CN111830297A - Anti-interference method for electric energy meter under 0.5mT power frequency magnetic field - Google Patents
Anti-interference method for electric energy meter under 0.5mT power frequency magnetic field Download PDFInfo
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- CN111830297A CN111830297A CN202010504739.1A CN202010504739A CN111830297A CN 111830297 A CN111830297 A CN 111830297A CN 202010504739 A CN202010504739 A CN 202010504739A CN 111830297 A CN111830297 A CN 111830297A
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Abstract
The invention discloses an anti-interference method for an electric energy meter under a 0.5mT power frequency magnetic field, which comprises the following steps: 1) power-on initialization; 2) sampling the output power of the electric energy meter, and entering a step 3) if the power is greater than a first preset value, or entering a step 4); performing a conventional metering function, returning to step 2); 4) comparing the sampled power with a second preset value, and if the sampled power is less than the second preset value for N times, entering step 5); 5) entering a power frequency magnetic field judging process, sampling voltage and current power data of the electric energy meter every second, setting a statistical period, and entering a step 6 after each statistical period is finished); 6) judging the power frequency magnetic field state of the previous statistical period according to the power sampled in the previous statistical period, and entering a step 7 if the power frequency magnetic field state is judged to be in the previous statistical period; 7) and shielding the current pulse signal when the electric energy meter is in the power frequency magnetic field state in the last statistical period.
Description
Technical Field
The invention relates to the technical field of electric power, in particular to an anti-interference method for an electric energy meter under a 0.5mT power frequency magnetic field.
Background
With the rapid development of economy, the automation and intelligence of production and life are more and more depended on by people, and the demand for electric power cannot be kept away. The scale of the power terminal is also continuously expanding as a ring of the grid terminal. And the electric energy meter is a very important electric power terminal.
The new standard 'single-phase intelligent electric energy meter technical specification' in 2013 of the state network has no load requirement on a 0.5mT power frequency magnetic field: the electric energy meter is in a working state, the current circuit has no current, the electric energy meter is placed in the interference of a 0.5mT power frequency magnetic field, and the test output of the electric energy meter does not generate more than one pulse. In the design of high-precision equipment such as an electric energy meter, because the sampling of an electric energy signal is accurate to a millivolt level, the metering can be misaligned due to small magnetic field fluctuation, and therefore, the magnetic field must be studied deeply to shield the interference.
The existing magnetic field shielding mode mainly starts from the aspect of manganin sampling, and has two modes: 1) changing the welding position of the sampling signal line to offset the induction voltages; 2) the winding mode of the sampling signal wire is changed, a gap is formed between the two signal wires under the condition that the two signal wires are not wound tightly, when the electric energy meter is in a magnetic field environment, the magnetic induction wire penetrates through the gap between the two wires, and induced voltage can appear on the wire to interfere the sampling signal; after the two wires are wound tightly, the gap between the wires can be ignored, the induction voltage is greatly reduced, and the error stability of the electric energy meter is improved. Such as the anti-interference intelligent electric energy meter disclosed in chinese patent application No. 201310008166.3, or a manganin shunt disclosed in chinese patent application No. 201810282319.6.
In the above manner, the magnetic field induction effect is basically negligible under the condition that the electric power is more than 10 w. Actually, according to the technical specification of the electric energy meter, the starting current of the single-phase electric energy meter is 0.4% Ib (according to the technical specification of the national south network intelligent electric energy meter, the Ib current is 5A, the reference voltage is 220V, and the starting power is 4.4 w). Under the condition of low current, magnetic field induction risks exist, the error deviation is large, and even under the condition that residents do not use electricity, the phenomenon that the electric energy meter is 'dull' is out of work due to the magnetoelectric induction principle is caused, so that normal use is influenced, and the interests of users are injured.
Disclosure of Invention
The technical problem to be solved by the invention is to provide an anti-interference method for an electric energy meter under a 0.5mT power frequency magnetic field, which can conveniently detect magnetic field induction and shield and avoid causing metering errors.
