架空线对入侵超高压变压器的特快速暂态过电压波前陡度的限制

Limiting the Steepness of VFTO Invaded Wave to the EHV Power Transformers Using Overhead Lines

在采用气体绝缘组合开关(GIS)的500kV变电站或发电厂中,陡波前的特快速暂态过电压(VFTO)对主变纵绝缘有很大的威胁。为此,分别从实验和仿真这2个方面详细探讨了连接于GIS母线与变电站或发电厂主变之间的架空线对到达主变端口的VFTO波前陡度的削弱作用,并采用ATP-EMTP仿真计算、分析了该段架空线长度与到达主变端口的VFTO波前陡度之间的定量关系。研究结果表明,长度为5～15m的架空线能够很好地保护主变纵绝缘:当架空线长度约为5m时,架空线能够非常明显地削弱到达主变端口的VFTO波前陡度;当架空线长度为10m时,对于大部分采用GIS的500kV变电站以及发电厂,到达变压器的VFTO波前陡度不会超出限制水平;当架空线长度达到15m时,对于各种采用GIS的500kV变电站以及发电厂,到达变压器的VFTO波前陡度都不会超出限制水平。

In 500 kV substations or power plants adopting gas insulated switchgears （GIS）, very fast transient overvoltage （VFTO） with a steep wavefront poses a big threat to the longitudinal insulation of power transformers. Through experiment and simulation, the effect of the overhead line between GIS bushing and transformer on the wavefront steepness of VFTO at the transformer＇s port was discussed. Moreover, using the software ATP-EMTP, the quantitative relation between the overhead line＇s length and the steepness of the VFTO at the transformer＇s port was also analyzed. The result shows that an overhead line with a length of 5 -15 m could effectively protect the longitudinal insulation of transformers： when the length is about 5 m, the steepness of VFTO drops dramatically at the transformer＇s port; the steepness wouldn＇t exceed the restriction level for most of 500 kV substations and power plants adopting GIS when the line length is about 10 m, and for almost all variety of 500 kV substations and power plants adopting GIS, when the length reaches 15 m.