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Orion/SCIRT66kV cable installation - Frequently Asked Questions

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1. Who is SCIRT?

SCIRT is made up of people from many organisations. The head contractual agreement within SCIRT is an alliance between owner participants (Christchurch City Council, Canterbury Earthquake Recovery Authority and New Zealand Transport Agency) and non-owner participants (City Care, Downer, Fletcher, Fulton Hogan and McConnell Dowell). There are also many other Christchurch-based companies working as consultants, suppliers or contractors. SCIRT is tasked with the infrastructure rebuild of the city.

2. Who is Orion?

Orion New Zealand owns and operates the electricity network in Christchurch and central Canterbury. The Orion network covers 8,000km2 between the Rakaia and Waimakariri rivers and from the Canterbury coast to Arthur’s Pass. Orion delivers electricity to more than 190,000 homes and businesses across this diverse geographical area.

3. Why are new cables needed?

The new cables are needed to strengthen the power supply to the north-eastern suburbs of Christchurch. This project is one part of a high voltage ring of underground power cables that will encircle Christchurch. This ring network will enable Orion to re-route power supply should one route fail. It will also make it easier for Orion to add to the network as Christchurch grows. This project is just one of $870 million worth of projects planned over the next 10 years to improve and enhance electricity supply in the Orion network area.

4. What is a 66kV cable?

66kV stands for 66,000 volts. There are different sized cables to carry different loads of power or voltages. A variety of cable sizes enables Orion to bring electricity to major substations for onward distribution to large and smaller customers. Basically the more power you want the bigger the cable needs to be. Orion’s power supply network can be compared to the city’s roading network:

  • The national grid which carries 220,000 volts can be compared to a state highway. It takes power from the generators to substations where it is typically stepped down to 66,000 volts (66kV – the type of cable to be laid in this project).
  • Orion then carries, via cables or overhead lines, 66kV to substations. These 66kV cables and lines are like ring roads. Instead of traffic they move power around the city.
  • At the Orion substations the 66kV load is stepped down to 11,000 volts (11kV) to bring power to suburban roads.
  • Lastly at street level the power is converted into a useable customer voltage of 230 volts to power houses and businesses.

5. What works will SCIRT be doing and what works will Orion be doing?

SCIRT, through their contractors Fletcher and McConnell Dowell, will excavate the cable route. Orion will use Connetics, specialised electrical contractors, to lay the cables. SCIRT will then backfill the trenches. SCIRT will also provide traffic management along the cable route during the construction works.

6. Why has Orion chosen the route from St Albans to Dallington?

Orion has selected the route because it provides the most stable ground to lay their cables between the McFaddens Road substation and Dallington Substation on Coopers Road.

7. How many cables will Orion install?

Orion will be installing three cables in each trench that SCIRT excavates.

8. Why does the trench need to be 900m long?

The special type of cable that Orion is using is manufactured in 900 metre lengths.

9. How deep will the trench be?

The trench will typically be one metre deep but may be up to two metres deep.

10. Will my power be cut off when you put the new cables in?

There will be no expected interruptions to the power to your house during the installation of the cables.

11. Will Orion be putting the overhead power lines underground at the same time?

Orion has a policy to underground most new extensions in urban areas of their network; hence the new 66kV cables are being installed underground. Putting existing overhead lines underground is very expensive. It costs approximately $700,000 to underground 1km of existing overhead lines. Orion will not be undergrounding any existing overhead power lines outside houses as part of this project.

12. If this is stage one of three, where are the other stages?

Stages two and three of Orion’s project will complete the north east section of Christchurch’s high voltage power supply ring. Stage two will link the Orion substation at Dallington to the national grid at Bromley. Stage three will connect Bromley to the new Orion substation in Rawhiti Domain. Orion will produce further newsletters as they get ready for Stages two and three.