The technical scheme adopted by the invention for solving the technical problems is as follows: a method for preventing interference of an electric energy meter under a 0.5mT power frequency magnetic field is characterized in that: the method comprises the following steps:
1) electrifying and initializing, and after the electric energy meter is electrified, opening a power frequency magnetic field judgment shield by default;
2) sampling the output power of a metering part of the electric energy meter, and entering a step 3) if the power is greater than a first preset value, or entering a step 4);
3) performing a conventional metering function, returning to step 2);
4) comparing the sampled power with a second preset value, wherein the second preset value is smaller than the first preset value, if the sampled power is continuously sampled for N times and is smaller than the second preset value, entering the step 5), and if not, repeating the step; n is a preset error tolerance value;
5) entering a power frequency magnetic field judgment process, sampling voltage and current power data of the electric energy meter every second, setting a statistical period, after each statistical period is finished, firstly judging the sampling frequency in the previous statistical period, if the sampling frequency is less than N', not performing power frequency magnetic field judgment, repeating the step, and otherwise, entering the step 6); n' is the preset lowest sampling frequency;
6) judging the power frequency magnetic field state of the previous statistical period according to the power sampled in the previous statistical period, judging whether the ratio of the power smaller than the second preset value is larger than the preset ratio, if so, indicating that the power in the previous statistical period fluctuates, preliminarily judging that the power frequency magnetic field state exists, and entering the step 7); if not, indicating that the power does not fluctuate in the last statistical period, and returning to the step 5);
7) and shielding the current pulse signal and not counting the effective electric energy value when the electric energy meter is in the power frequency magnetic field state in the last statistical period.
Preferably, in step 5), one minute is used as a statistical period.
Preferably, in order to ensure the normal metering of the available electric energy, in step 5), the sampled power is simultaneously compared in real time with a first preset value, and once greater than the first preset value, the procedure returns to step 3).
Preferably, in step 6), determining whether the ratio of the power smaller than the second preset value is larger than the preset ratio refers to whether the number of powers smaller than the second preset value in the power values sampled in one statistical period is larger than a certain value, where the ratio is a ratio of the number of powers smaller than the preset value to the number of sampling times.
Preferably, in order to avoid erroneous judgment caused by power sampling, a magnetic resistor sampling circuit is arranged in the electric energy meter, and whether the electric energy meter is in a power frequency magnetic field state or not is further determined by sampling the voltage of the magnetic resistor.
Preferably, the magnetic sensing resistance sampling circuit comprises a first resistance and a second resistance, the first resistance is a magnetic sensing resistance, one end of the first resistance is grounded, the other end of the first resistance is connected with one end of the second resistance, and the other end of the second resistance is connected to a power supply.
Preferably, the accuracy of power frequency magnetic field judgment is ensured, when the initial judgment in the step 6) is performed before the step 7) is performed when the power frequency magnetic field state is reached, the voltage value at two ends of the first resistor is sampled, and then whether the voltage value is greater than the preset voltage value is judged to further confirm whether the current magnetic field state is reached, if so, the magnetic field state is reached, and the step 7) is performed; if not, the magnetic field is not in the power frequency magnetic field state, and the step 5) is returned to.
Further, in step 7), the electric energy meter simultaneously records the relevant event records, including the entry time and exit time of the power frequency magnetic field state and the number of rate pulses in the process of the power frequency magnetic field state.
Furthermore, the electric energy meter transmits the relevant records to the electricity utilization information acquisition system through the communication channel, and the electricity utilization information acquisition system reads the power frequency magnetic field events monitored by the electric energy meter through the communication channel, positions the failed electric energy meter and eliminates the failure.
The communication channel is a carrier, an RS485, an infrared or wireless module.
