CN104808069A - Relative comparison method in combination with correlation analysis filtering performance - Google Patents

Relative comparison method in combination with correlation analysis filtering performance Download PDF

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CN104808069A
CN104808069A CN201510161603.4A CN201510161603A CN104808069A CN 104808069 A CN104808069 A CN 104808069A CN 201510161603 A CN201510161603 A CN 201510161603A CN 104808069 A CN104808069 A CN 104808069A
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卢毅
袁飞
杨震男
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Southeast University
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Abstract

本发明公开了一种抗干扰能力强、测量精度高、适用范围广的相对比较法,用于测量容性设备的相对介质损耗(Δtanδ)。在利用相对比较法测量容性设备的Δtanδ之前,首先充分利用相关函数的滤波性,通过将选取的两设备泄漏电流分别与标准基波相关,对泄漏电流先进行滤波处理;然后再利用互相关函数的时延特性,求得设备相对介质损耗,从而使得算法更加精确。本发明具有抗干扰能力强、测量精度高、适用范围广的特点,具有一定的实际应用价值。

The invention discloses a relative comparison method with strong anti-interference ability, high measurement precision and wide application range, which is used for measuring the relative dielectric loss (Δtanδ) of capacitive equipment. Before using the relative comparison method to measure the Δtanδ of the capacitive equipment, firstly make full use of the filtering property of the correlation function, and filter the leakage current by correlating the leakage current of the two selected equipment with the standard fundamental wave respectively; then use the cross-correlation The delay characteristic of the function is used to obtain the relative dielectric loss of the equipment, so that the algorithm is more accurate. The invention has the characteristics of strong anti-interference ability, high measurement precision and wide application range, and has certain practical application value.

Description

一种结合相关分析滤波性的相对比较法A Relative Comparison Method Combined with Correlation Analysis and Filtering

技术领域 technical field

本发明是一种应用于高压容性设备介质损耗在线监测的测量算法,属于高压容性设备在线监测技术领域。 The invention relates to a measurement algorithm applied to on-line monitoring of dielectric loss of high-voltage capacitive equipment, and belongs to the technical field of on-line monitoring of high-voltage capacitive equipment.

背景技术 Background technique

容性设备(电流互感器、耦合电容器、电容式电压互感器和高压套管等)在电力系统设备构成中占相当大的比重,这些设备的安全可靠是实现整个电力系统运行的基础。电气设备(尤其是高压设备)损坏事故中很大一部分是绝缘损坏引起的,而通过测量介质损耗(tanδ,以下简称介损)或相对介损可以发现电力设备绝缘系统处于早期发展阶段的整体性缺陷或较大的集中性局部缺陷。因此,高压容性设备tanδ的测量对于变电站乃至整个电力系统的安全、经济运行都具有极其重要的意义。 Capacitive devices (current transformers, coupling capacitors, capacitive voltage transformers and high-voltage bushings, etc.) account for a considerable proportion of power system equipment, and the safety and reliability of these devices is the basis for the operation of the entire power system. A large part of electrical equipment (especially high-voltage equipment) damage accidents is caused by insulation damage, and by measuring dielectric loss (tanδ, hereinafter referred to as dielectric loss) or relative dielectric loss, it can be found that the integrity of the electrical equipment insulation system is in the early development stage Defects or large concentrated local defects. Therefore, the measurement of tanδ of high-voltage capacitive equipment is of great significance to the safe and economical operation of substations and even the entire power system.

目前介损的测量主要有过零比较法、谐波分析法和相对比较法等。过零比较法的基本原理是:让电压和电流信号经过相同的两路信号预处理电路,然后进入过零比较器将交流信号过零整形为方波信号,通过比较这两个方波信号的上升沿或下降沿之间的时间差来求出两个信号的相位差,从而求得介损。谐波分析法的原理是:利用电压互感器和电流互感器分别获得被测试品的电压与电流信号,然后利用离散傅里叶变换(DFT)对电压电流信号进行谐波分解,得到基波电流、电压信号之间的相位差,进而求出被测试品的介损。相对比较法的原理是:选取两支容性设备泄漏电流值,其中一组设定为参考标准,进行相对比较求得相对介损,从而进行故障诊断。 At present, the measurement of dielectric loss mainly includes zero-crossing comparison method, harmonic analysis method and relative comparison method. The basic principle of the zero-crossing comparison method is: Let the voltage and current signals pass through the same two-way signal preprocessing circuit, and then enter the zero-crossing comparator to shape the AC signal zero-crossing into a square wave signal. By comparing the two square wave signals The time difference between the rising edge or the falling edge is used to find the phase difference of the two signals, so as to find the dielectric loss. The principle of the harmonic analysis method is: use the voltage transformer and current transformer to obtain the voltage and current signals of the tested product respectively, and then use the discrete Fourier transform (DFT) to perform harmonic decomposition on the voltage and current signals to obtain the fundamental current , The phase difference between the voltage signals, and then find the dielectric loss of the tested product. The principle of the relative comparison method is: select the leakage current values of two capacitive devices, one of which is set as the reference standard, and perform relative comparison to obtain the relative dielectric loss, so as to diagnose the fault.

