Understanding Safe Approach Distance/SAD
The safe approach distance (SAD) is based on an “exclusion zone” principle. This principle defines an area around an exposed conductor into which no part of the person, mobile plant or object (other than approved insulated objects) may encroach unless pre-determined control measures are in place.
Work practices must be established to ensure personnel, mobile plant and unapproved objects do not encroach on the SAD. These should include consideration of working beyond reach, and precautions to be applied when use of controlled movement is necessary.
To put it into context, the SAD is the minimum distance in air from exposed conductors, that must be maintained by a person, vehicle or mobile plant (including its load, controlling ropes and any other accessories) when approaching electrical apparatus, other than for work in accordance with an access authority. This applies to outdoor substations having exposed, energised conductors and indoor substations equipped with metal clad or similar switchgear.
The location/position of the SAD is relevant to the position of the electrical apparatus. If an electrical apparatus, such as a live conductor, moves, the SAD moves with it. This change to the SAD can place persons, tools, equipment, apparatus, branches and other items at risk if not carefully planned for. The SAD also applies to overhead power lines, where plant or equipment such as scaffold components, roofing or other building materials, cranes or irrigation equipment are operated or moved under or in the vicinity of the lines.
Extreme care must be taken to ensure that the inadvertent movement of persons, tools, equipment, apparatus, tree branches and other items do not encroach the SAD for which they do not have authorisation.
It is essential to understand the differences in approach distances across the electrical industry. The SAD can vary depending on:
- the location of the electrical apparatus (i.e. on a mine site or within a residential town);
- the legislative requirements associated with the location of the electrical apparatus (i.e. OSH Act & Regs; MSI Act & Regs);
- the type of electrical apparatus (i.e. overhead vs. underground power lines);
- the voltage of the electrical apparatus; and
- the qualifications and experience of the personnel conducting the work.
