System Operator Hydro Risk Curve Assumptions - September 2018 - Effective 25 September 2018 - Transpower
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Hydro Risk Curve Assumptions – September 2018 Effective 25 September 2018 System Operator
Hydro Risk Curve Assumptions - September 2018
IMPORTANT
Disclaimer
The information in this document is provided in good-faith and represents the opinion of Transpower New Zealand
Limited, as the System Operator, at the date of publication. Transpower New Zealand Limited does not make any
representations, warranties or undertakings either express or implied, about the accuracy or the completeness of the
information provided. The act of making the information available does not constitute any representation, warranty or
undertaking, either express or implied. This document does not, and is not intended to; create any legal obligation or duty
on Transpower New Zealand Limited. To the extent permitted by law, no liability (whether in negligence or other tort, by
contract, under statute or in equity) is accepted by Transpower New Zealand Limited by reason of, or in connection with,
any statement made in this document or by any actual or purported reliance on it by any party. Transpower New Zealand
Limited reserves all rights, in its absolute discretion, to alter any of the information provided in this document.
2 Copyright
The concepts and information contained in this document are the property of Transpower New Zealand Limited.
Reproduction of this document in whole or in part without the written permission of Transpower New Zealand is prohibited.
Contact Details
Address: Transpower New Zealand Ltd
Waikoukou, 22 Boulcott Street
PO Box 1021
Wellington
New Zealand
Telephone: +64 4 495 7000
Fax: +64 4 498 2671
Email: system.operator@transpower.co.nz
Website: https://www.transpower.co.nz/system-operatorHydro Risk Curve Assumptions - September 2018
VERSION HISTORY
Version1 Date Change
Historical n/a For prior versions please contact the System Operator
versions
55.0 4th May 2018 Updated demand forecast data, and updated generation
outages for the next two months.
56.0 13th June 2018 Updated generation outages for the next two months.
57.0 20th July 2018 Updated generation outages for the next two months.
Extended Ohaaki de-rating until 31 December 2018.
Updated Junction Road and Te Ahi O Maui 3
commissioning dates.
58.0 29th August 2018 Updated generation outages for the next two months.
Excluded Tekapo contingent storage from 1 October to
31 March
59.0 25th September 2018 Updated generation outages for the next two months.
Updated Te Ahi O Maui commissioning date.
1To qualify as a new version there needs to be a change to the HRC curves. Updates that change this document,
but do not affect the HRCs are denoted as sub-versions.Hydro Risk Curve Assumptions - September 2018
TABLE OF CONTENTS
Version History ........................................................................................................................................ 3
Table of Contents .................................................................................................................................... 4
1 Introduction....................................................................................................................................... 5
2 Hydro Risk Curve Assumptions ....................................................................................................... 5
2.1 Demand Assumptions ............................................................................................................. 5
2.2 Supply Assumptions ................................................................................................................ 8
2.3 Hydro Storage ....................................................................................................................... 10
2.3.1 Monitoring of storage ......................................................................................................... 10
2.4 Hydro conversion efficiency................................................................................................... 10
2.4.1 Contingent hydro storage .................................................................................................. 11
4 2.5 Thermal Fuel and Operational Limitations ............................................................................ 11
2.6 Planned Outages ................................................................................................................... 12
2.7 Forced Generation Outages .................................................................................................. 12
2.8 Generation De-ratings ........................................................................................................... 13
2.9 Transmission Assumptions.................................................................................................... 13
2.9.1 Security constraints ........................................................................................................... 13
2.10 HVDC Assumptions ............................................................................................................... 15
2.11 Market Behaviour and Generation Dispatch ......................................................................... 15
3 Appendix 1: The 2018 and 2019 Hydro Risk Curves ..................................................................... 16
3.1 How to read the Hydro Risk Curves ...................................................................................... 16
3.2 New Zealand Hydro Risk Curves for 2018 and 2019 ............................................................ 17
3.3 South Island Hydro Risk Curves for 2018 and 2019 ............................................................. 18
4 Appendix 2: Past changes to the Hydro Risk Curves .................................................................... 19
Tables
Table 1 Annual demand assumptions (total GWh) ................................................................................. 5
Table 2 Annual demand assumptions (average GWh/week) .................................................................. 6
Table 3 Monthly demand assumptions.................................................................................................... 6
Table 4 Generating plant assumptions.................................................................................................... 8
Table 5 Planned generation outages included in HRC modelling ......................................................... 12
Table 6 Security constraints included in HRC modelling ...................................................................... 13
Table 7 Determining the energy risk meter status ................................................................................ 16
Table 8 Changes to HRCs since January 2018 .................................................................................... 19Hydro Risk Curve Assumptions - September 2018
1 INTRODUCTION
Transpower in its role as System Operator aims to provide high quality security of supply related
information including the Hydro Risk Curves (HRCs) to all interested parties. The purpose of the HRCs
is to illustrate the New Zealand and South Island hydro storage level over a calendar year and indicate
the risk of a future shortage given a standardised set of assumptions.
