Paper insulated lead cables (PILC) have been in use for more than 100 years in medium voltage applications from 6.6 kV up to 36 kV, as well as in high voltage systems.
PILC has been preferred over the years due its high dielectric strength, low dissipation factor, relatively low dielectric loss, low sensitivity to dc testing and proven reliability. However, it has become less popular as it is being replaced by cross-linked polyethylene (XLPE) cables due to factors impacting its cost-effective use. Many cable manufactures around the world have discontinued production of PILC in response to the reduction in demand.
XLPE as an insulating medium has a lower dielectric constant, lower dielectric loss and high dielectric strength and operates at higher temperatures, enabling the cable to be more efficient, carrying more current than the same size cable of paper insulation impregnated cable. XLPE is generally preferred by customers for factors relating to ease of use, efficiency, fewer accessories and less complexity, among others.
Some of the factors that favour XLPE rather than PILC for MV cables are set out below.
- XLPE has a higher current rating compared to the same size PILC cable due to the fact that XLPE has a higher operating temperature.
- For PILC cables, the installation, maintenance and repair processes are more complex, intensive, time consuming and high on cost compared to XLPE cables.
- As many factories worldwide have discontinued production of paper insulated lead cables, the accessories such as jointing and termination kits are not easy to find.
- The shortage of skills for splicing, jointing and termination of paper insulated cable is also driving customers to move to XLPE cable. Many PILC cable failures reportedly result from suspected poor workmanship related to the skills gap.
- Although PILC cable performs better in providing radial water blocking properties with the lead sheath which is completely impermeable, XLPE is also available in cost-effective water blocking formats for both longitudinal and radial water blocking. It can be supplied on request, by leading cable manufacturers such Aberdare Cables in South Africa.
- XLPE cables are more flexible than PILC cables which are more rigid especially for larger sizes. This means XPLE can be used where a shorter bending radius is required.
- Environmental considerations also play a role. Paper insulated lead cable is oil impregnated with mineral oil or PIB and, with its lead sheath (heavy metal), it presents a higher risk of environmental contamination than XLPE. Consequently, XLPE is favoured in many situations where an environmental analysis is a key aspect in design decisions.
Aberdare Cables Pty Ltd in South Africa offers XLPE cables up to 132 kV for customers across Africa and around the world. For voltages higher than 132 kV, XLPE cables can be provided by Aberdare cables through its parent company, Hengtong Group in China.
For more information visit: https://aberdare.co.za/
