Characteristics of electric field change preceding negative first return stroke produced by preliminary breakdown

Understanding the initiation process of preliminary breakdown during negative CG lightning discharges to the ground is important to design a lightning protection system. We observed electric field change preceding negative cloud to ground lightning flashes related to preliminary breakdown in tropical region, Indonesia. The characteristics of electric field change of negative first return stroke produced by preliminary breakdown process were studied. The results showed that arithmetic mean and geometric mean of pre-return stroke separation is 57 ms and 32 ms, respectively. Other statistical parameters also are shown in this paper.