Project requirements · Water
Water tree resistant insulation (TR-XLPE)
The MV insulation compound slows water treeing for long life in wet ground.
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Constructions that meet it
- Tree-retardant XLPE (TR-XLPE): changes no layer: a property of the insulation compound. Tree-retardant XLPE compound instead of plain XLPE (TR-XLPE). Drawbacks: Same thickness and look; compound cost.
- HEPR / EPR insulation: changes no layer: a property of the insulation compound. EPR insulation (EPR). Drawbacks: Alternative accepted by ICEA AWTT.
- Swelling tapes over and under the metal screen: changes the cable's layers. Add longitudinal water blocking and a moisture-blocked jacket (swelling tape; XLPE jacket). Drawbacks: LS Cable offers a moisture-blocked XLPE jacket.
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Tests
- ANSI/ICEA S-94-649 clause 10.1.6: accelerated water treeing test (AWTT) at 3 U0 with thermal cycling, then AC breakdown. Pass: minimum AC withstand after wet ageing (value not read)
- AEIC CS8: utility specification for extruded MV cables (TR-XLPE listed). Pass: not read
How specifications state it
Named as 'TR-XLPE' with ICEA S-94-649 / AEIC CS8 in North America; in Europe often in utility specifications by compound name.
Where it is asked for
- North American URD and MV feeders
- utilities with wet soils
Sources
- Dow, 'Predicting cable longevity' 250-172-01 (ICEA S-94-649 10.1.6, AWTT at 3 U0) (quoted by others)
- LS Cable USA, Spec U15BTX TR-XLPE datasheet (AEIC CS8, ICEA S-94-649, UL 1072) (maker's catalogue)