Recent Use of Line Surge Arresters (EGLA) on overhead Transmission Lines in Japan and their Effect on Reducing Lightning Outages

Here, almost all LAs for OHLs in Japan are of the Externally Gapped Line Arrester (EGLA) type, featuring external gaps without any mechanical cutouts.

Our research institute and all 11 transmission system operator companies (TSOs) in Japan have organized an investigative committee to study lightning protection design and measures since 1954. The committee has collected data on lightning-related outages (hereinafter referred to as

"lightning outages") of OHLs since 1980 throughout Japan. Here, we report data on lightning outages in Japan and discuss the effects of LAs and lightning performances on the viewpoint from the lightning outages of OHLs. In this report, the lightning outage rate is defined as the number of lightning outages of OHLs over a line length of 100 km in a year. The yearly variations of the lightning outage rates of OHLs for all voltage levels from 1980 to 2022 are presented in this paper. We also gathered data on the yearly increase in LA installations in Japan since 1989. EGLAs for transmission lines rapidly cuts off insulator-strings flashovers due to lightning strokes before they transition to AC arc discharge, reducing lightning outages. The cumulative phase number of the application of LAs—including zinc oxide (ZnO) type EGLAs and the fault current interrupting arcing horn (FCIAH), categorized as current limited gaps

(CLGs)—reached about 499,000 phases in Japan as of March, 2023. In Japan, LA installation is concentrated in 66/77 kV lines, followed by 110-154 kV lines. The outage rate of lines below 154 kV has shown a decreasing trend after 2008, likely due to LA installation. It should be noted, however, that these nationwide data do not permit a definitive identification of the specific contribution made by LAs. Therefore, we investigated the detailed relationship between outages, EGLA installations, and lightning flashes in selected OHLs across all TSOs in Japan. In this paper, two examples from the investigated results are presented.

Example (a) describes a 77 kV double circuit line where EGLAs were installed on one circuit

(1L) in 2004 on almost all towers. Although lightning flashes continued—for instance, about 200 flashes near the line in 2008, 2013, and 2018—lightning outages occurred mainly on the other circuit (2L), which had no EGLAs. Example (b) describes another 77 kV double circuit line where EGLAs were installed on nearly all towers of circuit 1L in 2006 and circuit 2L in 2016. From 2006 to 2016, the outages occurred primarily on circuit 2L. Subsequently, after 2016, lightning outages became rare on both circuits.