This paper presents the assumptions used to derive the HRCs. The assumptions detailed in this paper,
and as a consequence the HRCs themselves, will be updated monthly as new information becomes
available to the System Operator.
The following changes have been incorporated in this HRC update, effective from 25th September 2018:
• Updated generation outages for the next two months.
• Updated Te Ahi O Maui commissioning date. 5
HRCs from October to December have increased due to the updated generation outages and
commissioning date.
The System Operator invites comments and feedback on the HRCs and their associated assumptions,
particularly supply assumptions including thermal fuel and operational limits, and the treatment of
contingent storage. All feedback should be directed to Market Security Services Manager, Bennet
Tucker at bennet.tucker@transpower.co.nz.
2 HYDRO RISK CURVE ASSUMPTIONS
This section details the assumptions the System Operator has used to derive the HRCs in this update.
2.1 DEMAND ASSUMPTIONS
The demand assumptions are based on Transpower’s 2018 long-term electricity demand forecast which
forecasts demand for electricity at the Grid Exit Point (GXP). The GXP forecast is adjusted to include
demand which has been served by embedded generation, but is exclusive of transmission losses. The
tables below show total annual GWh (inclusive of embedded generation such that the supply side
matches the demand side, see section 2.2 for supply side assumptions), and the annual and monthly
average demand figures as measured in GWh/week across both islands. Note that the model assumes
a 2% reduction in demand to account for price response2.
Table 1 Annual demand assumptions (total GWh)
Year North Island (GWh) South Island (GWh)
2017 (base year) 25,904 14,699
2018 25,995 14,856
2019 26,345 15,446
2020 26,617 15,628
2 The figures shown in Tables 1, 2 and 3 have not been adjusted to account for this price response.Hydro Risk Curve Assumptions - September 2018
Table 2 Annual demand assumptions (average GWh/week)
Year North Island (Average South Island (Average
GWh/week) GWh/week)
2017 (base year) 496.79 281.89
2018 498.54 284.91
2019 505.26 296.22
2020 509.07 298.89
Table 3 Monthly demand assumptions
Month North Island South Island
6 (Average GWh/week) (Average GWh/week)
Jan-18 458.02 273.68
Feb-18 474.22 280.11
Mar-18 475.10 276.17
Apr-18 481.19 275.96
May-18 508.21 284.24
Jun-18 539.99 295.61
Jul-18 553.95 300.88
Aug-18 546.52 296.02
Sep-18 518.81 283.83
Oct-18 496.70 279.34
Nov-18 485.94 293.19
Dec-18 462.86 287.35
Jan-19 464.19 285.96
Feb-19 480.61 292.67
Mar-19 481.50 288.55
Apr-19 487.67 288.34
May-19 515.06 296.99
Jun-19 547.27 308.87
Jul-19 561.41 314.37
Aug-19 553.88 309.30
Sep-19 525.80 296.56
Oct-19 503.39 291.87
Nov-19 492.49 297.52
Dec-19 469.10 291.60
Jan-20 467.69 288.53
Feb-20 484.24 295.31
Mar-20 485.14 291.15Hydro Risk Curve Assumptions - September 2018
Apr-20 491.35 290.94
May-20 518.95 299.67
Jun-20 551.40 311.65
Jul-20 565.65 317.20
Aug-20 558.07 312.08
Sep-20 529.77 299.23
Oct-20 507.19 294.50
Nov-20 496.20 300.20
Dec-20 472.64 294.23 7Hydro Risk Curve Assumptions - September 2018
2.2 SUPPLY ASSUMPTIONS
The table below shows the generation plant that is included in the HRC modelling.
