CN113607994A - Zero line detection circuit, zero line detection method and electric energy meter - Google Patents
Zero line detection circuit, zero line detection method and electric energy meter Download PDFInfo
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- G—PHYSICS
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R11/00—Electromechanical arrangements for measuring time integral of electric power or current, e.g. of consumption
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention discloses a zero line detection circuit, a zero line detection method and an electric energy meter, wherein the zero line detection circuit comprises: the sampling circuit comprises a sampling circuit, a load circuit and a first control circuit, wherein a first input end of the sampling circuit is connected with an A phase line, a second input end of the sampling circuit is connected with a B phase line, a third input end of the sampling circuit is connected with a C phase line, an output end of the sampling circuit is connected with the first control circuit, a first end of the load circuit is connected with the A phase line, the B phase line or the C phase line, and a second end of the load circuit is connected with a zero line; the sampling circuit is used for sampling voltage signals of the phase line A, the phase line B and the phase line C respectively and transmitting sampling results to the first control circuit; and the first control circuit is used for detecting whether the zero line has faults or not according to the sampling result. The invention improves the detection efficiency of the zero line fault on the basis of not increasing the hardware cost of a sensor circuit and the like.
Description
Technical Field
The invention relates to the field of circuit electronics, in particular to a zero line detection circuit, a zero line detection method and an electric energy meter.
Background
As is known, a three-phase four-wire system current transmission mode is mainly adopted in China, and a grounding zero line can be externally connected besides A/B/C three-phase current under normal conditions.
The zero line of three-phase smart electric meter breaks down or can cause the potential safety hazard after dropping, brings very serious influence to people's normal order of life and work facility, so three-phase smart electric meter need pay attention to the normal work and the operation of maintaining the zero line constantly.
At present, whether the zero line of a three-phase intelligent ammeter drops, is connected abnormally or is pulled out manually or not is mainly detected by using special test equipment on an ammeter installation site manually, but the detection mode is low in efficiency and high in labor cost.
Disclosure of Invention
The invention mainly aims to provide a zero line detection circuit, a zero line detection method and an electric energy meter, and aims to solve the problem of low efficiency of a mode of manually detecting whether a zero line of a three-phase electric meter has a fault.
In order to achieve the above object, the present invention provides a zero line detection circuit, including: the sampling circuit comprises a sampling circuit, a load circuit and a first control circuit, wherein a first input end of the sampling circuit is connected with an A phase line, a second input end of the sampling circuit is connected with a B phase line, a third input end of the sampling circuit is connected with a C phase line, an output end of the sampling circuit is connected with the first control circuit, a first end of the load circuit is connected with the A phase line, the B phase line or the C phase line, and a second end of the load circuit is connected with a zero line;
the sampling circuit is used for sampling voltage signals of the phase line A, the phase line B and the phase line C respectively and transmitting sampling results to the first control circuit;
and the first control circuit is used for detecting whether the zero line has faults or not according to the sampling result.
Optionally, the load circuit includes a G3-PLC communication unit and a second control circuit, a first end of the G3-PLC communication unit is connected to the a-phase line, a second end of the G3-PLC communication unit is connected to the neutral line, and a third end of the G3-PLC communication unit is connected to the second control circuit.
Optionally, the communication unit includes coupling module, filtering module, overvoltage protection module and G3-PLC communication module, coupling module's first end and A phase line are connected, coupling module's second end with G3-PLC communication module connects, filtering module's first end and A phase line are connected, filtering module's second end and zero line are connected, overvoltage protection module set up in between coupling module's second end and the zero line.
Optionally, zero line detection circuitry still includes power conversion circuit, power conversion circuit's first input end is connected with A looks line, power conversion circuit's second input end is connected with B looks line, power conversion circuit's third input end is connected with C looks line, power conversion circuit's fourth input end is connected with the zero line, power conversion circuit's output with first control circuit connects.
Optionally, the power conversion circuit includes a shaping circuit and an energy storage filter circuit, a first input end of the shaping circuit is connected with the phase line a, a second input end of the shaping circuit is connected with the phase line B, a third input end of the shaping circuit is connected with the phase line C, a fourth input end of the shaping circuit is connected with the zero line, an output end of the shaping circuit is connected with an input end of the energy storage filter circuit, and an output end of the energy storage filter circuit is an output end of the power conversion circuit.
Optionally, the power conversion circuit further includes a current limiting unit and a lightning protection unit, an input end of the current limiting unit is connected to the phase line a, the phase line B, the phase line C and the zero line, and an output end of the current limiting unit is connected to the first input end, the second input end, the third input end and the fourth input end of the shaping circuit; one end of the lightning protection unit is connected with the phase line A, the phase line B and the phase line C, and the other end of the lightning protection unit is connected with the zero line.
