CN110632375A - Differential residual current detection method - Google Patents
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Abstract
The invention relates to a differential residual current detection method, which comprises the steps of respectively selecting detection points on an output line and an input line of a cable by initializing a cable using environment, carrying out current sampling based on the detection points, carrying out current sampling and preprocessing on 2 detection points at a sampling frequency A from the stabilization of a sampling value, sequentially inputting the sampling values into a conversion module and an amplification module, and triggering residual current alarm when an output value of an output end of the amplification module is greater than 0. The invention mainly aims at single-phase residual current detection, realizes the detection of the residual current by adopting a mode of respectively detecting the current on the output line and the input line of the cable, such as a live wire and a zero line, has high detection precision, can effectively detect the residual current from 0 to a load current section, has convenient arrangement of a detection mechanism, can also be applied to the detection of larger residual current, and has safe use, low cost and high working efficiency.
Description
Technical Field
The invention belongs to the field of measuring electrical variables; the field of measuring magnetic variables, in particular to a differential residual current detection method for devices measuring current or voltage or indicating the presence or sign thereof.
Background
The residual current is the current generated by the non-zero sum of phase current vectors in each low-voltage distribution line, that is, the current flows to the ground from a charged body through a human body when an accident occurs on a power utilization side, so that the current in the incoming and outgoing lines of the main circuit is unequal in magnitude, and the instantaneous vector synthesis effective value of the current is called residual current and commonly called electric leakage.
The residual current is generated by aging and damage of an insulating layer of an electric wire, the installation and construction of a lead are not standard, construction is left to be lack of and close to inflammable matters, and artificial damage causes disconnection and the like, so that the ground insulation of a live conductor is damaged, according to the statistics of fire departments, in national fire accidents, an electric fire occupies about 1/3, in the electric fire accidents, due to the fact that a low-voltage line is in single-phase ground fault, the accidents occupy about 1/2 of the electric fire accidents, and therefore the line single-phase ground fault has the characteristics of severity and universality, and the detection of the residual current is quite important for the prevention and control of the fire.
In the prior art, a link of detecting residual current is utilized to start a protection device to trip, so that electric shock and fire caused by grounding electric arc are prevented, and generally, the residual current transformer is utilized to detect. The residual current transformer is a detecting element of a leakage protector, and is mainly used for detecting residual currents of a main circuit passing through a transformer core, such as earth fault currents of electric shock, leakage and the like, and converting the residual currents of a primary circuit into output voltages of a secondary circuit.
However, in the prior art, the residual current sensor needs to pass the mutual inductance iron core through the live wire and the zero line at the same time in the process of collecting current, and then obtains the residual current value, although the scheme is simple, the in-process of actual deployment is very inconvenient, the threading size is difficult to unify, the installation size is large, and the excessive residual current can cause the mutual inductor damage, cause the loss, and possibly influence the safety of the operator even.
Disclosure of Invention
The invention solves the problems that in the prior art, the residual current transformer is simple to collect current, but is very inconvenient in the actual deployment process, the threading size is difficult to unify, the installation size is large, and the transformer is damaged by overlarge residual current, so that loss is caused, and even the safety of operators is possibly influenced, and provides the optimized differential residual current detection method.
The technical scheme adopted by the invention is that a differential residual current detection method comprises the following steps:
step 1: initializing a cable use environment;
step 2: selecting 1 detection point on an output line and an input line of the cable respectively;
and step 3: adopting a high-speed AD sampling chip to perform current sampling on the 2 detection points until the sampling value is stable;
and 4, step 4: from the stabilization of the sampling value, current sampling is carried out on 2 detection points by using the sampling frequency A to obtain a current I1And I2After pretreatment is I1' and I2’；
And 5: inputting the processed currents of the 2 detection points into a conversion module and an amplification module in sequence;
step 6: and if the output value of the output end of the amplifying module is greater than 0, triggering residual current alarm, otherwise obtaining the next group of preprocessed current, and returning to the step 5.
Preferably, in step 1, initializing a cable use environment includes checking a mechanical damage point, a distortion point, and an insulation layer aging point in the cable, and if the distortion point exists, processing the cable, and if the mechanical damage point and the insulation layer aging point exist, directly giving an alarm.
Preferably, in step 2, the 2 detection points are respectively located on the live wire and the zero wire at the same position of the cable.
Preferably, in step 3, a high-speed AD sampling chip is used to perform current sampling on the 2 detection points, and when the current of each detection point is a stable sine wave, the sampling value is stable.
