There is a large selection of materials for permanent electric fencing available from several major suppliers. Temporary or portable fencing is described here.
Posts
The following types can be used for permanent fences:
- Pressure treated softwood posts are the most common type, used with insulators. These can be used for conventional fencing as required.
- Self-insulating hardwood posts are available from Gallagher fencing. These posts are made of an Australian hardwood which is durable without treatment, and does not require separate insulators. The wood is too hard to be stapled, and wires are attached by clips through pre-drilled holes.
- Posts made from recycled polypropylene, which are self-insulating and with pre-drilled holes.
Insulators
Most insulators are made of various types of plastic, with UV stabilisation an important quality to prevent deterioration in sunlight. The design should ensure at least 25mm (1″) ‘tracking distance’ between the live wire and the post, and should also maximise the distance between the live wire and any staple or nail used to attach the insulator to the post. Plastic insulators should not have a metal core, as this can also cause short-circuiting. A simple type of insulator is ‘Insultube’, which is cut to length as required, and can be used for intermediate and corner posts, and for insulating wires at stiles, water troughs and so on. It has the advantage of being simple with little to fail, but care must be taken to thread on the correct number as the fence is being erected, as they cannot be fitted afterwards.
Strain insulators are heavyweight insulators designed for use at straining posts.
An alternative system uses an insulated pad with a device that grips the strained wire, through a hole drilled through the straining post. This takes longer to fit, but is very durable.
Off-set insulators hold the wire at a distance from the fence, and are designed for either carrying the lead-out wire from the energiser to the fence, or for carrying a scare wire to keep animals off the fence. Various types are available for use with electrified wire, tape or rope, and for attaching to either posts or wires.
Wire
Barbed wire must never be electrified, or used in any fence that has part of it electrified. If an animal or person gets entangled in the barbed wire, there is a danger of injury or fatality from prolonged exposure to a series of electric pulses.
The gauge of the wire has to be balanced between the following:
- The finer the wire, the greater its resistance to current flow. This can be significant on long lengths of fencing.
- The thicker the wire, the greater its weight and cost. There are also more problems with change in tension due to temperature differences. A tension spring can be incorporated in the fence to overcome this problem.
Because there should be no direct pressure on electric wires from stock, lighter wire at lower tension can be used than for equivalent conventional fencing. Likewise, there is less strain on straining and turning posts.
High tensile 1.6mm or 2.5mm diameter wire is used for permanent electric fencing. Wire with an aluminium zinc coating, which provides high conductivity, is available from Gallagher. High tensile wires permit a larger spacing between posts. Provided straining posts are adequate, scare wires can be made of the same high tensile wire.
Stranded galvanised wire for temporary or semi-permanent systems should conform to BS443A. Wires not conforming to this standard may rust after only a year or so of use.
