WO2021068836A1 - 一种交直流漏电检测方法 - Google Patents

一种交直流漏电检测方法 Download PDF

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WO2021068836A1
WO2021068836A1 PCT/CN2020/119337 CN2020119337W WO2021068836A1 WO 2021068836 A1 WO2021068836 A1 WO 2021068836A1 CN 2020119337 W CN2020119337 W CN 2020119337W WO 2021068836 A1 WO2021068836 A1 WO 2021068836A1
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detection
leakage
value
current
frequency
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PCT/CN2020/119337
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French (fr)
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刘振
王建华
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青岛鼎信通讯股份有限公司
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Priority to EP20875103.2A priority Critical patent/EP4024056B1/en
Priority to CA3153755A priority patent/CA3153755C/en
Priority to US17/767,459 priority patent/US11828815B2/en
Publication of WO2021068836A1 publication Critical patent/WO2021068836A1/zh

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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/25Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52Testing for short-circuits, leakage current or ground faults
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R15/00Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
    • G01R15/14Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
    • G01R15/18Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R15/00Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
    • G01R15/14Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
    • G01R15/18Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
    • G01R15/183Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0007Frequency selective voltage or current level measuring
    • G01R19/0015Frequency selective voltage or current level measuring separating AC and DC
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16566Circuits 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
    • G01R19/16571Circuits 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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  • the invention belongs to the field of AC and DC leakage detection, and mainly relates to an AC and DC leakage detection method.
  • the residual current includes low-frequency AC, high-frequency AC, DC signals, etc.
  • the AC residual current is extremely harmful to the human body, and 50mA/s will cause ventricular tremor.
  • the current DC applications are widely used, including DC charging piles, inverter motors, etc., household appliances such as certain types of notebooks, microwave ovens, washing machines, etc., the problem of DC residual current detection has also become important.
  • DC leakage protectors are mainly AC type. AC leakage can only detect AC leakage, but cannot detect DC leakage current. At the same time, the AC type leakage protector does not cover the detection of high-frequency leakage current, so the existing leakage protector There are deficiencies in security protection.
  • the purpose of the present invention is to provide an AC and DC leakage detection method, which can effectively detect AC and DC leakage current and is suitable for magnetic cores of any material.
  • the H-bridge drive module is used to excite the magnetic core in the present invention.
  • the H-bridge When the H-bridge outputs a positive and negative level, a bidirectional square wave excitation is applied to the magnetic core, so that the magnetic core enters the saturation zone and detects DC and low-frequency AC ; When the output is low, the AC is detected by pure induction. Amplify the sampled signal and convert it into a digital signal through AD. In terms of signal processing, the processing of the sampled signal is divided into a DC detection channel, a low-frequency current detection channel, and a high-frequency current detection channel.
  • Step 1 Use a square wave for synchronization to distinguish between the response signal when the core is excited in the positive direction and the response signal when the core is excited in the negative direction;
  • Step 2 Extract the valid data in the detection signal corresponding to the rising edge and the falling edge of the square wave respectively;
  • Step 3 Find the average value of the valid data on the rising and falling edges
  • Step 4 Demodulate the difference between the average value of the effective data on the rising edge and the falling edge
  • Step 5 Compare the demodulation value yi with the threshold value and count the comparison result
  • Step 6 Add a window to process the demodulation sequence in the window
  • Step 7 Calculate the DC value corresponding to the demodulation sequence in the window
  • Step 8 Calculate the 50HZ AC value corresponding to the demodulation sequence in the window
  • Step 9 Correct the estimated 50HZ AC and DC current values.
  • Step 1 The AD sampling signal is filtered through a low-pass filter
  • Step 2 Down-sampling the AD sampling signal
  • Step 3 Compare the sampled signal voltage with the threshold Thr1 set by the software and count. When the count exceeds a certain value for a continuous period of time, the hardware generates an interrupt signal to the CPU.
  • Step 4 Add a window to the down-sampled data, and analyze the data sequence in the window;
  • Step 5 Perform FFT on the data sequence in the window
  • Step 6 Correct the amplitude of each frequency point obtained after FFT to obtain the true leakage current of each frequency point.
