ABSTRACT
Discoveries of water trees in XLPE cables occurred in the 1960s. Since then people began to pay attention to this phenomenon and study how to inhibit the formation of water trees, however until now theories of the cause and growth mechanism of water trees are still not completed. Water trees in cable insulation can be in the form of an air gap with shape of divergence or the tie under the action of high electric field (see Figure 1 and Figure 2). How to inhibit water tree formation effectively and
1 INTRODUCTION
Cross-linking polyethylene (XLPE) is widely used in power systems because of its outstanding electric properties and cut-price manufacturing cost. In the long-term operation of cables, some internal performances would deteriorate, which seriously affect the cable service life. Among them, the formation of water trees is one of the major factors. In the long-term use of XLPE cables, the water tree would produce under high intensity electric field under water environment, the cable may then break down and its service life is severely reduced. Therefore, the question of how to inhibit water treeing and increase the service life of the cable has in recent years become a hot research topic both in China and abroad (Crive and Jow 2005, Dang, Kang and Tu 2002).
