CN114062772A - Residual current measuring circuit - Google Patents
Residual current measuring circuit Download PDFInfo
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- CN114062772A CN114062772A CN202010786040.9A CN202010786040A CN114062772A CN 114062772 A CN114062772 A CN 114062772A CN 202010786040 A CN202010786040 A CN 202010786040A CN 114062772 A CN114062772 A CN 114062772A
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- 238000012545 processing Methods 0.000 claims abstract description 25
- 238000004891 communication Methods 0.000 claims abstract description 7
- 238000006243 chemical reaction Methods 0.000 claims abstract description 5
- 238000005259 measurement Methods 0.000 claims description 15
- 238000005070 sampling Methods 0.000 claims description 5
- 230000001143 conditioned effect Effects 0.000 claims description 4
- 239000000463 material Substances 0.000 claims description 3
- 230000035699 permeability Effects 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 2
- 238000001514 detection method Methods 0.000 description 8
- 239000004020 conductor Substances 0.000 description 5
- 230000005540 biological transmission Effects 0.000 description 4
- 238000013461 design Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000009413 insulation Methods 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000005452 bending Methods 0.000 description 2
- 230000006378 damage Effects 0.000 description 2
- 238000002955 isolation Methods 0.000 description 2
- 206010000369 Accident Diseases 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
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- 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
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
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- 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
- G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
- G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
- G01R19/16571—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533 comparing AC or DC current with one threshold, e.g. load current, over-current, surge current or fault current
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Abstract
The invention discloses a residual current measuring circuit, which comprises a current transformer (100), a signal processing circuit (200), a first microprocessor (300), a second microprocessor (400) or a fourth microprocessor (600), wherein the first microprocessor (300) has at least 7 paths of ADC (analog to digital converter) conversion output capacity with 16 bits or more and has an electric energy calculating function; the second microprocessor (400) has vector sum calculation and significant value mathematical operations, logical operation capabilities and communication and/or display functions. The circuit calculates the residual current value of the loop by measuring the phase current of each phase, and can replace the traditional method of measuring the residual current by adopting a zero sequence transformer. In the protection device with the metering mutual inductor, the functions of measuring and protecting residual current are realized under the condition that the zero sequence mutual inductor is not provided.
Description
Technical Field
The invention relates to a residual current measuring circuit, belonging to the field of low-voltage electrical appliances.
Background
The residual current is generated because the power utilization side is usually in fault, for example, the current passes through a human body from a conductor, the insulation layer is damaged due to line aging, or the insulation of the electrified conductor to the ground is reduced due to the problems of irregular construction and installation, artificial damage and the like, so that part of the current in the main loop does not flow back to the main loop any more, the effective value of the instantaneous vector sum of the circuit in the main loop is not zero, the difference value is the residual current, and the residual current is also called electric leakage; the reason for generating the residual current can be seen, electric shock accidents and equipment electric leakage can be shown through the detection of the residual current, and the residual current in the circuit can cause harm such as human electric shock and fire hazard. The electric shock accident and the fire accident can be effectively avoided through the residual current detection, the alarm and the protection, so the detection of the residual current is very important.
The existing technology usually adopts a zero sequence transformer to detect residual current, all buses of a main circuit need to pass through the zero sequence transformer, so that the size of the zero sequence transformer is very large, the buses of the main circuit need to pass through the zero sequence transformer, the structural complexity and the cost are increased, and the protection device also causes the overall size to be overlarge due to the addition of the zero sequence transformer, so that the internal space of a switch is crowded, the structural design is difficult, the heat dissipation effect is unsatisfactory, and other problems are solved. With the application of the protection device with the metering function, the high-precision measuring element and the high-precision metering element can be used for accurately measuring the residual current, so that the problems caused by the traditional residual current measuring mode are solved, and the protection device is a great progress in the aspects of cost and structure.