In addition, in order to achieve the above object, the present invention further provides a zero line detection method, where the zero line detection method is applied to the zero line detection circuit, and the method includes the steps of:
sampling voltage signals of the phase line A, the phase line B and the phase line C to obtain a phase voltage signal A, a phase voltage signal B and a phase voltage signal C;
and monitoring whether the A-phase voltage signal, the B-phase voltage signal and the C-phase voltage signal meet the preset zero line fault condition or not so as to detect whether the zero line has a fault or not.
Optionally, the step of monitoring whether the a-phase voltage signal, the B-phase voltage signal, and the C-phase voltage signal satisfy a preset zero line fault condition to detect whether a fault occurs in a zero line includes:
obtaining an A-phase voltage value, a B-phase voltage value and a C-phase voltage value through the A-phase voltage signal, the B-phase voltage signal and the C-phase voltage signal;
if the A-phase voltage value is zero, the rated voltage value is larger than the B-phase voltage value and is larger than the B-phase preset voltage or the rated voltage value is larger than the C-phase voltage value and is larger than the C-phase preset voltage, and the detection result shows that the zero line has faults.
Optionally, the step of monitoring whether the a-phase voltage signal, the B-phase voltage signal, and the C-phase voltage signal satisfy a preset zero line fault condition to detect whether a fault occurs in a zero line further includes:
acquiring an A phase voltage value, a B phase voltage value, a C phase voltage value, a first included angle between the B phase voltage and the C phase voltage and a second included angle between the C phase voltage signal and the A phase voltage signal through the A phase voltage signal, the B phase voltage signal and the C phase voltage signal;
calculating the A phase voltage value, the B phase voltage value and the C phase voltage value to obtain a first proportion between the B phase voltage value and a rated voltage value, a second proportion between the C phase voltage value and the rated voltage value, a third proportion between the A phase voltage value and the rated voltage value and voltage unevenness;
if the A-phase voltage value is greater than a first preset voltage, the B-phase voltage value is greater than a second preset voltage, the C-phase voltage value is greater than a third preset voltage, the first included angle is smaller than a first preset angle, the voltage unevenness rate conforms to a preset percentage interval, the first proportion is greater than a first preset proportion, the second proportion is greater than a second preset proportion, and the third proportion is smaller than a third preset proportion, the detection result is that the zero line fails;
or the phase voltage value of the A phase is greater than a first preset voltage, the phase voltage value of the B phase is greater than a second preset voltage, the phase voltage value of the C phase is greater than a third preset voltage, the second included angle is greater than a second preset angle, the voltage unevenness rate accords with a preset percentage interval, the first proportion is greater than a first preset proportion, the second proportion is greater than a second preset proportion, and the third proportion is less than a third preset proportion, and then the detection result is that the zero line breaks down.
In addition, in order to achieve the above object, the present invention also provides an electric energy meter, including a zero line detection circuit configured as the zero line detection circuit described above.
According to the invention, one end of the load circuit is connected with the phase line A, the phase line B or the phase line C, the second end of the load circuit is connected with the zero line, when the zero line fault occurs on the electric energy meter, because the load circuit is coupled on the phase line A, the phase line B or the phase line C of the electric energy meter, one phase connected with the electric energy meter has a load, so that the three-phase load unbalance phenomenon occurs, and at the moment, the first control circuit receives and calculates voltage signals on the phase line A, the phase line B and the phase line C, so that whether the zero line has the fault can be detected. Therefore, the fault of the zero line is intelligently detected at the end of the electric energy meter, the process of confirming the installation site of the electric energy meter by manpower is omitted, the labor cost is saved, and the detection efficiency is improved; furthermore, zero line fault event record information stored in the electric energy meter can be sent to a remote management end through a G3-PLC communication module of the electric energy meter, and timeliness of fault finding and management of the remote management end is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
FIG. 1 is a block diagram of a neutral line detection circuit according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of the phase voltage change before and after a zero line fault in the zero line detection circuit of the present invention;
FIG. 3 is a block diagram of another embodiment of a neutral detection circuit of the present invention;
FIG. 4 is a circuit diagram of the embodiment of FIG. 3;
fig. 5 is a schematic flow chart of a zero line detection method according to a first embodiment of the invention.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
The reference numbers illustrate:
Detailed Description
It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that all the directional indicators (such as up, down, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.