相对比较法的优点是:一、考虑到同相同电压等级设备相互之间运行工况、电压基准、环境影响的相似性,这些设备的介损测量数据应该有同时变化的迹象。如果设备绝缘状况良好,则两测试结果应基本相同;如果测试数据间有明显差异,则其中某台设备的绝缘状况可能出现异常。因此用它们的介损相对值的变化作为故障诊断的依据,稳定性会比较好,可使故障诊断的灵敏度大大提高。二,可在一定程度上抵消温湿度变化、相间干扰及电压互感器(PT)角 差等因素的影响,由此判断绝缘状态将更加精确。因此,相对比较法具有较好的应用前景。 The advantages of the relative comparison method are: 1. Considering the similarity of operating conditions, voltage references, and environmental influences between equipment with the same voltage level, the dielectric loss measurement data of these equipment should show signs of simultaneous changes. If the equipment insulation is in good condition, the two test results should be basically the same; if there is a significant difference between the test data, the insulation condition of one of the equipment may be abnormal. Therefore, using their relative dielectric loss changes as the basis for fault diagnosis will have better stability and greatly improve the sensitivity of fault diagnosis. Second, it can offset the influence of factors such as temperature and humidity changes, phase-to-phase interference, and potential transformer (PT) angle difference to a certain extent, so that the insulation state will be judged more accurately. Therefore, the relative comparison method has a good application prospect.

传统的相对比较法大多采用相关分析求得相对介损。根据两设备的泄漏电流的相位差,即可求得相对介质损耗,而相位差可通过时间差求得,如图1所示,公式为:Δδ=2πΔT/T。而利用互相关函数的时延特性可求得两泄漏电流的时间差△T,两泄漏电流信号的互相关函数波形图如图2所示,称波形图上的最高峰为相关峰,相关峰值位置与原点的差即是两泄漏电流信号的时间差△T。 Most traditional relative comparison methods use correlation analysis to obtain relative dielectric loss. According to the phase difference of the leakage current of the two devices, the relative dielectric loss can be obtained, and the phase difference can be obtained through the time difference, as shown in Figure 1 , the formula is: Δδ=2πΔT/T. The time difference △T of the two leakage currents can be obtained by using the time delay characteristics of the cross-correlation function. The waveform diagram of the cross-correlation function of the two leakage current signals is shown in Figure 2 . The difference from the origin is the time difference ΔT between the two leakage current signals.

但是,容性设备的介损在正常情况下是一个微小值,所以系统本身干扰(谐波干扰)以及外界干扰(环境干扰)对传统求取相对介损的测量方法会造成很大的影响,故传统的相对比较法在某些情况下(如谐波干扰或环境干扰较大时)将不再精确。因此寻求抗干扰能力强、高精度的相对介损测量方法一直是研究的重点与热点。 However, the dielectric loss of capacitive equipment is a small value under normal conditions, so the system's own interference (harmonic interference) and external interference (environmental interference) will have a great impact on the traditional measurement method for obtaining relative dielectric loss. , so the traditional relative comparison method will no longer be accurate in some cases (such as when harmonic interference or environmental interference is large). Therefore, it has been the focus and hot spot of research to seek a relative dielectric loss measurement method with strong anti-interference ability and high precision.

发明内容 Contents of the invention

本发明的目的是提供一种结合相关分析滤波性的相对比较法,在设备做介损相对比较之前先利用相关分析的滤波性,滤除绝大部分干扰,使相对比较法在测量容性设备的相对介损时具有抗干扰能力强,测量精度高,适用范围广等显著优势。 The purpose of the present invention is to provide a kind of relative comparison method combined with correlation analysis filter property, utilize the filter property of correlation analysis earlier before equipment is done the relative comparison of dielectric loss, filter out most interference, make relative comparison method measure capacitive equipment It has strong anti-interference ability, high measurement accuracy and wide application range.

为实现本发明目的采用的技术方案是:采用一种结合相关分析的滤波算法先进行滤波,然后计算设备的相对介损,进而进行诊断。 The technical solution adopted to realize the object of the present invention is: to use a filtering algorithm combined with correlation analysis to perform filtering first, then calculate the relative dielectric loss of the equipment, and then perform diagnosis.