Disclosure of Invention
In order to solve at least one of the above problems, the present invention provides a residual current detection circuit, which comprises the following specific schemes:
a residual current measuring circuit at least comprises a current transformer using a material with high initial magnetic permeability as a magnetic core, at least one group of signal processing circuit consisting of an electronic device, a first microprocessor, a second microprocessor or a fourth microprocessor,
the signal processing circuit conditions an external input voltage signal and a current signal and provides the conditioned signals to the first microprocessor;
the first microprocessor has at least 7 paths of ADC (analog to digital converter) capabilities with 16 bits and more, performs analog-to-digital conversion and calculation on the signal conditioned by the signal processing circuit, and outputs all or part of digital signals of a current effective value, a voltage effective value, power, a power factor, frequency, current ADC data and voltage ADC data to the second microprocessor or the fourth microprocessor;
the second microprocessor or the fourth microprocessor performs harmonic and vector sum calculation and adjusts or calibrates the vector sum calculated residual current value according to the magnitude of the harmonic value.
Preferably, the current transformer outputs a current signal in a linear relationship and in phase with the main circuit current within a rated range, has a milliampere resolution, and outputs a current signal in a duty ratio relationship with the main circuit current outside the rated range.
Preferably, the signal processing circuit conditions the analog signal output by the current transformer in a differential mode.
Preferably, the signal processing circuit performs linear step-down sampling on the loop voltage in an isolated or non-isolated manner.
Preferably, the second microprocessor compares the calculated residual current value with a set threshold value, and performs residual current pre-alarming and/or residual current protection.
Preferably, the second microprocessor locally displays and/or transmits data of effective current value, effective voltage value, power factor, frequency and the like of the loop in an external communication mode.
Preferably, the system further comprises a third microprocessor, the third microprocessor locally displays and/or transmits data of current effective values, voltage effective values, power factors, frequency and the like of the loop in an external communication mode, and the fourth microprocessor compares the calculated residual current value with a set threshold value to perform residual current pre-alarming and/or residual current protection.
The invention has the following beneficial effects:
the invention provides a residual current measuring circuit, which comprises a current transformer, a signal processing circuit and a microprocessor, wherein current data of each phase of main loop collected by the current transformer of each phase is utilized, voltage data of each phase of main loop is collected in an isolation or non-isolation mode, the microprocessor carries out ADC (analog to digital converter) conversion and phase angle calculation on the current and the voltage of each phase of loop, and the microprocessor calibrates the coefficient of the measuring circuit to complete the calculation of the effective value of the residual current in a circuit, so that the measurement precision of the residual current reaches the mA level.
According to the invention, as the zero sequence current transformer is not adopted, the internal space of the protection device is saved, the volume of the existing leakage protection switch can be compressed, the space of the complete set of cabinets can be further reduced, more loops can be installed under the same volume, and the cost can be saved for the leakage protection switch and the complete set of cabinets;
in addition, because a zero sequence current transformer is not adopted, the internal bus of the leakage protection switch does not need to pass through the zero sequence current transformer, the structural design of bending, insulation and the like of the internal bus is avoided, the product design complexity is reduced, the structural reliability is improved, meanwhile, the use of a bending piece and an insulating piece is reduced, and the product cost is reduced.
Meanwhile, the microprocessor of the circuit can finish the measurement of current, voltage, active power and apparent power of each phase loop, and can also transmit electric signals in a wired or wireless mode.
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 drawings without creative efforts.
Fig. 1 is a schematic diagram of a first embodiment of a residual current measuring circuit according to the present invention.
Fig. 2 is a schematic diagram of a second embodiment of the residual current measuring circuit of the present invention.
Fig. 3 is a schematic diagram of a third embodiment of the residual current measuring circuit of the present invention.
Detailed Description
Features and exemplary embodiments of various aspects of the present invention will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is in no way limited to any specific configuration set forth below, but rather covers any modification, replacement or improvement of elements, components without departing from the spirit of the invention.
Example one
As shown in fig. 1, the present embodiment discloses a residual current measuring circuit, which includes: current transformer 100, processing circuit 200, first microprocessor 300 and second microprocessor 400.
