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Health and Safety Forum is an open forum for members of the Electricity Supply Industry to discuss health and safety matters and learn from each other.
The Electricity Distribution Sector has a Health and Safety meeting every three months, to find out more contact Maarten Tinsel – maarten.tinsel@omexon.co.nz.
In terms of the ACOP for safety and health in tree work: Part 2, maintenance of trees around power lines, Clause 2.4 (b), I looked at this back in 2014. I queried with Tex On Site at that time regarding electrical testing of hydraulic tool circuits on EWPs, and also the portable hydraulic oil hoses used for hydraulic tools, e.g. podsaws. I was advised they do not do specific dielectric breakdown testing of hydraulic oil such as that done for mineral insulating oil used in transformers and switchgear. Hydraulic tool circuits on EWPs get tested as part of the insulated boom test. Hydraulic hose couplers, including that of the tool circuit, are bonded together with other metal components at the bucket area for this test. Hence, the hydraulic oil gets electrically tested as part of this test given the hydraulic oil is in contact with the couplers. In terms of portable hydraulic oil hoses used for hydraulic tools, electrical testing includes an end-to-end test. 40 kV ac is applied between the end hydraulic coupling fittings with the leakage current required to be under a certain micro-amp value. Again, given the hydraulic oil is in contact with the couplings, this test also electrically tests the oil.
ECP 46, Clause 2.6.10, refers to testing intervals. Based on ECP 46 High Voltage Live Line Work – Industry Practice Note, Table 2.6.10 within ECP 46 is to include “Insulated hydraulic hoses” and “Insulating hydraulic oil”, with test intervals “Not exceeding 6 months”.
In my view, both in terms of ACOP for safety and health in tree work: Part 2, maintenance of trees around power lines, and ECP 46, hydraulic oil is electrically tested as part of the standard range of periodic tests done on EWPs and hydraulic oil hoses used for hydraulic tools as detailed above. My understanding of mineral hydraulic oil is that it is inherently electrically non-conducting. Specific ‘electrically non-conducting’ hydraulic oil products are available. I have attached a technical data sheet of one ‘electrically non-conducting’ hydraulic oil product that has an electrical dielectric of > 30 kV. However, unless specifically stated as a requirement, dielectric breakdown testing of hydraulic oil in the same manner done for mineral insulating oil used in transformers and switchgear, would introduce unnecessary and costly compliance costs.
It my view, it would be prudent for the EEA NCLW
to review this issue and provide guidance to industry.