Having established to date in New Zealand almost saturation coverage of VLF test sets, it is of significant concern that only one company in the region to date has implemented the addition of a VLF tan Delta bridge to their existing High Voltage Inc VLF test set in order to determine and then trend the degree of issue with their older XLPE cable.
Priced at significantly less than a 60 kV VLF set, the VLF tan delta accessory will operate with any of the High Voltage Inc VLF test sets, including the new low-cost 25 kV set. They are extremely quick and simple to set up and total testing time per feeder is around 5 minutes.
Indeed, it makes very good sense to apply this test prior to the VLF pressure test, both to get a signature for later comparison purposes but also to determine (along with information from the preceding diagnostic insulation tests) what condition the cable is in prior to then specifying the VLF test. time. In some cases this might save 1.5 hours of testing alone with no reduction in outcome quality!!
Whilst primarily of concern for water tree assessment on XLPE cables, the technology can certainly also be applied validly to PILC cables or mixed runs. As a word of caution, it cannot be used to determine XLPE cable condition on mixed XLPE/PILC circuits in view of the tan delta results from paper cable being far greater than typically observed for XLPE cable.
Ask us about this today…we have arguably the lowest priced options on the market and certainly the VLF components are already there!! Why keep taking the risk when it is this easy to address?
VLF Tan Delta testing…simple, affordable, and ready now!!