  • Step 1 Pass the AD sampling signal through a band pass filter
  • Step 2 Add a window to the sampled data to multiplex the low-frequency detection channel FFT, and ensure that the number of points after the windowing is consistent with that of the low-frequency signal;
  • Step 3 Perform FFT on the data sequence in the window, and take the FFT channel with a frequency of 20.5 ⁇ 150KHZ for subsequent processing.
  • the method disclosed in the present invention supports the detection of DC leakage and AC leakage.
  • the DC leakage and low-frequency leakage current are measured by magnetic modulation technology, and the AC signal is measured by pure induction.
  • the two detection modes are time-sharing.
  • the collected leakage signal is converted into a digital signal through an AD converter.
  • the method of the present invention divides the processing of the leakage signal into three channels to process DC leakage, low-frequency AC leakage and high-frequency AC leakage respectively. Integrate the results of DC detection and AC detection to calculate the overall effective value of residual current.
  • the method in the present invention supports the detection of a sudden increase of current, and when a sudden increase of current occurs, the detection mode is switched by detecting the sudden increase of the current current.
  • Figure 1 is a block diagram of the AC and DC leakage detection algorithm proposed in the present invention.
  • Fig. 2 is a scheme of the H-bridge driving circuit for AC/DC detection in the present invention.
  • Fig. 3 is a schematic diagram of synchronization using an excitation square wave in the present invention.
  • Fig. 4 is a signal difference diagram with or without DC leakage in the present invention.
  • Fig. 5 is a schematic diagram of extracting effective data of rising and falling edges in the DC detection channel of the present invention.
  • Fig. 6 is a diagram of the relationship between the estimated DC leakage value and the true DC leakage value in the present invention.
  • the coil N1 represents the coil winding that is multiplexed for excitation and detection
  • N2 represents the winding of the leakage current
  • the current signal is collected on the resistance Rs.
  • DC detection a bidirectional square wave excitation is applied to the magnetic core through the H bridge, and the magnetic core enters the saturation zone in both directions to measure DC and low-frequency AC.
  • the H bridge When in the AC detection mode, the H bridge outputs low level, and the AC leakage signal is measured by pure induction at this time.
  • the signal collected on the sampling resistor Rs is amplified, and then the sampled signal is converted into a digital signal through AD, and the overall residual current value is obtained by processing the results of DC detection and AC detection.
  • the signal change detected on the sampling resistor is shown in Figure 3.
  • the dotted line represents the signal waveform of a 100mA DC leakage
  • the solid line represents the waveform of a non-leakage signal. It can be seen that the signal has gone up and down during the leakage. ⁇ Offset.
  • the AC signal can be seen as a splicing of DC signals of different time segments.
  • the process of the processing method of the DC leakage detection channel proposed by the present invention is as follows:
  • Step 1 Use excitation square wave for signal synchronization. As shown in Fig. 4, the rising and falling edge moments of the excitation square wave are used to distinguish the response signal when the magnetic core is excited in the positive direction and the response signal when the magnetic core is excited in the negative direction.
  • the horizontal axis represents the data number after AD sampling, and the vertical axis represents the voltage value on the resistor R.
  • Step 2 As shown in Figure 5, extract the effective data in the detection signal corresponding to the rising and falling edges of the square wave.
  • the flat area that changes slowly is the effective data area.
  • the horizontal axis in the figure represents the data after AD sampling.
  • the serial number, the vertical axis represents the voltage amplitude.
  • Step 3 Calculate the average value of the valid data on the rising and falling edges.
  • each excitation square wave cycle outputs two average values, which are the average value of the effective data at the rising edge. And the average value of the valid data on the falling edge
  • Step 4 Demodulate, the average value of the rising edge and the falling edge is the difference:
  • Step 5 Compare and count the demodulated value with the threshold, compare y i with the threshold set in advance,
  • Step 5 Add a window to the output sequence y:
  • the above-mentioned demodulation point is the current value corresponding to each square wave period, and the demodulated sequence is windowed. Assuming that the window time length is Ts and the square wave frequency is f, the amount of data in the 20ms window is
  • Step 6 Estimate the DC value in the window:
  • the DC quantity is obtained by averaging the demodulation sequence in the window.
  • Step 7 Calculate the AC value of 50HZ in DC detection mode:
  • the DC detection In order to deal with the sudden increase in current, the DC detection only calculates the amplitude for the 50HZ frequency point, and then corrects the preliminary estimate.