Table 4 Generating plant assumptions
Generator Capacity Generation profile
(MW)
Thermal Plant (North Island)
Huntly Rankines3 480
Huntly Unit 5 385
Huntly Unit 6 45
8 Taranaki Combined Cycle 377
Stratford Peakers 200
Whirinaki 155
Mckee Peaker 100
Junction Road4 95
Geothermal Plant (North Island)
Kawerau Onepu5 60 Profiled output
Kawerau 104 Profiled output
Te Ahi O Maui6 24 Profiled output
Nga Awa Purua 135 Profiled output
Ngatamariki 83.2 Profiled output
Ohaaki 40 Ohaaki will be de-rated from 40 MW to 30 MW
for the period between 18 December 2017
through to 31 December 2018
Poihipi 55 Profiled output
Mokai 112 Profiled output
Rotokawa 34.5 Profiled output
Tauhara A 23 Profiled output
Wairakei 132 Profiled output
Te Mihi 166 Profiled output
Ngawha 2 26 Profiled output
Co-generation plant (North Island)
Kinleith 28 Profiled output
Kiwi Cogen/Whareroa 70 Profiled output
Te Rapa 44 Profiled output
Glenbrook 74 Profiled output
3 Unit capacity of 243 MW.
4 Expected commissioning date of 1st June 2020
5 Includes both Cogen (TA2 & TA3), and Geothermal (KA24 and TOPP1) generators
6 Expected commissioning date of 30th September 2018Hydro Risk Curve Assumptions - September 2018
Generator Capacity Generation profile
(MW)
Kapuni 25 Profiled output
Hydro plant (North Island)
Tuai 59 Based on historical inflow sequences
Kaitawa 36 Based on historical inflow sequences
Piripaua 44 Based on historical inflow sequences
Aratiatia 78 Based on historical inflow sequences
Ohakuri 106 Based on historical inflow sequences
Atiamuri 74 Based on historical inflow sequences 9
Whakamaru 110 Based on historical inflow sequences
Maraetai 352 Based on historical inflow sequences
Waipapa 54 Based on historical inflow sequences
Arapuni 182 Based on historical inflow sequences
Karapiro 96 Based on historical inflow sequences
Rangipo 120 Based on historical inflow sequences
Tokaanu 240 Based on historical inflow sequences
Matahina 80 Profiled output
Mangahao 42 Profiled output
Patea 32 Profiled output
Wheao 24 Profiled output
Aniwhenua 25 Profiled output
Kaimai 38 Profiled output
Wind Plant (North Island)
Te Rere Hau 48.5 Profiled output
Tararua I, II & III 161 Profiled output
Te Uku 64 Profiled output
Te Apiti 90 Profiled output
Mill Creek 60 Profiled output
Westwind 142 Profiled output
Hydro Plant (South Island)
Tekapo A 30 Based on historical inflow sequences
Tekapo B 154 Based on historical inflow sequences
Ohau A 264 Based on historical inflow sequences
Ohau B 212 Based on historical inflow sequences
Ohau C 212 Based on historical inflow sequences
Benmore 540 Based on historical inflow sequences
Aviemore 220 Based on historical inflow sequencesHydro Risk Curve Assumptions - September 2018
Generator Capacity Generation profile
(MW)
Waitaki 105 Based on historical inflow sequences
Clyde 400 Based on historical inflow sequences
Roxburgh 320 Based on historical inflow sequences
Manapouri 800 Based on historical inflow sequences
Argyle/Branch 11 Profiled output
Highbank 26.8 Profiled output
Dillmans/Kumera 10 Profiled output
10 Patearoa/Paerau 12 Profiled output
Cobb 32 Based on historical inflow sequences
Coleridge 39 Based on historical inflow sequences
Waipori 83.6 Profiled output
Wind plant (South Island)
Mahinerangi 36 Profiled output
White Hill 58 Profiled output
2.3 HYDRO STORAGE
Potential hydro generation or hydro storage equates to a volume of water stored within one of the
numerous hydro lakes or catchments around the country, and it is typically expressed in terms of
potential energy or GWh’s. The amount of aggregated hydro storage in New Zealand is extremely
important to the energy balance in the New Zealand electricity system as it is the greatest source of
variability. Consequently, the level of hydro storage is an important companion to the HRCs themselves.
