Transpower, as the system operator (SO), uses the DIgSILENT Powerfactory software to undertake power systems analysis. The SO will make case files available in December each year for the Authority to publish for use by interested analysts. Additional case files will be provided when a significant update to either the generator or transmission model is made. See the notes below describing what constitutes a significant upgrade. The Powerfactory software provided by DIgSILENT is used to model the power flow cases. Each case includes a Peak Load and a Light Load study case. The DIgSILENT cases will include the system dynamic model and the power flow model. Where the dynamic model refers to confidential asset information provided to Transpower, the asset data will either be encrypted or removed entirely from the case if encryption is not possible. If the latter, the information will be represented by a 'generic' dynamics model for the particular asset. DIgSILENT Powerfactory cases are made available as binary files (.pfd) for use in the proprietary DIgSILENT software. The SO may export Powerfactory cases to PSS/E format (.sav files) and PSS/E Raw format (.raw files). If so, these files will also be made vailable. Two PSS/E raw (text) files containing only the power flow information (i.e. not the system dynamic model) - one each for the peak load case and light load cases will be provided. Triggers for significant updates: - Significant update for Generator Model: - Completion of commissioning or decommissioning of generator => 30MW per unit. Wind farms will be considered as single station/unit. - Power flow case files will be provided in DIgSILENT and PSS/E (Raw format) for base case and light load case. - Dynamic models for new generators may only be provided once the SO has received the information from the asset owners. This only pertains to the DIgSILENT cases. - Significant update for Network Model: - Completion of commissioning or decommissioning of asset: - Transmission circuit with voltage level 66kV and above - 220kV and 110kV interconnecting transformer - Reactive compensation devices connected to buses with voltage from 66kV and above - DIgSILENT and PSS/E power flow case files will only be provided once the SO receives the updated network model from the Grid Owner. - The December annual update will include the latest information received by the Grid Owner. Load pattern changes will not be considered grounds for a significant update. November 2023 update: - Transpower have provided two new PowerFactory case files: - 202311NorthIsland.pfd - 202311SouthIsland.pfd - The updates to each case are described in the PDF called '202311 EMI Powerfactory case file summary.pdf'. The update includes many enhancements which have been detailed in the aforementioned summary document, along with instructions on how to use the new features and updates. It is hoped that this update will enable participants performing Fault Ride Through and Connection Studies greater support with their dynamic and powerflow assessment. See https://www.emi.ea.govt.nz/Wholesale/Datasets/Transmission/PowerSystemAnalysis/PowerFactoryCaseFiles. October 2022 update: - Transpower have provided two new PowerFactory case files: - 202210NorthIsland.pfd - 202210SouthIsland.pfd - The updates to each case are described in the PDF called '202210 EMI Powerfactory case file summary.pdf'. See https://www.emi.ea.govt.nz/Wholesale/Datasets/Transmission/PowerSystemAnalysis/PowerFactoryCaseFiles. May 2021 update: - Transpower have provided two new PowerFactory case files: - 202105NorthIsland.pfd - 202105SouthIsland.pfd - The updates to each case are described in the PDF called '202105 EMI Powerfactory case file summary.pdf'. See https://www.emi.ea.govt.nz/Wholesale/Datasets/Transmission/PowerSystemAnalysis/PowerFactoryCaseFiles. August 2020 update: - Transpower have provided PSS/E (.sav binary) and PSS/E raw files (.raw text) derived from the peak load and light load PowerFactory scenario cases. See https://www.emi.ea.govt.nz/Wholesale/Datasets/Transmission/PowerSystemAnalysis/PSSErawFiles. - The following notes were provided by Transpower to accompany these new files: - The cleaned up PSS/E cases for the NIPS_rev5 and SIPS_rev2 are derived from the PowerFactory cases being used for the fault ride through studies. Network diagrams of the core 220kV grid (these have some 110kV buses also) have also been provided but these are byte-text files only readable within PSS/E (see the .sld files in the Line diagrams folder). - The SAV and RAW files are just positive sequence models prepared using PSS/E_32. They should be converged solutions directly as they are. Note that the RAW file is an export of the solved SAV file. - The cases should be useful for loadflow analysis (and 3 phase fault studies), and - with care - for steady state voltage studies. - The clean up of the PSS/E export from PowerFactory achieves a number of things: - 5-number bus numbers with consistent bus numbering - this allows the