This week's log:
- Monday: Halswell Junction Road with Jamie. 11kV XLPE-HDPE (high density polyethylene), spiked.
|Good 'spike'.. right through!|
- Tuesday: Orion EAC (entry approval certificate) course in the morning at CPIT Tradefit, afternoon Ensors Road with CJ and Nick to break into a 11kV PILCA with two XLPE for a kiosk.
- Wednesday: Timaru with John, Terry, and Mark to do 33kV 1200mm2 3x single core XLPE.
|Ends prepared for joining|
- Thursday: CPIT tradefit sub terminations with Steve.
- Friday: Halswell Junction Road 11kV XLPE-PILCA with Steve
33,000 volt joining in Timaru
On Wednesday I travelled to Timaru to see John, Terry and Mark joining 33kV cables for Alpine Energy. Cables come in drums of (?) length, and need to be joined the length of the full (?) run to a new substation.
The joining is done deep underground, under all other services. Connetics use a open-bottomed container as weatherproofing and for protection of the jointers.
|The 'joining container'|
The cables are 3x single 1200mm2 aluminium with neutral screen XLPE and MDPE (medium density polyethylene). Alpine's specification was to use crimp joiners rather than the newer 'shear bolt' joiners.
|Cable description on side|
|1200mm2 aluminium 33kV cable|
Both ends of the 33kV cable are stripped and prepared with the minimum wastage possible. They are measured and aligned for joining.
|Stripped and ready for joining|
The joint is performed using a large hydraulic crimper, which is a very flash and expensive piece of equipment! The cable is stripped back to measurements specified by the joint manufacturer, with the usual extra care for the semiconductor layer. Correct measurements are crucial to this operation, with no room for error (no pressure!).
John would like to lay claim to his 'John's jack system', which ensures the crimper is always at the correct height using a heavy duty hydraulic vehicle jack! Brilliance!
|John in action|
Seeing John and Terry (the joiner guru!) in action was great!
I travelled back, pausing at Highfield Road to stand on the Greendale fault, the cause of out M7.1 quake and $5,000,000,000 of damage in Canterbury. Kinda odd that Highfield Road is next to fields that have been pushed up... High.. sad I know...!
|On Highfield Road, the Greendale fault line|
Postscript.. NOTE: This is still before 22nd February. Post-quake coming soon.
The following hazards are associated with cable jointing:
- Electricity (obviously!) in kiosks and nearby cables
- Open flame/heat when heating cables for stripping and when heating heat shrink
- External noise and the driver for shearbolts
- Tools/sharp ones in particular for stripping
- Other contractors/public (including 'rubberneckers', which there are a surprising amount of!)
- Vehicles/heavy and diggers etc.
- Weather wind/sun/rain
- Dust, when windy
- Fumes from heating pitch in PILCA cables
- Oils on PILCA cables
- Sharp edges
- Holes/cave ins
- Kiosk and sub doors
- Lead poisoning
Teaching methods for hazards:
Brainstorming - drawing on previous knowledge of students
Practical (individuals or teams depending on formative or summative assessment)
Scenario work - field trip or photos/video (moodle?)
The semiconductor layer
The semiconductor layer is a thin layer in HV cables that usually surrounds the immediate first conductor insulation layer (usually XLPE). The function of the semiconductor layer is to 'spread the charge' if the XLPE layer fails insulation-wise. Special tools are used to strip the semiconductor layer carefully and NOT damage the XLPE layer. This layer is a modern measure used on HV cables. A special 'strip tool' is used to strip the semiconductor layer nicely without damaging the XLPE layer.
Another enjoyable week!
Next time: The 'block' starting 21st February to 17th March. Apologies due to delay caused by the February 22nd Magnitude 6.3 Christchurch earthquake which devastated Christchurch and killed hundreds. RIP the 'unlucky ones'.