The most important features of hydro storage are summarised below.
The System Operator reports on aggregate controlled hydro storage relative to the HRCs using data
from NZX, available through NZX Hydro7.
2.4 HYDRO CONVERSION EFFICIENCY
In order to derive the HRCs it is necessary to make assumptions about the conversion efficiency of
stored hydro to electrical power at different levels of storage across different hydro-electric schemes.
The System Operator uses conversion efficiencies to align with those used in NZX Hydro.
7 https://energy.nzx.com/Hydro Risk Curve Assumptions - September 2018
The System Operator has implemented a two-fold categorisation of hydro storage: controlled storage
and contingent storage:
▪ Controlled hydro storage means any hydro storage that is controllable and available for
generation of electricity from Lakes Tekapo, Pukaki, Te Anau, Hawea and Manapouri for the
South Island, and Lakes Taupo, Tekapo, Pukaki, Te Anau, Hawea and Manapouri for New
Zealand, but excludes contingent hydro storage.
▪ Contingent hydro storage means hydro storage that is available for the generation of
electricity only under emergency conditions or specifically to mitigate a risk of shortage.
The main significance of this categorisation is that the energy contribution from contingent storage is
deliberately ignored when calculating the HRCs8.
Contingent storage known to the System Operator at the present time is as follows: 11
▪ Lake Hawea: estimated 67 GWh of contingent storage
▪ Lake Pukaki: estimated 546 GWh of contingent storage
▪ Lake Tekapo: estimated 220 GWh of contingent storage between 1 October and 31 March; at
all other times this storage is treated as controlled storage
Tekapo contingent storage is currently included in NZX Hydro’s controlled storage value at all times
during the year, to correct for this, the System Operator will manually exclude Tekapo contingent storage
from the reported controlled storage between 1 October to 31 March each year.
2.5 THERMAL FUEL AND OPERATIONAL LIMITATIONS
To derive the HRCs it is necessary to assess the availability of thermal fuel for electricity generation.
The HRCs have been based on the assumption that thermal fuel will in the most part not constrain the
production of electricity, unless there are physical limitations that cannot easily be offset with commercial
arrangements.
Specifically, thermal generating plant is assumed to be unconstrained by primary fuel or operational
limitations with the following exceptions:
▪ Whirinaki is constrained to a limit of 30 GWh of generation p.a.
These assumptions are designed to reflect the limited fuel and available operating hours of the plant.
The System Operator is comfortable that thermal fuel supplies will not be limited in a way that impacts
the HRC model (other than those described above), and therefore the shortage risk facing New Zealand.
