Lightning protection system improvement on Extra High Voltage 500 kV Transmission Lines in Indonesia using extended mast terminal

500 kV Extra High Voltage Transmission Lines, which have higher insulation level than other transmission lines with lower voltage level, should have more strength against lightning strikes. But in reality several problems appear. Broken insulators due to lightning strikes are often found in 500 kV EHV lines. Research on these problems was carried out at Paiton-Kediri lines. It took place especially in the areas that have higher lightning density. Broken insulator can cause lack of insulation strength and potentially reduce lines performance due to outages on the lines. In order to improve transmission lines lightning performance, a new innovation had been done by using Extended Mast Terminal (EMT) attached to transmission tower. EMT is a pylon that was installed at the top of transmission tower consists of Early Streamer Emission air terminal, double shielded down conductor, lightning event counter, and peak lightning current measurement system using commercial magnetic tape. The purpose of this research is to install and observe the use of EMT in Transmission Lines lightning performance by reducing the number of broken insulators. Installation of EMT in EHV lines Paiton Kediri had been done at the end of 2006. Significant result has been obtained in the lightning performance by installing the EMT on the EHV lines Paiton-Kediri.