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Prysmian Group – 2015 Sustainability Report
Sustainable Innovation
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A key milestone has been reached in the field of extra high voltage (EHV) terrestrial cables, with the
qualification of systems with extruded sheathing for voltages in excess of 500 kV. In particular, the 525 kV
HVDC system with solid sheathing has been tested successfully. As known, HVDC power transmission
systems have a number of advantages with respect to HVAC systems: longer distances, absence of
dielectric losses dependent on frequency and greater power transmission capacity. The result is a
considerable decrease in the consumption of raw materials and energy at the manufacturing stage, as well
as in the losses associated with power transmission.
Lastly, again with regard to high voltage terrestrial cables, we are working on the optimisation of conductors
in order to reduce excess metal consumption and improve their efficiency.
Initial applications have already resulted in a 2% weight reduction for certain conductors.
P-Laser
With regard to development of the P-Laser technology, the first cable produced using recyclable raw
materials for eco-sustainable electricity networks, the pre-qualification of the HVDC terrestrial system,
together with accessories, has been successfully completed for the 320 kV class. This test was particularly
significant, since the conductor temperature of 90°C was higher than the qualification temperature normally
used for systems insulated using standard XLPE. The adoption of 90°C provides a greater safety margin
during operation, in the event of line overloads or in points where special laying conditions require an
increase in the thermal isolation of the cable. Additional tests, carried out using a special protocol defined by
the main Italian TSO, have also confirmed the superior performance of the P-Laser system for systems with
polarity inversion (LCC) up to 350 kV. This outcome is particularly significant, since the cable insulation was
significantly thinner than that for cables in the same voltage class made using "traditional" mesh solutions.
The above work has significant advantages in terms of lowering the environmental impact of HVDC systems,
both in the design phase and when manufacturing the cable. In particular, it is now possible to optimise the
design of the cable - and the system - in order to reduce the quantity of materials used, as well as the weight
and size of the various components. This applies to the conductor, which can have a narrower section given
the ability to withstand higher temperatures, and to the other components of the cable, including the
thickness of the insulation, which can be reduced in view of the excellent electrical properties of the P-Laser
material. In the manufacturing phase, on the other hand, the degasification stage can be eliminated. The
degasification treatment, which involves heating the insulated core suitably for as much as 2/3 months
before the next phase of processing, is particularly important and onerous for meshed HVDC systems. This
is due to the need to remove virtually all by-products from these cables, in order to avoid penalising their
electrical performance under operating conditions. P-Laser allows this treatment to be eliminated, with clear
advantages in terms of greenhouse gas emissions into the atmosphere and energy saving during the
manufacturing process.
Turning to Power Distribution, a special P-Laser cable has been designed for the Finnish market, with a
conductor that has longitudinal water resistance. The Finnish grid has carried out a pilot installation using
this cable, with entirely positive feedback from the local utility.