Preferably, the step 4 comprises the steps of:
step 4.1: from the stabilization of the sampling value, current sampling is carried out on 2 detection points by using the sampling frequency A to obtain a current I1And I2；
Step 4.2: for current I1And I2Carrying out synchronous amplification;
step 4.3: for the current I after synchronous amplification1And I2Filtering through a high-pass filtering module to filter low-frequency noise and power frequency interference;
step 4.4: for current I1And I2Synchronously reducing the sampling value;
step 4.5: using a time delay unit to sample the obtained current I1And I2To obtain processed I1' and I2’。
Preferably, A is 6.4 kHz.
Preferably, in step 5, the processed currents at the 2 detection points are sequentially input to the current-to-voltage module and the differential amplification module, and the adjustment parameter k is set to obtain the amplified voltage output by the current.
Preferably, the current-to-voltage module comprises resistors R arranged in sequence0And triode VT, I1' and I2Respectively inputting corresponding currents into corresponding current-to-voltage modules, and taking corresponding R0And a voltage U between VT1And U2。
Preferably, the differential amplification module comprises an amplifier;
U1through a resistance R1Connected to a first input of the amplifier, the first input and R1Intermediate pass resistance R2Grounding;
U2through a resistance R3Connected to a second input of the amplifier, the second input and3intermediate pass resistance R4Connected in parallel to the output of the amplifier;
the output end of the amplifier is connected with a voltmeter.
Preferably, when the voltage at the output end is greater than 0, a residual current alarm is triggered.
The invention provides an optimized differential residual current detection method, which comprises the steps of respectively selecting detection points on an output line and an input line of a cable by initializing a cable use environment, carrying out current sampling based on the detection points, carrying out current sampling and preprocessing on 2 detection points at a sampling frequency A from the stabilization of a sampling value, sequentially inputting the sampling values into a conversion module and an amplification module, and triggering residual current alarm when the output value of the output end of the amplification module is greater than 0.
The invention mainly aims at single-phase residual current detection, realizes the detection of the residual current by adopting a mode of respectively detecting the current on the output line and the input line of the cable, such as a live wire and a zero line, has high detection precision, can effectively detect the residual current from 0 to a load current section, has convenient arrangement of a detection mechanism, can also be applied to the detection of larger residual current, and has safe use, low cost and high working efficiency.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a schematic diagram of a current-to-voltage module according to the present invention;
fig. 3 is a schematic structural diagram of a differential amplifier module according to the present invention.
Detailed Description
The present invention is described in further detail with reference to the following examples, but the scope of the present invention is not limited thereto.
The invention relates to a differential residual current detection method, which mainly aims at single-phase residual current detection.
The method comprises the following steps.
Step 1: and initializing a cable use environment.
In the step 1, initializing a cable using environment includes checking a mechanical damage point, a distortion point and an insulation layer aging point in the cable, if the distortion point exists, processing, and if the mechanical damage point and the insulation layer aging point exist, directly giving an alarm.
In the present invention, the operator should first eliminate the obvious problems; when the cable has obvious defects, the cable with a twisted point needs to be straightened without adopting the current detection method, and when the cable has the problems of mechanical damage points and insulation layer aging, the cable needs to be directly replaced or maintained.
Step 2: 1 test point is selected on the output line and the input line of the cable, respectively.
In the step 2, the 2 detection points are respectively positioned on a live wire and a zero wire at the same position of the cable.
In the invention, the detection of the residual current is realized by respectively detecting the current of the live wire and the current of the zero line, and the live wire and the zero line are positioned at the same position of the cable in order to ensure the accuracy of a sampling value and eliminate interference factors as much as possible.
And step 3: and adopting a high-speed AD sampling chip to perform current sampling on the 2 detection points until the sampling value is stable.
In the step 3, a high-speed AD sampling chip is adopted to carry out current sampling on the 2 detection points, and when the current of each detection point is stable sine waves, the sampling value is stable.
In the invention, abnormal fluctuation may exist in the process of initially passing current, and the current sampling value at the moment is useless.
In the present invention, a stable sine wave means that there are uniform peaks and valleys.
And 4, step 4: from the stabilization of the sampling value, current sampling is carried out on 2 detection points by using the sampling frequency A to obtain a current I1And I2After pretreatment is I1' and I2’。
The step 4 comprises the following steps:
step 4.1: from the stabilization of the sampling value, current sampling is carried out on 2 detection points by using the sampling frequency A to obtain a current I1And I2；
A is 6.4 kHz.
