Frequently Asked Questions

The following questions and corresponding answers have been compiled from several sources. If you have a question that is not answered here or in any of the other documents published by the CCO, you are encouraged to use the Contact Us form to ask a question.


Question & Answer


What is a gas Critical Contingency?

Critical Contingencies occur when there is a shortage of gas supply relative to demand. The pressure on the gas transmission system can fall to a point where intervention is required to ensure a sufficient supply of gas in the transmission system to supply distribution networks.


Why does falling pressure matter?

If the pressure in a gas distribution network falls below critical safe levels the flames in consumers' gas appliances may go out.  If the gas appliance does not have any flame failure protection, there is a risk that there could be a dangerous build-up of gas in the appliance or room. Therefore, before the distribution network can be re-pressured, every consumer on that network must be visited to have their gas supply isolated at the meter. Only then can the pressure on the network be safely restored.  Once pressure in the network has been restored each consumer must again be visited by a gas fitter to have their supply reconnected.


What causes a Critical Contingency?

A Critical Contingency can be caused by a number of different events.  These generally fall into two main categories:

  • where demand for gas exceeds supply (for example because a major gas producer has an unplanned problem)
  • where there is a physical failure, breakdown or damage to the gas transmission system


Who is the Critical Contingency Operator (CCO)?

Core Group Ltd has been appointed as the CCO from March 2014 by the Gas Industry Company and operates under the Gas Governance (Critical Contingency Management) Regulations 2008.

The purpose of the Regulations is to achieve the effective management of critical gas outages and other security of supply contingencies without compromising long-term security of supply.

The CCO is required to:

• determine and declare a Critical Contingency

• determine the extent and location of required load shedding (curtailment) in order to balance supply and demand

• continually monitor the system and fine tune curtailment instructions as necessary

• coordinate restoration when it is safe for demand to return to normal

The CCO must issue their directions to the Transmission System Owners and keep key stakeholders informed.


Who is the Transmission System Owner (TSO)?

The transmission system in New Zealand is owned by First Gas Ltd.

The TSO remains in direct control and management of their system at all times, including during a Critical Contingency. However, they must comply with the directions of the CCO given under the regulations.

They do this by activating processes and procedures contained within their Critical Contingency Management Plan (CCMP) and emergency response plans.

The TSO must issue directions to gas retailers and large consumers that are consistent with the CCMP and the CCO directions.


What is a load curtailment?

Gas curtailment is where the CCO requires the TSO to give directions to large consumers and gas retailers to reduce gas demand.

The gas system is different from the electricity system.  The electricity system operator and the electricity distributors can shed load by remotely opening circuit breakers.  No such equivalent exists for gas.  The system is dependent on users reducing their use as instructed during a Critical Contingency.


Which customers will be curtailed first?

The process of curtailment of gas supply has been designed to prevent pressure falling to an unsatisfactory level on the pipeline as quickly as possible, while minimising the impact on consumers and maintaining essential services.  Gas storage facilities and major consumers connected directly to the transmission system such as power stations will be curtailed first.  If this is not sufficient to restore correct operating pressure the CCO will then instruct the TSO to curtail gas supply to large industrial and commercial gas consumers.  The priority throughout a critical gas contingency is to minimise risks to the safety and integrity of the gas system, as well as the health and safety of the public.


How is the curtailment determined?

The CCO and the TSO use demand prediction modelling systems and monitor actual system conditions using SCADA.  Decisions to curtail demand are based on the information from these systems and demand will only be curtailed where essential.


What do I need to do?

Know who your gas retailer is and ensure they have up to date contact information for your organisation.

If a critical contingency is declared and your retailer contacts you and instructs you to stop using gas, be ready to comply.  You should have a plan of how your organisation will do this.

If your organisation has special circumstances that mean it may be appropriate for it to be given priority use of gas during a Critical Contingency, discuss this with your gas retailer.  It may be appropriate to apply for a Critical Contingency designation.

Domestic gas users (i.e. private householders) are not covered by the regulations so will not be directed to stop gas use, but in severe critical contingencies may be asked to voluntarily reduce their gas use through media appeals.


What is a Critical Contingency designation?

Designations can provide a measure of priority to gas consumers who satisfy certain criteria. The designation categories are:

Critical Care for consumer sites that provide:

  • Hospital care
  • Residential care
  • Primary health care
  • Dispensing medicines
  • Operating a prison
  • Essential support services for any of the above eg. laundry services, cleaning or catering

Essential Services for consumer sites that provide:

  • Mortuary Services
  • Cremation of human remains
  • Treatment of biohazards to make them safe for disposal
  • Processing and supply of municipal drinking water
  • Treatment and processing of municipal sewage
  • Police, fire, and other emergency services

Critical Processing for an installation where the following process is performed:

A commercial or industrial process that fits the following criteria:

  • the process is underway; and
  • the process can be shut down in less than 18 hours; and
  • an immediate shutdown would require disposal of dangerous or toxic chemicals; or
  • extensive operations before the plant could resume operation

A process that requires gas for a defined period in order to:

  • avoid serious damage to plant; or
  • mitigate serious environmental damage; or
  • prevent inhumane or cruel treatment of animals already at an abattoir

Electricity Supply
to allow an electricity generating unit to start up and switch to an alternative fuel or to provide ancillary support to the electricity system.

The Gas Industry Company manages the process for application and approval of designations.  Guidance for making an application can be found at:


Where can I find out more?

This CCO website has a publications section which includes useful documents such as:

  • CCO's Communications plan (describes how the CCO will communicate with the TSO during an event)
  • CCO's Information Guide (describes how the CCO will communicate with stakeholders during an event)
  • The TSO's Critical Contingency Management Plan
  • The Critical Contingency Management Regulations

This website will be used to post information during an actual Critical Contingency.