CN114460346A - Zero line current sampling circuit and electric energy meter - Google Patents

Zero line current sampling circuit and electric energy meter Download PDF

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Publication number
CN114460346A
CN114460346A CN202210145396.3A CN202210145396A CN114460346A CN 114460346 A CN114460346 A CN 114460346A CN 202210145396 A CN202210145396 A CN 202210145396A CN 114460346 A CN114460346 A CN 114460346A
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electrically connected
main control
zero line
control module
resistor
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廖子桂
冯涛
黄保柱
邹可树
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Kelu International Technology Co ltd
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Kelu International Technology Co ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
    • G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
    • G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
    • G01R1/30—Structural combination of electric measuring instruments with basic electronic circuits, e.g. with amplifier
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R22/00—Arrangements for measuring time integral of electric power or current, e.g. electricity meters
    • G01R22/06—Arrangements for measuring time integral of electric power or current, e.g. electricity meters by electronic methods
    • G01R22/061—Details of electronic electricity meters
    • G01R22/066—Arrangements for avoiding or indicating fraudulent use
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/54—Testing for continuity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/58—Testing of lines, cables or conductors

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  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Measurement Of Current Or Voltage (AREA)

Abstract

The invention discloses a zero line current sampling circuit and an electric energy meter. Wherein, zero line current sampling circuit includes: the device comprises a first transformer, a first sampling unit and a second sampling unit. The first mutual inductor is used for being electrically connected with a zero line power supply and a ground end respectively; the first sampling unit is used for being electrically connected with the first mutual inductor and the main control module respectively and used for generating a first zero line signal; the second sampling unit is used for being electrically connected with the first mutual inductor and the main control module respectively, the second sampling unit is connected with the first sampling unit in parallel, and the second sampling unit is used for generating a second zero line signal; the main control module is used for carrying out current bypass detection according to the three-phase current and the first zero line signal, and the main control module is used for carrying out zero line falling detection according to the second zero line signal. The zero line current sampling circuit can simultaneously realize current bypass detection and zero line drop detection on the electric energy meter under the condition of only using one current transformer.

Description

Zero line current sampling circuit and electric energy meter
Technical Field
The invention relates to the technical field of current sampling, in particular to a zero line current sampling circuit and an electric energy meter.
Background
And the current bypass means that a lead is used in the electric energy meter to short the input end and the output end of a certain phase of the electric energy meter. In the related art, the current bypass enables the current detected by the electric energy meter to be reduced, and thus, there is an operation of stealing electricity through the current bypass in real life. Therefore, whether the electric energy meter is bypassed by current can be monitored through current bypass detection, so that the electricity stealing behavior can be prevented.
The zero line drop detection refers to the checking operation of monitoring whether the power grid has zero line drop faults or not, and is used for preventing the situation that the power utilization appliance is burnt due to the occurrence of the zero line drop faults.
In the related art, at least one current transformer is required to be used for detecting zero line current for current bypass detection of the electric energy meter, and at least one current transformer is required to be used for detecting zero line current for zero line falling detection of the electric energy meter, namely, the electric energy meter at least needs two current transformers for detecting the zero line current so as to realize the current bypass detection and the zero line falling detection functions of the electric energy meter at the same time. The method not only can increase the occupied physical space and influence the miniaturization design of the electric energy meter product, but also can increase the cost of the electric energy meter.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a zero line current sampling circuit which can simultaneously realize current bypass detection and zero line drop detection on an electric energy meter under the condition of only using one current transformer.
The invention also provides an electric energy meter with the zero line current sampling circuit.
The zero line current sampling circuit according to the embodiment of the first aspect of the present invention is applied to an electric energy meter, the electric energy meter includes a first sampling module and a main control module, the first sampling module is used for being electrically connected with a three-phase live wire power supply, the main control module and a ground respectively, the first sampling module is used for collecting three-phase current, and the zero line current sampling circuit includes:
the first mutual inductor is used for being electrically connected with a zero line power supply and the ground end respectively;
the first sampling unit is used for being electrically connected with the first mutual inductor and the main control module respectively and used for generating a first zero line signal;
the second sampling unit is used for being electrically connected with the first mutual inductor and the main control module respectively, the second sampling unit is connected with the first sampling unit in parallel, and the second sampling unit is used for generating a second zero line signal;
the main control module is used for carrying out current bypass detection according to the three-phase current and the first zero line signal, and the main control module is used for carrying out zero line loss detection according to the second zero line signal.