Compared with the prior art, the invention has the advantages that: judging whether the sampling power is in a power frequency magnetic field state or not by judging the sampling power, shielding a pulse signal generated in the power frequency magnetic field state, and not counting an effective electric energy value, so that the influence on normal use is avoided, and the benefit of a user is prevented from being injured; the monitoring of the environment of the electromagnetic field for users and the data transmission can be realized, and the electricity utilization condition of the electric energy meter can be fed back timely, quickly and accurately; meanwhile, the accuracy of power frequency magnetic field state judgment is further ensured through a magnetic resistor sampling circuit; the abnormal state of the user site can be timely and quickly acquired and timely processed; and the complete power frequency event record is provided, and the electric quantity data can be traced according to the rate pulse.
Drawings
FIG. 1 is a block diagram of a magnetic field monitoring system employed in the method of the present invention;
FIG. 2 is a reference variation diagram of a one minute sampling data of the environmental power of the 0.5mT magnetic field;
FIG. 3 is a schematic diagram of a magnetoresistive sampling circuit employed in the method of the present invention;
FIG. 4 is a flow chart of the method of the present invention.
Detailed Description
The invention is described in further detail below with reference to the accompanying examples.
Referring to fig. 1, the invention is to protect a method for preventing interference of an electric energy meter under a 0.5mT power frequency magnetic field, a magnetic field monitoring system is formed by the electric energy meter 1, a communication channel 2 and an electricity consumption information acquisition system 3, all components of the magnetic field monitoring system are the prior art, and the communication channel 2 mainly comprises: carrier wave, RS485, infrared, wireless module, etc. In order to ensure the accuracy of magnetic field monitoring, a magnetic resistor sampling circuit is further arranged in the electric energy meter 1 (on the main control circuit board), referring to fig. 3, the magnetic resistor sampling circuit comprises a first resistor RM1 and a second resistor 101, the first resistor RM1 is a magnetic resistor, one end of the first resistor RM1 is grounded, the other end of the first resistor RM1 is connected with one end of the second resistor 101, the other end of the second resistor 101 is connected to a power supply VCC, and the voltage at two ends of the first resistor RM1 is sampled through an ADC. Whether a power frequency magnetic field exists or not is judged together through power monitoring of the electric energy meter 1 and voltage monitoring of the magnetic resistor.
The principle of the invention is that through the research on the 0.5mT power frequency magnetic field environment, under the condition of reference voltage of 220V and no current, the influence of the magnetic field induction signal can be directly reflected on the effective value data of the output power of the metering chip of the electric energy meter 1, and according to one minute statistics, the fluctuation condition of the power can be shown in figure 2, wherein the abscissa is time and the ordinate is power.
According to the technical specification of the south China network, the starting power of the single-phase intelligent electric energy meter is 4.4W, and considering factors such as the precision of a metering chip, the internal anti-submergence of a conventional metering chip is arranged at 70% of the starting power, namely, the internal anti-submergence of the conventional metering chip is not accumulated in an electric energy register of the metering chip under 3W. Under the environment of a 0.5mT magnetic field, the power fluctuates, part of energy is accumulated and is included in an electric energy register of the metering chip, and when the accumulated electric energy reaches a certain value, the phenomenon of pulse running at the electric energy meter is caused.
In a normal starting test, the power value expressed by the electric energy meter is basically stabilized at about 4.4w, and the power fluctuation is greatly different from the power fluctuation in a 0.5mT magnetic field environment, so that the power utilization environment of the electric energy meter can be identified.