本发明步骤如下: The steps of the present invention are as follows:

(1)采集选取的两个设备的泄漏电流信号为i1(t)、i2(t),设定标准基波信号为i0(t); (1) Collect the leakage current signals of the two selected devices as i 1 (t) and i 2 (t), and set the standard fundamental wave signal as i 0 (t);

(2)分别使用标准基波信号i0(t)和两泄露电流信号i1(t)、i2(t)进行互相关处理,得到两泄露电流信号i1(t)、i2(t)滤波后的泄漏电流信号i10(t)、i20(t):具体步骤如下: (2) Using the standard fundamental wave signal i 0 (t) and two leakage current signals i 1 (t) and i 2 (t) for cross-correlation processing respectively, two leakage current signals i 1 (t) and i 2 (t ) filtered leakage current signals i 10 (t), i 20 (t): the specific steps are as follows:

(21)分别对标准基波信号为i0(t)、两个泄漏电流信号i1(t)、i2(t)做傅里叶变 换得到频域信号I0(f)、I1(f)和I2(f); (21) Perform Fourier transform on the standard fundamental wave signal i 0 (t) and two leakage current signals i 1 (t) and i 2 (t) to obtain the frequency domain signals I 0 (f), I 1 ( f) and I 2 (f);

(22)根据相关定理,分别得到标准基波频域信号I0(f)与泄露频域信号I1(f)、标准基波频域信号I0(f)与泄露频域信号I2(f)之间的互谱密度函数: (22) According to the relevant theorems, the standard fundamental frequency domain signal I 0 (f) and the leakage frequency domain signal I 1 (f), the standard fundamental frequency domain signal I 0 (f) and the leakage frequency domain signal I 2 ( f) The cross-spectral density function between:

II 1010 (( ff )) == II 11 (( ** ff )) II 00 (( ff ))

II 2020 (( ff )) == II 22 (( ** ff )) II 00 (( ff )) ;;

其中,I10(f)为标准基波频域信号I0(f)与泄露频域信号I1(f)的互谱密度函数, 为I1(f)的共轭;I20(f)为标准基波频域信号I0(f)与泄露频域信号I2(f)的互谱密度函数,为I2(f)的共轭。 Among them, I 10 (f) is the cross-spectral density function of the standard fundamental frequency domain signal I 0 (f) and the leakage frequency domain signal I 1 (f), is the conjugate of I 1 (f); I 20 (f) is the cross-spectral density function of the standard fundamental frequency domain signal I 0 (f) and the leakage frequency domain signal I 2 (f), It is the conjugate of I 2 (f).

(23)计算得到滤波后的两泄漏电流频域信号I10(f)、I20(f),并分别对得到的泄漏电流频域信号作傅里叶反变换,得到滤波后的泄漏电流信号i10(t)、i20(t); (23) Calculate the filtered two leakage current frequency domain signals I 10 (f) and I 20 (f), and perform inverse Fourier transform on the obtained leakage current frequency domain signals respectively to obtain the filtered leakage current signal i 10 (t), i 20 (t);

(3)对滤波后的泄漏电流信号i10(t)、i20(t)进行互相关处理,利用相关函数的时延特性,求出i10(t)与i20(t)之间的时延tdelay(3) Perform cross-correlation processing on the filtered leakage current signals i 10 (t) and i 20 (t), and use the time-delay characteristics of the correlation function to obtain the relationship between i 10 (t) and i 20 (t) time delay t delay ;

(4)根据公式Δδ=tdelay×360/N求取设备的相对介损角;其中N为每周期内的采样点数。 (4) Calculate the relative dielectric loss angle of the equipment according to the formula Δδ=t delay ×360/N; where N is the number of sampling points in each period.

本发明利用改进的相关分析先进行滤波,然后再求得相对介损,使滤波处理后相对比较法的抗干扰能力更强、测量精度更高。电力系统实际运行过程中干扰对测量结果影响是很大的,干扰主要有系统中的谐波以及外界的环境干扰。一般情况下,当谐波干扰或者外界的环境干扰不断增大时,相对比较法精度将无法满足要求。而经过本发明的结合改进相关分析的滤波算法滤波后,信号的波形明显改善,信号滤除了绝大部分干扰,波形平滑无毛刺,如图3;在严重的干扰条件下(放大谐波干扰和环境干扰,此时信噪比为5dB),经过本发明的结合改进相关分析的滤波算法滤波后的相对比较法测得的结果较为精确,满足诊断要求,对比图如图5图5(a)中的波形有较大毛刺,这对检测相关峰进而求时延有很大影响,测得的结果将极不精确,而图5(b)中的波形滤除了干扰,平滑无毛刺,可以精确测得相关峰位置,从而准确求得相对介损。所 以,本发明结合改进相关分析的相对比较法采用标准基波作为中间变量,充分结合了相关分析的滤波性能和时延特性,提高了算法的抗干扰能力与测量精度,适用范围更广,具有一定的实际应用价值。 The invention utilizes the improved correlation analysis to perform filtering first, and then obtains the relative dielectric loss, so that the anti-interference ability of the relative comparison method after filtering processing is stronger and the measurement accuracy is higher. During the actual operation of the power system, interference has a great influence on the measurement results. The interference mainly includes harmonics in the system and external environmental interference. In general, when the harmonic interference or external environmental interference is increasing, the accuracy of the relative comparison method will not be able to meet the requirements. And after filtering through the filtering algorithm of the present invention in combination with improved correlation analysis, the waveform of the signal is obviously improved, and the signal has filtered most of the interference, and the waveform is smooth without burrs, as shown in Figure 3 ; under severe interference conditions (amplification harmonic interference and Environmental interference, this moment signal-to-noise ratio is 5dB), the result measured by the relative comparison method after the filtering algorithm filtering of combining improved correlation analysis of the present invention is comparatively accurate, meets the diagnosis requirement, and contrast figure is as Fig. 5 , and Fig. 5 (a The waveform in ) has a large burr, which has a great impact on the detection of correlation peaks and the calculation of time delay. The measured results will be extremely inaccurate, while the waveform in Fig . Accurately measure the position of the correlation peak, so as to accurately obtain the relative dielectric loss. Therefore, the present invention uses the standard fundamental wave as an intermediate variable in combination with the relative comparison method of the improved correlation analysis, which fully combines the filtering performance and time delay characteristics of the correlation analysis, improves the anti-interference ability and measurement accuracy of the algorithm, and has a wider application range. Certain practical application value.