Step 4.2: for current I1And I2Carrying out synchronous amplification;
step 4.3: for the current I after synchronous amplification1And I2Filtering through a high-pass filtering module to filter low-frequency noise and power frequency interference;
step 4.4: for current I1And I2Synchronously reducing the sampling value;
step 4.5: using a time delay unit to sample the obtained current I1And I2To obtain processed I1' and I2’。
In the invention, since the detection points are only arranged at the same position as much as possible, certain errors and noise may exist between the sampling values of the current, generally speaking, the errors are very small, so that the sampled current needs to be amplified first, and the amplified current is filtered, thereby ensuring that the data instability caused by rough surface, background interferents and the like is removed.
In the invention, the filtering is median filtering in general, the median filtering is a nonlinear signal processing technology which is based on the ordering statistical theory and can effectively inhibit noise, the basic principle is that the value of one point in a digital image or a digital sequence is replaced by the median of each point value in a neighborhood of the point, and the surrounding pixel values are close to the true values, thereby eliminating isolated noise points.
In the invention, the processed current is synchronously reduced to the initial sampling state, and then the two current waves are aligned to ensure that the phase change time is corresponding to the time of 0.
And 5: and sequentially inputting the processed currents of the 2 detection points into the conversion module and the amplification module.
In the step 5, the processed currents of the 2 detection points are sequentially input into the current-to-voltage conversion module and the differential amplification module, and an adjustment parameter k is set to obtain the amplified voltage output by the currents.
The current-to-voltage conversion module comprises resistors R arranged in sequence0And triode VT, I1' and I2Respectively inputting corresponding currents into corresponding current-to-voltage modules, and taking corresponding R0And a voltage U between VT1And U2。
The differential amplification module comprises an amplifier;
U1through a resistance R1Connected to a first input of an amplifier, firstInput terminal and R1Intermediate pass resistance R2Grounding;
U2through a resistance R3Connected to a second input of the amplifier, the second input and3intermediate pass resistance R4Connected in parallel to the output of the amplifier;
the output end of the amplifier is connected with a voltmeter A.
In the invention, inaccuracy may exist when the current difference is made, and the sensor may be damaged when the current difference is too large, so that the current is converted into voltage for processing, and the resistor R can be better selected based on the prejudgment of the residual current0And a triode VT, so that the output voltage meets the actual differential amplification requirement.
In the invention, the detection premise is that the residual current exists, when blind measurement is carried out, a voltage amplifying circuit is added at any input end, conversion is carried out according to the regulation ratio of the voltage amplifying circuit, the output voltage displayed by the voltmeter A is checked, and the existence of the residual current is judged.
In the present invention, R is2With a first input terminal and R1Voltage at the point of connection between is UnWith the second input terminal and the sum R3With a voltage of U betweenpWith output voltage as UoThe simultaneous equations are:
U1R2/（R1+R2）=Un；
（Uo-Up）/R4=（Up-U2）/R3=Up；
to obtain R3Uo=（R3+R4）R2U1/（R1+R4）-R4U2。
In the present invention, R is set when a residual current does exist1=R3，R2=R4The ratio of the output voltage to the residual voltage difference can be simply calculated.
In the present invention, generally, U1And U2Should remain within 15v of each other,if not, an adjustment parameter k should be set so that the difference is reduced.
Step 6: and if the output value of the output end of the amplifying module is greater than 0, triggering residual current alarm, otherwise obtaining the next group of preprocessed current, and returning to the step 5.
And when the voltage of the output end is greater than 0, triggering residual current alarm.
In the invention, the current of the live wire is equal to the current of the zero line under normal conditions, when the equipment leaks electricity, a part of current flows away through the ground wire, the current of the live wire is equal to the sum of the current of the zero line and the current of the ground wire, the measured result of the voltage value is a number which is more than 0 and is not positive infinity, and therefore, the residual current alarm is required.
When the residual current exceeds the protection threshold value of the leakage protector, the leakage breaker can be immediately tripped and cut off the power supply.
In the invention, when the output value is 0, the circuit is a normal circuit, and the next group of data can be processed.
The method comprises the steps of initializing a cable using environment, respectively selecting detection points on an output line and an input line of the cable, carrying out current sampling based on the detection points, carrying out current sampling and preprocessing on 2 detection points at a sampling frequency A from the stabilization of a sampling value, sequentially inputting the detection points into a conversion module and an amplification module, and triggering residual current alarm when an output value of an output end of the amplification module is greater than 0.
