Event Categorisation

Under the Security Policy section of the Policy Statement, the system operator categorises credible events according to the nature of the control required to manage their effects.  This is determined periodically when we carry out a  credible event review, as detailed in the Policy Statement (see  clause 13.1).

The last credible event review was completed in 2014. We commenced the current review in 2017, which is to be completed by 2019.

For this review, we have adopted a new staged approach to our assessment. Details of this approach along with an assessment on what will be included in the current review is detailed in the following Credible Event Review Scope document.

Credible Event Review Scope [ pdf 805.43 KB ]

Response to Industry Feedback [ pdf 60.9 KB ]

Interim Policy

A review of the interconnecting transformer classification was completed in July 2018, details are provided on this page under ‘Updated Event Categorisation’. Changes will be effective from 1 October 2018. The interim policy for interconnecting transformers will continue to apply until this time. Prior to 1 October 2018, if short notice outages are required on any ICT, Transpower may choose to reconfigure the grid. Any grid reconfiguration will be available in POCP.

The interim policy currently in effect is set out below.

The interim policy effectively classes a number of ICT’s on the system as CE risks.  Remaining ICT’s will continue to be classed as ECE risks and will only be managed post contingently.

  • The ICTs classed as a CE risk during the interim period are:

HAM T6 T9

HAY T1 T2 T3

HEN T1 T5

ISL T3 T6 T7

KIK T2

MDN T5 T6

NPL T8

OTA T2 T3 T4 T5

RDF T3 T4 (for asset protection reasons)

SFD T10

STK T7

TRK T2 T3

WIL T8

 

 

  • The ICTs classed as an ECE risk during the interim period (and only to be managed post-contingently) are:

ALB T4

BPE T1 T2 T3

BRY T5 T6

CML T5A T5B T8

CUL T22 T23

DOB T11 T12

EDG T4 T5

HWB T4 T6

INV T1

KAW T12 T13

KMO T2 T4

PEN T6 T10

ROX T10

STK T3

WPR T12 T13

WTK T23 T24

 

 

Updated Event Categorisation

The completed assessments under the credible event review for the 2017-2019 period are detailed below. A summary of classifications effective from 1 October 2018 is available in the following document.

Summary of Event Classifications [ pdf 662.56 KB ]

Core Grid Busbars (voltage)

Transpower has completed assessment of all busbars connected to the core grid assessing impacts to equipment loading and related voltage issues. The final report and classifications can be viewed below along with the accompanying reports with results by grid zone. The categorisations are effective from 10 November 2017.

Participants were invited to comment on our report; a summary of feedback can be viewed below.

he following documents are available for your information/comment:

Busbar Classification Review [ pdf 5.39 MB ]
Results GZ01 Northland [ pdf 1.06 MB ] Results GZ08 Wellington [ pdf 786.1 KB ]
Results GZ02 Auckland [ pdf 1.16 MB ] Results GZ09 Nelson [ pdf 935.31 KB ]
Results GZ03 Hamilton [ pdf 1.08 MB ] Results GZ10 Christchurch [ pdf 901.38 KB ]
Results GZ04 Edgecumbe [ pdf 1.41 MB ] Results GZ11 Canterbury [ pdf 689.08 KB ]
Results GZ05 Hawkes Bay [ pdf 781.46 KB ] Results GZ12 West Coast [ pdf 875.91 KB ]
Results GZ06 Taranaki [ pdf 1.07 MB ] Results GZ13 Otago [ pdf 985.06 KB ]
Results GZ07 Bunnythorpe [ pdf 1.22 MB ] Results GZ14 Southland [ pdf 1.1 MB ]
Summary of Industry Comments [ pdf 455.1 KB ]  

Interconnecting Transformers

Transpower has completed an assessment of all core interconnecting transformers, assessing impacts to equipment loading and related voltage issues. Following this review, participants were invited to provide feedback. 

The final report and classifications can be viewed below along with a summary of industry feedback.

The categorisations will come into effect on 1 October 2018.

The following documents are available for your information:

Interconnecting Transformer Classification Review [ pdf 1021.15 KB ]

Appendix 1 - North Island ICTs [ pdf 3.27 MB ]

Appendix 2 - South Island ICTs [ pdf 2.05 MB ]

Summary of Industry Submissions [ pdf 457.13 KB ]

For More Information

For questions regarding the interim policy please contact Scott Avery

For questions regarding the Credible Event Review project please contact Bharti Patel.

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