the input terminal of the isolation transformer T1 is connected to the incoming line terminal 3, and the output terminal is connected to the circuit board; the ratio of the primary and secondary coils of the isolation transformer T1 is 1:1 , Block the DC interference in the AC signal, and the common mode interference voltage can be suppressed because it cannot form a loop. In order to suppress common-mode interference and eliminate harmonics, the primary coil of the isolation transformer T1 is surrounded by an electrostatic shielding layer connected to the analog ground GND1 of the circuit board.

The components on the circuit board include digital chips such as carrier chips, metering chips, and main control MCUs. The carrier chips are used to communicate with the host computer; the ground terminals of the digital chips are connected to the digital ground GND2 of the circuit board; these digital chips are covered with static electricity. Shielding cover; in order to prevent external strong electrical interference, the digital chip that is susceptible to interference is sealed with an electrostatic shielding cover; the bottom of the electrostatic shielding cover is welded to the copper-clad wiring on the circuit board to connect the digital ground GND2 of the circuit board;

The circuit on the circuit board also includes a power decoupling filter circuit and a power supply unit (including step-down, rectification, voltage stabilization, etc.) for power supply to the circuit board; the output terminal of the isolation transformer T1 is connected to the input of the power supply unit through the power decoupling filter circuit The ground terminal of the power supply unit is connected to the analog ground GND1 of the circuit board. When multiple ammeters use the same incoming power supply, the internal resistance of the power supply will become the common resistance of multiple ammeter circuits. When the current in a certain circuit changes, the voltage generated on the common impedance will become a source of interference to other circuits. The power decoupling filter circuit filters out the coupling interference from the internal impedance of the incoming power supply.

The power supply decoupling filter circuit is shown in Figure 3, including resistors R1, R2, R3, R4, capacitors C1 and C2; resistors R1 and R2 are connected in series to form the first branch, resistors R3 and R4 are connected in series to form the second branch, the first One end of the branch and the second branch are respectively connected to the two output ends of the isolation transformer T1, and the other ends of the first branch and the second branch are respectively connected to the power supply unit; the capacitor C1 is connected to the connection node of the resistors R1 and R2 and the resistor R3 and R4 are connected between the nodes; the capacitor C2 is connected between the other end of the first branch and the other end of the second branch.

The analog ground GND1 of the circuit board and the digital ground GND2 of the circuit board are connected with magnetic beads. The magnetic beads are made of ferrite material with good impedance characteristics in the high frequency band, and are specially used to suppress high frequency noise and spikes on signal lines and power lines. interference, and also has the ability to absorb static pulses.

Finally, referring to Fig. 4, the floating shielding structure of the incoming line of the utility model is analyzed. The signal ground of the signal source Us is connected to the shielding layer of the incoming cable, and the shielding layer of the incoming cable is connected to the digital ground GND2 of the circuit board; the electrostatic shielding cover on the digital chip is connected to the digital ground GND2 of the circuit board as the inner shielding layer of the smart meter. The conductive film connected to the site ground wire serves as the outer shielding layer of the smart meter; the site ground wire is the ground wire directly connected to the earth at the site where the meter is installed. In the above structure, the signal ground of the input signal is floating and not connected to the field ground wire, so that the common-mode input impedance is greatly improved, and the common-mode current caused by the common-mode voltage in the input loop is greatly reduced, thereby suppressing the common-mode interference. sources to minimize common-mode interference. The electrostatic shielding cover is welded on the digital ground copper wire on the circuit board, and the cable shielding layer of the incoming line is also welded on the digital ground copper wire on the circuit board, forming a floating ground, and the attenuation of magnetic field interference can reach 55DB.

The grounding structure of the utility model can suppress common-ground interference, and basically solve the problem of carrier signal crosstalk; a good shielding structure can suppress radiation interference, and solve the problem of strong external electromagnetic interference.

Claims (6)

1. an anti-error intelligent electric meter of checking meter, comprises shell (1), it is characterized in that, also comprises and is located at isolating transformer T1 in shell (1) and wiring board; The input end of isolating transformer T1 taps into line terminals (3), output end wiring road plate;

Shell (1) adopts permeability magnetic material, and shell (1) inwall scribbles conductive film; Conductive film on shell (1) inwall is for connecting on-the-spot ground wire;

The equal connection line plate of the earth terminal of digit chip digitally GND2 on wiring board, digit chip is all located in electrostatic shielding cover, described electrostatic shielding cover connection line plate digitally GND2;

The power supply unit that circuit on wiring board also comprises power supply decoupling filtering circuit and powers for wiring board; The output terminal of isolating transformer T1 connects power supply unit input end by power supply decoupling filtering circuit, the earth terminal connection line plate GND1 in analog of power supply unit;

Wiring board in analog GND1 and wiring board digitally GND2 magnetic bead be connected;

The inlet wire of this intelligent electric meter adopts Floating ground shield structure.

2. anti-error intelligent electric meter of checking meter as claimed in claim 1, is characterized in that:

Uncap in the outside of shell (1) gap (101) place, input terminal (3) periphery gap (301) place filling have conductive rubber mud.

3. anti-error intelligent electric meter of checking meter as claimed in claim 1, is characterized in that:

The permeability magnetic material of shell (1) is iron-nickel alloy 1J76.

4. anti-error intelligent electric meter of checking meter as claimed in claim 1, is characterized in that:

Isolating transformer T1 primary coil outside is surrounded with the electrostatic screening layer of link plate GND1 in analog.

5. anti-error intelligent electric meter of checking meter as claimed in claim 1, is characterized in that:

Power supply decoupling filtering circuit comprises resistance R1, R2, R3, R4, electric capacity C1 and C2; Resistance R1 and R2 is connected into the first branch road, and resistance R3 and R4 is connected into the second branch road, and one end of the first branch road and the second branch road connects two output terminals of isolating transformer T1 respectively, and the other end of the first branch road and the second branch road connects power supply unit respectively; Electric capacity C1 is connected on resistance R1 and R2 connected node and between resistance R3 and R4 connected node; Electric capacity C2 is connected between the first branch road other end and the second branch road other end.

6. anti-error intelligent electric meter of checking meter as claimed in claim 1, is characterized in that:

The Floating ground shield structure of inlet wire comprises: the signal ground of signal source connects inlet wire cable shield, inlet wire cable shield connection line plate digitally GND2; Digitally GND2 is as the internal shield of intelligent electric meter for electrostatic shielding cover link plate, and the conductive film on shell (1) inwall connects the external shielding layer of on-the-spot ground wire as intelligent electric meter.