Use of combined approaches towards mitigating faults caused by lightning on TNB distribution overhead lines

TNB is continuously seeking effective methods to improve the lightning withstand performance of its medium voltage distribution overhead lines. Through engineering practice assessment findings, improvement initiatives can be strategized and rectification regimes can be implemented to mitigate transient interruption on the medium voltage distribution overhead lines. However, due to the multiplicity of causes contributing to the frequent transient interruptions, a combination of approaches needs to be subscribed to improve the lightning withstand performance of these medium voltage distribution overhead lines. Shielding of equipment from direct lightning strikes is considered the first line of defence as some of TNB medium voltage distribution overhead lines are unshielded and are designed to be used with wooden cross-arm. Without shielding, these overhead lines require the use of surge arresters as protection from voltage surges caused by direct lightning strikes. However, these surge arresters are highly exposed to risks of being damaged by lightning surges due to the high incidences of lightning strikes in Malaysia. With the surge arresters failing, the probability for the equipment installed on the medium voltage overhead to be damaged by lightning surges is very likely. Finally, in order to ensure effective discharge of the lightning current to ground, effective grounding is necessary. Unfortunately, some TNB medium voltage distribution overhead lines run through sandy or rocky grounds where soil resistivity can be very high. This paper attempts to illustrate the combined methodologies that have been used to reduce transient interruptions on medium voltage distribution overhead lines and mitigate failures of the various overhead line equipment especially automatic circuit reclosers.