A covered conductor line is only as good as its weakest fitting. The XLPE covering prevents faults from branches and clashing phases, but every clamp, joint and tap is a place where that covering is gripped, pierced or cut. Fittings designed for bare conductor, or careless stringing, can damage the covering on the day of installation and leave a weak point that fails years later. This guide sets out the accessory set and the practices that protect it.
The accessory set
| Accessory | What it does |
|---|---|
| Suspension clamp | Carries the conductor at intermediate poles and grips the covering without cutting it. |
| Anchoring or dead-end clamp | Takes the full line tension at section and terminal poles through a grip on the covering. |
| Insulation piercing connector (IPC) | Makes a live electrical connection by piercing the covering with toothed contacts, without stripping. Used for covered-to-covered, bare-to-covered and tap connections. |
| Pre-insulated junction sleeve | Joins two lengths of conductor mid-span, with insulation restored over the joint. |
| Arc protection device | Moves the root of a flashover arc away from the conductor and insulator so the arc does not burn through the conductor at one spot. |
| Surge arrester | Limits lightning and induced overvoltages that could puncture the covering. |
Accessories for covered conductor lines are governed by EN 50397-2. APAR supplies suspension clamps, insulation piercing connectors, anchoring and dead-end clamps and pre-insulated aluminium alloy junction sleeves to that standard, rated for use from minus 30°C to 70°C, with its covered conductors.
Stringing without damaging the covering
The covering is tough but it is not armour. Pay the conductor out from the drum under controlled back-tension, and keep it off the ground, off rock and off pole-top steelwork. Stringing blocks should have lined sheaves of a diameter suited to the conductor, since small unlined pulleys can crush or score the outer layer. Conductor grips used during tensioning must be of the type approved for covered conductor; a bare-conductor come-along can bite through the covering. Inspect the covering as it comes off the drum and after tensioning, and cut out any length with cuts or abrasion that reach the inner layer.
Sagging and clamping
Sag to the table supplied for the covered conductor, not to a bare-conductor table of the same size, since the covering adds weight and changes the sag-tension relationship. Fit anchoring clamps at the positions shown in the line design and tighten them to the manufacturer’s torque. Suspension clamps should sit squarely on the conductor with no kink at the clamp mouth.
Joints and taps
Insulation piercing connectors usually carry shear-head bolts that break off at the correct torque. Tighten until the head shears and do not add extra turns afterwards. Fit end caps on any cut conductor end so that water cannot enter the strands, even on a longitudinally water-tight conductor. Mid-span joints should use pre-insulated sleeves, and the covering should be restored over any point where it has been removed for a tool.
Arc protection and surge arresters
On a bare line, a lightning flashover travels along the conductor and clears. On a covered line the arc root can stay where the covering has been punctured and burn through the conductor. Arc protection devices, fitted at insulators, give the arc a defined path away from the conductor. Surge arresters at intervals set by the line design limit the overvoltage in the first place. Both should be shown on the line drawings and fitted at the time of construction.
Earthing points for maintenance
A covered line cannot be earthed for work by clipping a clamp onto bare metal. Plan permanent earthing points at section poles, using fittings that give access to the conductor, so that maintenance crews can apply working earths safely.
For conductor choice and route suitability see the MVCC selection guide. APAR’s team can confirm the accessory schedule against the route and conductor size for a project.