13. Does this mean the emergency overhead cable at Rawhiti Domain will go underground?

The cable across the Rawhiti Domain is part of stage three of Orion’s project. Stage three will connect the national grid at Bromley to the new substation in Rawhiti Domain. Once the whole project is complete, Orion’s temporary 66kV overhead lines will be removed as permanent solutions will be in place to carry power into north-east Christchurch.

14. What happens if there is another earthquake and we have a power outage before the new cables are installed?

Should the temporary overhead lines fail, Orion have installed large diesel generators on the grounds at QEII Park to provide some backup power. Orion can also ‘switch around’ other parts of the electricity network to provide a temporary power supply, though this is complicated and can take time.

15. Why are Orion and SCIRT working together?

Orion and SCIRT are working together to minimise disruption to residents, businesses and road users along the cable route, and to save on construction costs, where possible.

16. You have already fixed my street, why is SCIRT digging it up again to lay the cable?

Where possible SCIRT tries to work with other utility providers, such as Orion, to coordinate rebuild activities. In some cases however due to the arrangement of services, the level of damage, or the timeframe for the rebuild, works may have to be undertaken separately.

17. Why can’t Orion just install the cable in areas where SCIRT are working now?

As the specialised cable is manufactured in 900m lengths it needs to be laid in sequence so that the end of one cable meets the start of the next.

18. What are the shipping containers on my street?

Where two 900 metre cables meet they need to be joined. Where the two cables meet, a shipping container is placed over the trench to protect the cables until they can be joined and the trench backfilled. Joining cables is a very complex process and takes specialised skills, much like a surgeon reattaching a finger to a hand. All of the various sections need to be attached exactly for it to work properly. Orion is using specialist electrical cable jointers to join the cables together.

19. Will you need to close my street when you dig the trench and lay the cable?

Whether SCIRT needs to close roads to excavate the trench for the cable depends on the width of the street, the location of other services, and the location of the trench in the street. This will vary from street to street. It is SCIRT’s preference to keep streets open whenever possible; however for the safety of residents and road users, and our workers, it is sometimes necessary to close roads. When SCIRT closes a road, access is maintained for residents, although at times vehicle access to properties may be unavailable. SCIRT will keep those along the cable route informed using work notices in letterboxes.

20. How will you control traffic during the construction works?

Traffic management will be in place during the excavation of the trench, the laying of the cable and backfilling of the trench. SCIRT asks that residents, businesses and road users follow all on-site signage and drive to the conditions. SCIRT will keep those along the cable route informed of how traffic is being managed using work notices in letterboxes, traffic signs and information signs.

21. Will I still be able to get into my driveway when you are laying the cable outside my house?

There may be periods when vehicle access to your property is unavailable during construction. SCIRT will try to minimise disruption to your access, including using steel plates over the trench to provide temporary access during the laying of the cable. SCIRT will keep you informed of any disruption to your access. Access to your property on foot or by bicycle will be maintained at all times.

22. How long will you be digging outside my house?

How long it takes to dig the trench depends on a number of factors including the ground conditions and weather conditions. A 900 metre trench will take on average three months to excavate and prepare. Orion will then lay the cable in the trench and SCIRT will then backfill the trench up to the cable joins.

23. Who do I ring if I have construction questions?

SCIRT contractors’ Fletcher and McConnell Dowell will be excavating the cable route. Fletcher is working on the section of cable route from the McFaddens Road substation (at 75 McFaddens Road) to Hills Road. McConnell Dowell is working on the section of cable route from Hills Road to the Dallington substation at Coopers Road. McConnell Dowell can be contacted on 0508 718 719 and Fletcher on 0800 444 919.

24. How long will the project take?

Stage one of the project has already started with the SCIRT Fletcher team starting works near the McFaddens Road substation. Stage one is expected to be complete by April 2013.

25. How do I get information on the project?

SCIRT will keep residents, businesses and road users along the cable route informed using work notices in letterboxes. Orion will also produce newsletters for later stages of the project.