In addition, the descriptions related to "first", "second", etc. in the present invention are for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
At present, two methods are mainly used for detecting whether a zero line of a three-phase electric energy meter drops or not, whether abnormal connection exists or whether the zero line is pulled out manually or not, and the other method is to detect the current of the zero line by using special test equipment through manual work on the installation site of the electric energy meter; the other method is to add a zero line current detection sensor and a corresponding detection circuit in the intelligent electric energy meter to identify the zero line current. However, the two existing detection methods have respective disadvantages: in the first detection method, the electric energy meter cannot automatically sense and recognize the requirement of manual intervention, the hysteresis on fault discovery time exists, the efficiency is low, and the requirement of timely discovering the fault and timely processing the fault cannot be fundamentally met; the second detection method can realize automatic fault identification of the electric energy meter, but a zero line current detection sensor and a corresponding detection circuit are required to be added in the intelligent electric energy meter, so that the cost of the electric energy meter is increased.
Based on the phenomenon, the invention provides the zero line detection circuit, the zero line detection method and the electric energy meter, so that whether the zero line of the electric energy meter has faults or not can be detected on the basis of not increasing circuits such as a sensor and the like, and the detection efficiency is improved.
Referring to fig. 1, the present invention provides a zero line detection circuit, which in one embodiment includes:
the circuit comprises a sampling circuit 10, a load circuit 20 and a first control circuit 30, wherein a first input end of the sampling circuit 10 is connected with an A phase line, a second input end of the sampling circuit 10 is connected with a B phase line, a third input end of the sampling circuit 10 is connected with a C phase line, an output end of the sampling circuit 10 is connected with the first control circuit 30, a first end of the load circuit 20 is connected with the A phase line, the B phase line or the C phase line, and a second end of the load circuit 20 is connected with a zero line;
the sampling circuit 10 is configured to sample voltage signals of the phase line a, the phase line B, the phase line C and the zero line, respectively, and transmit sampling results to the first control circuit 30;
the first control circuit 30 is configured to detect whether a zero line fails according to the sampling result.
The zero line detection circuit can be arranged in various circuits which need to detect zero line faults in a three-phase line, and the first control circuit 30 and the sampling circuit 10 can be arranged according to actual needs, for example, the first control circuit 30 comprises a micro control unit MCU and peripheral circuits thereof, and when the zero line detection circuit is specifically implemented, the zero line detection circuit can comprise peripheral circuits which need a metering chip, an MCU and the like; the sampling circuit 10 may be a resistive sampling circuit, such as a sampling circuit composed of a plurality of resistors connected in series, or other equivalent circuits.
It can be understood that, referring to fig. 2, taking the example that the load circuit 20 is connected with the phase a line, under normal conditions, there is no potential difference between the neutral point "O" of the three-phase four-line system power supply and the neutral point 0 of the three-phase electric energy meter, if the zero line of the three-phase electric energy meter is interrupted, the three-phase load of the electric energy meter actually forms a star connection (Y) with the neutral point not connected with the zero line, and then an asymmetric star connection neutral point 0 offset phenomenon occurs, that is, the line voltages of the three-phase load are equal, but the phase voltages are not equal. The larger the three-phase load difference, the larger the offset of 0, the larger the phase voltage difference, the smaller the phase voltage loaded, and the larger the phase voltage loaded.
Referring to the following table, the phase voltage parameters of each phase in the zero line interruption experiment are as follows:
since the load circuit is applied to the phase a, which is loaded more than the other two phases, when the zero line is generated, the voltage of the phase voltage UA decreases, and the voltages of the phase voltage UB and the phase voltage UC increase.
In this embodiment, one end of the load circuit is connected to the a-phase line, the B-phase line or the C-phase line, and the second end of the load circuit is connected to the zero line, when the zero line fault occurs in the electric energy meter, because the load circuit is coupled to the a-phase line, the B-phase line or the C-phase line of the electric energy meter, one phase connected to the electric energy meter will have a load, so as to generate a three-phase load imbalance phenomenon, at this time, the first control circuit 30 receives and calculates the voltage signals on the a-phase line, the B-phase line and the C-phase line, so as to detect whether the zero line has a fault or not. Therefore, the fault of the zero line is intelligently detected at the end of the electric energy meter, the process of confirming the installation site of the electric energy meter by manpower is omitted, the labor cost is saved, and the detection efficiency is improved; furthermore, the storage and recording condition of the zero line fault event in the electric energy meter can be sent to a remote management end through a communication module of the electric energy meter, and the timeliness of fault finding and management is improved.
Further, referring to fig. 3, the load circuit 20 includes a G3-PLC communication unit 21 and a second control circuit 22, a first end of the G3-PLC communication unit 21 is connected to the a-phase line, a second end of the G3-PLC communication unit 21 is connected to the neutral line, and a third end of the G3-PLC communication unit 21 is connected to the second control circuit 22.
