My time on Academic Study Leave learning Cable Jointing and Line Mechanic work with Connetics from February to July 2011 and the subsequent recovery and strengthening of the Christchurch power distribution network
December 2012 - The first pull of new 66kV subterranean cables for Christchurch
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On December 4 I observed the laying of the first part of the strengthening of the Christchurch distribution network by the 'pull' and lay of the first 900 metre section of 66kV by the Connetics underground department.
Contractors dug the trench and laid the concrete bedding for the power cables over the last couple of months. My previous post illustrates the map and location of the first joint hole, 900m from the McFadden Zone substation.
Having not witnessed the laying of a really heavy power cable before, this was a particularly exciting time for me. Rollers were laid in the trenches and on the corners with cable layers at intervals to assist the passage of the cable. Conduit was installed in sections and guides inserted into the entries of the conduit.
Rollers with the nylon pulling cable in place for the first cable.
Corner rollers with conduit protective entry
A nylon cable was used to pull the cable and was attached using a cable puller and drawn by a torque-controlled winch set to 7 Newton-metres strain.
The winch
The giant cable drum was mounted on a roller machine with nylon bearings and a makeshift braking system using an 8x4 block of wood.
Me in front of the giant cable drum (with full PPE, of course!)
The drum on it's own
The cable specs on the drum
The drum 'jack' specifications.
I'm 90% sure (!) this is a nylon bearing.
The 7-ton breakaway swivel (the black bit).
The cable puller was attached to a 7-ton breakaway swivel for safety in case of jamming. The cable itself is rated at 7.9 Newton-metres breaking strain.
It seems that, as with a lot of trades, a successful objective can only be achieved with excellent preparation. Everything from placement of rollers to conduit placement and cable lubrication, if done properly, should (being the key word!) lead to a successful outcome. Teamwork and good radio communication is paramount.
So the pull begins. A team of around 6 'follow' the cable down the run, after a an initial 'take up the slack' and check all is running correctly.
The start of the cable run
The nylon drawcable wearing on the conduit insert
Video: the winch
Video: the cable running
Video: Lubricating the cable
Lubrication is essential for the cable as it goes around corners in conduit to ensure the cable is not damaged and also the conduit is not compromised by the friction of the cable.
The lubricating medium.. goop!
Nearly finished.. comms cables to go in..
After nearly a week, delayed by a couple of days of bad weather causing trench issues, the laying of the power cables was complete as well as two (I think!) communications cables (only one shown in the picture, I was too busy to get a photo at the right time!).
The cables are being laid on top of reinforced concrete (in places) and encased in a flowable thermal backfill (a weak concrete) with a red coloured top layer.
The next step is jointing. I'm not sure if I will be able to cover that process, but I did see some terminating at the McFaddens zone substation.. see below:
Analysis: 66kV oil-filled transition jointing
During my 22-week stint with Connetics from January to July 2011, I kept bumping into a couple of guys doing work on mainly paper-insulated cables.
Sean Baker and Barry Kelly are Cable-Jointing gurus, both ex-UK and supreme at the trade. Their workmanship is second-to-none, and they are effectively the engineering equivalent of surgeons, precision work being their game.
The first time I saw them was doing the final terminations for the 66kV temporary overhead line circuit at the Dallington zone substation in April 2011.
Sean doing 66kV terminations
The beginnings of a SERIOUS lead wipe..
The finished product
The second time I saw them was jointing a damaged 66kV oil-filled cable on Armagh St in the Christchurch city 'Red Zone' in May 2011.
Oil-filled Cable Jointing
Third; a 66kV pole installation near Islington substation.
Barry polishing the XLPE insulation
The pole under construction
And more recently, doing the terminations at McFaddens Zone substation for the new 66kV circuit at the start of this post.
The kit comes together. Shaun and Barry have workhands to assist.
The cables to be joined
Perfectionists; Barry keeps his tools in perfect order and condition while working.
I'd like to thank Shaun and Barry. They're so passionate about their trade, and have been more than happy to share their trade with me. Nice guys, and great role models.
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Christchurch has had 3 major, 10 moderate, and around 7000 minor earthquakes and aftershocks at this point in time. The following is a personal account of the damage based on my personal experiences and the different side-effects of earthquakes. I need to stress at this point in time, I am NO geologist, seismologist, or network analyst. So some of this information may not be accurate, it's simply based on my logic as an Electrical Tutor! I apologize in advance if I say anything incorrect, and feel free to post anonymous comments (this has been done, already, thank you!) and correct me. In my opinion there have been four major side-effects of a quake (in Christchurch's case): Ground shaking Liquefaction Lateral spread L andslides/building collapse/rockfalls. Christchurch did not experience tsunami related to our own quakes at any stage. I will cover each category for some systems in the Christchurch distribution network that...
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