  • Step 8 Correction of AC and DC estimates:
  • Figure 6 shows the estimated There is a linear relationship with the real current value, so the real DC leakage current value can be obtained by linear correction.
  • Step 1 The AD sampled signal first passes through a low-pass filter to filter out the high frequency part, and at the same time serves as an anti-aliasing filter for downsampling;
  • Step 2 In this embodiment, the AD sampling rate is 1Msps, and the AD sampling signal is down-sampled;
  • Step 3 For the situation of sudden increase of DC or sudden increase of AC in the current AC detection mode, compare the sampled signal voltage with the threshold Thr1 set by the software, and count when the threshold is exceeded, and when it continues for a period of time After the time count exceeds a certain value, the hardware generates an interrupt signal to the CPU, and the software controls the switching of the detection mode or directly performs the tripping action.
  • Step 4 Add window, add 20ms window, you can choose Hamming window, Hanning window or rectangular window, etc.;
  • Step 5 Perform FFT analysis on the data in the window, take the absolute value of the FFT results of each channel, and then divide the extracted absolute value of each channel by N, where N is the number of FFT points to obtain the amplitude of the leakage signal at each frequency point value.
  • Step 6 Correct the 50HZ signal, and then calibrate it as a whole to obtain the signal amplitude of each frequency point.
  • Step 1 The sampled signal first passes through the band pass filter
  • Step 2 Add windows.
  • the window length is 2ms to ensure that the number of data points in the window is consistent.
  • Step 3 Perform FFT analysis on the data in the window, and take the absolute value of the FFT result to obtain the leakage signal amplitude information at each frequency point;
  • N is the number of data points in the window, k ⁇ 0,1,2,...,N-1 ⁇ .

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

