Beyond reach and controlled movement
The Safe Approach Distances discussed above rely on the beyond reach principle : that workers should not be in a position where accidental movements encroach on SADs . In other words , workers use controlled movements to remain in working positions where , at full reach , it is impossible to put any body part within the SAD .
Examples of beyond reach include making sure that the aerial appliance basket is set up so that workers cannot reach into the SAD , using climbing techniques to prevent uncontrolled swings within the SAD , or remaining far enough away from SADs that trips or slips will not encroach on the minimum distance .
Automatic Circuit Reclosers
Distribution networks will usually include Automatic Circuit Reclosers ( ACRs ) or autoreclosers . These function as temporary circuit breakers designed to handle a short closeopen duty cycle , usually configured to a set number of attempted close operations before reverting to lockout . Where the network experiences a temporary earth or short-circuit , for example during a lightning strike , surge or contact with a foreign object , the ACR works by re-closing the circuit once the temporary fault has passed .
Most ACRs can be remotely operated and interrogated by the network authority . Where a vegetation management worker has been injured , it may be possible for the rescue command centre to gain critical information on whether conductors have been contacted by communicating with the network authority :
• If the local ACR has entered lockout , it is likely that the casualty or tree is continuously in contact with the conductor ( reclose prevented ).
• If the local ACR has cycled but has not reverted to lockout , it is likely that the casualty or tree contacted the conductor during the accident but did not remain in contact .
• If the local ACR has not cycled , it is possible that the conductors were not contacted during the incident .
Vegetation management workers will often arrange for local auto-reclose suspension whilst working on the network . This is a protective measure to ensure that if vegetation or workers short-circuit the network , it will not subsequently become live again .
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