Incorrect application of international standards governing horizontal post insulators could be introducing unintended mechanical risks into overhead power line designs, particularly as utilities and developers push for more compact pole-top configurations to accommodate growing electricity demand.
A technical paper, presented by Allan Muir of South Africa-based Mace Technologies during the CIGRE Southern Africa Regional Conference in Pretoria in October 2025, highlights persistent misunderstandings about the use of combined load formulae set out in IEC 61952, which governs composite line post insulators for overhead lines above 1 kV.
Horizontal post insulators, commonly used on wooden, concrete and steel monopoles between 11 kV and 132 kV, have become increasingly prevalent as space constraints, servitude limitations and the move towards monopole structures drive more compact line designs. However, Muir warns that, as these insulators are deployed at higher voltages with longer spans and heavier conductor bundles, they are being pushed closer to their mechanical limits.
