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The level of water tree degradation:
Do you have a network consisting of polymer-insulated cable? Did failures occur or are you concerned with the reliability of the insulation? Water treeing became a serious problem in polymer-insulated cables from the seventies and it is still teasing cable network managers.
Insulating and semi-conductive materials have improved over the years since the background of water trees became clearer in the 1980s. Many cables of the first generations are in operation, however, and some later generations appear still to suffer from water treeing. Once breakdowns occur in a cable network due to water treeing there is a great risk of more failures following soon.
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Assessment
KEMA has developed a methodology to assess the level of water tree degradation in cables. The methodology comprises two test methods: - A high voltage breakdown test followed by a microscopic assessment. The breakdown voltage and the length of water trees are determined. These are used to evaluate the reliability of the cable. The outcome is a classification as 'good', 'bad' or 'in between' based on a benchmark with the extensive KEMA database. Also, other irregularities in the insulation will be determined.
- A sole microscopic investigation. The level of water tree degradation of the insulation and other irregularities is determined. This is a faster and cheaper test than the previous one. It is not as precise, however. The outcome is a classification as 'bad', or 'not regarded as bad'.
Benefits of option 1: - Benchmark of the cable investigated with the extensive KEMA database
- Judgement with the weight of an internationally recognized test method
- Foundations for asset management
Benefit of option 2:- Fast and budget evaluation
- Recommendation for replacement if cable is found bad
- Foundations for asset management
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