8 The reasons for this are documented in a summary document published by the System Operator following an
extensive consultation process: https://www.transpower.co.nz/system-operator/security-supply/hydro-storage-
informationHydro Risk Curve Assumptions - September 2018
2.6 PLANNED OUTAGES
In determining the HRCs, the System Operator has assumed there will be no planned outages, except
those considered critical for the ongoing safe operation of the plant, those with a long associated
contingent return to service period or those that have been fully committed and cannot be deferred. The
specific planned outages that have been assumed are as follows.
Table 5 Planned generation outages included in HRC modelling
Plant De-rating (MW) Start End
Stratford Peakers 100 30/05/2018 22/09/2018
Stratford Peakers 200 22/09/2018 23/09/2018
12
Stratford Peakers 100 23/09/2018 14/10/2018
Stratford Peakers 100 15/10/2018 30/11/2018
Kumara 4 29/07/2018 2/11/2018
Wairakei 2 4/09/2018 28/09/2018
Wairakei 3 8/10/2018 19/10/2018
Huntly Unit 6 45 30/09/2018 4/10/2018
Patea 13 1/10/2018 12/10/2018
Patea 13 15/10/2018 19/10/2018
Patea 13 29/10/2018 2/11/2018
Mokai 58 7/10/2018 7/10/2018
Mokai 153 7/10/2018 18/10/2018
Mokai 24 18/10/2018 10/11/2018
Mokai 44 11/11/2018 11/11/2018
Mokai 34 11/11/2018 11/11/2018
Mokai 24 11/11/2018 13/11/2018
Tekapo A 30 15/10/2018 19/10/2018
Coleridge 13 15/10/2018 17/10/2018
Huntly Unit 5 385 26/10/2018 11/12/2018
Ngatamariki 26 26/10/2018 30/11/2018
2.7 FORCED GENERATION OUTAGES
The System Operator has assumed a 3% factor on all thermal and geothermal capacity to reflect forced
outages when deriving the HRCs.Hydro Risk Curve Assumptions - September 2018
2.8 GENERATION DE-RATINGS
Resource Consent limitations, temporary engineering issues with plant, and operational factors can all
cause plant capacity to be de-rated. The following plant de-rating assumptions are used to derive the
HRCs:
▪ Short notice maintenance outages: One Huntly unit is assumed to be out of service for
maintenance three weekends in five
▪ Ancillary services requirements: Total thermal generation has been de-rated by 21MW at all
times to reflect spinning reserve (16MW) and frequency keeping (5MW) requirements.
2.9 TRANSMISSION ASSUMPTIONS
13
The Energy Link model includes a comprehensive nodal representation of the electricity system. This
model attempts to approximate the physical characteristics of the grid to ensure transmission losses9,
constraints and limits within the grid are correctly accounted for when deriving the HRCs.
The current grid assumptions, including line information, constraint equations and future upgrades,
includes a total of 316 lines and 224 nodes. Grid assumptions are available upon request.
The model includes security constraints 10 that have the potential to constrain generation in a dry year.
The following table outlines the constraint equations and the transfer limits for each constraint. The pre-
contingent steady state power flow on the two circuits listed must not exceed the transfer limit given.
For example, power flow from Hamilton to Karapiro on the circuits HAM_KPO2.2 multiplied by a factor
of -1.06, plus the power flow from Hamilton to Karapiro on the circuit HAM_KPO1.2 multiplied by a factor
of -0.89, must not exceed 60MW (summer rating).
Table 6 Security constraints included in HRC modelling
Constraint Transfer Limit
Summer Shoulder Winter
0.86*BOB_OTA2.2 + 1.09*BOB_OTA1.2 121
-1.06*HAM_KPO2.2 + -0.89*HAM_KPO1.2 60 67 74
-1.05*HAM_KPO2.1 + -0.89*HAM_KPO1.1 63 67 73
-1.24*OHK_WRK.1 + -1.01*ATI_WKM.1 427 444 462
-1.03*KIN_TRK1.2 + -1.02*KIN_TRK2.2 51 57 64
-1.36*BRK_SFD1.1 + -0.42*BRK_SFD2.1 327
RDF_T3 + RDF_T4 129
-1.04*FHL_RDF2.1 + -0.92*FHL_RDF1.1 52 59 66
-1.28*BPE_TKU1.1 + -0.5*BPE_TKU2.1 410 424 444
1.4*RPO_TNG1.1 + -0.24*BPE_TKU2.1 342 378 415
1*BPE_WDV1.1 + -0.04*HAY_LTN1.1 55 55 64
9 Transmission losses are modelled and accounted for, distribution losses are not (because the
demand used is at the GXP level).
