28 February 2025
Nicky McLean
By email
: [FYI request #29936 email]
Tēnā koe Nicky,
Your request
Thank you for your request, received on 30 January 2025, under the Official Information Act 1982
(the Act) for the following information:
“Via your organisation's web site Electricity Authority - EMI (market statistics and tools) there
are links to seven sub-directories, each containing monthly data files offering half-hourly data
on various aspects of electricity generation and consumption in most of New Zealand. Each
file contains data for multiple data series, each identified by a sequence of code letters and
digits. A straightforward check finds some 2,311 different name sequences across the various
files, though some names appear in more than one sub-directory! Many of these names can
be deciphered (hopefully correctly, a separate issue), but the problem here is that other name
sequences are unintelligible.
My request therefore is for information that would elucidate the correct interpretation so that
the data series may be placed into proper relationships with other data series. For instance,
given names A1, A2, A3, and A it might be that A = (A1 + A2 + A3), or, the total "A" action is (A
+ A1 + A2 + A3), or, these are all variants of the single activity at A.
Instead of more hand-waving generalities, here are specifics on some two hundred and
seventeen names whose interpretation is dark to me.
First, a col ection of names for which every supplied datum is zero:
[…]
Most of these name sequences do not identify the unit of measurement; those that do state
KWH (in a half-hour) as in the penultimate example. Could it be that units are instead
Megawatt-hours? This would cause small numbers to appear, though this would have no
effect on the all-zero values. But if not, many of the values are being specified to a fraction of a
watt-hour (as for the last example), something surely out-of-place in statistics on the national
network where a kilowatt is a small thing. Given that this data collection is given the heading
"Metered-Data", one wonders just what meters where are measuring this sort of value, and
what it means.
Many name sequences include the text DEF - one could guess a meaning for this, but it would
be better to have definite information in place of guesswork, and for the other name parts too.
IN-CONFIDENCE: ORGANISATION
Since this is all information that you publish, I hope that you also have information on the
meaning that you can provide.”
The Electricity Authority Te Mana Hiko (Authority) has interpreted your request as for:
1. A description of the seven data series mentioned and their relationship with other data
series
2. Clarification on codes used, and the consistency of units.
Our response
The Authority is not able to provide you with the level of detail you have requested as we do not
hold this information. Set out below is the information that we are able to provide in response to
your request.
The seven datasets you referred to are a legacy collection (loosely referred to as the ‘metered data
collection), which wil be discontinued when the Authority has a reliable and appropriately
documented replacement. In the meantime, we continue to collect and publish this data, on a best
endeavours basis, as a courtesy to those who may have been using it for some time. The data is
not used internally by the Authority.
The seven datasets are created from three source datasets. While there is some overlap across
the three sources, it is not possible to combine them in their entirety and treat them as a single
dataset. Other than splitting one of these three sources into five smaller (mutually exclusive
subsets), there is no transformation undertaken on the received data; we simply publish it on EMI
in an ‘as is’ state.
Due to overlaps and extra information between the three datasets, we combine parts of these
datasets together to create an eighth (legacy) dataset. This is available here:
www.emi.ea.govt.nz/Wholesale/Datasets/Generation/Generation_MD. Our preference is to obtain and publish a reliable and documented replacement for the metered
data so the metered data series can be decommissioned, rather than create a documented
schema for the metered data. However, a table with a list of column names with definitions and
specification of the units is included in Appendix A, for your information.
Your rights
You have the right to seek an investigation and review by the Ombudsman of this decision.
Information about how to make a complaint is availabl
e at www.ombudsman.parliament.nz or
freephone 0800 802 602.
If you wish to discuss this decision with us, please feel free to contact us by emailing
[email address]. Nāku noa, nā,
Airihi Mahuika
GM Legal, Monitoring and Compliance
IN-CONFIDENCE: ORGANISATION
Appendix A
Provider
Informal
Notes
EMI destination
Structure
name
Reconciliation RM
An inappropriately named dataset that
Metered_data/Embedded_generation
POC (Point of connection)
Manager
Embedded contains both generation and offtake, from
Nwk_Code (Network or direct
Generation both embedded and grid connected NSPs.
connect/connecting asset owner)
Presumably from half-hourly submissions
Participant_Code (The trader participant)
to the RM.
