变电站局放检测中的电磁干扰统计特性

Statistical Characteristics of Electromagnetic Interferences for Partial Discharge Detection in Substation

变电站现场复杂的电磁干扰是造成当前局部放电在线检测出现误报漏报的重要原因,也是长期以来困扰局放在线检测技术发展的关键瓶颈。为此,选取地理位置、电压等级等方面具有代表性的变电站,采用超高频(UHF)和高频电流两种检测方式,通过现场实测方式系统研究了不同变电站电磁干扰信号的时域、频域以及统计特征,并对来源进行了定位。研究表明,移动通讯信号和变电站设备外部的放电是局放检测最主要的电磁干扰形式;UHF检测干扰信号的幅值及辐射的电场强度分别在1.3~215 mV和0.1~21.5 mV/mm之间,通讯信号主要位于0.8~1 GHz和1.8~2 GHz频带内,脉冲型干扰频谱分布一般<900 MHz;高频检测干扰信号的幅值及对应的电流强度分别在5.8~501 mV和0.5~45 mA之间,频谱分布一般<90 MHz。因此,从特征上看电磁干扰信号强,与局放信号极为相似,极易对局放检测造成影响。

Complex electromagnetic interference is a most important cause for wrong alarming and failing to alarm of on-line partial discharge（PD） detection in substation, and also a key bottleneck for the development of on-line PD detection. Therefore, typical substations in geographical position and voltage level were selected as the objects of research, and ultrahigh frequency（UHF） and high frequency current PD detection method were used to systematically study the characteristics of electromagnetic interference signal in substation in time-domain, frequency-domain and statistics by field testing.Moreover, the location of the interference signal source was performed. It is found that the mobile communication signals and the external discharge of HV equipment in substation are the main forms of the electromagnetic interferences for PD detection. The amplitude and the electric field intensity for radiation of interference signals in UHF detection are between 1.3~215 m V and 0.1~21.5 m V/mm, the distribution of spectrum of communication signals is mainly between 0.8~1 GHz and 1.8~2 GHz, the spectrum of pulse interferences is generally below 900 MHz. The amplitude and the current intensity of interference signals in high-frequency current PD detection are between 5.8~501 m V and 0.5~45 m A, the spectrum distribution is generally below 90 MHz. Therefore, electromagnetic interferences are great in amplitude and similar to PD signals extremely according to the characteristics, and very easily to affect PD detection.