The interference prevention method comprises the following steps:
1) after the electric energy meter 1 is powered on, a power frequency magnetic field judgment shield is started by default, small signal current and power are shielded, pulses are shielded, current impact in the power-on process is prevented, and the electric energy meter enters a power frequency magnetic field judgment flow too early;
2) sampling the output power (such as 1 time in 1 second) of a metering part of the electric energy meter 1, and if the power is greater than a first preset value (such as 10W), entering a step 3), otherwise, entering a step 4);
3) perform the conventional metering function: the sampled power is used as effective power to be stored, and an effective electric energy value is obtained through accumulation; returning to the step 2);
4) comparing the sampled power with a second preset value, such as 3W, wherein the second preset value is smaller than the first preset value, if the sampled power is continuously sampled for N times and is smaller than the second preset value, entering the step 5), and if not, repeating the step; n is a preset error tolerance value and can be a natural number which is more than or equal to 1;
5) entering a power frequency magnetic field judging process, sampling voltage and current power data of the electric energy meter 1 every second, taking one minute as a statistical period, after each statistical period is finished, firstly judging the sampling frequency in the previous statistical period, if the sampling frequency is less than N', not judging the power frequency magnetic field, repeating the step, and otherwise, entering the step 6); n' is a preset minimum sampling number, which is a natural number not greater than 60, and in this embodiment, is preferably 20; this is because the timing of each minute is not changed and the time for entering the sampling is variable when sampling is performed after power-on, and if sampling is performed after 58s, which may be inserted from one minute, the number of sampling times in the statistical period is too small, which easily causes errors and loses statistical significance, and thus statistics is not performed; in the step, the sampled power is compared with a first preset value in real time, and once the sampled power is greater than the first preset value, the step 3) is returned;
6) judging the power frequency magnetic field state of the previous statistical period according to the power sampled in the previous statistical period, judging whether the ratio of the power smaller than the second preset value is larger than a preset ratio or not, namely whether the number of the powers smaller than the second preset value is larger than a certain numerical value or not in the power value sampled in one minute, wherein the ratio is the ratio of the number of the powers smaller than the preset value to the sampling frequency, if the preferred ratio is 80%, indicating that the power in the previous minute fluctuates, namely preliminarily judging that the power frequency magnetic field state exists, and entering the step 7); if not, the power is not fluctuated in the last minute, and the step 5) is returned;
7) sampling voltage values at two ends of the first resistor RM1 through an ADC (analog to digital converter), and then judging whether the voltage values are greater than a preset voltage value or not to further confirm whether the current magnetic field environment is in a power frequency magnetic field state or not, if so, indicating that the current magnetic field environment is in the power frequency magnetic field state, and entering the step 8); if not, indicating that the magnetic field is not in the power frequency magnetic field state, and returning to the step 5);
8) shielding the current pulse signal in the last statistical period and under the condition that the electric energy meter 1 is in a power frequency magnetic field state, not counting an effective electric energy value, and simultaneously recording related event records, including state entry time, exit time and the number of rate pulses in the process; transmitting the related records to a power utilization information acquisition system 3 through a communication channel 2;
9) the power utilization information acquisition system 3 reads the power frequency magnetic field events monitored by the electric energy meter 1 through the communication channel 2, positions the fault electric energy meter 1, and eliminates the fault, namely timely maintains and corrects the abnormity.
When the power frequency magnetic field state is determined to enter, the electric energy meter 1 and the electricity utilization acquisition system 3 realize data interaction through the communication channel 2, and abnormal events and alarm signals detected on site by the electric energy meter 1 can be transmitted to the electricity utilization information acquisition system 3 in real time.
In the above process, the electric energy meter 1 is in a power frequency strong magnetism prevention state by default.
Claims (10)
1. A method for preventing interference of an electric energy meter under a 0.5mT power frequency magnetic field is characterized in that: the method comprises the following steps:
1) electrifying initialization, and after the electric energy meter (1) is electrified, opening a power frequency magnetic field judgment shield by default;
2) sampling the output power of a metering part of the electric energy meter (1), and entering a step 3) if the power is greater than a first preset value, or entering a step 4);
3) performing a conventional metering function, returning to step 2);
4) comparing the sampled power with a second preset value, wherein the second preset value is smaller than the first preset value, if the sampled power is continuously sampled for N times and is smaller than the second preset value, entering the step 5), and if not, repeating the step; n is a preset error tolerance value;
5) entering a power frequency magnetic field judgment process, sampling voltage and current power data of the electric energy meter (1) every second, setting a statistical period, after each statistical period is finished, firstly judging the sampling frequency in the previous statistical period, if the sampling frequency is less than N', not performing power frequency magnetic field judgment, repeating the step, and otherwise, entering the step 6); n' is the preset lowest sampling frequency;
6) judging the power frequency magnetic field state of the previous statistical period according to the power sampled in the previous statistical period, judging whether the ratio of the power smaller than the second preset value is larger than the preset ratio, if so, indicating that the power in the previous statistical period fluctuates, preliminarily judging that the power frequency magnetic field state exists, and entering the step 7); if not, indicating that the power does not fluctuate in the last statistical period, and returning to the step 5);
7) and shielding the current pulse signal and not counting the effective electric energy value when the electric energy meter (1) is in the power frequency magnetic field state in the last statistical period.
