Saturday, January 12, 2013

December 2012 - The first pull of new 66kV subterranean cables for Christchurch

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.
Now THAT is a lead wipe..!
The finished product
The final product is achieved with an Ericsson 52-84kV Transition joint kit.

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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