Multipurpose Lines Help Lead the Way for PP Cable
One of the new trends in power cable manufacturing is the rise of PP (polypropylene) based thermoplastic materials for the medium voltage application. Thus, we have two designed multipurpose line concepts suitable for PP based medium voltage cables.
Currently, power cables are predominantly XLPE and rubber, but now advances in material development make it possible to also consider thermoplastics. Our commitment is to follow the markets needs and provide solutions for all applications and materials.
Considering the options
One option is a horizontal extrusion line with a triple extrusion group that runs PP based MV, XLPE MV as well as any other low voltage cable construction. Another possibility is a multipurpose catenary CV line which is used for PP, XLPE or rubber cable production. By choosing these multipurpose lines the cable manufacturer is not restricted by the material and can effortlessly match the needs of the end customer. Also existing lines can be easily modified to be suitable for PP based cable production.
Progress in PP
The progress made with several PP technologies at our R&D Center, results in developments to our equipment, including a new high output screw specific for PP insulation. Globally there have been eight Maillefer lines modified to run PP cables comprising of horizontal Monosil lines, catenary lines and vertical HV lines.
Traditionally the polypropylene based materials have not been suitable for the requirements of MV cable application. Mainly they have been too stiff, and subject to stress whitening and void formation. Advances in catalysts technologies have resulted in materials that have improved elasticity, are softer and better suited for MV cables.
Weighing the advantages
The advantage over XLPE cables is that PP does not go through crosslinking to make it withstand higher operation temperatures. This means that there is no methane degassing step, as required with the XLPE cables after being produced. On the other hand, PP has lower thermal conductivity, which has certain disadvantages. Once installed and under operation, a PP insulated cable with a similar construction as XLPE will have a higher conductor temperature. This is seen as electrical loss at the conductor.
Looking towards the future
Cable manufactures wanting to adopt PP based technologies still face several practical questions: When will the materials be commercially available for them? How will the material cleanliness and lack of established supply chain be solved? What quality control methods will be specified for PP cables? Will PP cable be competitive from utilities point of view? As the market develops, Maillefer is providing the versatile machinery solutions that accompanies those who have begun and those who are ready to lead the future of PP cable.
Janne Harjuhahto
R&D
janne.harjuhahto@maillefer.net