附图说明 Description of drawings

图1是本发明相对比较法的原理 Fig. 1 is the schematic diagram of relative comparison method of the present invention;

图2是本发明所采用两种设备的信号波形图; Fig. 2 is the signal waveform figure of two kinds of equipments that the present invention adopts;

图3是相关函数波形图; Fig. 3 is correlation function waveform diagram;

图4是滤波前后的波形对比,其中:实线为采用本发明的结合相关分析的滤波算法滤波前的波形图,虚线为滤波后的波形图; Fig. 4 is the waveform contrast diagram before and after filtering, and wherein: solid line is the waveform diagram before adopting the filtering algorithm filtering of the present invention in conjunction with correlation analysis, and dotted line is the waveform diagram after filtering;

图5是严重干扰情况下的相关处理结果; Fig. 5 is the relevant processing result in the case of severe interference;

其中(a)为未采用本发明的结合相关分析的滤波算法而直接相对比较的处理结果,(b)为采用本发明的结合相关分析的滤波算法后的处理结果。 Wherein (a) is the processing result of direct relative comparison without using the filtering algorithm combined with correlation analysis of the present invention, and (b) is the processing result after adopting the filtering algorithm combined with correlation analysis of the present invention.

具体实施方式 Detailed ways

为了说明本发明的结构特点及运行原理,下面结合具体实施例进行说明。 In order to illustrate the structural features and operating principles of the present invention, the following will be described in conjunction with specific embodiments.

本发明的相对比较法步骤如下: Relative comparison method step of the present invention is as follows:

(1)采集选取的两个设备的泄漏电流信号为i1(t)、i2(t),设定标准基波信号为i0(t); (1) Collect the leakage current signals of the two selected devices as i 1 (t) and i 2 (t), and set the standard fundamental wave signal as i 0 (t);

标准基波信号为工频信号,幅值、相角任取,因为是应用于电力系统中,故为工频(50Hz)信号,相关分析处理的也是共频信号(同一频率),即i1(t)、i2(t)也是工频信号,而其幅值与相角对计算结果并无影响,可任取。 The standard fundamental wave signal is a power frequency signal, and the amplitude and phase angle are optional. Because it is applied in the power system, it is a power frequency (50Hz) signal, and the correlation analysis is also a common frequency signal (same frequency), that is, i 1 (t) and i 2 (t) are also power frequency signals, and their amplitude and phase angle have no influence on the calculation results and can be chosen arbitrarily.

(2)分别使用标准基波信号i0(t)和两泄露电流信号i1(t)、i2(t)进行互相关处理,得到两泄露电流信号i1(t)、i2(t)滤波后的泄漏电流信号i10(t)、i20(t): (2) Using the standard fundamental wave signal i 0 (t) and two leakage current signals i 1 (t) and i 2 (t) for cross-correlation processing respectively, two leakage current signals i 1 (t) and i 2 (t ) filtered leakage current signal i 10 (t), i 20 (t):

由于直接求取互相关函数是在时域中计算,运算量较大,难以满足在线监测条件下的实时性要求,故实际计算时利用相关定理,即信号的互相关函数与互谱密度函数是一对傅里叶变换,通过相关定理将时域计算转化到频域计算, Since the direct calculation of the cross-correlation function is calculated in the time domain, the amount of calculation is large, and it is difficult to meet the real-time requirements under the condition of on-line monitoring. Therefore, the correlation theorem is used in the actual calculation, that is, the cross-correlation function of the signal and the cross-spectral density function are A pair of Fourier transforms, which convert time-domain calculations to frequency-domain calculations through related theorems,

大大简化计算,满足了实时性的要求。以Y1(f)和Y2(f)分别表示函数y1(t)和y2(t) The calculation is greatly simplified and the real-time requirement is met. Denote the functions y 1 (t) and y 2 (t) by Y 1 (f) and Y 2 (f) respectively

的傅立叶变换,并用*表示对复函数取共轭,信号的互谱密度函数,由下列公 The Fourier transform of , and use * to represent the conjugate of the complex function, the cross-spectral density function of the signal is given by the following formula

式确定: The formula is determined:

G i 1 i 2 ( f ) = Y ( f * ) 1 Y 2 ( f ) (定义域f>0) G i 1 i 2 ( f ) = Y ( f * ) 1 Y 2 ( f ) (Domain f>0)

因此可以采用计算两个信号的互谱密度函数,然后对之进行傅立叶反变换的方法来实现工程上的快速计算互相关函数。 Therefore, the cross-spectral density function of the two signals can be calculated, and then the method of Fourier inverse transform can be used to realize the fast calculation of the cross-correlation function in engineering.