The zero line current sampling circuit provided by the embodiment of the invention at least has the following beneficial effects: the first mutual inductor converts the zero line current signal and then outputs the zero line current signal to the first sampling unit and the second sampling unit respectively, the first sampling unit generates a first zero line signal carrying current bypass information, the second sampling unit generates a second zero line signal carrying zero line information, and the first sampling module collects three-phase current. The main control module carries out current bypass detection according to the three-phase current and the first zero line signal and carries out zero line falling detection according to the second zero line signal. The zero line current sampling circuit of this embodiment can realize carrying out the electric current bypass to the electric energy meter simultaneously and detect and fall the zero line and detect under the condition that only uses a current transformer, consequently reduced the physical space who occupies, be applicable to the miniaturized design of electric energy meter product, reduced the cost of electric energy meter simultaneously.
According to some embodiments of the invention, the first sampling unit comprises:
one end of the first resistor is used for being electrically connected with one end of the first mutual inductor, and the other end of the first resistor is used for being electrically connected with the second sampling unit;
the first overvoltage preventing subunit is used for being electrically connected with the first resistor, the first port of the main control module and the second port of the main control module respectively.
According to some embodiments of the invention, the second sampling unit comprises:
one end of the second resistor is used for being electrically connected with the other end of the first transformer, and the other end of the second resistor is used for being electrically connected with the other end of the first resistor;
and the second overvoltage preventing subunit is used for being electrically connected with the second resistor, the third port of the main control module and the fourth port of the main control module respectively.
According to some embodiments of the invention, the first overvoltage protection subunit comprises:
a cathode of the first diode is used for being electrically connected with one end of the first resistor and a first port of the main control module respectively, and an anode of the first diode is used for being electrically connected with the other end of the first resistor and a second port of the main control module respectively;
and the cathode of the second diode is used for being electrically connected with the anode of the first diode and the second port of the main control module respectively, and the anode of the second diode is used for being electrically connected with the cathode of the first diode and the first port of the main control module respectively.
According to some embodiments of the invention, the second overvoltage protection subunit comprises:
the anode of the third diode is used for being electrically connected with one end of the second resistor and the fourth port of the main control module respectively, and the cathode of the first diode is used for being electrically connected with the other end of the second resistor and the third port of the main control module respectively;
and the cathode of the fourth diode is used for being electrically connected with the anode of the third diode and the fourth port of the main control module respectively, and the anode of the fourth diode is used for being electrically connected with the cathode of the third diode and the third port of the main control module respectively.
According to some embodiments of the invention, the first sampling module comprises:
the third sampling unit is used for being electrically connected with the live wire power supply, the main control module and the load of one phase respectively;
the fourth sampling unit is used for being electrically connected with the other phase of the live wire power supply, the main control module and the load respectively;
the fifth sampling unit is used for being electrically connected with the live wire power supply of the other phase, the main control module and the load respectively;
one end of the third resistor is electrically connected with the live wire power supply and the third sampling unit respectively, and the other end of the third resistor is grounded;
and one end of the fourth resistor is used for being electrically connected with the live wire power supply and the fourth sampling unit, and the other end of the fourth resistor is grounded.
According to some embodiments of the invention, the third sampling unit comprises:
the second mutual inductor is used for being electrically connected with the live wire power supply and the load respectively;
the fifth resistor is used for being electrically connected with the second mutual inductor and the main control module respectively;
the fourth sampling unit includes:
the third mutual inductor is used for being electrically connected with the live wire power supply and the load respectively;
the sixth resistor is used for being electrically connected with the third mutual inductor and the main control module respectively;
the fifth sampling unit includes:
the fourth transformer is used for being electrically connected with the live wire power supply and the load respectively;
and the seventh resistor is used for being electrically connected with the fourth transformer and the main control module respectively.
According to an embodiment of the second aspect of the invention, an electric energy meter comprises:
the zero line current sampling circuit according to the above-described first aspect of the present invention.
