Orion Electricity Network: Infrastructure and Development
The Orion electricity network serves as a critical piece of infrastructure, ensuring a steady flow of power to thousands of customers across Christchurch and its surrounding regions. By managing a complex web of cables, substations, and transformers, Orion bridges the gap between high-voltage national transmission and the end-user's electrical socket.
Key Facts
- Total Line Length: 11,992 km of lines and cables.
- Customer Base: 223,047 customer connections.
- Energy Delivery: 3,479 GWh of energy delivered.
- Peak Demand: 692 MW.
- Reliability Metrics: An average interruption duration (SAIDI) of 85 minutes and an interruption frequency (SAIFI) of 0.71.
- Asset Value: A regulatory asset base of $1,566 million.
Network Architecture and Technical Specifications
Orion receives power from the national grid via seven Transpower grid exit points (GXPs), which are the interfaces where electricity leaves the high-voltage transmission network. These points are located at Bromley, Islington, Kimberley, Hororata, Coleridge, Castle Hill, and Arthur's Pass.
The distribution of power is handled through a tiered system. The majority of Christchurch is served by a 66 kV subtransmission network (the intermediate stage of voltage reduction) and an 11 kV distribution network. In the Selwyn district, Banks Peninsula, and western Christchurch, a combination of 66 kV and 33 kV subtransmission is utilized alongside the 11 kV distribution lines. Finally, electricity is delivered to residential homes at the New Zealand standard of 230/400 volts (phase-to-neutral/phase-to-phase).
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Infrastructure Components
The scale of the network is supported by a vast array of hardware designed to step down voltage and route power efficiently:
- Substations: 52 zone substations and 10,972 distribution substations.
- Transformers: 10,828 transformers in total, including 81 zone substation transformers and 12,156 distribution transformers.
- Physical Assets: 87,065 poles supporting the network.
| Parameter | Value |
|---|---|
| Regulatory asset base | $1,566 million |
| Line charge revenue | $238.1 million |
| Capital expenditure | $136.9 million |
| Operating expenditure | $81.6 million |
| Distribution & low-voltage overhead lines | 4,834 km |
| Distribution & low-voltage underground cables | 6,504 km |
| Subtransmission lines and cables (66/33 kV) | 654 km |
Network Development and Earthquake Recovery
The 2011 Christchurch earthquake caused severe damage to the distribution network, particularly in the eastern suburbs. Liquefaction—the process where saturated soil loses strength and behaves like a liquid—destroyed the New Brighton zone substation and the 66 kV cables connecting the Dallington and New Brighton substations to the Bromley GXP.
To restore power to the northeastern suburbs, Orion implemented a phased recovery plan. Initially, a temporary transformer replaced the New Brighton substation, and single 66 kV overhead lines were built to link New Brighton and Dallington to Bromley. To ensure backup power, four 1 MW diesel generators were stationed at Queen Elizabeth II Park.
By 2015, permanent solutions were established. A new zone substation was constructed at Rawhiti Domain, and replacement 66 kV cables from Bromley to Dallington and Rawhiti were completed, allowing for the removal of temporary overhead lines. Additionally, a new 66 kV cable was installed from Dallington to the McFaddens Road zone substation in Saint Albans to create a second supply route.
Addressing Future Demand
Growth in the northern and southwestern suburbs, as well as the Rolleston-Lincoln area of the Selwyn district, has increased pressure on the grid. To manage this, a new zone substation was built at Waimakariri Road in Harewood, connected to the Papanui (Greers Road) substation via a 66 kV cable.
Future developments include a new 66 kV cable linking the Waimakariri and Rawhiti zone substations via Marshland. This upgrade will allow the QEII Park generators to be relocated to the Belfast area to secure the northern supply. Eventually, a new zone substation at Marshland will be constructed to further reduce the load on the Papanui substation.
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Note: This network excludes the 22kv transmission lines around Coutts Island and Kainga areas, which are managed by MainPower.
Frequently Asked Questions
How does Orion receive electricity from the national grid?
Orion takes power from seven Transpower grid exit points: Bromley, Islington, Kimberley, Hororata, Coleridge, Castle Hill, and Arthur's Pass.
What voltage is delivered to residential homes in the Orion network?
Following New Zealand standards, electricity is delivered to homes at 230/400 volts (phase-to-neutral/phase-to-phase).
How did the 2011 earthquake affect the network?
The earthquake caused significant damage, especially in eastern suburbs, where liquefaction destroyed the New Brighton zone substation and critical 66 kV cables linking to the Bromley GXP.
What is being done to handle increasing demand in northern Christchurch?
Orion has constructed a new zone substation at Waimakariri Road and plans to build a new substation at Marshland, along with new 66 kV cables to secure the supply and offload the Papanui substation.
What are SAIDI and SAIFI in the context of the Orion network?
SAIDI (System Average Interruption Duration Index) measures the average outage duration per customer, which is 85 minutes for Orion. SAIFI (System Average Interruption Frequency Index) measures the average number of interruptions per customer, which is 0.71.