具体步骤如下: Specific steps are as follows:

(21)分别对标准基波信号为i0(t)、两个泄漏电流信号i1(t)、i2(t)做傅里叶变换得到频域信号I0(f)、I1(f)和I2(f); (21) Perform Fourier transform on the standard fundamental wave signal i 0 (t) and two leakage current signals i 1 (t) and i 2 (t) to obtain the frequency domain signals I 0 (f), I 1 ( f) and I 2 (f);

(22)根据相关定理,分别得到标准基波频域信号I0(f)与泄露频域信号I1(f)、标准基波频域信号I0(f)与泄露频域信号I2(f)之间的互谱密度函数: (22) According to the relevant theorems, the standard fundamental frequency domain signal I 0 (f) and the leakage frequency domain signal I 1 (f), the standard fundamental frequency domain signal I 0 (f) and the leakage frequency domain signal I 2 ( f) The cross-spectral density function between:

II 1010 (( ff )) == II 11 (( ** ff )) II 00 (( ff ))

II 2020 (( ff )) == II 22 (( ** ff )) II 00 (( ff )) ;;

其中,I10(f)为标准基波频域信号I0(f)与泄露频域信号I1(f)的互谱密度函数, 为I1(f)的共轭;I20(f)为标准基波频域信号I0(f)与泄露频域信号I2(f)的互谱密度函数,为I2(f)的共轭。 Among them, I 10 (f) is the cross-spectral density function of the standard fundamental frequency domain signal I 0 (f) and the leakage frequency domain signal I 1 (f), is the conjugate of I 1 (f); I 20 (f) is the cross-spectral density function of the standard fundamental frequency domain signal I 0 (f) and the leakage frequency domain signal I 2 (f), It is the conjugate of I 2 (f).

(23)计算得到滤波后的泄漏电流频域信号I10(f)、I20(f),并分别对得到的泄漏电流频域信号作傅里叶反变换,得到滤波后的泄漏电流信号i10(t)、i20(t); (23) Calculate the filtered leakage current frequency domain signals I 10 (f), I 20 (f), and perform inverse Fourier transform on the obtained leakage current frequency domain signals respectively to obtain the filtered leakage current signal i 10 (t), i 20 (t);

f(t)是t的周期函数,如果t满足狄里赫莱条件: f(t) is a periodic function of t, if t satisfies the Dirichlet condition:

1)函数在任意有限区间内连续,或只有有限个第一类间断点(当t从左或右趋于这个间断点时,函数有有限的左极限和右极限); 1) The function is continuous in any finite interval, or has only a limited number of discontinuity points of the first type (when t tends to this discontinuity point from left or right, the function has finite left and right limits);

2)在一个周期内,函数有有限个极大值或极小值; 2) In a period, the function has a finite number of maximum or minimum values;

3)f(t)在单个周期内绝对可积,即 3) f(t) is absolutely integrable in a single period, namely

则有下式成立。 Then the following formula is established.

Ff (( ωω )) == Ff [[ ff (( tt )) ]] == ∫∫ -- ∞∞ ∞∞ ff (( tt )) ee -- jwtjwt dtdt

ff (( tt )) == Ff -- 11 [[ Ff (( ωω )) ]] == 11 22 ππ ∫∫ -- ∞∞ ∞∞ Ff (( ωω )) ee jwtjwt dωdω

上式称为积分运算f(t)的傅立叶变换和F(ω)的傅立叶逆变换。其中,F(ω)叫做f(t)的像函数,f(t)叫做F(ω)的像原函数,F(ω)是f(t)的像,f(t)是F(ω)原像(ω=2πf,故ω与f含义一样,均代表频域里的自变量)。 The above formula is called the Fourier transform of the integral operation f(t) and the inverse Fourier transform of F(ω). Among them, F(ω) is called the image function of f(t), f(t) is called the original function of F(ω), F(ω) is the image of f(t), f(t) is F(ω) The original image (ω=2πf, so ω has the same meaning as f, and both represent independent variables in the frequency domain).

