Page 3: Creating a new product
Electricity is distributed in rural areas by the use of bare aluminium conductors supported by wooden poles. This method of electricity distribution is used world-wide, particularly in rural areas where the use of more expensive (but less visually obtrusive) underground cable cannot be justified due to the length of the line and the relatively low amounts of electricity supplied.
A disadvantage of such overhead line systems is that they can be subject to a large number of faults caused by obstructions on the lines (birds, tree branches etc.), by the touching of the lines in high winds or the failure of insulators. Most of these faults are temporary and will disappear once the current is re-established after a short interruption. To keep system interruption down to a minimum, pole mounted auto-reclosers are used.
Essentially, an auto-recloser is a poletop mounted reclosing circuit breaker which is used to protect sections of the overhead line supply network, usually in remote locations. An electronic control unit operates a mechanism which opens the main circuit contacts when it detects faults in the current supply on the overhead lines which it monitors. It then recloses. If the fault is still present, the auto-recloser will open and close two more times before finally locking out. If the fault has cleared, the auto-recloser sequence ends with the main contacts closed and the supply re-established. Auto-reclosers must be highly reliable and require little or no maintenance because they are:-
- intended to improve the reliability of the distribution network.
- unlike other forms of protection device which very rarely operate, an auto-recloser’s normal duty is to operate many times under fault conditions.
- installed in remote locations of the network