ABSTRACT
Earthing and lightning protection systems protect people from the danger of electrocution and equipment from over-voltages by dissipating the excess energy into the earth, and at the same time reducing the potential difference between equipment and earth. This study investigated the effect of lightning strikes on people, buildings, communication towers and equipment by determining the number of lightning strikes on the structures depending on their location and height as well as the earthing resistances. With the aid of data obtained from April 1995 to February 2003, from the National Aeronautic and Space Agency (NASA), Lightning Imaging Sensor (LIS) Science Team and from NASA's Optical Transient Detector and colour coded onto a map, the annual flash rate for Zaria was obtained. Based on this, the number of lightning strikes on two structures; the control tower of the Zaria Aerodrome and the communication tower of the Zaria Nitel Exchange; were determined. The Fall-of-Potential Method (also referred to as Earth-Spike Method) was method used for the earth resistance measurement. The null-balance analogue type Megger Earth Tester was used as the test instrument to determine the earth resistance of the following locations within Zaria: Department of Electrical Engineering, Zaria Aerodrome Control Tower, Commercial Complex, No. 8 Sokoto Road and Nitel Exchange Communication Tower. The earth resistance measurements taken for the various locations were in conformity with the general standards: