Wednesday, May 4, 2011

Week 13 - Pole straightening, live line work, Bromley Substation

Apologies, I'm a week late with this post.. I attended a conference at CPIT for Trades Innovation Institute staff. I presented with my colleague Rob Mattson at this conference and we were very well received.

Previous weeks' log:

Monday 18th April: Lift and repair liquefaction-sunken pole Netley Place, Aranui.

Pole lifted

Carl and James restraining cables

Tuesday 19th April: Live line switch pole replacement 11kV, Hoskyns Road, West Melton (see analysis).

Nik and Andre in action in full glove-and-barrier kit

Wednesday 20th April: Live line switch pole replacement 11kV, West Coast Road, SH73, Darfield (see analysis).

Lines being held temporarily whilst pole is erected.

Thursday 21st April: Fill large circuit breaker terminal block with bichemical insulator, Transpower Bromley Substation.

Above Steve is bracing to secure the large cast-iron circuit breakers in case of future earthquakes. These multi-tonne machines ripped their floor restraining bolts out during the magnitude 6.3 Christchurch earthquake. 
One of the circuit breakers.
Analysis: Live line work


The possibility exists with overhead where the power cannot be de-energized. Line mechanics gain qualifications to work in these situations, two I know of are 'hot stick' and 'glove and barrier'. I have not yet witnessed 'hot stick', but I have seen 'glove and barrier' on two occasions, one at West Melton and one at Darfield. Both were 11kV and both were replacing poles with old style switching equipment with new style switching equipment.

Removal of existing pole:


'Glove and barrier' involves the use of high-voltage rated gloves, gauntlets on the line mechanics, and the use of large insulating sheets clipped to all live parts of the lines and pole. The live lines are disconnected from the pole and associated insulators whilst being held in place using a large fully-insulated extension arm attached to the HIAB crane on one vehicle. A cherry picker vehicle allows the line mechanics to work on the lines. A point of note is the last extension of the cherry picker truck before the bucket is fully insulated. All vehicles are bonded to earth and together as part of the process.

The existing pole to be replaced
The new pole (minus switchgear) to go in.

Insulators being attached

The last extension of the cherry picker 

Cherry picker bucket ready with insulated pads and clips

Earthed vehicle
Full safety harness

The boys with HV glove and arm protectors

A 'link stick' and lugall winch hold the conductors aerially using strops to prevent any chance of the live conductors dropping and contacting the ground, causing short circuits and potential 'step voltage', which could kill people near the downed conductor.

The conductors held aloft temporarily by a fully insulated extension arm on the HIAB crane

The new pole being erected. The existing pole is held vertically by a crane and cut off at the base, then carefully lowered. The underground section is excavated and a new hole for the new pole is dug.

Installing the pole


Straightening the pole

Insulating covers being attached

Crimping conductors

Insulators removed



Switch operation demonstrated by me above..

The finished product. Note restraining wire in the ground, pole identifying number, and reflector for oncoming traffic.

This process was quite difficult to photograph, as the whole point of glove and barrier is to put a barrier up, which blocks electricity and photographers!

Pedagogy:

I should point out that different electrical companies use different 'glove and barrier', and 'hot stick' procedures, and Connetics' procedures may be different to other companies' ones. This I will be taking into account when teaching. However, these procedures all contain heavy safety elements and common sense, which simply saves lives.

Consultation with electricity supply companies may enable a 'live line teaching procedure' template to be designed that will satisfy the needs of all workers. It would be a 'best practice' procedure and would have to be accepted as a training tool to be used by CPIT to train lines companies' workers.

This process could also apply to cable jointing, as seen earlier in my blog. Cable jointing relies on a 'recipe' of instruction to complete different types of joints, and an error in sequence in completing a joint can be a $1500 mistake, which is why the ability to follow procedural instruction is crucial in the electricity supply industry, and demands significant teaching focus.

Anything can be achieved with excellent safe procedures, must see video see HERE.

My time in lines is over (temporarily), I'm off to the Substations Department until later in May, when I will go back to Lines to see helicopters running lines near Lake Coleridge.

My camera in action!

1 comment:

Selena said...

HI Andrew,

good to see you are back out there again and the weather seems to be better out in the country than in town!

Keep up the good work, Selena