The number of the current transformers 100 is a plurality, the current transformers 100 are respectively sleeved on the phase pole main loop and the N pole main loop conductor, in this embodiment, A, B, C and the N pole main loop conductor are respectively sleeved with one current transformer 100, and the current transformers 100 adopt a material with high initial permeability as a magnetic core to measure circuit information on the corresponding main loop conductor and output current signals. It should be noted that the output current signal of the current transformer 100 within the rated range and the main circuit current are in a linear relationship and in phase, and have a milliamp resolution, and the output current signal outside the rated range and the main circuit current are in a duty ratio relationship, and the output signal is transmitted to the signal processing circuit 200.
The signal processing circuit 200 is composed of electronic devices, conditions the output current analog signal of the current transformer 100 in a differential manner, performs linear step-down sampling on the loop voltage in an isolated or non-isolated manner, and transmits the output signal to the first microprocessor 300. The signal processing circuit 200 is at least one group.
The first microprocessor 300 has at least 7 ADC circuits with 16 bits or more, and can calculate and output a current effective value, a voltage effective value, current ADC data, voltage ADC data, power factor, frequency, etc. of a loop, and output signals thereof to the second microprocessor 400.
The second microprocessor 400 communicates the calculated result of the first microprocessor 300 with the external communication transmission and/or local display of the data of current effective value, voltage effective value, power factor, frequency, etc. in the loop.
The second microprocessor 400 performs harmonic sum vector calculation on the current ADC data and the voltage ADC data output from the first microprocessor 300, and adjusts or calibrates the vector sum to calculate a residual current value according to the magnitude of the harmonic value. Further, the second microprocessor 400 compares the calculated residual current value with a set threshold value, and is used for performing residual current pre-alarming and/or residual current protection.
In addition, the second microprocessor 400 can perform coefficient calibration on the current measurement deviation of the current transformer 100, modify the measurement deviation of the current transformer 100 caused by temperature rise, correct and/or compensate the inherent null shift of the circuit, and output a duty ratio signal according to the rated amount of the current transformer 100 for current overload detection and protection.
The circuit can realize the measurement, calculation and display, transmission, residual current pre-alarm and/or protection and current overload detection and protection of the residual current, current effective value, voltage effective value, power factor and frequency of the loop.
Example two
As shown in fig. 2, another form of residual current measurement circuit is disclosed, the circuit comprising: current transformer 100), processing circuit (200), first microprocessor 300), third microprocessor 500 and fourth microprocessor 600.
As in the first embodiment, the output current signal of the current transformer 100 in the rated range and the main circuit current are in a linear relationship and in the same phase, and have a resolution in milliamp level, and the output current signal outside the rated range and the main circuit current are in a duty ratio relationship, and the output signal is transmitted to the signal processing circuit 200.
The signal processing circuit 200 conditions the current analog signal output by the current transformer 100 in a differential manner, performs linear step-down sampling on the loop voltage in an isolated or non-isolated manner, and transmits the output signal to the first microprocessor 300.
The first microprocessor 300 includes at least 7 ADCs with 16 bits or more, and calculates and outputs a current effective value, a voltage effective value, current ADC data, voltage ADC data, power factor, frequency, and the like of a loop, and outputs signals to the third microprocessor 500 and the fourth microprocessor 600, respectively.
The fourth microprocessor 600 performs harmonic and vector summation calculation on the current ADC data and the voltage ADC data output by the first microprocessor 300, and adjusts or calibrates the vector and the calculated residual current value according to the magnitude of the harmonic value, thereby implementing residual current pre-alarm and/or protection and current overload detection and protection.
The third microprocessor 500 performs local display and/or external communication on the effective value of the current, the effective value of the voltage, the power factor, the frequency output by the first microprocessor 300 and the residual current value output by the fourth microprocessor 600.
In the first embodiment, the third microprocessor 500 and the fourth microprocessor 600 replace the second microprocessor 400.
The circuit can realize the measurement, calculation and display, transmission, residual current pre-alarm and/or protection and overload current three-section protection of residual current, current effective value, voltage effective value, power factor and frequency of the loop. And the second example adopts two microprocessors to complete the task of the first example, so the processing speed is higher.
Example three:
as shown in fig. 3, a third embodiment of a residual current measuring circuit is disclosed, the circuit comprising: current transformer 100, signal processing circuit 200, first microprocessor 300 and second microprocessor 400.
