This paper investigated the impact on the earthing systems of cabinets of Telekom Malaysia (TM) when subjected to dangerous voltages due to current injection from remote sources. TM have received numerous cases regarding the failures of their cabinets due to power related issues (PRI) as well as lightning. These failures may have occurred partly due to the existing earthing systems installations. This research aims to determine earthing impedance of 5 ohms or less of TM cabinets with respect to local soil conditions. Low impedance earthing is not easy to realize mainly due to the local soil resistivity, layering and structures. To achieve a low impedance of below 5 ohms as per Telekom Malaysia's requirement, three types of earthing electrodes were modelled and simulated using CDEGS computer simulation software. Results have demonstrated that the existing earthing system of 3 rods practice by TM is sufficient for areas of resistivity less than 500ٹ-m. Combination of rectangular and vertical rods for resistivity of 500ٹ-m above is the preferred choice of earthing. Analysis and discussions presented in this study can be used as a guide for TM for their cabinet installations. Results also highlighted that achieving less than 5ٹ does not constitute a safe earthing system. Other parameters have to be taken into account before ascertain which type of earthing to be used in a specific location of a TM installation.
Influence of LV neutral grounding on global Earthing Systems
