PILC is the traditional UK distribution cable: shaped copper conductors insulated with mass-impregnated paper tapes, enclosed in a lead or lead alloy sheath that keeps moisture out, then bedded, armoured and sheathed. It has been superseded by XLPE for new work, but very large quantities remain in service on 11 kV networks, so the cable and its accessories are still supplied for repairs, extensions and joints onto existing circuits. The paper insulation is extremely durable and PILC circuits routinely run for many decades.
Key applications
- Repairs and diversions on existing 11 kV PILC networks
- Transition joints between PILC and XLPE cable
- Extensions to legacy distribution circuits where matching cable is required
- Substation interconnections on older industrial sites
- Direct buried MV circuits on established networks
- Replacement lengths following cable damage
Features and benefits
- Impregnated paper insulation is exceptionally long-lived in service
- Lead sheath is a complete moisture barrier and an effective earth fault path
- Shaped conductors give a compact cable for the cross-section carried
- Compatible with existing network accessories and jointing practice
Specification notes and limitations
PILC must only be worked on by personnel trained in paper cable jointing: the lead sheath has to be wiped or sealed so that moisture cannot reach the paper, and an unsealed end will draw in damp and fail. Minimum bending radius is twelve times the overall diameter, and the lead sheath work-hardens and cracks if bent repeatedly or handled in cold weather. The impregnant can migrate on steep or vertical runs unless non-draining compound is used, and the lead sheath itself is heavy and a toxicological hazard when cut, wiped or burned, so control of lead dust and fume is required. Conductor temperature is lower than XLPE, so current ratings are not interchangeable — never assume a PILC circuit can carry the rating of the XLPE cable replacing part of it.
