The Antamina Mine is located in the Antamina valley in the Andes Mountains in the Ancash region of north-central Peru, approximately 270 kilometers north of Lima, Peru. Antamina Mine operations began in late 2001, with an estimated mine life of more than 20 years. The deposit is one of the largest copper-zinc ore bodies in the world. Antamina Mine is electrically connected to five 220 kV transmission lines located in regions with isokeraunic levels from 15 to 90 thunderstorm days per year. In

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... e period from 2002 to 2006, 80 nonschedule outages due to lightning which have affected the process productive have been observed in these lines. Antamina has too a 23 kV overhead shielded distribution ring network in which outages due to lightning have been also observed. In the middle of 2003 Antamina started to work in partnership with Tyco Electronics in order to evaluate the lightning performance of the distribution and transmission lines. With basis in these studies from January 2006 till June 2007, approximately 450 units of line arresters were installed along the distribution network and 265 gapless transmission line arresters (TLA) were installed along the sections of the two 220 kV transmission lines with poorer lightning performance. From October 2006 on only one outage due to lightning was recorded in these two lines, proving the effectiveness of this protection system. This paper presents details about the transmission line lightning performance studies and evaluation carried out by Tyco Electronics and Antamina in this partnership project. Methods to select the arresters characteristics and to define the quantity and the optimized arresters location along the lines are presented. Field experience obtained in these two first years and the line performance / reliability of the system after the TLA application in comparison with the performance before the arresters' installation are presented and discussed