一种交直流漏电检测方法,支持直流漏电和交流漏电的检测。通过磁调制的技术测量直流漏电和低频漏电电流,通过纯感应的形式测量交流信号,两种检测模式分时进行。通过AD转换器将采集的漏电信号转换为数字信号,本发明中的方法将漏电信号的处理分成三个通道,分别处理直流漏电、低频交流漏电以及高频交流漏电。综合直流检测以及交流检测的结果,计算整体的剩余电流有效值。本发明中的方法支持突加大电流的检测,当出现突加大电流时,通过检测当前电流的突变进行检测模式的切换。

Description

一种交直流漏电检测方法
本申请要求于2019年10月9日提交中国专利局、申请号为201910954739.9、发明名称为“一种适于交直流漏电检测的复杂波形信号处理方法”的中国专利申请的优先权,其全部内容通过引用结合在本申请中。
技术领域
本发明属于交直流漏电检测领域,主要涉及一种交直流漏电检测方法。
背景技术
随着经济发展,电力行业发展迅速,各类家用电器的规模也日渐丰富,保证住户的用电安全变的尤为重要。在目前的用电环境中,剩余电流包括低频交流、高频交流、直流信号等,其中交流剩余电流对人身危害极大,50mA/s即产生心室颤抖。随着用电类型的增多,目前的直流电应用广泛,包括直流充电桩、变频电机等,家用的如某些类型的笔记本、微波炉、洗衣机等,直流剩余电流检测的问题同样变的重要。造成直流漏电的原因有很多,比如二次回路绝缘材料不合格,或年久失修、严重老化,设备损伤缺陷,二次回路及设备受潮、进水等原因。目前国内的漏电保护器主要为AC型,AC型漏电只能检测交流漏电,不能检测出直流漏电电流,同时AC型漏电保护器并未覆盖高频漏电电流的检测,因此现有的漏电保护器存在着安全保护上的不足。
发明内容
本发明的目的在于提供一种交直流漏电检测方法,能够有效检测交直流漏电电流,并且适用于任何材质的磁芯。
为达到上述目的,在本发明中采用H桥驱动模块对磁芯进行激励,当H桥输出正负电平时为磁芯施加双向的方波激励,使得磁芯进入饱和区,检测直流和低频交流;当输出低电平时,采用纯感应的方式检测交流。对采样信号进行放大,通过AD转换为数字信号。在信号处理上,将所述采样信号的处理分为直流检测通道、低频电流检测通道以及高频电流检测通 道。
(一)当处于直流检测模式时:
步骤1:采用方波进行同步,用于区分磁芯正向激励时的响应信号和负向激励时的响应信号;
步骤2:分别提取方波上升沿和下降沿对应的检测信号中的有效数据;
步骤3:求上升沿和下降沿有效数据的均值;
步骤4:解调,将上升沿与下降沿有效数据均值做差
步骤5:将解调值y i与阈值进行比较对比较结果计数;
步骤6:加窗,对窗口内解调序列进行处理;
步骤7:计算窗口内解调序列对应的直流值;
步骤8:计算窗口内解调序列对应的50HZ的交流值;
步骤9:对估计的50HZ交流电流和直流电流值进行校正。
(二)处于低频交流检测模式时:
步骤1:AD采样信号通过低通滤波器进行滤波;
步骤2:对AD采样信号进行下采样;
步骤3:将采样的信号电压与软件设定的阈值Thr1进行比较并计数,当连续一段时间内的计数超过一定值后,由硬件产生中断信号给CPU。
步骤4:对下采样后的数据进行加窗,分析窗口内的数据序列;
步骤5:对窗口内的数据序列做FFT;
步骤6:对FFT后获得的各个频点的幅值进行校正,获得真实的各个频点的漏电电流。
(三)处于高频检测通道时:
步骤1:将AD采样信号通过带通滤波器;
步骤2:对采样数据加窗,为复用低频检测通道FFT,加窗后保证与低频信号的加窗后的点数一致;
步骤3:对窗口内的数据序列做FFT,取频点为20.5~150KHZ的FFT通道进行后续处理。
本发明公开的方法,支持直流漏电和交流漏电的检测。通过磁调制的技术测量直流漏电和低频漏电电流,通过纯感应的形式测量交流信号,两 种检测模式分时进行。通过AD转换器将采集的漏电信号转换为数字信号,本发明中的方法将漏电信号的处理分成三个通道,分别处理直流漏电、低频交流漏电以及高频交流漏电。综合直流检测以及交流检测的结果,计算整体的剩余电流有效值。本发明中的方法支持突加大电流的检测,当出现突加大电流时,通过检测当前电流的突变进行检测模式的切换。
附图说明
图1是本发明中提出的交直流漏电检测算法框图。
图2是本发明中的交直流检测H桥驱动电路方案。
图3是本发明中采用激励方波进行同步的示意图。
图4是本发明中有无直流漏电时的信号差异图。
图5是本发明中直流检测通道中分别提取上升沿和下降沿有效数据的示意图。
图6是本发明中估计的直流漏电值与真实的直流漏电值之间的关系图。
具体实施方式
下面结合图2的H桥驱动检测电路方案和图1的交直流检测算法框图对本发明所提出的交直流漏电检测方案和信号处理方法进行说明。
如图2中所示,其中线圈N1表示激励和检测复用的线圈绕组,N2表示漏电电流的绕组,在电阻Rs上采集电流信号。在直流检测时,通过H桥对磁芯施加双向的方波激励,通过磁芯双向进入饱和区来测量直流和低频交流。当在交流检测模式时,H桥输出低电平,此时通过纯感应的形式测量交流漏电信号。将采样电阻Rs上采集到的信号进行放大,然后通过AD将采样信号转为数字信号,通过处理直流检测和交流检测的结果,得到整体的剩余电流值。
