Electric shocks incidents involving people in their homes due to faults on HV distribution assets in the neighbourhood reminded engineers of the risk to the public from these assets. Concerns about these risks, whilst valid, were tempered by the realisation that electricity is an established utility. The public, including you and me, all take for granted the ongoing supply of electrical energy. So, some Australian earthing engineers teamed up to understand how to do earthing design better. Now the world is listening to Australia on this subject.
What constitutes a ‘safe’ design?
The designer of distribution earthing systems has a problem. How to determine a ‘safe’ and affordable design within a quite limited design budget? And this begs the question what constitutes a ‘safe’ design?
The last two decades have seen a lot of work done to answer the question “What constitutes a ‘safe’ earthing system”. As those close to this area know, it’s more a question of reducing risks to acceptably low levels in accord with current best practices and to as low as reasonably practicable. Rather than designs being assessed with a binary outcome, i.e., either ‘satisfactory’ or ‘unsatisfactory’, best practice suggests that ‘safe’ is no longer the right approach. The ENA Power System Earthing Guide (EG-0) Part 1 Management Principles documented how earthing risks could be quantified and an approach for completing designs using quantitative risk assessment. Recently revised Australian Standards such as AS2067, AS4853 and AS7000 now also follow this approach. Earthing designs are now approached through the lens of reducing risk levels through the transition from unacceptable to negligible risk.