Lightning Outage Transmission Line Reliability Improvement with Surge Arresters

Comision Federal de Electricidad (CFE), is the Mexican Power Utility, with several thousand kilometers of 230 and 400 kV transmission lines built along the country: 26,915 km and 23,627 km, respectively as per June 2013, which are considered as the main transmission line voltages. These lines, seriously affected by lightning and whose performance has been very poor, were chosen to be protected with surge arresters even though the shielding angle and the tower footing resistance may have been improved in several structures. This paper presents shielding and backflashover results obtained for two typical transmission lines running along regions over flat and mountain terrains, with high lightning flash density. These lines used to have high outage rates before being protected with surge arresters. As for these protection devices, the selected location of them is for improving the reliability of the transmission lines as shown by each study done. Besides, the latest experiences obtained, during some years of using surge arresters (externally gapped) on these transmission lines running along different parts of the country, are also included.