当发生直流漏电时,采样电阻上检测到的信号变化如图3所示,其中虚线表示发生100mA直流漏电的信号波形,实线表示的是无漏电信号的波形,可见,漏电时信号发生了上下的偏移。当检测低频漏电电流时,交流 信号可以看作由不同时间片段的直流信号拼接而成。
根据上述现象和原理,本发明提出的直流漏电检测通道的处理方法流程如下:
步骤1:使用激励方波进行信号同步。如图4中所示,利用激励方波的上升沿和下降沿时刻,用于区分磁芯正向激励时的响应信号和负向激励时的响应信号。横轴表示AD采样后的数据序号,纵轴表示电阻R上的电压值。
步骤2:如图5中所示,分别提取方波上升沿和下降沿对应的检测信号中的有效数据,其中变化缓慢的平坦区域为有效数据区域,其中图中横轴表示AD采样后数据的序号,纵轴表示电压幅值。
步骤3:求上升沿和下降沿有效数据的均值。
假设上一步中提取的上升沿对应的有效序列为
Figure PCTCN2020119337-appb-000001
下降沿提取出来的对应的有效序列为
Figure PCTCN2020119337-appb-000002
对上升沿和下降沿提取的有效序列分别求均值,有
Figure PCTCN2020119337-appb-000003
经过上述操作,每一个激励方波周期输出两个均值,分别为上升沿有效数据均值
Figure PCTCN2020119337-appb-000004
和下降沿有效数据均值
Figure PCTCN2020119337-appb-000005
步骤4:解调,上升沿和下降沿的均值做差:
Figure PCTCN2020119337-appb-000006
其中
Figure PCTCN2020119337-appb-000007
Figure PCTCN2020119337-appb-000008
为步骤3中输出的上升沿有效数据均值和下降沿有效数据均值;
步骤5:将解调值与阈值比较并计数,将y i与提前设定的阈值进行比较,
当y i连续超过阈值一定数量后,认为产生突加大电流,直接从当前位置开始加窗,然后对窗口内数据进行分析或者直接脱扣动作。
步骤5:对输出序列y加窗:
上述的解调点为每一个方波周期对应的电流值,对解调出来的序列进行加窗,假设窗口时间长度为Ts,假设方波频率为f,则20ms的窗口内的数据数量为
Figure PCTCN2020119337-appb-000009
步骤6:估算窗口内的直流值:
假设窗口内的解调点的序列为y=[y 0,y 1,...,y L-1],L为窗口内的数据长度。通过对窗口内的解调序列求均值得到直流量。
Figure PCTCN2020119337-appb-000010
当检测绕组线圈匝数为N1且采样电阻值为R时,直流电流初始估计值
Figure PCTCN2020119337-appb-000011
步骤7:计算直流检测模式时的50HZ的交流值:
为了应对突加大电流的情况,直流检测中只针对50HZ频点计算幅值,然后对初步估计进行校正。
Figure PCTCN2020119337-appb-000012
步骤8:交直流估计值校正:
对前两步的交直流估计值进行线性校正以获得真实的直流漏电电流和50HZ漏电电流。图6中所示为估计的
Figure PCTCN2020119337-appb-000013
与真实电流值之间为线性关系,因此可以通过线性校正的方式得到真实的直流漏电的电流值。
(二)当切换到低频交流通道检测时,该通道的处理流程如下:
步骤1:AD采样的信号首先经过低通滤波器,滤除高频部分,同时作为下采样的抗混叠滤波;
步骤2:在该实施例中,采用AD采样速率为1Msps,对AD采样信号进行下采样;
步骤3:针对当前处于交流检测模式时,出现突加大直流或突加大交 流的情况,将采样的信号电压与软件设定的阈值Thr1进行比较,当超过该阈值时进行计数,当连续一段时间内的计数超过一定值后,由硬件产生中断信号给CPU,由软件控制检测模式的切换或直接进行脱扣动作。
步骤4:加窗,添加20ms的窗,可以选用汉明窗、汉宁窗或者矩形窗等;
步骤5:对窗口内的数据做FFT分析,对FFT各通道的结果取绝对值,然后将提取的各个通道绝对值除以N,其中N为FFT点数,得到各个频点上的漏电信号的幅值。
对所提取的通道而言:
Figure PCTCN2020119337-appb-000014
其中k∈{0,1,2,...,N-1}。
步骤6:对50HZ的信号进行校正,然后整体校正,得到各个频点的信号幅值。
(三)当切换到高频检测通道时,该通道的检测流程如下:
步骤1:采样信号首先通过带通滤波器;
步骤2:加窗。为了复用低频FFT,窗口长度为2ms,保证窗口内的数据点数是一致的。
