Integration of a ground-based lightning warning system into a mining operation in the Democratic Republic of the Congo

Abstract

Central Africa is a global lightning hot spot, with the tropical areas including the top 10 highest lightning-flash-rate densities in the world. There are no lightning-locating-system networks available across most of Africa, however, and it becomes necessary to make use of real-time, ground-based lightning early warning systems. Such a system was established in the southern Congo basin at the Kinsevere copper mine and has been operational since early 2015. The early warning system includes an electrical-field meter and a lightning-flash sensor, which produce two states of warning. Two years of data (July 2015–June 2016 and July 2016–July 2017) indicated a clear annual and daily peak in lightning activity, with an average lightning warning duration of 1.18 h and a maximum storm duration of 8.60 h. The seasonal flash occurrence was reasonably constant over the two years but was variable at a monthly level during the lightning season. Analysis of alarm state showed that the majority of events start with an escalation to an alarm state of 2 but that, over two years, 69.3% escalated further to an alarm state of 3. Alarm-duration analysis indicated that more time was spent in alarm state 3 (warning) than alarm state 2 (caution). It was concluded that a single warning state would be suitable at this location and would simplify the warning system but that appropriate alarm-activation thresholds in electric field and flash distance need further assessment.