Research On Partial Discharge Online Detection Of Substation Equipment

Under the influence of electric field, discharge only occurs in some regions of the operating electric equipment, and no voltage is applied throughout the conductor. namely, there is no electrical break-down. This phenomenon is called partial discharge. Partial discharge occurs due to local electric field distortion and field intensity concentration,which result in gas discharge or breakdown within the partial insulated medium. It may happen at the edge of the conductor and the surface or interior part of the insulator. Partial discharge seriously harm the electrical equipment insulation, because local heating and charged particles impact as well as chemically active product and ray severely damage the insulator. It is a slow process,besides, being influenced by many factors, it starts from the local, and is likely to develop into a breakdown, which will pose risk to running high-voltage electric equipment.As a kind of pulsed discharge, partial discharge will produce a series of physical phenomena and chemical changes such as light, sound, electric as well as mechanical vibration inside and around electric equipment. These physical phenomena and chemical changes could provide a detection signal for monitoring electrical equipment internal insulation.Nowadays, the commonly used partial discharge detection techniques mainly include HF(High Frequency), UHF(Ultra High Frequency), AE(Acoustic Emission) and TEV(Transient Earth Voltage) technology. HF technology is a detection method that could collect, analyze and judge the partial discharge signals whose frequency is between3MHz-30MHz. UHF is targeted at partial discharge signals whose frequency is between300MHz-3000MHz, and AE refers to20kHz-200kHz range signals. Partial discharge will produce an instantaneous ground voltage in grounded metal surface, which may be spread in all directions along the metal surface. TEV specialize in identification and location for electrical equipment by detecting this ground voltage[1].Partial discharge of electrical equipment will produce different physical and chemical phenomena due to different equipment structure, insulation design and operation mode, which mainly embody the frequency range, amplitude, frequency cycle relevance of sound and electric signal. These detection techniques have different validity and sensitivity for different equipment. Through actual operation, the partial discharge detection of main transformer apply to HF and AE technology, the combination of UHF and AE is suitable for GIS(Gas Insulated Switchgear), while TEV and AE are combined for switch-gear type of equipment. This paper mainly studies the type, characteristics and detection methods of GIS and switch-gear equipment partial discharge. Detailed analysis of GIS UHF and AE, switch-gear TEV and AE technology is carried out. Combined with regulations and actual operation cases, in-depth inquiry of detection principle, process, data analysis and defect diagnostics is carried out. Charged detection in electrical equipment is studied and summarized in this paper,some views for the existing problems and the future direction of development it also put forward.