Outage Planning

Outage Co-ordination is an essential part of managing the operation of the power system in a secure and efficient manner.

Outage Planning Policy

This policy is to clarify how, in Transpower's dual roles as system operator and owner of the national grid, we will meet our obligations around outage planning, coordination and assessment.

This policy will mean:

  • our approaches in both roles are more transparent,
  • in our system operator role we:
  1. will continue to publish assessments where there are outages that may cause a security concern
  2. will consider economic impacts of outages and the mitigation of security violations where this is relevant.

The policy is an internal policy, but one that we have published and that we have discussed with industry participants to gain their feedback.

It draws on our Code obligations, particularly those which deal with the general considerations we, as grid owner, must make in planning outages, and those that are relevant to our system operator role in assessing outages and notifying interested parties. These are the areas where we want to be clearer about our approach, and clearer about how we will maintain impartiality in our system operator service.

Some of our other obligations, particularly in our role as owner of the national grid are described in the Outage Protocol, which steps through how we will publish and consult on our annual outage plan, and how we will make changes to the Annual Outage Plan. This policy does not detail these types of procedural responsibilities.

SP-OC-759 Outage planning policy [ pdf 821.39 KB ]

The situations where we, as system operator, will publish assessments to POCP (Planned Outage Coordination Process)

As part of the policy, and particularly principle four, we will publish assessments, from four weeks out from outage start date, in some situations. This is to provide more up-to-date information to industry participants, so they can be made more aware of potential security risk and take appropriate action. Most situations will be when planned outages are causing an actual or perceived tighter security situation. This may include energy and reserve shortfalls, voltage stability violations or thermal violations. 

We have published a document outlining the triggers for providing the assessments to POCP, and the assumptions we will use in our assessments. This covers general situations but particularly two key regions of the electricity system:

  • Upper North Island or Zone 1 voltage stability where we will publish an assessment where the assessment shows the voltage stability margin exceeds 97.5%
  • The HVDC where we will publish an assessment when:
    • the calculated power limit is within 50MW of the expected HVDC transfer or
    • the deficit generation from NZGB for the base scenario is < 50MW (for N-1-G).

A supporting document with further technical detail can be found below. This is also an internal document which has been published to enable participants to understand the triggers and assumptions underlying the assessments.

Guidelines for Notifying and Publishing an Assessment [ pdf 126.05 KB ]

Planned Outage Co-ordination Process

The Planned Outage Co-ordination Process (POCP) was agreed by the Planned Outage Forum in October 2002 and presented to the Grid Security Committee in November 2002.

Reviews of the POCP was completed in 2006, 2009 and 2013.

A POCP website has been established to host the outage database and a detailed User Guide.

Outage Notification Guidance

This guidance is provided to assist Asset Owners in accessing which outages or reduction in equipment capability may impact the system operator’s ability to plan to meet its Principal Performance Obligations. They have been produced in response to recommendations from the 2019 POCP review.

Contact OPS.Planner@transpower.co.nz for further assistance or specific outage queries.

Outage Disclosure Guidance [ pdf 341.98 KB ]

Attachment 1 - Minimum Outage Disclosure Requirements [ pdf 91.9 KB ]

POCP Review - Outage Notification Guidance Presentation [ pdf 474.07 KB ]

Questions and Answers

We have listed below common questions we have received from industry along with our responses.  We will continue to update this section and share with participants any updates.

Number Description

Is demand Response to be included as it is not offered in and therefore is not shown in the forward schedules?

System Operator Response 23 March 2021

At this stage demand response only needs to be disclosed to the system operator if;

  1. it meets one of the other criteria for outage disclosure, and
  2. the decision to initiate the demand response is made prior to the publication of the relevant forward schedule (i.e. more than 36 hours from real-time)

Demand response is an evolving part of the electricity system and the system operator will continue to monitor the impacts of demand response on system security.


Are Wind Farms included in the 20 MW requirement?

System Operator Response 4 March 2021

Yes they are, we have considered this question and whilst wind farm station output is usually considered to be 0MW during planning security studies for specific outages, an element of Wind farm Station output is considered in other assessments such as NZGB.

Duration of load outages that require notification i.e. >24 hrs?

System Operator Response 23 March 2021

All grid owner outages and GXP Ties that meet the disclosure guidelines require disclosure regardless of duration. All other outages require disclosure when their duration exceeds one trading period (30 minutes).


Does the load requirement apply to conforming and non-conforming loads?

System Operator Response 4 March 2021

Yes it does.