The electric energy meter provided by the embodiment of the invention at least has the following beneficial effects: this electric energy meter has realized under the condition that only uses a current transformer through adopting above-mentioned zero line current sampling circuit, realizes carrying out the electric current bypass simultaneously and detects and fall the zero line and detect the electric energy meter, has consequently reduced the physical space that occupies, is applicable to the miniaturized design of electric energy meter product, has reduced the cost of electric energy meter simultaneously.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The invention is further described with reference to the following figures and examples, in which:
FIG. 1 is a block diagram of a particular embodiment of a zero line current sampling circuit of the present invention;
FIG. 2 is a schematic circuit diagram of an embodiment of an electric energy meter according to the invention;
FIG. 3 is a circuit schematic of an embodiment of a zero line current sampling circuit of the present invention;
fig. 4 is a schematic circuit diagram of a main control module according to an embodiment of the present invention.
Reference numerals:
the sampling circuit comprises a first transformer 100, a first sampling unit 200, a second sampling unit 300, a main control module 400, a zero line power supply 500, a first sampling module 600, a three-phase live wire power supply 700, a first overvoltage preventing subunit 210, a second overvoltage preventing subunit 310, a third sampling unit 610, a fourth sampling unit 620 and a fifth sampling unit 630.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
In the description of the present invention, it should be understood that the orientation or positional relationship referred to in the description of the orientation, such as the upper, lower, front, rear, left, right, etc., is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description and simplification of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
In the description of the present invention, the meaning of a plurality is one or more, the meaning of a plurality is two or more, and the above, below, exceeding, etc. are understood as excluding the present numbers, and the above, below, within, etc. are understood as including the present numbers. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.
In the description of the present invention, unless otherwise explicitly defined, terms such as set, mounted, connected, electrically connected, etc. should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific contents of the technical solutions.
In the description of the present invention, reference to the description of the terms "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
As shown in fig. 1 and 2, an embodiment of the present invention provides a zero line current sampling circuit, which is applied to an electric energy meter, where the electric energy meter includes a first sampling module 600 and a main control module 400, the first sampling module 600 is used to be electrically connected to a three-phase live wire power supply 700 (i.e., an AC-a live wire power supply, an AC-B live wire power supply, and an AC-C live wire power supply in fig. 2), the main control module 400, and a ground terminal, respectively, and the first sampling module 600 is used to collect a three-phase current. Zero line current sampling circuit includes: a first transformer 100, a first sampling unit 200 and a second sampling unit 300; the first transformer 100 is used for being electrically connected with a neutral power supply 500 (i.e. an AC-N neutral power supply in fig. 2) and a ground terminal respectively; the first sampling unit 200 is used for being electrically connected with the first transformer 100 and the main control module 400 respectively, and the first sampling unit 200 is used for generating a first zero line signal; the second sampling unit 300 is used for being electrically connected with the first transformer 100 and the main control module 400 respectively, the second sampling unit 300 is connected with the first sampling unit 200 in parallel, and the second sampling unit 300 is used for generating a second zero line signal; the main control module 400 is configured to perform current bypass detection according to the three-phase current and the first zero line signal, and the main control module 400 is configured to perform zero line drop detection according to the second zero line signal.
Specifically, the first sampling unit 200 is configured to be electrically connected to one end of the coil of the first transformer 100, and the second sampling unit 300 is configured to be electrically connected to the other end of the coil of the first transformer 100. The first transformer 100 is configured to convert a zero line current, and output the converted zero line current to the first sampling unit 200 and the second sampling unit 300, respectively, where the first sampling unit 200 generates a first zero line signal for performing a current bypass test, and the second sampling unit 300 generates a second zero line signal for performing a zero line drop test. The first sampling module 600 is used for acquiring three-phase currents, namely, acquiring a current of AC-a, a current of AC-B and a current of AC-C. The main control module 400 performs current bypass detection according to the three-phase current and the first zero line signal, and performs zero line drop detection according to the second zero line signal.