10 The security constraints are sourced from the system operator’s System Security Forecast:
https://www.transpower.co.nz/system-operator/key-documents/system-security-forecast.Hydro Risk Curve Assumptions - September 2018
Constraint Transfer Limit
Summer Shoulder Winter
1*BPE_HAY1.1 + 1*BPE_HAY2.1 + -1*HAY_LTN1.1 +
1046
1*BPE_WIL1.2 + -1*MGM_WDV1.1
1*LIV_NSY.1 + -0.42*CYD_TWZ1.2 304
-1.23*AVI_BEN2.1 + -0.89 * AVI_BEN1.1 255 278 302
-1.12*GOR_ROX.1 + -0.06*INV_ROX1.1 77 n/a n/a
-1.05*EDN_INV.1 + -0.65*GOR_ROX.1 77 n/a n/a
14
Note, the Energy Link model aggregates parallel transmission branches into a single branch – as a
result some of the above constraints have been modelled as branch limits rather than equation
constraints.Hydro Risk Curve Assumptions - September 2018
2.10 HVDC ASSUMPTIONS
▪ Maximum north (BEN_HAY) transfer 1000 MW
▪ Maximum south (HAY_BEN) transfer 550 MW
2.11 MARKET BEHAVIOUR AND GENERATION DISPATCH
In order to derive the HRCs, it is necessary to make assumptions about the merit order of electricity
generating plant. For the purpose of deriving the HRCs, it has been assumed that electricity generating
plant will be offered in such a way as to minimise the use of hydro storage. In practice, this means the
model for determining HRC will typically dispatch thermal generation before dispatching hydro
generation.
It is also necessary to make assumptions about the merit order of hydro generation between the North 15
and South Island. For example, deciding what preference, if any, we place on storage in Lake Taupo
versus storage in the South Island. For the purpose of deriving the HRCs, the water value of each
storage lake has been calculated and storage is dispatched according to this value. This optimisation
of water use is carried out at the national level (i.e. the use of storage is optimised across the country
for both the NZ and SI HRCs).Hydro Risk Curve Assumptions - September 2018
3 APPENDIX 1: THE 2018 AND 2019 HYDRO RISK CURVES
The charts in this section show the 2018 and 2019 New Zealand & South Island HRCs measured in
GWh of New Zealand & South Island aggregate controlled storage.
3.1 HOW TO READ THE HYDRO RISK CURVES
The hydro risk curves are quantified by potential energy (in GWh) stored in controlled hydro lakes, and
are calculated for between 6-18 months into the future. If the amount of controlled storage intersects
the 10% risk curve, one in ten historical inflow sequences from the last 80 years would lead to controlled
storage running out. The risk status depends on where controlled storage sits on the graph in relation
to the risk curves.
