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1、6.2.1 局部放电的在线监测系统 6.2.1 On-line monitoring system of PD 6.2.2 局部放电分析与故障诊断 6.2.2 PD analysis and fault diagnosis,6.2 局部放电在线监测 6.2 On-line monitoring of partial discharge,局部放电的在线检测分为电测法和非电测法两大类，其中电测法中的脉冲电流法是离线条件下测量电气设备局部放电的基本方法，也是目前在局部放电在线检测的主要手段，其优点是灵敏度高。 On-line monitoring methods of partial dischar
2、ge can be divided into two major categories：electrical method and non-electric method of which pulse current method of electric method is basic way to measure partial discharge of electrical equipment in off-line condition. It is also principal means in on-line detection of partial discharge current
3、ly which has advantage of high sensitivity.,6.2.1 局部放电的在线监测系统 6.2.1 On-line monitoring system of PD,电测法中的射频测量法等也都应用到了在线检测中。电测法的缺点是由于现场存在着严重的电磁干扰，将大大降低检测灵敏度和信噪比。 RF measurements of electrical method are also applied to the online detection. The shortcomings of electrical method is the serious electro
4、magnetic interference in the scene. It will greatly reduce detection sensitivity and signal to noise ratio. 脉冲电流法在线检测的组成及关键技术： The composition and key technology of on-line monitoring of pulse current method: 1.电流传感器 (Current sensor) 2. 抗干扰技术 (Anti-interference technology),图66 局部放电检测系统原理框架图 Figure 6
5、-6 Principle framework plans of partial discharge detection system,电流信号i1(t)和二次侧线圈两端的感应电压（即输出信号）e(t)的关系为： The relationship between current signal i1 (t) and the inductive voltage of secondary side of the coil (the output signal) e (t) is :,1.电流传感器 current sensor,（6-3）,传感器的积分方式有两种，分别适用于宽带型和窄带型传感器。 Th
6、ere are two types integral of sensor , which are applicable to sensor of broadband and narrowband type respectively.,宽带型电流传感器 sensor of broadband type,（6-6）,谐振型电流传感器 Resonance type of Current Sensor,（6-15）,干扰来源 : Interference sources： 线路或其它邻近设备的电晕放电和内部的局部放电 Corona discharge and inner partial dischar
7、ge of the line or other adjacency equipment 电力系统的载波通信和高频保护信号对检测的干扰 Interference of the carrier communication of power system and high-frequency protection detection signal 可控硅整流设备引起的干扰 Interference cause by silicon-controlled rectifier equipment 无线电广播的干扰 Interference of radio broadcast 其他周期性干扰 Other
8、 cyclical interference,上述干扰可能通过以下三种途径进入检测系统： These interference mentioned above enter the detection system by the following three ways : (1)从检测系统的工频电源进入，故检测系统的电源宜由隔离变压器加上低通滤波器供电，以抑制这种干扰。 It can enter the power supply of the detection system. So the power of the detection system should supply through
9、 isolation transformer adding low-pass filter to avoid this kind of interference.,（2）通过电磁耦合进入检测系统，故检测系统包括连线应很好的屏蔽，或利用光电隔离和光纤传输信号，以减少干扰。 It can enter the detection system through electromagnetic coupling. So the detection system including connection lines should be shield well. In order to reduce int
10、erference we can use photoelectric isolation and optical fiber for transmission signals,. （3）干扰信号通过传感器进入检测系统，这种干扰和局部放电信号混合在一起，上述方法不能抑制这种干扰，需要采用其他的措施。 Interference signals enter the detection system through sensor which is mixed by partial discharge signals. The methods mentioned above can not reject
11、 this kind of interference. So other measures are adopted.,2. 抗干扰技术 Anti-interference technology 差动平衡系统：差动平衡系统主要用于抑制共模干扰 Difference balance system : difference balance system is mainly used to suppress common mode interference. 其他 Other,图610差动平衡系统原理图 Figure 6-10 Difference balance system schematics,
12、6.2.2 局部放电分析与故障诊断 6.2.2 PD analysis and fault diagnosis,局部放电信号分析是指如何从测试信号中提取有关放电的信息，一般采用数字信号处理技术，目前常用的方法主要有： PD signal analysis refers to how to extract related discharge information from testing signal which is generally using digital signal process technology. The methods are mainly used are: 时域分析
13、 Time domain analysis 频域分析 Frequency-domain analysis 时频联合分析 Joint time-frequency analysis 人工神经网络分析 Artificial neural network analysis,局部放电信号分析 PD signal analysis,时域分析是最基本的数学分析方法，例如分析放电信号的幅值，幅值与时间（或相位）、放电次数的关系，并且在显示设备上输出信号的波形，为此需要根据波形的采集要求确定所需的采样率和采集的数据长度，并将信号完整地记录下来。 Time-domain analysis is the basi
14、c mathematical analysis methods, such as analyzing amplitude of discharge signal, the relationship between amplitude and time (or phase), number of discharges, and output signal waveform in the display device. So according to the acquisition requirement of waveform it determines the sampling rate an
15、d the length of the data acquisition and records the signal integrity.,频域分析又称频谱分析，是分析某些放电特征在频域上的变化，如幅度谱、相位谱、能量谱和功率谱等，目前最常用的方法是快速傅里叶变换（FFT）。 Frequency domain analysis is also known as spectrum analysis which is a method to analyze some discharge characteristics in the frequency domain, such as amplit
16、ude spectrum, phase spectrum, energy spectrum and power spectrum and so on. At present the most common used method is fast Fourier transform (FFT).,2.放电类型的模式识别 Pattern recognition of discharge types 模式识别是一种重要的诊断手段，于90年代应用于电力设备的放电识别，目前已被广泛应用于局部放电在线检测与故障诊断。,Pattern Recognition is an important diagnostic tool, which is used in discharge recognition of electrical equipment in the 1990s . Now it has been widely used in on-line partial discharge detection and fault diagnosi
