Extra High Voltage Underground Cables

The high reliability, cost effectiveness, low dielectric losses and low environmental impact of crosslinked polyethylene (XLPE), have made it the insulation of choice for high voltage (HV) underground cables. 

However, as the voltage rating of cables increases, the electrical stress on the XLPE compound also increases.  Therefore, the elevated electrical stresses of extra high voltage (EHV) cables, operating above 220kV, require even better performance from insulation systems. 

Borealis addresses this need with Superclean™ XLPE insulation compounds, which are significantly enhanced beyond those used for HV cable applications.

XLPE cleanliness essential to insulation performance

In addition to correct design and care in manufacturing, cable system reliability is dependant on the use of high quality, clean XLPE compounds.  Contaminants in material under high electrical stress reduce insulation performance and raise the risk of critical system failure.  Minimising this risk requires the highest level of material cleanliness.  Based on Borealis’ dedicated clean production technology, Superclean XLPE compounds provide for:

• exclusion of contaminants >100µ;
• control of contaminants <70µ;
• very clean, consistent quality materials.

Dedicated clean delivery system

The high level of ‘as produced’ cleanliness is preserved during transfer to cable extrusion plants through the Borealis’ developed EHV Octabin System.  These special containers are filled and emptied under clean room conditions.

Of key importance for the cable maker, Superclean XLPE compounds offer cable manufacturing advantages through better scorch safety, longer production runs before equipment needs to be cleaned, lower degassing burden, and shorter production cycles by 10-20%.

Complementary semiconductive screen materials

At higher electrical stresses a smooth interface between insulation and shielding increases the potential for reliable, uninterrupted power supply.  Borealis’ Supersmooth™ semiconductive compounds provide the solution.  These compounds give very smooth and even surfaces when extruded as the semiconductive screen in conjunction Superclean XLPE insulation.  Supersmooth compounds help:

• eliminate small contaminants and surface pips;
• reduce electrical stresses;
• minimise the risk of power failure.

Borealis is the leading supplier of XLPE compounds to the world’s largest EHV power distribution projects.