Loss_Code, large generators need their own
independent loss code, grid connections =
The registry manager informs the
‘DEF’)
reconciliation manager which locations
Flow_Direction (I= Injection, X = Offtake)
‘qualify’ for this dataset. But we’re not
Trading_Date
familiar with all of the conditions that
Trading period 1-50 values. (kWh)
apply.
Pulled in to supplement the legacy
Generation_MD series for (known)
embedded generation.
EMS
EMS Unit
May be higher than the aggregated EMS
Metered_data/Unit_level_generation_IR
POC (Point of connection)
Level
Grid Metering values below due to also
Unit_Code (Identifying separately metered
Generation including reserve injection values.
plant at the same site)
And IR
Participant_Code (The Generators participant
Pulled into Generation_MD series where
code)
we can usefully identify separate fuel
Gen_Measure (Always kWh)
types per unit, eg, Huntly.
Flow_Direction (Always I=Injection)
Gen_Type (Always F =
Level 7, AON Centre, 1 Wil is Street, PO Box 10041, Wellington, New Zealand | www.ea.govt.nz
Unknown/Unused/Final?)
Trading_Date
Trading period 1-50 values. (kWh)
EMS
EMS Grid
A combination of grid-level metering
Metered_data/HVDC_Flows
POC (Point of connection)
Metering
measures, subsets of which create the
Nwk_Code (Network or direct
following five data sets.
connect/connecting asset owner)
Generation_Type (Always DC)
Trader (Always TPNZ = Transpower)
Unit_Measure (Always kWh)
Flow_Direction (I= Injection, X = Offtake)
Status (Always F = Unknown/Unused/Final?)
Trading_Date
Trading period 1-50 values. (kWh - as per
Unit_Measure above)
Metered_data/Grid_export
POC (Point of connection)
Nwk_Code (Network or direct
connect/connecting asset owner)
Generation_Type (Grid. GG, GN, GD)
Trader (The trading participant)
Unit_Measure (Always kWh)
Flow_Direction (I= Injection, X = Offtake)
Status (Always F = Unknown/Unused/Final?)
Trading_Date
Trading period 1-50 values. (kWh - as per
Unit_Measure above)
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Metered_data/Grid_export_to_Tiwai
POC (Point of connection – Always TWI2201)
Nwk_Code (Network or direct
connect/connecting asset owner)
Generation_Type(Grid. GN)
Trader (The trading participant)
Unit_Measure (Always kWh)
Flow_Direction (I= Injection, X = Offtake)
Status (Always F = Unknown/Unused/Final?)
Trading_Date
Trading period 1-50 values. (kWh - as per
Unit_Measure above)
Metered_data/Grid_import
POC (Point of connection)
Nwk_Code (Network or direct
connect/connecting asset owner)
Generation_Type (Grid. GG, GN, GD)
Trader (The trading participant)
Unit_Measure (Always kWh)
Flow_Direction (I= Injection)
Status (Always F = Unknown/Unused/Final?)
Trading_Date
Trading period 1-50 values. (kWh - as per
Unit_Measure above)
Metered_data/Reactive_power
POC (Point of connection)
Nwk_Code (Network or direct
connect/connecting asset owner)
Generation_Type (Grid. GG, GN, GD)
Page 5 of 6
Trader (The trading participant)
Unit_Measure (Always kVArh)
Flow_Direction (N= None)
Status (Always F = Unknown/Unused/Final?)
Trading_Date
Trading period 1-50 values. (kVArh - as per
Unit_Measure above)
Notes:
DEF = Default Loss Code, which should translate to Grid Connected.
Al units are kilowatt-hours, unless otherwise stated, ie, Reactive_power = kVArh
As for the number of decimal places, we agree some of the decimal precision is spurious but, as above, we pass through what is received.
Page 6 of 6
Document Outline