In the current bypass detection, the main control module 400 detects the first zero line signal, compares the vector sum of the three-phase current with the zero line current in the first zero line signal, and indicates that a current bypass occurs when the ratio of the difference between the vector sum of the three-phase current and the zero line current to the larger one of the two items divided by the larger one is greater than a preset percentage (e.g., 6.25%, 10%, 12.5%, etc.), that is, an electricity stealing behavior may exist.
In the zero line drop detection, the main control module 400 detects a second zero line signal, and when the second zero line signal indicates that the zero line current is smaller than a preset current value (for example, 2.2mA), it indicates that the zero line is disconnected, that is, the power grid has a zero line drop fault.
According to the zero line current sampling circuit provided by the embodiment of the invention, the first sampling unit 200 generates a first zero line signal for performing a current bypass test, the second sampling unit 300 generates a second zero line signal for performing a zero line dropping test, and the first sampling module 600 acquires a three-phase current. The main control module 400 performs current bypass detection according to the three-phase current and the first zero line signal, and performs zero line drop detection according to the second zero line signal. The zero line current sampling circuit of this embodiment can realize carrying out the electric current bypass to the electric energy meter simultaneously and detect and fall the zero line and detect under the condition that only uses a current transformer, consequently reduced the physical space who occupies, be applicable to the miniaturized design of electric energy meter product, reduced the cost of electric energy meter simultaneously.
As shown in fig. 3 and 4, in some embodiments of the present invention, the first sampling unit 200 includes: a first resistor Rn1, and a first overvoltage protection subunit 210. One end of the first resistor Rn1 is used for being electrically connected with one end of the first transformer 100, and the other end of the first resistor Rn1 is used for being electrically connected with the second sampling unit 300; the first overvoltage protection subunit 210 is configured to be electrically connected to the first resistor Rn1, the first port of the main control module 400 (i.e., the "21" pin of the main control chip U1 in fig. 4), and the second port of the main control module 400 (i.e., the "22" pin of the main control chip U1 in fig. 4), respectively.
Specifically, one end of the first resistor Rn1 is electrically connected to one end of the coil of the first transformer 100, the first overvoltage protection subunit 210 is connected to the first resistor Rn1 in parallel, one end of the first resistor Rn1 connected to the first overvoltage protection subunit 210 is electrically connected to the first port of the main control module 400, and the other end of the first resistor Rn1 connected to the first overvoltage protection subunit 210 is electrically connected to the second port of the main control module 400. The first overvoltage protection subunit 210 is configured to prevent the first neutral line signal from being overvoltage.
After being converted by the first mutual inductor 100, the neutral current flows through the first resistor Rn1 and is converted into a first neutral signal by the first resistor Rn1, and the first neutral signal comprises: a first positive zero line differential signal INP and a first negative zero line differential signal INN. A first port of the main control module 400 receives the first positive zero line differential signal INP, and a second port of the main control module 400 receives the first negative zero line differential signal INN. The main control module 400 obtains a corresponding zero line current signal according to the first positive zero line differential signal INP and the first negative zero line differential signal INN.
As shown in fig. 3 and 4, in some embodiments of the present invention, the second sampling unit 300 includes: a second resistor Rn2, and a second overvoltage protection subunit 310. One end of the second resistor Rn2 is used for being electrically connected with the other end of the first transformer 100, and the other end of the second resistor Rn2 is used for being electrically connected with the other end of the first resistor Rn 1; the second overvoltage protection subunit 310 is configured to be electrically connected to the second resistor Rn2, the third port of the main control module 400 (i.e., the "23" pin of the main control chip U1 in fig. 4), and the fourth port of the main control module 400 (i.e., the "24" pin of the main control chip U1 in fig. 4), respectively.
Specifically, the second resistor Rn2 is connected in series with the first resistor Rn1, one end of the first resistor Rn1 is electrically connected to one end of the coil of the first transformer 100, and one end of the second resistor Rn2 is electrically connected to the other end of the coil of the first transformer 100. The second overvoltage protection subunit 310 and the second resistor Rn2 are connected in parallel, one end of the second resistor Rn2 connected to the second overvoltage protection subunit 310 is electrically connected to the third port of the main control module 400, and the other end of the second resistor Rn2 connected to the second overvoltage protection subunit 310 is electrically connected to the fourth port of the main control module 400. The second overvoltage protection subunit 310 is configured to prevent the second neutral line signal from being overvoltage.