G3-PLC is a new Power Line Communications (PLC) specification that uses reliable, safe, and efficient orthogonal frequency division multiplexing communication techniques to transmit digital information over Power lines to smart grids. Smart meters can be managed, controlled, and monitored in power transmission networks, energy management, EV charging, lighting control, and other smart grid applications. At present, the method has the characteristics of wide coverage, no need of special wiring, high transmission speed, reliability, safety, long-distance communication and the like, and is becoming a very attractive communication mode.
It will be appreciated that the G3-PLC communication unit 21 may be connected with phase a, phase B or phase C, and preferably the G3-PLC communication unit 21 is coupled between phase a and neutral connections. The G3-PLC communication unit 21 has two roles here, the first being the role of the load and the second being the communication role for the electric energy meter and the remote communication.
It should be noted that the second control circuit 22 is used for controlling the G3-PLC communication unit 21 and storing data transmitted and received by the G3-PLC communication unit 21, and the second control circuit 22 and the first control circuit 30 may be connected to each other so as to interact with each other; the second control circuit 22 may be a micro control unit MCU or an equivalent circuit.
The communication between the electric energy meter and the remote management end is realized by arranging the G3-PLC communication unit 21, when the zero line fails, the electric energy meter intelligently detects the fault of the zero line, meanwhile, the G3-PLC communication unit 21 can cause the communication interruption of the G3-PLC due to the falling-off of the zero line, and the management end prompts the fault of the electric energy meter by sensing the abnormal G3-PLC communication, so that the management end can find the problem in time and troubleshoot the problem in time, and the requirement of finding the fault in time and processing the fault in time is fundamentally met.
Further, referring to fig. 4, the G3-PLC communication unit 21 includes a coupling module 210, a filtering module 211, and a G3-PLC communication module 212, wherein a first end of the coupling module 210 is connected to the phase a line, a second end of the coupling module 210 is connected to the G3-PLC communication module 212, a first end of the filtering module 211 is connected to the phase a line, and a second end of the filtering module 211 is connected to the neutral line.
It can be understood that the structure of the G3-PLC communication unit 21 including the coupling module 210, the filtering module 211 and the G3-PLC communication module 212 may be set according to actual needs, for example, the filtering module 211 may include a first capacitor C1, a first end of the first capacitor C1 is a first end of the filtering module 211 connected to the phase a line, a second end of the first capacitor C1 is a second end of the filtering module 211 connected to the neutral line and the ground line, respectively, the coupling module 210 may include a second capacitor C2, a first end of the second capacitor C2 is connected to a first end of the first capacitor C1, and a second end of the second capacitor C2 is an output end of the coupling module 210; the above-mentioned G3-PLC communication module 212 may include a G3-TXD data transmission part and a G3-RXD data reception part, the G3-TXD data transmission part and the G3-RXD data reception part being connected to the output terminal of the coupling module 210 and the second control circuit 22, respectively.
Through the arrangement of the G3-PLC communication module 212, the communication interaction between the electric energy meter and the remote management end is more timely, so that the remote management end timely knows whether the zero line of the electric energy meter breaks down or not and whether the fault is eliminated or not, and the data transmitted to the G3-PLC communication module is more accurate and stable through the arrangement of the filtering module 211.
Further, the G3-PLC communication unit 21 further includes an overvoltage protection module 213, and the overvoltage protection module 213 is disposed between the output end of the filtering module 211 and the neutral line.
The overvoltage protection module 213 is configured to protect the G3-PLC communication module 212 when the a-phase line and the zero line are impacted by transient high energy, and may be set according to actual needs, for example, the overvoltage protection module 213 may include a transient diode TVS, one end of the transient diode TVS is connected to the second end of the second capacitor C2, and the other end of the transient diode TVS is connected to the zero line and the ground, or may be an equivalent circuit with an overvoltage protection function.
Further, referring to fig. 3 again, the zero line detection circuit further includes a power conversion circuit 40, a first input end of the power conversion circuit 40 is connected to the phase line a, a second input end of the power conversion circuit 40 is connected to the phase line B, a third input end of the power conversion circuit 40 is connected to the phase line C, a fourth input end of the power conversion circuit 40 is connected to the zero line, and an output end of the power conversion circuit 40 is connected to the first control circuit.
In this embodiment, by providing the power conversion circuit 40, the three-phase power can be converted into a dc power to supply power to circuits such as a controller in the electric energy meter that require a dc power.
