Outage Planning Policy

In May 2018 we restructured part of our business and formed an Operations Division which brings together the real time operations we run as owner of the national grid and as system operator. The Operations Division now also includes the parts of our business that plan and coordinate outages on the grid and assess the impact of outages on overall system security.

Following these changes, we drafted this policy to clarify how, in our dual roles as system operator and owner of the national grid, we will meet our obligations around outage planning, coordination and assessment.

These are existing obligations we have under the Electricity Industry Participation Code (Code). For the most part, our approach remains unchanged. We do expect, though, 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.

This 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 245.97 KB ]

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

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 ]