After being converted by the first mutual inductor 100, the neutral current flows through the second resistor Rn2 and is converted into a second neutral signal by the second resistor Rn2, and the second neutral signal comprises: a second positive zero line differential signal ILNP and a second negative zero line differential signal ILNN. The second positive zero line differential signal ILNP is received by the third port of the main control module 400, and the first negative zero line differential signal ILNN is received by the fourth port of the main control module 400. The main control module 400 may obtain a corresponding zero line current signal according to the first positive zero line differential signal ILNP and the first negative zero line differential signal ILNN.
As shown in fig. 2 and 4, in some embodiments of the invention, the first sampling module 600 includes: the sampling circuit comprises a third sampling unit 610, a fourth sampling unit 620, a fifth sampling unit 630, a third resistor R3 and a fourth resistor R4. The third sampling unit 610 is used for being electrically connected with a phase live wire power supply, the main control module 400 and a load respectively; the fourth sampling unit 620 is used for being electrically connected to another phase live wire power supply, the main control module 400 and the load, respectively; the fifth sampling unit 630 is used for being electrically connected to another phase live wire power supply, the main control module 400 and the load, respectively; one end of the third resistor R3 is electrically connected to a live wire power supply and the third sampling unit 610, respectively, and the other end of the third resistor R3 is grounded; one end of the fourth resistor R4 is electrically connected to a live power supply and the fourth sampling unit 620, and the other end of the fourth resistor R4 is grounded.
Specifically, the third sampling unit 610 is electrically connected to a one-phase live line power supply AC-a and is configured to collect a current signal of the AC-a; the fourth sampling unit 620 is electrically connected with a one-phase live wire power supply AC-B and is used for collecting a current signal of the AC-B; the fifth sampling unit 630 is electrically connected to a one-phase live power AC-C and is used to collect a current signal of the AC-C. The third sampling unit 610 is electrically connected to a fifth port (i.e., pin "13" of the main control chip U1 in fig. 4) of the main control module 400 and a sixth port (i.e., pin "14" of the main control chip U1 in fig. 4) of the main control module 400; the fourth sampling unit 620 is electrically connected to the seventh port (i.e., the "16" pin of the main control chip U1 in fig. 4) of the main control module 400 and the eighth port (i.e., the "17" pin of the main control chip U1 in fig. 4) of the main control module 400; the fifth sampling unit 630 is electrically connected to the ninth port (i.e., the "19" pin of the main control chip U1 in fig. 4) of the main control module 400 and the tenth port (i.e., the "20" pin of the main control chip U1 in fig. 4) of the main control module 400.
As shown in fig. 2 and 4, in some embodiments of the present invention, the third sampling unit 610 includes: the second transformer CTa is used for being electrically connected with a live wire power supply and a first load respectively; the fifth resistor Ra is used for being electrically connected to the second transformer CTa and the main control module 400, respectively. The fourth sampling unit 620 includes: the third transformer CTb is used for being electrically connected with a live wire power supply and a second load respectively; the sixth resistor Rb is electrically connected to the third transformer CTb and the main control module 400, respectively. The fifth sampling unit 630 includes: the fourth transformer CTc is used for being electrically connected with a live wire power supply and a load respectively; the seventh resistor Rc is configured to be electrically connected to the fourth transformer CTc and the main control module 400, respectively.
Specifically, the coil of the second transformer CTa is connected in parallel to a fifth resistor Ra, one end of the fifth resistor Ra connected to the second transformer CTa is electrically connected to the fifth port of the main control module 400 (i.e., the "13" pin of the main control chip U1 in fig. 4), and the other end of the fifth resistor Ra connected to the second transformer CTa is electrically connected to the sixth port of the main control module 400 (i.e., the "14" pin of the main control chip U1 in fig. 4). The coil of the third transformer CTb is connected in parallel with a sixth resistor Rb, one end of the sixth resistor Rb connected with the third transformer CTb is electrically connected with a seventh port (i.e., a "16" pin of the main control chip U1 in fig. 4) of the main control module 400, and the other end of the sixth resistor Rb connected with the third transformer CTb is electrically connected with an eighth port (i.e., a "17" pin of the main control chip U1 in fig. 4) of the main control module 400. The coil of the fourth transformer CTc is connected in parallel with a seventh resistor Rc, one end of the seventh resistor Rc connected with the fourth transformer CTc is electrically connected with the ninth port of the main control module 400 (i.e., the "19" pin of the main control chip U1 in fig. 4), and the other end of the seventh resistor Rc connected with the fourth transformer CTc is electrically connected with the tenth port of the main control module 400 (i.e., the "20" pin of the main control chip U1 in fig. 4).
