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Standards for Insulating links
ANSI/CPLSO-14
ANSI/UL2737 (Withdrawn)
ASTM F2973
MIL-L-24410 (Withdrawn)
Tests by Independent Organizations
Load Insulator
Miller & Hirtzer
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PAGE 3 Design Verification Testing ELECTRICAL TESTING COMMENTS DC is not appropriate for testing as most of the lines are AC. One could develop a nearly perfect capacitive device where during slow rate of rise testing there is basically no leakage current observed. I was made aware of links that had been used in the field for years. Therefore, an aging test of some type would be required. Some materials degrade significantly in the presence of ultraviolet light and would over time lose their ability to withstand an applied voltage at the time of need. Some links might show cracks that would allow moisture to wick into the internal mechanisms. One of the ways that insulation fails is by an internal failure mechanism called partial discharge. Links that have a high level of partial discharge when energized have a high probability of internal failure unseen on the external material. This would of course be dependent on the specific design but should not be ignored. Such tests should also be done after mechanical cycling to see what impacts the mechanical stressed have on the electrical performance. Initially it was considered that some of the electrical testing should be performed while under mechanical load. Depending on how a link is manufactured there are designs where the material is compressed and potentially deformed when under load. This deformation and or thinning of the insulation could affect the ability of the link to sustain its rating. This deformation might also form voids or separation of materials creating areas where partial discharge might deteriorate the internal material. Best practice now is for electrical testing after a full mechanical life cycling has occurred to determine the failure of the internal structure and the potential cracking of the external surfaces that are so essential to limiting the leakage current. The following tests should be included in addition to those listed in the ASTM Standard as a minimum: 1) Slow rate of rise tests at rated to twice voltage on links that are clean and dry. Test performed in accordance with IEEE#4 and IEC 507. Measure and record the maximum leakage current at each voltage level. 2) Slow rate of rise tests of links that are contaminated. Test performed in accordance with IEEE#4 and IEC507. Measure and record the maximum leakage current at each voltage level.
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