use of one diagram for all cases (of each island) and one dynamics file etc - all buses at a site start with the standard 3 number code - the 4th number of the bus number is a voltage level indicator (6 =220, 5=110, 4=66, 3=33, 2=25/22/20, 1=11, 0=other) - shunts are correctly sized and out of service shunts are represented - the PSS/E power flow solution matches the PowerFactory solution well to within 1% node voltages and within 1 or 2 MW/MVAr flows across the grid - The clean up still leaves some issues particularly for the light load case: - some out of service equipment is not exported and may be missing from the light load case - the most important (e.g. PAK-WKM circuits) have been restored (out of service) but there may be some outaged equipment not present in these models. Missing items can be restored using the data from the peak load case. - some open points used at light load result in a different collapsing of the PowerFactory busbar representation to the PSSE nodes (e.g. around RDF) - so some nodes end up with a different number of 'busbar nodes' and the lines then terminate at different nodes to the peak load case. This can be fairly easily reconfigured by reference to the peak load case if necessary. - in all the cases the representation of the Grid dynamic devices varies (some are generators, some are switched shunts (continuously variable) and some are fixed shunts). Users would need to check that the operating points are sensible for any significant changes to the loadflow solutions. This would be particularly important if these models are considered for studying expected grid voltage levels. - The HVDC representation is just set up manually at present. It is not used as the slack bus, it has the required Power transfer and has Qg = Qmax = Qmin for each pole: - The HVDC is represented by generators at 220kV - these are negative generators when the island is exporting MW. - The MVAr represented on the DC flow should always be a MVAR absorption of 50 to 55% the numerical value of MW - e.g. for import or export of 200MW, a pole would be a 110 MVAR load (for the generator representation used this would be -110 MVAr). - Using the HVDC as the slack bus is often preferred - this can be done by expanding the Qmax and Qmin limits and setting up the DC 'generators' to use a fixed power factor solution - but this has 2 issues: - it makes voltage control of the HAY220 kV busbar in particular very difficult to get correct - in PSSE the slack bus machines control the bus voltage and Plant models set to also control that bus become unpredictable. Getting the HAY condensers to give sensible MVAr output with HAY220kV as the slack bus is therefore time consuming and needs adjustment for every disturbance to the operating point - PSSEv32 does not have the flexibility of control of the Slack bus behaviour which is available in PowerFactory. One option is to set all the Condensers to control the 110kV bus voltage - that could be a workable solution - but is not how the PowerFactory case works (or the real grid). - a bit of care is needed to ensure PSS/E does not reverse Q flow when it reverses P flow. Q must always be a reactive power demand at both ends of the DC. December 2019 update: - Transpower have made some adjustments this year to the dynamic simulations so they solve correctly including: - Corrected the deadbank in SPL-TUR model - Corrected lookup arran in SPL-G1-GOV-ST model - Corrected THI AVR usetp initialisation - Corrected AVR and PSS initialisation in PRI(PQLIM and PSSCTRL) - SIPS the light load characteristics attached as the light load and peak was the same in the previous release. - NIPS light load corrected OHK-G1 MVAR absorption as it was providing a solution but not a credible solution. - Transpower have engaged DigSilent Australia to perform an audit of the December 2019 cases, which they intend to have complete around April next year. As a result of this audit, Transpower expect to have some actions to complete to improve dynamic simulations further. Provoided these actions are completed before the end of 2020, another case file release will occur during the 2020 year. December 2018 update: - The case file was tested in Powerfactory 2018 SP2 and is advised to be used in this version. - The case file was derived from the TP case file version 1.4.5 released on the 3rd September 2018. - The case file was tested for RMS for 3 phase fault conditions on the 220kV busbar cleared in 120ms. The faults were thrown separately and found to be stable. Further to that generator and load trip were event were done separately and GOV of the machines responded accordingly. - There is a warning regarding KTW- "No convergence. Maximum number of outer-loop iterations for dynamic model equations of element 'KTW_G6_PSSCTRL' has been reached." KTW Plant model has been switched out of service. - These warnings are due to the Asset Owners (KTW) own models that are not numerically tuned correctly. These warnings have no effect on response and is stable. For