The Authority occasionally obtains line diagram files from Transpower. We will publish them in this folder whenever we
get them.  

Transpower's existing customers, contractors and consultants are able to obtain the most recent line diagrams directly
from Transpower's website at: https://www.transpower.co.nz/system-operator/electricity-market/scheduling-and-dispatch.

The New Zealand power system consists of the North Island Power System (NIPS) and the South Island Power (SIPS)
system connected by an HVDC link between the two islands. NIPS and SIPS are an electrical representation (single
line diagrams) of the New Zealand Power system. These diagrams are intended to give an overview of the New Zealand
power system and therefore show only the electrical connections on the system. 

The following line diagram files were provided by Transpower in August 2020:
	- NI-2020-dig-220-LNI110-issue.sld
	- SI-2020-dig-220-110-issue.sld
These two files are network diagrams of the core 220kV grid with some 110kV buses also. The diagrams are byte-text files
and are only readable within the PSS/E software.

The following line diagrams were provided by Transpower back in 2013:
	- NIPS 1-5     - North Island Power System Diagram
	- NIPS 6       - North Island Loadflow Diagram
	- NIPS 8       - North Island Transformer Rating Table
	- SIPS 1-4     - South Island Power System Diagram
	- SIPS 6       - South Island Loadflow Diagram

The Archive folder contains line diagram files from before 2013.

The loadflow drawings (NIPS/SIPS 6) are intended for quick reference purposes only. They give an indication as to
line ratings, substation loads, reactive plant where installed, and grid connected generation.  The line ratings
shown are the summer rating only, and give no indication as to whether these are component limits (i.e. hard limits)
or conductor limits which may have  a short term rating.   

The load information shown is the peak load observed at the station to date, not necessarily the peak load observed in
the preceeding 12 months. This number will therefore only decrease in the event of a change being made to the grid
configuration by permanently moving load from one GXP to another.

Only grid connected generation is shown on NIPS 6, whereas SIPS 6 shows embedded generation also. This is a function of
space on the drawing. Note the data on these drawings should not be used for modelling purposes as it is indicative only. 

The power system drawings show different levels of detail, with SIPS 1-4 showing significantly more detail than NIPS 1-5.
As with the loadflow drawings, this difference in detail is a function of the space available on the drawings. As the North
Island system is more complex, the level of detail is correspondingly less to allow both drawings to be of comparable size.
Note these drawings also show some equipment not owned by Transpower. The majority of this is owned by the varying generator
companies, but there is some equipment owned by other network companies shown. This is limited to instances where the equipment
can effectively form part of the grid. 

The power system drawings display a reasonable degree of accuracy at the date they are produced. They are updated on a periodic
basis and do not reflect changes that are made between updates. Conversely at the time of update, some forthcoming changes may
be included before they are implemented on the grid.

Last updated August 2020.
Contact: emi@ea.govt.nz