Electricity + Control October 2018

CABLES + ACCESSORIES

Developing next generation cable accessories

Ruben Grund and Michael Zerrer, Pfisterer

Power distribution networks are changing rapidly as integration of renewables and creeping urbanisation require updated concepts in power infrastructure.

Take Note!

1. Modern cable joints en- sure simple installation of the waterproof exter- nal housing as well as 2. Treatment of the cable shielding can be adapted individually for cable type and customer needs.

C ompactness is no longer only a desirable but a crucial performance requirement. Similarly, downtime has to be minimised while safety aspects are more complex. Increasing transmission capacity Urbanisation requires higher transmission capaci- ty that could be either triggered by increasing cus- tomer numbers or fluctuating power generation and consumption due to integration of renewa- bles. Moreover, energy has to be transported over long distances since points of generation and de- mand often do not overlap. This requires detailed consideration of power losses and one approach to reduce these has been increased system volt- age, as has occurred over past decades. While the first three-phase ac line in 1891 had a system volt- age of 25 kV and carried power over 176 km, these days system voltage of 550 kV is used for extra high voltage cable lines, allowing power transmis- sion up to 1.5 GVA. The main reason for higher system voltages is power loss reduction. For ex- ample, increasing system voltage by 10 leads to a reduction in power losses by a factor of 100, using same diameter cable. If cable diameter is reduced

by 10, power losses are still reduced by a factor of 10.

Cable accessories up to UM=550 kV Accessories are increasingly available for high volt- age cables up to 550 kV. These include dry, plug- gable cable connections for transformers and gas insulated substations (GIS), cable terminations, cable joints and pluggable cable joints as well as blind dummy plugs. These components are type tested and can be used for all types of XLPE cable, independent of core diameter, thickness of insu- lation or manufacturer. All field control units and electrically stressed materials are pre-fabricated and routine-tested, which ensures highest long- term operational safety. Pluggable systems One type of dry pluggable system can handle cable diameters of 3000 mm² CU or AL conductor, carry- ing up to 4000 A nominal current. Maximum diame- ter over insulation is 144 mm. An additional benefit is the housing, which is touch-proof, waterproof and salt-water resistant, meaning it can be used in coastal areas as well as in offshore surroundings.

12 Electricity + Control

OCTOBER 2018