Improved Technical Requirements for Potential Refurbishment on Tower Earthing Systems for Inundated-prone Areas

It provides a controlled path for current from lightning strikes, or excess current to safely dissipate into the earth, preventing unintentional tripping/outages and reducing the risk of electrical shock to personnel and the public. Refurbishing existing overhead line may include the assessment in the integrity of the earthing system. The integrity of tower earthing systems in inundated areas, especially, are often found compromised with faster degradation rate due to environmental factors, underscoring the critical need for timely mitigation measures to ensure system reliability and public safety. Operationally, this has caused for increased operation and maintenance costs through replacements of earthing components at multiple locations, labour expenses from frequent inspections and patrolling following unintentional outages and other associated expenses, especially when it involves contracted works for the rectification of tower earthing systems.

The work involved has focused on selected sites of a total of 28 towers of overhead lines of various voltage systems, in inundated-prone locations or areas with known high-water table in four regions of the Peninsular Malaysia. Soil samples from these sites were collected and then characterised based on its corrosion risks towards the tower earthing components. Several earthing component types were tested with these soils in the laboratory that served as mock-up sites. The rates of corrosion were established and average rates obtained for specific regions with similar soil types. Estimated lifespan of the components were estimated and then compared across the various results obtained from the selected regions. The tested earthing components were galvanised steel tape, galvanised stranded wire, solid pure copper rod and solid copperbonded rod. The metal samples from each component were subjected to the weight-loss method procedure for the determination of the average uniform corrosion rate and the estimated total lifespan.

Several mitigation options such as (a)increasing the thickness in galvanising layer of the earthing components, (b)embedding or encapsulating earthing components into Earth

Enhancement Compound (EEC) and/or cement and (c)opting for components made with superior material(s) were explored. The uniform corrosion rates and estimated total lifespans were obtained for each mitigation approach and compared. The mitigation approach with the best corrosion outcomes were identified and then incorporated into the technical specifications as enhancement and fortification of requirements, ready for its deployment for future refurbishments overhead lines.