As shown in fig. 2, 3 and 4, in a specific embodiment, the main control chip U1 of the main control module 400 includes a plurality of analog-to-digital converters (ADCs), and the ADCs are all of the same specification. The pin 21 and the pin 22 of the main control chip U1 correspond to one ADC, the pin 23 and the pin 24 of the main control chip U1 correspond to one ADC, the pin 13 and the pin 14 of the main control chip U1 correspond to one ADC, the pin 16 and the pin 17 of the main control chip U1 correspond to one ADC, and the pin 19 and the pin 20 of the main control chip U1 correspond to one ADC. Assuming that the resistance of the first resistor Rn1 is 10 Ω, the resistance of the second resistor Rn2 is 80.6 Ω, the resistances of the third resistor R3 and the fourth resistor R4 are both 100K Ω, the electric energy meter is a three-phase electric energy meter of 5(100) a specification and 0.5 level, the maximum differential input peak values of the ADCs in the main control chip U1 are all 800mV, the specifications of the first transformer 100, the second transformer CTa, the third transformer CTb and the fourth transformer CTc are all 5(100) a, and the input-output transformation ratio is 2500: 1.
In the current bypass detection, the electric energy meter is a three-phase electric energy meter with 5(100) a standard and 0.5 level, so that the starting current of each phase of the electric energy meter is 5A × 0.4% ═ 20mA, the minimum guaranteed precision current of each phase is 5A × 5% ═ 250mA, and the zero line current range required to be detected by the ADC in the current bypass detection is 20mA to 100A. The main control module 400 compares the vector sum of the three-phase current with the zero line current signal in the first zero line signal, and when the larger one of the two items of the vector sum of the three-phase current and the zero line current is greater than or equal to the minimum guaranteed precision current, and the ratio of the difference value of the two items of the vector sum of the three-phase current and the zero line current divided by the larger one of the two items is greater than 10%, it indicates that a current bypass occurs.
If the current of AC-a is Ia, the current of AC-B is Ib, the current of AC-C is Ic, the current flowing through the third resistor R3 is Ir3, and the current flowing through the fourth resistor R4 is Ir4, then, referring to fig. 2, the zero line current In should satisfy:
Figure BDA0003508082660000081
in a normal power supply network, the phases Ia, Ib, Ic are in turn 120 ° apart. When the effective values of Ia, Ib and Ic are equal,
Figure BDA0003508082660000082
namely, it is
Figure BDA0003508082660000083
Since the resistance values of the third resistor R3 and the fourth resistor R4 are both 100K Ω, the zero line current In is:
Figure BDA0003508082660000091
when the effective values of Ia, Ib and Ic are not equal, the values of Ia, Ib and Ic are far more than Ir3 and Ir4, so that the zero line current is at the moment
Figure BDA0003508082660000092
In a normal power supply network, zero line current In does not appear<2.2 mA. Therefore, In the zero line drop detection, when the main control module 400 detects that the second zero line signal represents the zero line current In<And when the voltage is 2.2mA, the fault that the zero line of the power grid is lost can be determined, namely, the ADC needs to be capable of detecting the zero line current smaller than 2.2mA in the detection of the zero line.
The maximum differential input peaks of the plurality of ADCs in the main control chip U1 are all 800mV, and then the effective maximum values of the signals that the ADCs can effectively process are:
Figure BDA0003508082660000093
the minimum valid signal that the ADC can recognize is: 565mV/213About. 0.06897 mV. The specification of the first transformer 100 is 5(100) a, the input-output conversion ratio is 2500:1, the resistance value of the first resistor Rn1 is 10 Ω, and when the zero line current is the maximum current 100A, the effective value of signals acquired by the ADC corresponding to the pin 21 and the pin 22 of the main control chip U1 is about 400mV, so that the first resistor Rn1 meets the sampling requirement of the ADC, and can perform current bypass detection. Because the resistance value of the second resistor Rn2 is 80.6 Ω, the minimum zero line current collected by the corresponding ADC is (0.06897mV/80.6) × 2500 ═ 2.1392mA, which is less than 2.2mA, and therefore the second resistor Rn2 meets the zero line loss detection requirement.