步骤(21)中关于傅里叶变换的公式推导为: In step (21), the formula about Fourier transform is derived as:

II 00 (( ff )) == Ff [[ ii 00 (( tt )) ]] == 11 22 ππ ∫∫ -- ∞∞ ∞∞ ii 00 (( tt )) ee -- jj 22 πftπft dtdt

II 11 (( ff )) == Ff [[ ii 11 (( tt )) ]] == 11 22 ππ ∫∫ -- ∞∞ ∞∞ ii 11 (( tt )) ee -- jj 22 πftπft dtdt

II 22 (( ff )) == Ff [[ ii 22 (( tt )) ]] == 11 22 ππ ∫∫ -- ∞∞ ∞∞ ii 22 (( tt )) ee -- jj 22 πftπft dtdt

步骤(23)中关于傅里叶反变换的公式推导为: In the step (23), the formula about the inverse Fourier transform is derived as:

ii 1010 (( tt )) == Ff -- 11 [[ II 1010 (( ff )) ]] == ∫∫ -- ∞∞ ∞∞ II 1010 (( ff )) ee jj 22 πftπft dfdf

ii 2020 (( tt )) == Ff -- 11 [[ II 2020 (( ff )) ]] == ∫∫ -- ∞∞ ∞∞ II 2020 (( ff )) ee jj 22 πftπft dfdf

互相关处理如下: Cross-correlation is handled as follows:

相关函数反映的是两个同频信号或者信号自身不同时刻的相似程度。将检测所得到的两个信号作比较,取得相关函数,并以此为基础的分析叫做相关分析。 The correlation function reflects the similarity between two signals of the same frequency or the signals themselves at different times. Comparing the two signals obtained by detection to obtain a correlation function, and the analysis based on this is called correlation analysis.

设两信号为y1(t)、y2(t),则y1(t)、y2(t)的相关函数,即公式 Suppose the two signals are y 1 (t) and y 2 (t), then the correlation function of y 1 (t) and y 2 (t) is the formula

RR ythe y 11 ythe y 22 (( ττ )) == limlim TT →&Right Arrow; ∞∞ 11 22 TT ∫∫ -- ∞∞ ++ ∞∞ ythe y 11 (( tt )) ythe y 22 (( tt ++ ττ )) dtdt

假设信号s(t)受到外界的干扰形成复合信号y1(t)和y2(t),即y1(t)=s(t)+n(t),y2(t)=s(t+τ)+m(t),(s(t)是有用信号,而n(t)、m(t)是两噪声信号),那么互相关函数将仅含有y1(t)、y2(t)中的相关部分s(t)的信号,而排除了外来噪声的干 扰,即此时互相关函数为: Suppose the signal s(t) is disturbed by the outside to form composite signals y 1 (t) and y 2 (t), that is, y 1 (t)=s(t)+n(t), y 2 (t)=s( t+τ)+m(t), (s(t) is a useful signal, and n(t), m(t) are two noise signals), then the cross-correlation function will only contain y 1 (t), y 2 The signal of the relevant part s(t) in (t), and the interference of external noise is excluded, that is, the cross-correlation function at this time is:

Ry1y2(τ)=E[y1(t)y2(t+τ)]=αRxx(τ-τ1) R y1y2 (τ)=E[y 1 (t)y 2 (t+τ)]=αR xx (τ-τ 1 )

式中α为相对吸收系数,即两信号的相关峰峰值大小。对于函数Ry1y2(τ)来说,它是α,τ1和Rxx的函数,并且在当τ=τ1处,由于信号与自身的相关性为1(即Rxx(0)=1),有Ry1y2(τ)=αRxx(0)=α,具有最大值,即为相关峰值点。于是,时间差可以用互相关函数估计,相关峰值位置与原点的差即对应两路信号的时间差。 In the formula, α is the relative absorption coefficient, that is, the relative peak-to-peak value of the two signals. For the function R y1y2 (τ), it is a function of α, τ 1 and R xx , and when τ=τ 1 , since the correlation between the signal and itself is 1 (that is, R xx (0)=1) , there is R y1y2 (τ)=αR xx (0)=α, which has a maximum value, which is the correlation peak point. Therefore, the time difference can be estimated by the cross-correlation function, and the difference between the correlation peak position and the origin corresponds to the time difference of the two signals.

滤波算法如下: The filtering algorithm is as follows:

由于信号中存在干扰,实际应用时,当干扰不断增加时直接采用相对比较法求得两信号的相位差准确度迅速下降。分析发现,这是由于n(t)、m(t)具有一定的相关性,干扰增强后相关性增强,导致测量结果不够精确。 Due to the presence of interference in the signal, in practical applications, when the interference increases, the accuracy of the phase difference between the two signals directly decreases rapidly by using the relative comparison method. The analysis found that this is because n(t) and m(t) have a certain correlation, and the correlation is enhanced after the interference is enhanced, resulting in inaccurate measurement results.

为了消除n(t)和m(t)相关带来的影响,本发明引入了中间变量——标准的基波(只包含共频基波)y0(t),即y0(t)=s(t0)。分别使用y0(t)和含有干扰信号的信号y1(t)、y2(t)进行相关处理,就可以提出信号y1(t)、y2(t)的基波成份y10(t)、y20(t),这就是相关函数的滤波性。而两个信号分别与同一标准的基波相关后波形平滑完整并保留相位差信息,将滤波后的基波成份y10(t)、y20(t)再次进行相关,此时再利用相关函数的时延特性,就可以得到两信号的相位差,这就是本发明的结合改进相关分析的滤波算法的核心。 In order to eliminate the influence brought by the correlation between n(t) and m(t), the present invention introduces an intermediate variable—the standard fundamental wave (only comprising the common-frequency fundamental wave) y 0 (t), that is, y 0 (t)= s(t 0 ). Using y 0 (t) and the signals y 1 (t) and y 2 (t) containing the interference signal for correlation processing respectively, the fundamental component y 10 ( t), y 20 (t), this is the filtering property of the correlation function. After the two signals are correlated with the fundamental wave of the same standard, the waveforms are smooth and complete and the phase difference information is retained, and the filtered fundamental wave components y 10 (t) and y 20 (t) are correlated again, and then the correlation function is used The time delay characteristics of the two signals can be obtained, which is the core of the filter algorithm combined with improved correlation analysis of the present invention.

