Possums walking overhead conductors cause phase-to-phase faults, nuisance tripping, burnt spans and callouts — and the possum rarely survives it. A rotating possum guard fixes the problem mechanically: the animal cannot get purchase on a sleeve that spins.
This guide covers how the guards are sized, spaced and installed, and — just as importantly — when a possum guard is the wrong product for the problem you have.
Read this before anything else
Never attempt to install a possum guard on a live conductor, and never work within reach of an overhead line that has not been isolated and proven de-energised. Overhead lines carry enough energy to kill without being touched — arcing across an approach distance is sufficient.
- Network-owned lines (anything from the street to your point of attachment) are the property of your distribution network operator. Only the DNSP or an Accredited Service Provider may work on them. Contact your network operator and report the possum activity — in most areas they will assess and fit guards themselves, often at no cost, because outages cost them more than the hardware does.
- Consumer mains and private overhead spans — between a house and a shed, across a rural property, or on a private distribution network — must be isolated at the source and installed by a licensed electrician.
- Unauthorised persons must stay outside the minimum approach distance for the voltage involved. If you are not sure what that is, you are not the person who should be doing this work.
The rest of this guide is written for licensed installers, and for property owners and facilities managers specifying the work so they can order the right parts.
How a rotating possum guard works
The guard is a lightweight polyethylene sleeve that fits loosely over the conductor and is free to rotate around it. A possum stepping onto the span puts its weight off-centre; the sleeve turns under it, the animal loses grip and drops clear. Nothing electrifies, traps or injures it, and after a couple of attempts the span stops being a route.
Because the guard is not bonded to the conductor and carries no current, it does not affect the electrical performance of the line. The FASTNAS guard is LDPE with a volume resistivity above 1016 (ASTM D257), CABAC PPG-type.
Choosing the right size
Guards are specified by internal diameter. The sleeve must be comfortably larger than the conductor — if it grips, it cannot spin, and a guard that cannot spin does nothing.
| Internal diameter | Suits |
|---|---|
| 38mm ID (1-1/2") | Most LV service and consumer mains, single conductors and smaller bundles, 10–240mm² |
| 70mm ID (2-3/4") | Larger bundled conductors, aerial bundled cable, and spans where the 38mm will not pass over a joint or fitting |
Both are supplied in 800mm (31-1/2") lengths and are joined end to end to make up the run.
How many do you need?
Possums are agile. Guarding one metre of a span simply moves the crossing point, so the guard has to cover more than the animal can bridge.
- Identify the access points — where the possum gets onto the line. Usually a pole, a tree limb, a fascia, a fence or a shed roof close to the span.
- Guard outward from each access point, not the middle of the span. A possum cannot start mid-air; it always boards at an end.
- Allow at least 2–3 metres (7–10 feet) of guarded conductor from each access point — that is 3 to 4 sleeves per end. Less than 2 metres and a determined animal will simply lunge past it.
- Guard both ends of a span unless one end is genuinely unreachable.
A typical single-span job between a pole and a house is around 6 to 8 sleeves. Order a spare — running one short at height is an expensive way to save the price of a sleeve.
Installation
For licensed personnel, on an isolated and proven de-energised conductor.
- Isolate and prove dead. Apply locks and tags. Confirm with a tester you have proven immediately before and after.
- Open the sleeve along its split and pass it over the conductor. It should close around the cable with clearance all round — you should be able to spin it by hand with one finger. If it binds, you have the wrong size.
- Butt the next sleeve hard against the first and continue along the span. Gaps between sleeves give a possum a foothold, which defeats the whole system.
- Secure the run with cable ties at the joints, as the design intends. Tie firmly enough that the sleeves cannot separate or migrate along the span — but never so tight that you deform the sleeve or clamp it to the conductor. It must still rotate freely.
- Trim the tie tails flush. Long tails give purchase and collect debris.
- Spin-test every sleeve before you come down. Any sleeve that does not turn freely is doing nothing.
- Cut back the access route where you can. A guard plus an overhanging branch trimmed to 2m clearance is far more effective than a guard alone.
Common mistakes
- Cable-tying too tight. The single most common failure. A guard that cannot rotate is just a plastic tube.
- Guarding too short a length. Two sleeves at one end looks tidy and does nothing.
- Leaving gaps between sleeves. Any exposed conductor is a foothold.
- Ignoring the tree. If a branch overhangs the guarded section, the possum bypasses the whole install.
- Wrong diameter. Sizing down for a snug fit is exactly backwards.
When a possum guard is the wrong product
This is a product for overhead conductors. It is not a general possum deterrent, and it will not help you if:
- Possums are getting into your roof. That is an exclusion job — seal the entry points after dark once the animal has left, and provide a nest box. A cable guard is irrelevant.
- You want to protect a tree or garden. That is a tree guard or possum spikes — a different product entirely. Spikes deny a landing point; a rotating guard removes grip along a span. They solve different problems.
- Possums are walking a fence or pergola. A conductor guard needs a round, free conductor to spin on.
In Australia possums are protected native wildlife. It is illegal to harm, poison or relocate them in most states. A rotating guard is legal precisely because it does not hurt the animal — it simply makes the route unusable.
Maintenance
Polyethylene sleeves are UV-exposed for their whole life and will eventually chalk and embrittle. Inspect at any scheduled line inspection: look for split sleeves, sleeves that have migrated and opened a gap, and — most importantly — sleeves that have stopped rotating because a tie has tightened or debris has packed in behind them. Replacement is a like-for-like swap.
Ordering
FASTNAS supplies the rotating possum / critter guard in 38mm and 70mm internal diameter, 800mm lengths, dispatched from Sydney. Cable ties for the install are in the cable ties range.
Not sure which diameter suits your conductor? Email fastnasau@gmail.com with the cable type and we will confirm before you order.