Further, referring to fig. 4 again, the power conversion circuit 40 includes a shaping circuit 401 and a tank filter circuit 402, a first input end of the shaping circuit 401 is connected to the phase a, a second input end of the shaping circuit 401 is connected to the phase B, a third input end of the shaping circuit 401 is connected to the phase C, a fourth input end of the shaping circuit 401 is connected to the zero line, an output end of the shaping circuit 401 is connected to the input end of the tank filter circuit 402, and an output end of the tank filter circuit 402 is the output end of the power conversion circuit 40.
Specifically, the shaping circuit 401 may include a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, a seventh diode D7, an eighth diode D8, a third capacitor C3, and an inductor L;
the anode of the first diode D1 and the cathode of the second diode D2 are respectively connected to the a-phase line, the anode of the third diode D3 and the cathode of the fourth diode D4 are respectively connected to the B-phase line, the anode of the fifth diode D5 and the cathode of the sixth diode D6 are respectively connected to the C-phase line, the anode of the seventh diode D7 and the cathode of the eighth diode D8 are connected to a neutral line, the cathode of the first diode D1, the cathode of the third diode D3, the cathode of the fifth diode D5 and the cathode of the seventh diode D7 are respectively connected with the first input end of the first inductor L, an anode of the second diode D2, an anode of the fourth diode D4, an anode of the sixth diode D6, and an anode of the eighth diode D8 are respectively connected to a second input terminal of the inductor L, and an output terminal of the inductor L is an output terminal of the shaping circuit 401; one end of the third capacitor C3 is connected to the first input terminal of the inductor L, and the other end of the third capacitor C3 is connected to the second input terminal of the inductor L.
The inductor L may be a common-mode inductor for suppressing common-mode interference, and the energy storage filter circuit 402 may be set according to an actual circuit. After the rectification and filtering processing of the phase line A, the phase line B, the phase line C and the zero line is carried out through the shaping circuit 401 and the energy storage filter circuit 402, the signals transmitted to the rear-end switching power supply are more accurate.
Further, the power conversion circuit 40 further includes a current limiting unit 403, an input end of the current limiting unit 403 is connected to the phase line a, the phase line B, the phase line C, and the zero line, respectively, and an output end of the current limiting unit 403 is connected to the first input end, the second input end, the third input end, and the fourth input end of the shaping circuit 401, respectively.
Specifically, the current limiting unit 403 may include a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4; one end of a first resistor R1 is connected to the phase line a, the other end of the first resistor R1 is connected to the common end of the anode of the first diode D1 and the cathode of the second diode D2, one end of the second resistor R2 is connected to the phase line B, the other end of the second resistor R2 is connected to the common end of the anode of the third diode D3 and the cathode of the fourth diode D4, one end of the third resistor R3 is connected to the phase line C, the other end of the third resistor R3 is connected to the common end of the anode of the fifth diode D5 and the cathode of the sixth diode D6, one end of the fourth resistor R4 is connected to the neutral line, and the other end of the fourth resistor R4 is connected to the common end of the anode of the seventh diode D7 and the cathode of the eighth diode D8. The first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 may be single resistors, or may be formed by connecting a plurality of resistors in series, and function as a current limiter.
Further, the power conversion circuit 40 further includes a lightning protection unit 404, one end of the lightning protection unit 404 is connected to the phase line a, the phase line B and the phase line C, and the other end of the lightning protection unit 404 is connected to the zero line.
Specifically, the lightning protection unit 404 may include a first varistor RV1, a second varistor RV2, and a third varistor RV 3; one end of a first voltage dependent resistor RV1 is connected with the phase line A, one end of a second voltage dependent resistor RV2 is connected with the phase line B, one end of a third voltage dependent resistor RV3 is connected with the phase line C, and the other ends of the first voltage dependent resistor RV1, the second voltage dependent resistor RV2 and the third voltage dependent resistor RV3 are connected with a zero line. The circuit damage of the electric energy meter caused by the induced current surge in the circuit when the conditions such as lightning strike occur is avoided.
In summary, based on the above hardware structure, because the G3-PLC communication module is coupled to the phase line a of the electric energy meter, when the electric energy meter has a zero line fault, the phase line a has a load, so that a three-phase load imbalance phenomenon occurs, at this time, the first control circuit 30 receives the voltage signals on the phase line a, the phase line B, and the phase line C processed by the sampling circuit 10, and determines whether the zero line has a fault through a preset calculation formula and determination conditions, so as to achieve automatic and intelligent detection of the zero line fault, save labor cost, and improve detection efficiency; the zero line falls off to cause G3-PLC communication interruption, then the remote management end can prompt the fault of the ammeter by sensing G3-PLC communication abnormity, after the zero line fault is eliminated, the first control circuit 30 detects that the fault is eliminated, and G3-PLC communication is recovered to be normal, and then fault elimination information can be sent to the remote management end, so that the requirement of timely finding the fault and timely processing the fault is met.