As shown in fig. 3 and 4, in some embodiments of the present invention, the first overvoltage protection subunit 210 includes: a first diode D1, a second diode D2. A cathode of the first diode D1 is configured to be electrically connected to one end of the first resistor Rn1 and a first port (i.e., a "21" pin of the main control chip U1 in fig. 4) of the main control module 400, respectively, and an anode of the first diode D1 is configured to be electrically connected to the other end of the first resistor Rn1 and a second port (i.e., a "22" pin of the main control chip U1 in fig. 4) of the main control module 400, respectively; the cathode of the second diode D2 is electrically connected to the anode of the first diode D1 and the second port of the main control module 400, respectively, and the anode of the second diode D2 is electrically connected to the cathode of the first diode D1 and the first port of the main control module 400, respectively.
Specifically, the first diode D1 and the second diode D2 are connected in parallel, the cathode of the first diode D1 is electrically connected to the anode of the second diode D2, the anode of the first diode D1 is electrically connected to the cathode of the second diode D2, one end of the first diode D1 connected to the second diode D2 is electrically connected to the first port of the main control module 400, and the other end of the first diode D1 connected to the second diode D2 is electrically connected to the second port of the main control module 400. When the voltage of the first zero line signal exceeds 900mV, the first diode D1 and the second diode D2 are conducted, so that the voltage of the first zero line signal is controlled to be about 900mV, and the function of preventing overvoltage is realized.
As shown in fig. 3 and 4, in some embodiments of the present invention, the second overvoltage protection subunit 310 includes: a third diode D3, a fourth diode D4. An anode of the third diode D3 is used to be electrically connected to one end of the second resistor Rn2 and the fourth port of the main control module 400 (i.e., the "24" pin of the main control chip U1 in fig. 4), respectively, and a cathode of the first diode D1 is used to be electrically connected to the other end of the second resistor Rn2 and the third port of the main control module 400 (i.e., the "23" pin of the main control chip U1 in fig. 4), respectively; the cathode of the fourth diode D4 is electrically connected to the anode of the third diode D3 and the fourth port of the main control module 400, respectively, and the anode of the fourth diode D4 is electrically connected to the cathode of the third diode D3 and the third port of the main control module 400, respectively.
Specifically, the third diode D3 and the fourth diode D4 are connected in parallel with each other, a cathode of the third diode D3 is electrically connected to an anode of the fourth diode D4, an anode of the third diode D3 is electrically connected to a cathode of the fourth diode D4, one end of the third diode D3 connected to the fourth diode D4 is electrically connected to the third port of the main control module 400, and the other end of the third diode D3 connected to the fourth diode D4 is electrically connected to the fourth port of the main control module 400. When the voltage of the second zero line signal exceeds 900mV, the third diode D3 and the fourth diode D4 are conducted, so that the voltage of the second zero line signal is controlled to be about 900mV, and the function of preventing overvoltage is realized.
An embodiment of the present invention further provides an electric energy meter, including: the zero line current sampling circuit described in the above embodiments.
According to the electric energy meter provided by the embodiment of the invention, by adopting the zero line current sampling circuit, the electric energy meter can simultaneously carry out current bypass detection and zero line falling detection under the condition of only adopting one current transformer, so that the occupied physical space is reduced, the electric energy meter is suitable for the miniaturized design of electric energy meter products, and the cost of the electric energy meter is reduced.
The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention. Furthermore, the embodiments of the present invention and the features of the embodiments may be combined with each other without conflict.

