Independent Report on Orion's Earthquake Response

A shallow magnitude 7.1 earthquake occurred near Christchurch on 4 September 2010. Widespread damage occurred in Christchurch and the surrounding area. Then, on 22 February 2011, a magnitude 6.3 earthquake ruptured a fault almost directly beneath the city. The February earthquake generated extensive liquefaction and extreme shaking resulting in damage to or collapse of many buildings and other assets.

For many years, Orion has actively sought continued service improvements to meet customer needs. Orion’s approach has included identifying and initiating work to improve network resilience so as to minimise economic impacts caused by outages including outages caused by earthquakes.

The improvement programme can be traced back to the mid-1990s Christchurch Lifelines report, Risks and Realities. This report led to the inception of an ongoing seismic strengthening programme that commenced in 1996 and progressed systematically each year.

Since the mid 1990s, Orion has invested $41 million in increasing the resilience of its network, learning from events such as the 1987 Edgecumbe earthquake and from engineering and geotechnical assessments. All new structural assets and existing strategic structural assets, e.g. subtransmission lines and zone substations, are designed to withstand a 500 year seismic event with little or no service disruption. The seismic strengthening component cost $6 million, an investment estimated to have saved Orion $30 to $50 million in direct asset replacement costs in the earthquakes. The balance between costs and benefits is even more pronounced when societal benefits (i.e. gains to the community that don’t appear in Orion’s accounts) are taken into account.

The February 2011 earthquake had a very much larger impact than the September 2010 event. It took about 10 days to restore electricity to 90 per cent of consumers compared to just one day in September. February direct costs have been estimated at over $40 million compared with $4 million in September. Major damage occurred to the underground network – 50 per cent of Orion’s 66 kV cables suffered multiple damage in February.

Orion and Orion's contractors worked effectively to restore electricity as rapidly as possible following the earthquakes. Design and construction work for new overhead lines following the February earthquake were achieved extremely quickly. For example, an 3.5 km 66 kV line to supply the New Brighton substation, together with installation of a temporary transformer, were completed in March. Orion’s operations and engineering groups experienced huge workload increases following both earthquakes – the teamwork culture that Orion fosters assisted greatly in maintaining morale and restoration momentum.

Much of the earthquake damage to electricity (and other) assets was a result of liquefaction and lateral spreading. The seismic strengthening generally, and successfully, addressed shaking hazards.

Little can be done to mitigate risks to buried assets such as cables arising from ground failure. While much electricity supply was lost as a result of cable damage, the extensive interconnections in Orion’s 11 kV and 400 V network facilitated electricity restoration by providing routing options not available in radial (non-networked) distribution systems.

The earthquakes are likely to have shortened the life of some underground and (to a lesser extent) overhead assets.

Orion notes that permanent earthquake repairs will take 3 years and cost $70 million overall. Full restoration to previous levels of reliability is expected to take three to five years. To put this in context, Orion’s Asset Management Plan includes around $730 million in capital and operating expenditures across the network.

Full Report link below

http://www.oriongroup.co.nz/downloads/Kestrel_report_resilience_lessons.pdf

© Scoop Media