The present invention also provides a zero line detection method, referring to fig. 5, in a first embodiment of the zero line detection method, the zero line detection method includes the steps of:
step S10, voltage signals of the phase line A, the phase line B and the phase line C are sampled to obtain a phase voltage signal A, a phase voltage signal B and a phase voltage signal C;
and step S20, monitoring whether the A-phase voltage signal, the B-phase voltage signal and the C-phase voltage signal meet the preset zero line fault condition or not so as to detect whether the zero line has faults or not.
The A-phase voltage signal, the B-phase voltage signal and the C-phase voltage signal contain information of phase voltage values, phase angles and the like of all phases, and the preset zero line fault condition is a condition which is met by the phase voltage signals obtained by zero line fault experiments and experience summary.
Specifically, a zero line fault flag bit can be set in a first control circuit 30 of the zero line detection circuit, when the device is powered on and initialized, the zero line fault flag bit is cleared, a sampling circuit 10 samples voltage signals of an a phase line, a B phase line and a C phase line in a preset sampling period, the preset sampling period can be set according to actual needs, if 1 second is a period, the sampled a phase voltage signal, B phase voltage signal and C phase voltage signal are monitored, if a preset zero line fault condition is met, the zero line fault can be judged, the zero line fault flag bit can be set at the moment, the fault can be recorded, and the remote management end can sense the abnormal condition of the electric meter through the communication abnormality of G3-PLC, so that the remote management end can find the fault in time and troubleshoot the fault in time. After the fault is eliminated, the A-phase voltage signal, the B-phase voltage signal and the C-phase voltage signal obtained by sampling again do not meet the preset zero line fault condition any more, then the zero line fault can be judged to be eliminated, at the moment, the zero line fault flag bit can be cleared, and the fault eliminated state is sent to the remote management end through the G3-PLC communication module, so that the remote management end carries out corresponding recording.
In the embodiment, the voltage signals of the phase line A, the phase line B and the phase line C are sampled and monitored, so that whether the zero line has a fault or not is detected, the fault of the zero line is automatically and intelligently detected, the labor cost is saved, and the detection efficiency is improved; and then the remote management end can sense the abnormity of the electric meter through the communication abnormity of the G3-PLC, thereby meeting the requirements of timely finding and timely processing faults.
Further, the step of monitoring whether the a-phase voltage signal, the B-phase voltage signal and the C-phase voltage signal satisfy a preset zero line fault condition to detect whether a zero line has a fault includes:
step a, obtaining an A phase voltage value, a B phase voltage value and a C phase voltage value through the A phase voltage signal, the B phase voltage signal and the C phase voltage signal;
and B, if the A phase voltage value is zero, the rated voltage value is larger than the B phase voltage value and is larger than the B phase preset voltage or the rated voltage value is larger than the C phase voltage value and is larger than the C phase preset voltage, and the detection result shows that the zero line has faults.
And analyzing the sampling signal to obtain an A-phase voltage value Ua, a B-phase voltage value Ub and a C-phase voltage value Uc, wherein the B-phase preset voltage and the C-phase preset voltage are set according to actual conditions. Referring to the following table, in the zero line interruption experiment, the phase voltage parameters of each phase when the zero line is interrupted and the phase voltage of the phase A is interrupted are as follows:
| sample table 1 | Sample table 2 | Sample table 3 | Sample table 4 | Sample table 5 | |
| A phase voltage (V) | 0 | 0 | 0 | 0 | 0 |
| B phase voltage (V) | 206 | 151.1 | 215 | 206 | 206 |
| C phase voltage (V) | 228.9 | 168.5 | 231.4 | 228.9 | 228.8 |
| Rate of voltage imbalance | 100％ | 100％ | 100％ | 100％ | 100％ |
According to experimental data and experience, the B-phase preset voltage and the C-phase preset voltage can be respectively set to be 5V, the rated voltage Un is generally the commercial power standard voltage, the specific value of the rated voltage can be correspondingly marked on the ammeter, and the preset zero line fault condition can be expressed as follows: (Ua ═ 0) & (5V < Ub < Un | |5V < Uc < Un).