the purpose of the user, it was decided to switch KTW Plant model out of service. - The SIPS model has a warning when you initialise it: these warning are not related to dynamic modelling or affecting the response. - Inconsistent argument in DSL division by x: denominator argument x is zero; x=E-6 will be assumed. - Argument x is variable 'i_cap_int_lim'. - Inconsistent argument in DSL division by x: denominator argument x is zero; x=E-6 will be assumed. - Argument x is variable 'i_ind_int_lim'. May 2018 (interim) update: The updates in this May 2018 South Island only case are: - Gore Interconnecting Transformers (2x220/110 kV 150MVA Transformers) - Murchison upgrade of Transformer 1 (5MVA to 10MVA) December 2017 update: Some of the major updates in the December 2017 cases are: - ACI data for Lines, 2-winding, and 3-winding transformers has been updated. - ACS data for generators, 2-winding, and 3-winding transformers has been updated. - Additional North Island detailed substation models are now available. - Detail AVR with UEL and OEL and Governor models for TOPP1, TeRapa, Waitaki, AVI, BEN, CYD, Ohau A B C. - Minor and cosmetic changes. December 2016 update: One new North Island case file and one new South Island case file. Each contains a peak load and a light load study case: - 201612_EA_North_Island_SOCase_v1.4.1b.pfd - compatible with 2015 PowerFactory version 1.4.1b - 201612_EA_South_Island_SOCase_v1.4.1b.pfd - compatible with 2015 PowerFactory version 1.4.1b - No PSS/E files have been made available at this time. Some of the major updates in the cases are: - HTI-TMU 110 kV line added - PAO Transformers have been added - Minor configuration changes at PEN, WRD, OTA and TRK, ASY - Updated generator parameters. - Updated the ratings for many transformers and lines. December 2015 update: One new North Island case file and one new South Island case file. Each contains a peak load and a light load study case: - 201512_EA_North_Island_SOCase_v15.1.4.pfd - compatible with version 15.1.4 of the DIgSILENT software - 201512_EA_South_Island_SOCase_v15.1.4.pfd - compatible with version 15.1.4 of the DIgSILENT software Some of the major updates in the cases are: - OTC and SWN units set out of service (models retained) - ISL C4 and C5 decommissioned - CYD-ROX and AVI-LIV-WTK duplexing updated June 2015 update: Two North Island case files, each containing a peak Load and a light load study case: - 201506_EA_North_Island_SOCase_v14.pfd - compatible with version 14.1 of the DIgSILENT software - 201506_EA_North_Island_SOCase_v15.pfd - compatible with version 15.1.4 of the DIgSILENT software Some of the major updates in the cases are: - Modelling of the new BPE_PRM_HAY_1 and BPE_PRM_HAY_2 circuits. Moved the PRM load so it is now supplied from these new circuits. - Updated generator parameters. - Updated the ratings for all the Transformers and lines. No South Island files provided with the June update as only minor changes to the grid have occurred. Both North and South Island files will be provided in December 2015 in both DIgSILENT PowerFactory and PSS/E raw formats. December 2014 update: Major updates to the North Island case are as follows: - Composite substation model added for the following substations: - ARI - BPE - OTA - WKN - HAY - WIL - HEN - PAK - Modelled a new line WRK-WKM-1 220 kV - Opened CB at MVE-PAO-2 since this circuit is normally open - Inserted transformers Tarukenga transformer T3 (TRK-TF-T3), Kaiwharawhara transformer T2 (KWA-TF-T2) - Added 27 MW of load to Whareroa (WAA) generation - Updated the ratings for all the Transformers and lines in the NIPS case. Major updates to the North Island case are as follows: - Addition of Timaru transformer (TIM-T4) and Bromley transformer (BRY-T7) - Updated the rating of CYD-ROX-2 line - Cromwell transformers CML-T5A and CML-T5B are now modelled separately - Updated the ratings of all the Transformers and lines in the SIPS case Please be aware that these cases have been submitted in version 15.1.4 only, as exporting cases using version 14 was creating problems. This issue has been raised with DIgSILENT and they are looking into it at the moment. Once this issue is addressed the Dec 2014 case files will be released in version 14.1 also. April 2014 update: Major changes made to the North Island case are as follows: - Otahuhu condensers and transformers removed as Transpower no longer contracts for these machines - Arapuni CB-48 split added to the model - NAaN changes moved from future grid to the base grid. New cables commissioned in NAaN are as follows: - ALB-WRD-4 - HOR-WRD-1 - HOB-PEN-1 - PEN-PAK-3 - HVDC stage 2 equipment added - Marsden STATCOMs added - KAW-TF-12 upgrade from 100MVA 2 phase to 250MVA 3 phase - Updated transformer ratings in the North Island file - Vector's HOB-LST-1 cable rating updated to 907 A Major changes made to the South Island case are as follows: - No changes, as there have not been any major upgrades in the South Island. Last updated December 2023 emi@ea.govt.nz