Journal of Emerging Trends in Engineering and Applied Sciences: Research Areas

Article Title: Improved Lightning Protection of Distribution Transformers in Kenya
by Livingstone Ngoo, James Muriuki, Christopher Muriithi, and George Nyakoe,

Abstract:
In Kenya two main causes of high failure rate of Terminal Distribution Transformers (TDTs) have been identified as harmonics and Lightning strikes. Although harmonics have been a current phenomena due to the filtrations of electronic components in the domestic and commercial sectors, lightning strikes as a natural phenomena has been with the power sector for a long time and mostly affects the terminal Distribution Transformers. These transformers are most susceptible to faults emanating from lightning strikes and associated overvoltage especially in regions of Mt Kenya, Western Kenya and Coastal region. However, some parts of the Rift valley are also affected. In the recent times, the failure rate of the TDTs has been on an upward trend despite the provision of standard earthing and protection systems. The useful life span for TDTs has thus been reduced to less than a year due to frequent voltage surges and vandalism of earthing materials. Records show that the failed TDTs are quickly replaced without due diligence for innovative ideas to prevent future failures. This paper provides a novel and innovative solution for TDTs by extending the Medium Voltage (MV) power line one span away from the TDT where installation of Terminal Surge Diverters Earth (TSDE) and Terminal Medium Voltage Earth (TMVE) are installed. The earthing is done with the objective of ensuring that TMVE and TSDE are less than that of the TDTs so that in the event of lightning strikes; voltage surges will flow through the low resistance path. In addition, all the TDTs must have an Aerial Earth Wire (AEW) for providing an easy path for the voltage surges to flow through to the TMVE, TSDE and to the ground. The results show that the novel and innovative arrangement significantly reduces the failure rate of TDTs.

Keywords: Earthing system, Harmonics, Failure rate, Lighting strikes, Terminal Distribution Transformers, Voltage surges.

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