Further, the step of monitoring whether the a-phase voltage signal, the B-phase voltage signal and the C-phase voltage signal meet a preset zero line fault condition to detect whether a zero line has a fault includes:
step C, obtaining an A phase voltage value Ua, a B phase voltage value Ub, a C phase voltage value Uc and a first included angle between the B phase voltage and the C phase voltage through the A phase voltage signal, the B phase voltage signal and the C phase voltage signal
And a second angle between the C-phase voltage signal and the A-phase voltage signal
Step d, calculating the A-phase voltage value Ua, the B-phase voltage value Ub and the C-phase voltage value Uc to obtain a first proportion between the B-phase voltage value Ub and a rated voltage value Un, a second proportion between the C-phase voltage value Uc and the rated voltage value Un, a third proportion between the A-phase voltage value Ua and the rated voltage value Un and voltage unevenness;
e, if the A phase voltage value Ua is greater than a first preset voltage, the B phase voltage value Ub is greater than a second preset voltage, the C phase voltage value Uc is greater than a third preset voltage, and the first included angle is formed
When the voltage unevenness rate is smaller than a first preset angle, the voltage unevenness rate accords with a preset percentage interval, the first proportion is larger than a first preset proportion, the second proportion is larger than a second preset proportion, and the third proportion is smaller than a third preset proportion, the detection result is that the zero line has a fault;
or the A phase voltage value Ua is larger than a first preset voltage, the B phase voltage value Ub is larger than a second preset voltage, the C phase voltage value Uc is larger than a third preset voltage, and the second included angle is formed
And if the voltage unevenness rate is greater than a second preset angle and accords with a preset percentage interval, the first proportion is greater than a first preset proportion, the second proportion is greater than a second preset proportion, and the third proportion is less than a third preset proportion, the detection result is that the zero line fails.
The first included angle is an included angle between the phase voltage B and the phase voltage C
The second included angle is an included angle between the C-phase voltage signal and the A-phase voltage signal
The first proportion is the ratio of the voltage value of the phase B voltage to the rated voltage value, namely Ub/Un; the second proportion is the ratio Uc/Un of the voltage value of the C phase line and the rated voltage value; the third proportion is the ratio Ua/Un of the voltage value of the phase line A and the rated voltage value; voltage unbalance rate (maximum voltage-minimum voltage)/maximum voltage 100%;
preferably, the first preset voltage, the second preset voltage and the third preset voltage may be set to 5V, the first preset angle is preset to 110 °, and the second preset angle is preset to 250 °; if the preset percentage interval is (95%, 100%), the first preset ratio is 1.2, the second preset ratio is 1.2, and the third preset ratio is 0.1, then in this embodiment, the preset zero line fault condition may be represented as:
1)、Ua>5V&&Ub>5V&&Uc>5V；
2)、
3) and (100% > voltage unevenness > 95%) & (Ub > 120% Un) & (Uc > 120% Un) & (10% Un > Ua > 0).
According to the scheme, zero line faults under various conditions such as zero line interruption, zero line interruption and A-phase voltage interruption, zero line interruption and B-phase voltage interruption, zero line interruption and C-phase voltage interruption, zero line interruption and three-phase upper load 5A current can be effectively detected by judging whether the sampling voltage meets the fault condition of the part, and the detection accuracy is greatly improved.
The invention further provides an electric energy meter, which comprises a zero line detection circuit, wherein the zero line detection circuit is used for detecting whether a zero line of the electric energy meter has a fault or not, and the structure of the zero line detection circuit can refer to the embodiment and is not described herein again. It should be understood that, because the electric energy meter of the present embodiment adopts the technical solution of the zero line detection circuit, the electric energy meter has all the beneficial effects of the zero line detection circuit.
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. A zero line detection circuit, comprising: the sampling circuit comprises a sampling circuit, a load circuit and a first control circuit, wherein a first input end of the sampling circuit is connected with an A phase line, a second input end of the sampling circuit is connected with a B phase line, a third input end of the sampling circuit is connected with a C phase line, an output end of the sampling circuit is connected with the first control circuit, a first end of the load circuit is connected with the A phase line, the B phase line or the C phase line, and a second end of the load circuit is connected with a zero line;
the sampling circuit is used for sampling voltage signals of the phase line A, the phase line B and the phase line C respectively and transmitting sampling results to the first control circuit;
and the first control circuit is used for detecting whether the zero line has faults or not according to the sampling result.
2. The neutral line detection circuit of claim 1, wherein the load circuit includes a G3-PLC communication unit and a second control circuit, a first end of the G3-PLC communication unit is connected to the a-phase line, a second end of the G3-PLC communication unit is connected to the neutral line, and a third end of the G3-PLC communication unit is connected to the second control circuit.
3. The zero line detection circuit according to claim 2, wherein the G3-PLC communication unit comprises a coupling module, a filter module, an overvoltage protection module and a G3-PLC communication module, a first end of the coupling module is connected with the phase line A, a second end of the coupling module is connected with the G3-PLC communication module, a first end of the filter module is connected with the phase line A, a second end of the filter module is connected with the zero line, and the overvoltage protection module is arranged between the second end of the coupling module and the zero line.
4. The zero line detection circuit according to claim 1, further comprising a power conversion circuit, wherein a first input terminal of the power conversion circuit is connected to the a-phase line, a second input terminal of the power conversion circuit is connected to the B-phase line, a third input terminal of the power conversion circuit is connected to the C-phase line, a fourth input terminal of the power conversion circuit is connected to the zero line, and an output terminal of the power conversion circuit is connected to the first control circuit.
5. The zero line detection circuit according to claim 4, wherein the power conversion circuit includes a shaping circuit and a tank filter circuit, a first input terminal of the shaping circuit is connected to the phase A line, a second input terminal of the shaping circuit is connected to the phase B line, a third input terminal of the shaping circuit is connected to the phase C line, a fourth input terminal of the shaping circuit is connected to the zero line, an output terminal of the shaping circuit is connected to an input terminal of the tank filter circuit, and an output terminal of the tank filter circuit is an output terminal of the power conversion circuit.
6. The zero line detection circuit according to claim 5, wherein the power conversion circuit further comprises a current limiting unit and a lightning protection unit, wherein an input end of the current limiting unit is connected with the phase line A, the phase line B, the phase line C and the zero line respectively, and an output end of the current limiting unit is connected with a first input end, a second input end, a third input end and a fourth input end of the shaping circuit respectively; one end of the lightning protection unit is connected with the phase line A, the phase line B and the phase line C, and the other end of the lightning protection unit is connected with the zero line.
7. A zero line detection method, characterized in that it is applied to the zero line detection circuit of any one of claims 1 to 6, said method comprising the steps of:
sampling voltage signals of the phase line A, the phase line B and the phase line C to obtain a phase voltage signal A, a phase voltage signal B and a phase voltage signal C;
and monitoring whether the A-phase voltage signal, the B-phase voltage signal and the C-phase voltage signal meet the preset zero line fault condition or not so as to detect whether the zero line has a fault or not.
8. The neutral line detection method of claim 7, wherein the step of monitoring whether the a-phase voltage signal, the B-phase voltage signal, and the C-phase voltage signal satisfy a preset neutral line fault condition to detect whether a fault occurs in a neutral line comprises:
obtaining an A-phase voltage value, a B-phase voltage value and a C-phase voltage value through the A-phase voltage signal, the B-phase voltage signal and the C-phase voltage signal;
if the A-phase voltage value is zero, the rated voltage value is larger than the B-phase voltage value and is larger than the B-phase preset voltage or the rated voltage value is larger than the C-phase voltage value and is larger than the C-phase preset voltage, and the detection result shows that the zero line has faults.
9. The neutral line detection method of claim 7, wherein the step of monitoring whether the a-phase voltage signal, the B-phase voltage signal, and the C-phase voltage signal satisfy a preset neutral line fault condition to detect whether a fault occurs in a neutral line comprises:
acquiring an A phase voltage value, a B phase voltage value, a C phase voltage value, an included angle between the B phase voltage and the C phase voltage and an included angle between the C phase voltage signal and the A phase voltage signal through the A phase voltage signal, the B phase voltage signal and the C phase voltage signal;
calculating the A phase voltage value, the B phase voltage value and the C phase voltage value to obtain a first proportion between the B phase voltage value and a rated voltage value, a second proportion between the C phase voltage value and the rated voltage value, a third proportion between the A phase voltage value and the rated voltage value and voltage unevenness;
if the A-phase voltage value is greater than a first preset voltage, the B-phase voltage value is greater than a second preset voltage, the C-phase voltage value is greater than a third preset voltage, the first included angle is smaller than a first preset angle, the voltage unevenness rate conforms to a preset percentage interval, the first proportion is greater than a first preset proportion, the second proportion is greater than a second preset proportion, and the third proportion is smaller than a third preset proportion, the detection result is that the zero line fails;
or the phase voltage value of the A phase is greater than a first preset voltage, the phase voltage value of the B phase is greater than a second preset voltage, the phase voltage value of the C phase is greater than a third preset voltage, the second included angle is greater than a second preset angle, the voltage unevenness rate accords with a preset percentage interval, the first proportion is greater than a first preset proportion, the second proportion is greater than a second preset proportion, and the third proportion is less than a third preset proportion, and then the detection result is that the zero line breaks down.
10. An electric energy meter, characterized by comprising a zero line detection circuit configured as the zero line detection circuit of any of claims 1-6.
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