How much does studying Polyethylene tell us about XLPE?

Today technical publications often use the generic term “standard” polyethylene and cable. In this paper, we are trying to highlight the variations between different high pressure polyethylenes since the properties may vary between different resins. For example, one parameter that influences the properties of low density polyethylene is the type and content of the chain-transfer-agents that are used to control the chain length of low density polyethylene. They can be of different chemical nature and therefore strongly influence all properties of polyethylene. Moreover, the processing of the polymer during production of the cable has a significant influence on the morphology and thus the electrical properties. This is highlighted in various publications demonstrating a further factor that has to be taken into account when studying polyethylene. The morphology of the cross-linked polyethylene can depend on several factors that are outlined in this paper. We studied additionally the properties of cross-linked polyethylene, which is normally used in power cable applications for AC and DC applications. Since these cables are designed for a lifetime of more than 40 years, the influence of the different antioxidants that are used on the electrical properties are summarized, morphology and crystalline melting point were evaluated, highlighting a 8 K difference between virgin and stabilized polyethylene. Likewise, the history and construction of cables that are studied should be evaluated carefully, since the whole cable will influence the results and certain cable constructions are not used for higher voltages. The influence of tapes, for example, has not been studied anywhere in too much detail. In conclusion, we can say that a “standard” polyethylene and thus a “standard” cable does not exist and therefore care should be taken extrapolating data from one scientific study to a cable produced under different conditions.