IEC 60055-2: Paper-Insulated Metal-Sheathed Cables

Paper-Insulated Cables: Obsolete or Still the Best Choice for Extreme Environments?

IEC 60055-2 specifies paper-insulated metal-sheathed cables. While XLPE has dominated MV distribution, millions of kilometers of paper-insulated cable remain in service — especially in legacy urban networks, industrial plants, and marine systems.

Paper insulation unique advantages: Oil-impregnated paper has a higher partial discharge inception voltage than XLPE of equivalent thickness, because oil fills all micro-voids. Paper also ages better than pure polymers under high temperature (>90 °C) and radiation exposure — explaining why some nuclear plants still specify paper-insulated cable.

Achilles heel: Moisture ingress. Once the metal sheath is breached, water penetrates the paper, and insulation resistance drops by an order of magnitude within hours. A Polarization Index (PI) below 1.5 on an aged paper-insulated cable typically indicates moisture — replacement, not repair, is the only safe option.

TN Lab — Paper-insulated cables are not obsolete technology; they are specialized equipment requiring different maintenance strategies.