Electrical jointing

Image: © Bob Harvey Taken: 18 Apr 2021

This is near the top of the pole in Image, where I have already mentioned that this looks like 6600V connections. The stand-offs that support the joint between the dropwires and the downfeed cables are interesting too. I suspect they are Metal Oxide Varistors - devices that absorb transient over-voltages caused by electrical storms. In this case that will be to protect the (rather thin) insulation within the downfeed cables, rather than whatever is on the other end of those cables. There is an integral disk in the insulating sleeve at the top of the downfeed cables. This is part of the pre-moulded termination kit supplied for those cables. Just below the disk it covers a steel spring that connects the earthing pigtail to the screen, or shield that encloses the cable with an earthed metallic layer. Above the disk it covers an area known as the Stress Cone. In the stress cone a partially conductive layer (of highish resistance) conveys the protective earth shield part of the way up, and the true insulation within extends all the way to the tip. The net effect is to ensure that the electric field caused by the high voltage is carefully controlled and precisely known - this is why the ends are splayed rather than neatly tucked next to the pole. The overall purpose of all this technology is to reduce corona effects which attract conductive dirt and which can by themselves denature even modern synthetic insulation.

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