*Pic: Pete Godfrey sent in this diagram, Comment 16. Pete says: “#4 kelvin, I have never seen an armoured cable that did not have a layer of insulation under and over the armouring. Especially one designed to be underwater. The picture I have of the Basslink cable that I hope Linz can attach to the article shows that it has the cable, then insulation, then a lead sheathing, then insulation, then armour, more poly sheathing, then string. I cannot see how the oil from the paper insulation can possibly ooze out unless the lead sheath was damaged also. It would also mean that the poly sheathing over the lead sheathing was damaged too. Meaning the cable was punctured.”
*Pics: The damage ... and the culprit? Geelong Star, before its renaming. And below, Basslink cable damage: the gouge. What caused it ... ?
Basslink from a technical perspective
This is the fourth article* on what started out as a single article trying to focus on the “paucity” of technical knowledge on the Basslink Saga. My aim was to indicate (with a degree of plausibility) what caused Basslink to fail …
… Something, I believe, that the public would very much like to know.
The original scenario has been improved courtesy of many good comments coming from readers … either adding or reinforcing some strategic points.
However, there are two important points mentioned in my first article ( HERE: Likely cause of Basslink failure is the Geelong Star ): One alluded to and the Second materially corrected by one commentator.
These have now become of paramount importance; these two points have a relationship with each other.
Firstly, perhaps Basslink may contain an intrinsic protection feature against internal faults? Cables, by their nature, rely on materials technology for their safe function. Many hidden and clever safety features are incorporated in these materials that a casual examination would not reveal.
The big enemy of submerged cables in the event of damage is from water ingress. The amour provided to a cable can only protect against a known level of potential external threat. It is, however, possible to design a cable which will not rupture the integrity of the protective alloy sheath from an internal failure - so preventing water ingress and the need for extensive cable replacement.
Unlike the external threat, the amount of energy expended on an internal failure can be controlled by the protection system. That amount of energy can be allowed for in the design of the cable’s mechanical construction and the ability of materials to withstand violent heat, pressure and sheath expansion for the very short time before the protection equipment operates.
Therefore, for spot internal insulation failure the cable could have inbuilt protection. However, the cable manufacturer would be needed to verify if this type of protection has been incorporated into the Basslink cable design.
Secondly, in the first article ( HERE: Likely cause of Basslink failure is the Geelong Star ) it was noted that the cable seemed to have been hit by a suitably-shaped moving object cutting obliquely a single element of the outer binding. This left its inner strands separated and protected from any hot gases by the striking object.
At this time I had wrongly stated the strands were metal. One of the commentators corrected me and it does appear that the strands are polypropylene. Polypropylene melts and fuses easily.
If an internal insulation short was the problem, then assuming the cable sheath did burst hot gases would have escaped between the gaps of the individual main armour cables. These hot gases would have melted the polypropylene rather than the neatly cut strands as shown in the insert.
To me the swelling on the cable, which is caused by electrostatic forces around the point where the short is established, does not appear to be anywhere sufficient to rupture the sheath. Indicating that the protection system functioned as designed.
During the period these articles have run there has been a considerable release of information on the Insurance, Basslink corporate, Hydro, and State Government fronts.
Insurance seems to have accepted a force majeure claim from Basslink. This does not indicate if the cable was subject to external force or had an internal failure. Force majeure in English law has a degree of foreseeablility added against the original French version. Which means that the circumstances are mostly likely the criteria; not the type of actual type of failure.
The State Government seems biased toward internal failure. Perhaps this stance is related to regulations for fishing vessels. These laws as far as currently determined, seem to indemnify fishing vessels striking the Basslink from any liability or wrongdoing.
Hydro does not accept force majeure and by default it would seem to believe that the cable was damaged by a foreseeable event that possibly could have been prevented.
No doubt all three entities have their own interests at heart for their positions.
This exercise over the last weeks has only been to to find what did cause Basslink to fail …
… Therefore what is your view ... external trauma or internal failure by causes unable to be determined?
*Bio of Kelvin Jones: Technically trained and qualified in the UK by a major electrical engineering manufacturing company in Power Engineering and industrial electronics, moving in to defence systems, commissioning RADAR and development of underwater weapons. TV transmission, field work and commissioning industrial electronics and HVAC carrier protection. Research in cellular and fibre optics communications. Field work on scientific, bio, and medical instrumentation with extensive experience on Medical Imaging particularly CT scanners and Nuclear imaging. Mature age university studies in computer science and Technology with emphasis on the viability of renewable energy technology on legacy power grids. Green by practical evolution.
SUNDAY, November 6 ...
*THE THREE earlier articles on Tasmanian Times ...
• John Hawkins in Comments: Steve Davy has recycled the Hydro press release in his Mercury article referenced above. We are very badly served by the Examiner and the Mercury who employ nobody who will conduct investigative journalism. Well done Kelvin and TT … for pursuing this the most important Tasmanian story. This complex matter will end up in the courts as one of the parties involved is not bound by the Silence of the Lambs in Tasmania. Basslink will sue over nonpayment and the can of Hydro worms will be sprung wide open. Those who rule the roost in Singapore do not buy silence.
• Pete Godfrey in Comments: #4 kelvin, I have never seen an armoured cable that did not have a layer of insulation under and over the armouring. Especially one designed to be underwater. The picture I have of the Basslink cable that I hope Linz can attach to the article shows that it has the cable, then insulation, then a lead sheathing, then insulation, then armour, more poly sheathing, then string. I cannot see how the oil from the paper insulation can possibly ooze out unless the lead sheath was damaged also. It would also mean that the poly sheathing over the lead sheathing was damaged too. Meaning the cable was punctured.”