(3)对滤波后的泄漏电流信号i10(t)、i20(t)进行互相关处理,利用相关函数的时延特性,求出i10(t)与i20(t)之间的时延tdelay(3) Perform cross-correlation processing on the filtered leakage current signals i 10 (t) and i 20 (t), and use the time-delay characteristics of the correlation function to obtain the relationship between i 10 (t) and i 20 (t) time delay t delay ;

(4)根据公式Δδ=tdelay×360/N求取设备的相对介损角;其中N为每周期内的采样点数。 (4) Calculate the relative dielectric loss angle of the equipment according to the formula Δδ=t delay ×360/N; where N is the number of sampling points in each period.

当δ很小时,一般介损角的正切值与介损角接近,则有 When δ is very small, the tangent of the general dielectric loss angle is close to the dielectric loss angle, then there is

Δtanδ=|tanδx1-tanδx2|=tan|(δx1x2)|≈|(δx1x2)|=Δδ Δtanδ=|tanδ x1 -tanδ x2 |=tan|(δ x1x2 )|≈|(δ x1x2 )|=Δδ

其中,δx1、δx2为两台同相同母线的电容型设备的介损角。将同相同母 线两设备的泄漏电流进行相位比较,即可得到相对介质损耗角Δδ,该指标反映设备的相对绝缘状况。当比较的两台设备绝缘良好时,其相对介质损耗角Δδ一般很小;若其中一台设备出现绝缘缺陷,其Δδ将明显增大,导致Δtanδ也明显变化。以此类推,通过比较多组设备的δ,就能发现设备的绝缘缺陷。 Among them, δ x1 and δ x2 are the dielectric loss angles of two capacitive devices with the same bus. Comparing the leakage currents of two devices on the same bus, the relative dielectric loss angle Δδ can be obtained, which reflects the relative insulation status of the devices. When the insulation of the two devices being compared is good, the relative dielectric loss angle Δδ is generally small; if one of the devices has an insulation defect, its Δδ will increase significantly, resulting in a significant change in Δtanδ. By analogy, by comparing the δ of multiple groups of equipment, the insulation defect of the equipment can be found.

具体算例:  Concrete calculation example:

由于容性设备的相对介损(Δtanδ)在正常情况下很小,为了更为直观,算例将直接计算相对介质损耗角(Δδ)。通常电容型设备的δ大多在0.001~0.02范围内,因此对测量δ的准确度要求较高。而一般δ的规定阈值为0.01,则δ的误差的绝对值应控制在0.001~0.002之间。 Since the relative dielectric loss (Δtanδ) of capacitive equipment is usually small, in order to be more intuitive, the calculation example will directly calculate the relative dielectric loss angle (Δδ). Generally, the δ of capacitive equipment is mostly in the range of 0.001 to 0.02, so the accuracy of measuring δ is required to be high. Generally, the specified threshold of δ is 0.01, so the absolute value of the error of δ should be controlled between 0.001 and 0.002.

电力系统实际运行过程中干扰对测量结果影响是很大的,干扰主要有系统中的谐波以及外界的环境干扰。但是实际上谐波大小由系统本身决定,研究时可设为定值;而环境干扰是不可控的,天气、温度、湿度、噪声等都可能影响环境干扰,所以测量算法能否在严重环境干扰下正确运行是衡量算法性能的重要指标。算例通过将环境干扰不断放大,对比此时加入滤波算法后测量算法的准确性。 During the actual operation of the power system, interference has a great influence on the measurement results. The interference mainly includes harmonics in the system and external environmental interference. But in fact, the size of the harmonic is determined by the system itself, which can be set to a fixed value during research; however, environmental interference is uncontrollable, and weather, temperature, humidity, noise, etc. may affect environmental interference, so whether the measurement algorithm can be used in severe environmental interference Correct operation is an important indicator to measure the performance of the algorithm. The calculation example continuously amplifies the environmental interference, and compares the accuracy of the measurement algorithm after adding the filtering algorithm at this time.

为了测试环境干扰放大时的具体实验效果,设定谐波干扰一定,环境干扰不断放大,对比此时有无滤波算法时的实验结果(计算时Δδ均在0~0.02范围内),其中Δδ1为无滤波算法的计算结果,Δδ2为采用滤波算法的计算结果,具体数据见表1In order to test the specific experimental effect when the environmental interference is amplified, the harmonic interference is set to be constant, and the environmental interference is continuously amplified. Compared with the experimental results with or without the filtering algorithm at this time (the calculation Δδ is in the range of 0 to 0.02), where Δδ 1 is the calculation result without filtering algorithm, and Δδ 2 is the calculation result using filtering algorithm. The specific data are shown in Table 1 .