Claims (8)

1. Zero line current sampling circuit, its characterized in that is applied to the electric energy meter, the electric energy meter includes first sampling module, host system, first sampling module be used for respectively with three-phase live wire power host system, ground end electricity is connected, first sampling module is used for gathering three-phase current, zero line current sampling circuit includes:
the first mutual inductor is used for being electrically connected with a zero line power supply and the ground end respectively;
the first sampling unit is used for being electrically connected with the first mutual inductor and the main control module respectively and used for generating a first zero line signal;
the second sampling unit is used for being electrically connected with the first mutual inductor and the main control module respectively, the second sampling unit is connected with the first sampling unit in parallel, and the second sampling unit is used for generating a second zero line signal;
the main control module is used for carrying out current bypass detection according to the three-phase current and the first zero line signal, and the main control module is used for carrying out zero line loss detection according to the second zero line signal.
2. The zero line current sampling circuit of claim 1, wherein the first sampling unit comprises:
one end of the first resistor is used for being electrically connected with one end of the first mutual inductor, and the other end of the first resistor is used for being electrically connected with the second sampling unit;
the first overvoltage preventing subunit is used for being electrically connected with the first resistor, the first port of the main control module and the second port of the main control module respectively.
3. The zero line current sampling circuit of claim 2, wherein the second sampling unit comprises:
one end of the second resistor is used for being electrically connected with the other end of the first transformer, and the other end of the second resistor is used for being electrically connected with the other end of the first resistor;
and the second overvoltage preventing subunit is used for being electrically connected with the second resistor, the third port of the main control module and the fourth port of the main control module respectively.
4. A zero line current sampling circuit according to claim 3, wherein the first overvoltage protection subunit comprises:
a cathode of the first diode is used for being electrically connected with one end of the first resistor and a first port of the main control module respectively, and an anode of the first diode is used for being electrically connected with the other end of the first resistor and a second port of the main control module respectively;
and the cathode of the second diode is used for being electrically connected with the anode of the first diode and the second port of the main control module respectively, and the anode of the second diode is used for being electrically connected with the cathode of the first diode and the first port of the main control module respectively.
5. A zero line current sampling circuit according to claim 4, wherein the second overvoltage protection subunit comprises:
the anode of the third diode is used for being electrically connected with one end of the second resistor and the fourth port of the main control module respectively, and the cathode of the first diode is used for being electrically connected with the other end of the second resistor and the third port of the main control module respectively;
and the cathode of the fourth diode is used for being electrically connected with the anode of the third diode and the fourth port of the main control module respectively, and the anode of the fourth diode is used for being electrically connected with the cathode of the third diode and the third port of the main control module respectively.
6. A zero line current sampling circuit according to any of claims 1 to 5, wherein the first sampling module comprises:
the third sampling unit is used for being electrically connected with the live wire power supply, the main control module and the load of one phase respectively;
the fourth sampling unit is used for being electrically connected with the other phase of the live wire power supply, the main control module and the load respectively;
the fifth sampling unit is used for being electrically connected with the live wire power supply of the other phase, the main control module and the load respectively;
one end of the third resistor is electrically connected with the live wire power supply and the third sampling unit respectively, and the other end of the third resistor is grounded;
and one end of the fourth resistor is used for being electrically connected with the live wire power supply and the fourth sampling unit, and the other end of the fourth resistor is grounded.
7. The zero line current sampling circuit of claim 6, wherein the third sampling unit comprises:
the second mutual inductor is used for being electrically connected with the live wire power supply and the load respectively;
the fifth resistor is used for being electrically connected with the second mutual inductor and the main control module respectively;
the fourth sampling unit includes:
the third mutual inductor is used for being electrically connected with the live wire power supply and the load respectively;
the sixth resistor is used for being electrically connected with the third mutual inductor and the main control module respectively;
the fifth sampling unit includes:
the fourth transformer is used for being electrically connected with the live wire power supply and the load respectively;
and the seventh resistor is used for being electrically connected with the fourth transformer and the main control module respectively.
8. An electric energy meter, comprising:
a zero line current sampling circuit according to any of claims 1 to 7.
CN202210145396.3A 2022-02-17 2022-02-17 Zero line current sampling circuit and electric energy meter Pending CN114460346A (en)

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CN202210145396.3A CN114460346A (en) 2022-02-17 2022-02-17 Zero line current sampling circuit and electric energy meter

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
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CN114460346A true CN114460346A (en) 2022-05-10

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