16 Table 7 Determining the energy risk meter status
Risk Status Level of controlled hydro storage
Normal Above the 1% risk curve
Watch On or below the 1% risk curve
Alert Below the 4% risk curve
Emergency Below the 10% risk curve
Note that because the HRCs are not calculated retrospectively, outdated HRCs are still seen in Figures
3.1 and 3.2. See Appendix 2 for more detail on past changes to the HRCs.NZ Actual Controlled Storage and Risk Curve
Updated: 25 September 2018
4000
Nominal NZ full
3500
(Lakes Taupo, Tekapo, Pukaki,
Hawea, Te Anau & Manapouri)
3000
2500
Hydro Risk Curve Assumptions - September 2018
2000
Storage GWh
1500
1000
500
3.2 NEW ZEALAND HYDRO RISK CURVES FOR 2018 AND 2019
0
1-Jul-18
1-Jul-19
1-Jan-18
1-Jan-19
1-Oct-18
1-Oct-19
1-Jun-18
1-Jun-19
1-Apr-18
1-Apr-19
1-Feb-18
1-Feb-19
1-Mar-18
1-Mar-19
1-Dec-18
1-Dec-19
1-Sep-18
1-Sep-19
1-Aug-18
1-Aug-19
1-Nov-18
1-Nov-19
1-May-18
1-May-19
Month
Nominal NZ Full 1% Risk 4% Risk Emergency Zone - 10% Risk HRC updates
refers to an update to the HRCs: see Appendix 2 for more information
1718
SI Actual Controlled Storage and Risk Curve
Updated: 25 September 2018
4000
(Tekapo, Pukaki, Hawea,
Te Anau & Manapouri)
3500
Nominal SI full
3000
2500
Hydro Risk Curve Assumptions - September 2018
2000
1500
Storage GWh
1000
500
3.3 SOUTH ISLAND HYDRO RISK CURVES FOR 2018 AND 2019
0
1-Jul-18
1-Jul-19
1-Jan-18
1-Jan-19
1-Oct-18
1-Oct-19
1-Jun-18
1-Jun-19
1-Apr-18
1-Apr-19
1-Feb-18
1-Feb-19
1-Mar-18
1-Mar-19
1-Dec-18
1-Dec-19
1-Sep-18
1-Sep-19
1-Aug-18
1-Aug-19
1-Nov-18
1-Nov-19
1-May-18
1-May-19
Month
Nominal SI Full 1% Risk 4% Risk Emergency Zone - 10% Risk
refers to an update to the HRCs: see Appendix 2 for more informationHydro Risk Curve Assumptions - September 2018
4 APPENDIX 2: PAST CHANGES TO THE HYDRO RISK CURVES
This table below describes the changes to the HRCs since January 2018. These changes are caused
by updates to the assumptions used to derive the HRCs.
There has been 9 updates since 1 January 2018. Descriptions of earlier changes are available on
request.
Table 8 Changes to HRCs since January 2018
Effective from Changes to assumptions Impact of changes
31ST January 2018 ▪ Updated generation and transmission outages for An increase in HRCs
for February and March
the next two months.
2018.
19
28th February 2018 ▪ Updated demand forecast data, generator An increase in HRCs
capacity assumptions, generation profiles,
frequency keeping and instantaneous reserves
assumptions, and generation outages and de-
ratings.
22nd March 2018 ▪ Updated generation outages for the next two An increase in HRCs
for April and May 2018.
months.
27th April 2018 ▪ Updated generation outages for the next two An increase in HRCs
for May 2018 and a
months.
slight decrease in
HRCs for June 2018.
4th May 2018 ▪ Updated demand forecast data to include A slight increase in the
October, November
increased Tiwai load, and updated generation
and December 2018
outages for the next two months. HRCs, and a significant
increase in the 2019
HRCs.
13th June 2018 ▪ Updated generation outages for the next two An increase in HRCs
for June, July and
months. August 2018.
20th July 2018 ▪ Updated generation outages for the next two A slight increase in
2018 HRCS, and a
months. Extended Ohaaki de-rating until 31 significant increase in
December 2018. Updated Junction Road 2019 HRCs as well as
commissioning date to 1 June 2020. Updated Te October 2018.
Ahi O Maui commissioning date to 31st August
2018
29th August 2018 ▪ Updated generation outages for the next two A decrease to HRCs
for January to March
months. Excluded Tekapo contingent storage and October, and an
from 1 October to 31 March increase to HRCs for
other months.
25th September 2018 ▪ Updated generation outages for the next two An increase to HRCs
for October to
months. Updated Te Ahi O Maui commissioning
December 2018.
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