The invention mainly aims at single-phase residual current detection, realizes the detection of the residual current by adopting a mode of respectively detecting the current on the output line and the input line of the cable, such as a live wire and a zero line, has high detection precision, can effectively detect the residual current from 0 to a load current section, has convenient arrangement of a detection mechanism, can also be applied to the detection of larger residual current, and has safe use, low cost and high working efficiency.
Claims (10)
1. A differential residual current detection method is characterized in that: the method comprises the following steps:
step 1: initializing a cable use environment;
step 2: selecting 1 detection point on an output line and an input line of the cable respectively;
and step 3: adopting a high-speed AD sampling chip to perform current sampling on the 2 detection points until the sampling value is stable;
and 4, step 4: from the stabilization of the sampling value, current sampling is carried out on 2 detection points by using the sampling frequency A to obtain a current I1And I2After pretreatment is I1' and I2’；
And 5: inputting the processed currents of the 2 detection points into a conversion module and an amplification module in sequence;
step 6: and if the output value of the output end of the amplifying module is greater than 0, triggering residual current alarm, otherwise obtaining the next group of preprocessed current, and returning to the step 5.
2. The differential residual current detection method according to claim 1, wherein: in the step 1, initializing a cable using environment includes checking a mechanical damage point, a distortion point and an insulation layer aging point in the cable, if the distortion point exists, processing, and if the mechanical damage point and the insulation layer aging point exist, directly giving an alarm.
3. The differential residual current detection method according to claim 1, wherein: in the step 2, the 2 detection points are respectively positioned on a live wire and a zero wire at the same position of the cable.
4. The differential residual current detection method according to claim 3, wherein: in the step 3, a high-speed AD sampling chip is adopted to carry out current sampling on the 2 detection points, and when the current of each detection point is stable sine waves, the sampling value is stable.
5. The differential residual current detection method according to claim 1, wherein: the step 4 comprises the following steps:
step 4.1: from the stabilization of the sampling value, current sampling is carried out on 2 detection points by using the sampling frequency A to obtain a current I1And I2；
Step 4.2: for current I1And I2Carrying out synchronous amplification;
step 4.3: for the current I after synchronous amplification1And I2Filtering through a high-pass filtering module to filter low-frequency noise and power frequency interference;
step 4.4: for current I1And I2Synchronously reducing the sampling value;
step 4.5: using a time delay unit to sample the obtained current I1And I2To obtain processed I1' and I2’。
6. The differential residual current detection method according to claim 5, wherein: a is 6.4 kHz.
7. The differential residual current detection method according to claim 1, wherein: in the step 5, the processed currents of the 2 detection points are sequentially input into the current-to-voltage conversion module and the differential amplification module, and an adjustment parameter k is set to obtain the amplified voltage output by the currents.
8. The differential residual current detection method according to claim 7, wherein: the current-to-voltage conversion module comprises resistors R arranged in sequence0And triode VT, I1' and I2Respectively inputting corresponding currents into corresponding current-to-voltage modules, and taking corresponding R0And a voltage U between VT1And U2。
9. The differential residual current detection method according to claim 8, wherein: the differential amplification module comprises an amplifier;
U1through a resistance R1Connected to a first input of the amplifier, a first outputInput terminal and R1Intermediate pass resistance R2Grounding;
U2through a resistance R3Connected to a second input of the amplifier, the second input and3intermediate pass resistance R4Connected in parallel to the output of the amplifier;
the output end of the amplifier is connected with a voltmeter.
10. The differential residual current detection method according to claim 7, wherein: and when the voltage of the output end is greater than 0, triggering residual current alarm.
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Cited By (4)
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| CN113030559A (en) * | 2021-05-21 | 2021-06-25 | 杭州并坚科技有限公司 | Method for detecting residual current of detector |
| CN114487578A (en) * | 2021-12-31 | 2022-05-13 | 杭州拓深科技有限公司 | Novel residual current detection method |
| CN114498552A (en) * | 2022-03-01 | 2022-05-13 | 国网山东省电力公司青岛供电公司 | Residual current-based low-voltage power distribution network leakage protection method |
| CN119574963A (en) * | 2025-01-25 | 2025-03-07 | 南京瑞泓晟电力科技有限公司 | Current detection device and method |
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Application publication date: 20191231 |