Many thanks for the overview and our phone discussion as most useful and clarified a few potential issues.
Like you, I have my concerns about handling corrugated Al sheathed cable – it has probably been my “least favourite” cable protection system, even though an earlier employer of mine manufactured both MV and HV cables of this type and I had to joint/terminate and test them (but I also had a team of highly qualified “old school” jointers who were familiar with all types of metal sheathed cables and could solder/plumb them easily with the aggressive fluxes and equally potentially hazardous solders that were then available) .
I’ve just checked my “working tool-bag” and unfortunately, I no longer have the cutting tool for this particular cable component. However, removing corrugated aluminium sheaths is easier than smooth aluminium sheaths and a standard pipe-cutter should suffice. I could easily acquire one from a specialist tool store here in CA if we need one (some relatively minor modification, such as brazing additional material to ensure it “bridges” the corrugations while it is rotated around the cable should enable it to perform satisfactorily).
As we discussed, it is the electrical connection to the sheath which represents the bigger problem because we need something that will comfortably handle the high fault/short circuit currents that could be experienced during a system failure and this is a significant safety issue. Neither you or I currently have the skills to handle this particular aspect of cable jointing in front of a customer – were we to try, we’d risk losing credibility and respect and that isn’t the situation we want when introducing a product….
I’m now starting a series of inquiries to try to find out how this issue is handled in other countries, in the hope that we can find a simple, cost effective “mechanical” (i.e. doesn’t use a flame and any type of soldering procedure) connection system and will report back to you what I discover. By copy of this e-mail, I’ll request that Alexander advises us what is the current practice for “non-soldered” connections for Al corrugated sheaths in the EMEA region.
You have listed systems for the external sealing and protection of the HV joints we’d offer but would there also be the option of utilising the system they currently use for their three core 22kV joints? The overall size of a 66/72kV joint wouldn’t be very different from the current PG MV joint, so it would require about the same amount of tapes (“spacer tape”, sealing tape and “restricting tape”) and maybe a little less resin (as there are not interstices to fill), though maybe for the higher voltage situation and to provide additional insulation for any sheath testing, perhaps double the insulation thickness may be advisable. How practical do you think that would be? PG really seems to favour this particular protection system and if we need something they would readily accept, then do you think there would be value in including it amongst the options available to them?
With regard to the outer protection, we need to know what field testing will be done to test the integrity, both directly after installation and then periodically and also prior to reenergising after repairs. Maybe you could add this to your list of questions that you will pose to PG when you meet with them?
I have very little presentation material on the TPJ, as for the last few years we’ve been under heavy pressure to promote only the OPJ from China. I will need to obtain more quality illustrations and additional information so that we are in a position to provide a professional presentation package that will address most of their concerns and give them confidence. I think we can cover the connector issue fairly well (there are a number of engineers in PG that are not “sold” on mechanical connectors) but it is the actual joint insulation replacement that we need to cover in detail. Our usage history from EMEA should be valuable supportive information that will help us overcome any reservations PG may still harbour.
As soon as I have some feedback on handling/preparing the cable, I’ll provide you and update.