The current transformer 100 outputs a current signal in a linear relationship and in phase with the main loop current within a rated range, and has milliampere resolution. The output current signal is in duty ratio relation with the main circuit current outside the rated range, and the output signal is transmitted to the signal processing circuit 200.
The signal processing circuit 200 conditions the output current analog signal of the current transformer 100 in a differential manner, performs linear step-down sampling on the loop voltage in an isolated or non-isolated manner, and transmits the output signal to the first microprocessor 300.
The first microprocessor 300 has at least 7-way 16-bit or more ADCs, can calculate and output loop current ADC data, and transmits the same to the second microprocessor 400.
The second microprocessor 400 performs harmonic and vector sum calculation on the current ADC data output by the first microprocessor 300, adjusts or calibrates the vector and calculated residual current value according to the magnitude of the harmonic value, and implements local display of residual current and/or external transmission and pre-alarming and protection of residual current.
The signal processing circuit 200 of example one, example three processes only the loop current, the first microprocessor 300 performs ADC conversion only according to the current, the second microprocessor 400 performs harmonic sum vector calculation only according to the current ADC, and adjusts or calibrates the deviation of the vector sum calculated from the residual current value according to the magnitude of the harmonic value.
The third circuit of the embodiment only realizes the measurement and display, pre-alarming and/or protection and current overload detection and protection of the residual current of the loop, and does not have the measurement and display of the loop circuit, so the circuit is simpler and the processing speed is higher.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes may be made to the embodiment of the present invention by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. A residual current measuring circuit at least comprises a current transformer (100) adopting a material with high initial permeability as a magnetic core, at least one group of signal processing circuit (200) consisting of electronic devices, a first microprocessor (300), a second microprocessor (400) or a fourth microprocessor (600), and is characterized in that:
the signal processing circuit (200) conditions an external input voltage signal and a current signal and provides the conditioned signals to the first microprocessor (300);
the first microprocessor (300) has at least 7-channel ADC capability with 16 bits or more, performs analog-to-digital conversion and calculation on the signal conditioned by the signal processing circuit (200), and outputs all or part of digital signals of a current effective value, a voltage effective value, power, a power factor, a frequency, current ADC data, and voltage ADC data to the second microprocessor (400) or the fourth microprocessor (600);
the second microprocessor (400) or the fourth microprocessor (600) performs harmonic sum vector calculation and adjusts or calibrates the vector sum calculated residual current value according to the magnitude of the harmonic value.
2. The residual current measurement circuit according to claim 1, wherein: the current transformer (100) outputs a current signal in a linear relation and the same phase with the current of the main circuit within a rated range, has milliampere resolution capability, and outputs a current signal in a duty ratio relation with the current of the main circuit outside the rated range.
3. The residual current measurement circuit according to claim 1, wherein: the signal processing circuit (200) conditions the analog signal output by the current transformer (100) in a differential mode.
4. The residual current measurement circuit according to claim 1, wherein: the signal processing circuit (200) performs linear step-down sampling on the loop voltage in an isolated or non-isolated manner.
5. The residual current measurement circuit according to claim 1, wherein: and the second microprocessor (400) compares the calculated residual current value with a set threshold value, and performs residual current pre-alarming and/or residual current protection.
6. The residual current measurement circuit according to claim 1, wherein: the second microprocessor (400) displays the effective value of the current, the effective value of the voltage, the power factor, the frequency and other data of the loop locally and/or transmits the data to the outside for communication.
7. The residual current measurement circuit according to claim 1, wherein: the device is characterized by further comprising a third microprocessor (500), wherein the third microprocessor (500) displays data such as current effective values, voltage effective values, power factors and frequencies of the loop locally and/or transmits the data in an external communication mode, and the fourth microprocessor (600) compares the calculated residual current value with a set threshold value to perform residual current pre-alarming and/or residual current protection.
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| CN202010786040.9A CN114062772A (en) | 2020-08-07 | 2020-08-07 | Residual current measuring circuit |
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| CN202010786040.9A CN114062772A (en) | 2020-08-07 | 2020-08-07 | Residual current measuring circuit |
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2020
- 2020-08-07 CN CN202010786040.9A patent/CN114062772A/en active Pending
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