ALTERNATIVE POLYETHYLENE CROSSLINKING CONCEPTS FOR POWER CABLE INSULATION
Doctoral thesis, 2019

We currently witness an accelerating shift from fossil energy sources to renewables driven by the urgent need to reduce carbon emissions. Wind, solar and hydro power is most abundant in places far away from the end user, which necessitates the efficient transport of electricity over long distances. Alternative grid designs are needed that complement high-voltage alternating current (HVAC) with high-voltage direct current (HVDC) cables. The most advanced power cable technology uses crosslinked polyethylene (XLPE) insulation, which is produced by peroxide crosslinking of low-density polyethylene (LDPE). However, peroxide crosslinking gives rise to by-products that compromise the cleanliness of LDPE and raise the electrical conductivity of the insulation material. Therefore, a by-product free curing process, which maintains the processing advantages and high electrical resistivity of LDPE, would considerably ease cable manufacturing and is therefore in high demand.

This thesis introduces alternative concepts for the crosslinking of polyethylene that fulfil these requirements. In particular, the suitability of click-chemistry epoxy ring opening reactions for curing of an ethylene-glycidyl methacrylate copolymer has been explored. Three main concepts for by-products free cable insulation have been studied: (i) crosslinking of LDPE copolymers with low molecular-weight multifunctional curing agents, (ii) Lewis acid assisted crosslinking of LDPE copolymer formulations, and (iii) reactive blending of LDPE copolymers. After extensive characterization of the thermo-mechanical properties of the materials, as well as preliminary conductivity studies, it can be anticipated that the concepts introduced in this thesis are a viable, by-product free and sustainable alternative to peroxide-based crosslinking of polyethylenes.

epoxy

crosslinking

HVDC

polymer blends

click-chemistry

polyethylene

Renewable Energy

High-voltage insulation

Vasa A-salen, Vasa Hus 2-3 entréhall, Vera Sandbergs Allé 8, Göteborg
Opponent: Professor Eva Malmström Jonsson, Kungl. Tekniska Högskolan, Stockholm Sweden

Author

Massimiliano Mauri

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Christian Müller Group

Byproduct-free curing of a highly insulating polyethylene copolymer blend: An alternative to peroxide crosslinking

Journal of Materials Chemistry C,; Vol. 6(2018)p. 11292-11302

Journal article

Click chemistry crosslinking of a low-conductivity polyethylene copolymer ternary blend for power cable insulation - M. Mauri, A. I. Hofmann, D. Gómez-Heincke, P.-O. Hagstrand, T. Gkourmpis, O. Prieto and C. Müller

Today most of the energy consumed worldwide comes from non-renewable resources such as coal, oil and natural gas. Consequently, a vast amount of green-house gases is released into the atmosphere, contributing to global warming. Driven by the urgent need to reduce carbon emissions, we currently witness an accelerating shift from fossil energy sources to renewables. However, wind, solar and hydro power are most abundant in places far away from the end user, which necessitates the efficient transport of electricity over long distances. High voltage direct-current (HVDC) cables are a critical component of tomorrow’s power grids that seamlessly integrate green energy derived from renewable sources. HVDC cables are particularly attractive because they permit the efficient transport of power. To further reduce transmission losses the development of new insulation materials is necessary, which therefore receives considerable attention. Low density polyethylene (LDPE) is the most widely used material for high voltage power cable insulation. Typically, crosslinking of LDPE is necessary to prevent deformation of cables at elevated temperatures and under high load. Today LDPE is commonly crosslinked with peroxides, but the process releases by-products in the polymer mass which compromise the electrical properties of the cable. In order to remove volatile by-products from the insulation, cables must be degassed at elevated temperatures for several weeks, which is both time consuming and costly. Therefore, by-product free crosslinking concepts that mitigate the associated increase in electrical conductivity are in high demand. To avoid the by-products that results from peroxide curing, in my studies I explored alternative crosslinking concepts for LDPE based on click chemistry type reactions. In this thesis I demonstrate how click chemistry crosslinking of polyethylene copolymers is a promising alternative to peroxide curing, and that this technology can (1) be compatible with established cable production, (2) avoid the release of harmful volatile compounds and (3) provide the mechanical strength and low electrical conductivity required from the insulation material.

Polyolefins for electricity energy distribution

Borealis AB, 2012-01-01 -- 2016-12-31.

Borealis Plus 3

Borealis AB, 2017-01-01 -- 2021-04-30.

Subject Categories

Polymer Chemistry

Chemical Process Engineering

Energy Systems

Driving Forces

Sustainable development

Innovation and entrepreneurship

Areas of Advance

Energy

Materials Science

Roots

Basic sciences

ISBN

978-91-7597-841-3

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4522

Publisher

Chalmers University of Technology

Vasa A-salen, Vasa Hus 2-3 entréhall, Vera Sandbergs Allé 8, Göteborg

Opponent: Professor Eva Malmström Jonsson, Kungl. Tekniska Högskolan, Stockholm Sweden

More information

Latest update

2/18/2019