步骤3:对窗口内的数据做FFT分析,并对FFT结果取绝对值,得到各频点的漏电信号幅度信息;
对所提取的通道而言:
Figure PCTCN2020119337-appb-000015
其中N为窗口内的数据点数,k∈{0,1,2,...,N-1}。
(四)对上述各检测模式计算得到的直流漏电值和交流漏电值进行判断,当各个频点超过一定阈值或总体的有效值超过一定阈值后,即可判断为产生了漏电故障。
以上所述只是本发明的优选实施方式,对于本技术领域的普通技术人员来说,在不脱离本发明原理的前提下,还可以做出若干改进和变化。凡 在本发明的精神和原理之内所作的任何修改、等同替换、改进等,均应包含在本发明的保护范围之内。

Claims (8)

  1. 一种交直流漏电检测方法,其特征在于:在正负方波激励的模式中,磁芯进入到深度饱和区,在此模式下检测直流和低频交流;在纯感应的模式中,检测低频交流和高频交流;
    在交流检测模式中,检测到突然的大电流变化则切换到直流检测模式;在直流检测模式中,检测到突然的大电流变化则在当前时刻进行重新开窗;当超过检测阈值后,则进行脱扣。
  2. 根据权利要求1所述的交直流漏电检测方法,其特征在于:采用激励线圈和检测线圈复用的电路结构,H桥驱动模块输出正向激励、负向激励以及零激励三态电压,当输出正负电平时,给磁芯施加双向激励进入饱和区,测量直流和低频交流;当输出低电平时,处于纯感应的检测模式,检测交流。
  3. 根据权利要求1所述的交直流漏电检测方法,其特征在于:
    分时进行直流检测和交流检测,同时直流检测中还进行低频交流的检测;交流检测模式只对交流漏电和突加直流漏电进行检测。
  4. 根据权利要求1所述的交直流漏电检测方法,其特征在于:通过检测电流的突变控制检测模式的即时切换,当在交流检测模式时,突加大交流或大直流,检测到在一定时间内检测到的电流幅值连续超过阈值一定次数,则切换检测模式;当在直流检测时,当检测到电流幅值连续超过阈值一定次数,在当前时刻进行开窗;以适应突加大电流情况下的快速检测和快速脱扣。
  5. 根据权利要求1所述的交直流漏电检测方法,其特征在于:在直流检测模式中,检测信号的处理包括以下几个步骤:
    步骤1:采用激励方波进行同步,区分采样信号上对应方波上升沿和下降沿对应的有效数据;
    步骤2:分别提取同步对齐后的采样电阻上的上升沿有效数据和下降沿有效数据;
    步骤3:分别求提取的上升沿有效数据序列和下降沿有效数据序列的平均值,
    Figure PCTCN2020119337-appb-100001
    其中,上升沿对应的有效数据序列为
    Figure PCTCN2020119337-appb-100002
    下降沿提取的有效数据序列为
    Figure PCTCN2020119337-appb-100003
    步骤4:解调,通过减去无漏电模板信号的均值差解调;
    Figure PCTCN2020119337-appb-100004
    步骤5:将解调值y i与阈值进行比较对比较结果计数;
    步骤6:当计数值在连续一段时间内计数值超过一定数值,则在当前位置重新开窗;
    步骤7:估算窗口内的直流值,窗口内的解调序列为y=[y 0,y 1,...,y L-1],则估计的直流值为
    Figure PCTCN2020119337-appb-100005
    步骤8:计算直流检测模式时的50HZ的交流值,
    Figure PCTCN2020119337-appb-100006
    步骤9:对估计的直流值和50HZ交流值进行校正。
  6. 根据权利要求1所述的交直流漏电检测方法,其特征在于:在低频交流检测模式中,检测信号的处理包括如下步骤:
    步骤1:AD采样信号通过低通滤波器;
    步骤2:对AD采样信号进行下采样,降低低频信号分析的采样速率;
    步骤3:将采样的信号值与设定的阈值Thr1进行比较,对比较结果进行计数,当计数值超过预定值后,切换到直流检测模式,否则继续在交流模式分析;
    步骤4:当继续在交流模式分析时,对采样数据加窗;
    步骤5:对窗口内数据做FFT,对FFT结果取绝对值并除以N,N为FFT点数;
    步骤6:对各个频点的信号幅值进行校正。
  7. 根据权利要求1所述的交直流漏电检测方法,其特征在于:在高频交流检测模式中,将AD采样信号通过低通滤波器,并加窗,对加窗后的数据进行FFT分析。
  8. 根据权利要求1所述的交直流漏电检测方法,其特征在于:通过综合前面检测出的直流电流值、低频各频点的电流值以及高频各频点的电流值,计算漏电电流的整体电流值;并根据电流值判定是否进行脱扣动作。
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