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System Imbalance Event (May 2017)

A Critical Contingency was declared by the Critical Contingency Operator (CCO) at 10:50 on Tuesday 23 May 2017. 

The cause of the event was low linepack due to downstream delivery points taking significantly more gas than was being injected into the pipeline, which was exacerbated during a planned outage of the Pohokura Production Station.  During the period of this outage, the imbalance between supply and demand caused pipeline linepack and pressures to fall to the point where the critical contingency threshold of 3 hours to 37.5 barg at the Kapuni Gas Treatment Plant was breached.

The Critical Contingency was terminated at 18:15 the same day, after Pohokura returned to expected flows and the CCO considered that the supply of gas into the system was sufficient to meet expected demand. Further information on the event can be found on the CCO website here.


The CCO is required to produce a performance report that assesses the effectiveness of the critical contingency arrangements and, where applicable, identifies any improvements. On 30 June, a draft report was released for public comment, as well as a feedback form for submissions. The draft report can be found below. The final performance report can be found on the CCO website here 


Under regulations 67 to 72, Gas Industry Co is required to engage an independent industry expert to determine a critical contingency price to be applied to contingency imbalances sustained by interconnected parties and shippers during a critical contingency event.  Tim Denne of Covec was engaged for this work, and his draft report, workshop slides and final critical contingency price report are available below.

Under regulation 77, Gas Industry Co is required to publish the contingency imbalances incurred during an event, and a table setting out this information is available below

Page last saved: August 01, 2017
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P 04 472 1800
A Gas Industry Co
Level 8, The Todd Building
95 Customhouse Quay
PO Box 10-646
Wellington 6143

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