表中加粗的为不符合误差要求(0.001~0.002)的数据。 The bold data in the table are data that do not meet the error requirements (0.001-0.002).

表1 放大环境干扰时的实验结果 Table 1 Experimental results when enlarging environmental interference

分析表1可知,在信噪比为30dB时,无滤波算法所得结果的精度已经不再满足要求;而采用滤波算法的测量结果在信噪比为5dB时依旧能满足要求,这充分体现了本发明算法的优越性。 Analysis of Table 1 shows that when the signal-to-noise ratio is 30dB, the accuracy of the results obtained by the non-filtering algorithm no longer meets the requirements; while the measurement results using the filtering algorithm can still meet the requirements when the signal-to-noise ratio is 5dB, which fully reflects the The superiority of the invented algorithm.

以上所述仅是本发明的优选实施方式,应当指出: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润饰,这些改进和润饰也应视为本发明的保护范围。 The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (1)

1.一种结合相关分析滤波性的相对比较法,其特征在于:步骤如下:1. a relative comparison method in conjunction with correlation analysis filter property, it is characterized in that: the steps are as follows: (1)采集选取的两个设备的泄漏电流信号为i1(t)、i2(t),设定标准基波信号为i0(t);(1) Collect the leakage current signals of the two selected devices as i 1 (t) and i 2 (t), and set the standard fundamental wave signal as i 0 (t); (2)分别使用标准基波信号i0(t)和两泄露电流信号i1(t)、i2(t)进行互相关处理,得到两泄露电流信号i1(t)、i2(t)滤波后的信号i10(t)、i20(t):具体步骤如下:(2) Using the standard fundamental wave signal i 0 (t) and two leakage current signals i 1 (t) and i 2 (t) for cross-correlation processing respectively, two leakage current signals i 1 (t) and i 2 (t ) filtered signals i 10 (t), i 20 (t): the specific steps are as follows: (21)分别对标准基波信号为i0(t)、两个泄漏电流信号i1(t)、i2(t)做傅里叶变换得到频域信号I0(f)、I1(f)和I2(f);(21) Perform Fourier transform on the standard fundamental wave signal i 0 (t) and two leakage current signals i 1 (t) and i 2 (t) to obtain the frequency domain signals I 0 (f), I 1 ( f) and I 2 (f); (22)根据相关定理,分别得到标准基波频域信号I0(f)与泄露频域信号I1(f)、标准基波频域信号I0(f)与泄露频域信号I2(f)之间的互谱密度函数:(22) According to the relevant theorems, the standard fundamental frequency domain signal I 0 (f) and the leakage frequency domain signal I 1 (f), the standard fundamental frequency domain signal I 0 (f) and the leakage frequency domain signal I 2 ( f) The cross-spectral density function between: II 1010 (( ff )) == II 11 (( ff )) ** II 00 (( ff )) II 2020 (( ff )) == II 22 (( ff )) ** II 00 (( ff )) ;; 其中,I10(f)为标准基波频域信号I0(f)与泄露频域信号I1(f)的互谱密度函数,为I1(f)的共轭;I20(f)为标准基波频域信号I0(f)与泄露频域信号I2(f)的互谱密度函数,I2(f)的共轭;Among them, I 10 (f) is the cross-spectral density function of the standard fundamental frequency domain signal I 0 (f) and the leakage frequency domain signal I 1 (f), is the conjugate of I 1 (f); I 20 (f) is the cross-spectral density function of the standard fundamental frequency domain signal I 0 (f) and the leakage frequency domain signal I 2 (f), the conjugate of I 2 (f); (23)计算得到滤波后的两泄漏电流频域信号I10(f)、I20(f);并分别对得到的泄漏电流频域信号作傅里叶反变换,得到滤波后的泄漏电流信号i10(t)、i20(t);(23) Calculate and obtain the filtered two leakage current frequency domain signals I 10 (f), I 20 (f); and perform inverse Fourier transform on the obtained leakage current frequency domain signals respectively to obtain the filtered leakage current signal i 10 (t), i 20 (t); (3)对滤波后的泄漏电流信号i10(t)、i20(t)进行互相关处理,利用相关函数的时延特性,求出i10(t)与i20(t)之间的时延tdelay(3) Perform cross-correlation processing on the filtered leakage current signals i 10 (t) and i 20 (t), and use the time-delay characteristics of the correlation function to obtain the relationship between i 10 (t) and i 20 (t) time delay t delay ; (4)根据公式Δδ=tdelay×360/N求取设备的相对介损角;其中N为每周期内的采样点数。(4) Calculate the relative dielectric loss angle of the equipment according to the formula Δδ=t delay ×360/N; where N is the number of sampling points in each period.
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