Diagnosis of oxidation in XLPE cable by tan delta characteristics

The authors investigated the relationship between the density of oxidation products and the temperature dependence of tan delta in LDPE (low-density polyethylene) films. From a comparison of the temperature dependence of tan delta of PE in XLPE (cross-linked PE) cable with that of tan delta in PE film samples, it was found that tan delta gives accurate information about the oxidation in the insulating layer of the cable. The temperature dependence of tan delta in the oxidized PE film has a peak around 0 degrees C, which is caused by the motion of the polar group. After oxidation has begun, tan delta increases to above 40 degrees C. This is attributed to the motion of a small section produced by chain scission. The increase of tan delta as a function of the density of oxidation products is obtained.<
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