2. The method for preventing interference of the electric energy meter under the power frequency magnetic field of 0.5mT of claim 1, wherein the method comprises the following steps: in step 5), one minute is taken as a statistical period.
3. The method for preventing interference of the electric energy meter under the power frequency magnetic field of 0.5mT of claim 1, wherein the method comprises the following steps: in step 5), the sampled power is simultaneously compared in real time with a first preset value, and once greater than the first preset value, the procedure returns to step 3).
4. The method for preventing interference of the electric energy meter under the power frequency magnetic field of 0.5mT of claim 1, wherein the method comprises the following steps: in step 6), determining whether the ratio of the power smaller than the second preset value is larger than a preset ratio refers to whether the number of powers smaller than the second preset value in the power values sampled in one statistical period is larger than a certain value, where the ratio is a ratio of the number of powers smaller than the preset value to the number of sampling times.
5. The method for preventing interference of the electric energy meter under the power frequency magnetic field of 0.5mT of claim 1, wherein the method comprises the following steps: a magnetic resistor sampling circuit is arranged in the electric energy meter (1), and whether the electric energy meter is in a power frequency magnetic field state or not is further confirmed by sampling the voltage of the magnetic resistor.
6. The method for preventing interference of the electric energy meter under the power frequency magnetic field of 0.5mT of claim 5, wherein: the magneto-resistor sampling circuit comprises a first resistor (RM1) and a second resistor (101), wherein the first resistor (RM1) is a magneto-resistor, one end of the first resistor (RM1) is grounded, the other end of the first resistor is connected with one end of the second resistor (101), and the other end of the second resistor (101) is connected to a power supply (VCC).
7. The method for preventing interference of the electric energy meter under the power frequency magnetic field of 0.5mT of claim 5, wherein: when the step 6) preliminarily judges that the magnetic field is in the power frequency magnetic field state and before the step 7), the voltage value at two ends of a first resistor (RM1) is sampled, and then whether the voltage value is greater than a preset voltage value is judged to further confirm whether the magnetic field is in the magnetic field environment currently, if so, the magnetic field is in the power frequency magnetic field state, and the step 7) is carried out; if not, the magnetic field is not in the power frequency magnetic field state, and the step 5) is returned to.
8. The method for preventing interference of the electric energy meter under the power frequency magnetic field of 0.5mT of claim 1, wherein the method comprises the following steps: in the step 7), the electric energy meter (1) simultaneously records the relevant event records, including the entry time and exit time of the power frequency magnetic field state and the number of rate pulses in the process of the power frequency magnetic field state.
9. The method for preventing interference of the electric energy meter under the power frequency magnetic field of 0.5mT of claim 8, wherein: the electric energy meter (1) transmits the relevant records to the electricity utilization information acquisition system (3) through the communication channel (2), and the electricity utilization information acquisition system (3) reads the power frequency magnetic field events monitored by the electric energy meter (1) through the communication channel (2), positions the fault electric energy meter (1) and eliminates the fault.
10. The method for preventing interference of the electric energy meter under the power frequency magnetic field of 0.5mT of claim 9, wherein: the communication channel (2) is a carrier, an RS485, an infrared or wireless module.
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