阅读说明：本技术 一种差分式剩余电流检测方法 (Differential residual current detection method ) 是由 梁昆 王观亮 张轩铭 王利强 钱伟 于 2019-09-14 设计创作，主要内容包括：本发明涉及一种差分式剩余电流检测方法,通过初始化电缆使用环境,分别在电缆的输出线路和输入线路上选择检测点,基于检测点进行电流采样,自采样值稳定起,以采样频率A对2个检测点进行电流采样、预处理并顺次输入转换模块和放大模块,当放大模块的输出端的输出值大于0时,则触发剩余电流报警。本发明主要针对单相剩余电流检测,采用对电缆的输出线路和输入线路,如火线和零线上的电流分别检测的方式实现剩余电流的检测,检测精度高,能有效检测从0到负载电流区间段的剩余电流大小,检测机构部署便利,亦可以应用于较大剩余电流的检测,使用安全,成本低,工作效率高。(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.)

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.

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.

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 U_nWith the second input terminal and the sum R₃With a voltage of U between_pWith output voltage as U_oThe simultaneous equations are:

U₁R₂/（R₁+R₂）=U_n；

（U_o-U_p）/R₄=（U_p-U₂）/R₃=U_p；

to obtain R₃U_o=（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.