SSF Section Location of Change SSF Issue Change(s) Comments Chapter Part B All Multiple Formatting, spelling and minor Changes applied -

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1 SSF Update December 2017 Summary of Changes This table only mentions SSF chapters that were updated. All other SSF chapters were checked and confirmed as still being uptodate. SSF Section Location of Change SSF Issue Change(s) Comments Chapter All Multiple Formatting, spelling and minor Changes applied grammar errors. 2.2 Committed Generation Projects Table 2.1 Summary of Committed Generation 15MW step increase in WKM 220kV Hydro owned by Mercury Inserted table entry to indicate committed 15MW step WKM 220kV Hydro is increasing from 105MW to 120MW by 2019 New upgrade: PEN T10 to be replaced with strategic spare. Inserted new table entry describing upgrade. Fixed incorrect transformer unit numbers in the upgrade: "Replacement of Bunnythorpe T1 and T2 220/110 kv interconnecting transformer with two 150 MVA units. Decommission of Bunnythorpe T3 220/110 kv interconnecting transformer." 2018 commissioning date SSF now reads: "Replacement of Bunnythorpe T2 and T3 220/110 kv interconnecting transformer with two 150 MVA units. Decommission of Bunnythorpe T1 220/110 kv interconnecting transformer." Multiple upgrades now commissioned Gore 220/110 kv Tee interconnection and new Gore 110 kv bus configuration Updated SSF: struckthrough the expected commissioning date and included the word "Commissioned" for each completed upgrade. Expected commisioning date revised from 2017 to Also, the following note is included: "In the initial project scope Gore 110 kv bus will normally be split, but can be closed for some maintenance outages. This split is being reviewed and may be removed from the scope due to changing system requirements." now complete: * Bromley T5 now 180MVA and T6 decommissioned. * HWA bus upgrade and series reactor decommissioning. * Aviemore Waitaki Livingstone kv circuit now duplexed * ABY T2 supply transformer Project to decommission HWB 220/110 kv ICT T4 and to replace HWB 110/33 kv supply transformers with a single new 220/33 kv transformer Two separate table rows have been created to reflect that this project has been split into two separate projects: (1) T4 decommissioning; (2) T1 & T2 replacement. T4 has been decommissioned. T1 and T2 will be replaced by 2018.

2 2.4 HVDC Capacity Change in HVDC operation Removed the words "500/500MW" from "It is possible to operate the HVDC link as a balanced 500/500 MW bipole or as an unbalanced bipole with 700/500 MW (on HVDC Pole 3/Pole 2)." Rewording to reflect the recent change to run 1000MW as 420/580MW not 500/500MW Limitations on HVDC North Transfer Limitations to HVDC South Transfer currently only described in GZ08, not in in. Added the following crossreference: "For limitations on HVDC south transfer see, GZ08, Section 4. " In the next full SSF review a new section will be added to for HVDC south transfer limitations. 3. DEMAND FORECAST Tables 31 and 32 Demand Forecasts expected regional and island peaks Expected demand forecast None to Did not change these tables because the expected demand forecast is only revised for the full SSF review. But 24 specific GXPs are forecast to experience steps in demand of 0.2 to 13MW when compared with the last forecast. These forecasted demand steps were studied. Only the 9MW load at WIR required an SSF revision (see, GZ02, Section 5). 4. GENERATION Table 4 1 Location, type, and capacity of generators 5.1 CAPACITORS Table 5 1 List of static 5.1 CAPACITORS Table 5 1 List of static 5.1 CAPACITORS Table 5 1 List of static 5.1 CAPACITORS Table 5 1 List of static 5.1 CAPACITORS Table 5 1 List of static WKM 220kV Hydro is now 105MW not 100MW Henderson 220 kv (C1) is currently unavailable Corrected the WKM 220kV Hydro table entry from 100MW to 105MW * Revised the Total MVAr to "75 (0)" * Substracted 75MVAr from table "Total (NZ)" * Added table footnote: "Henderson C1 is currently unavailable, the expected return to service date is June 2019" Removed F1 and F2 entries from table BEN filters F1 and F2 are decommissioned BEN filters F3 and F4 rated Two x ( ). Now reads 2 x 79.4 values are incorrect New BEN filters F5, F6 and F7 New ratings added: "2 x 79.8, 1 x 80" Islington 66 kv (C15) is currently unavailable until Jan 2018 * Revised the Total MVAr to "111 (74)" * Substracted 75MVAr from table "Total (NZ)" 5.2 REACTORS Table 5 2 List of reactors HWA series reactor R72 now decommissioned HWA R72 table entry struckthrough and the word "Decommissioned" added to table For all assests commissioned and decommissioned since the last full SSF review, these have been retained in the SSF with the word "(De)commissioned" rather than removing them so that the reader can see what has changed. Statements about these assets will be removed from the SSF at the next full update.

3 5.4 STATIC VAR COMPENSATORS & STATCOMS Table 5 4 List of Static Var Compensators (SVC) and STATCOMS ISL SVC9 has been returned to full service of 75/+150MVAr from 75/+40 ahead of schedule Size and total MVAr changed to state 75/+150MVAr HangatikiTe Awamutu Overload Protection Scheme renamed and commissioned. ArapuniKinleith 110 kv Overload Kawerau T13 Overload Redclyffe Interconnecting Transformers Overload Hawera Reactor and Auto Bus Splitting Scheme BunnythorpeMataroa Reactor and Overload Temuka Overload Protection Scheme Two previously separate have recently been combined: Bells PondWaitaki Overload Black PointWaitaki Overload * This SPS has been renamed to "ArapuniTe Awamutu Overload ". * Removed the sentence "to be commissioned in 2017". Comment added: "Scheme to be modified in 2019 to trip feeders after some work at Kinleith is complete." Comment added "Scheme currently withdrawn" Commissioning date revised from 2017 to 2018 Comment added "Scheme withdrawn " Commissioning date revised from 2017 to 2018 Comment added "Commissioned" The two table entries for these have been merged into a single entry for the combined scheme called "OamaruWaitaki Overload " Roxburgh Export Overload New scheme added Comment added: "(Stage 2 to be implemented after GOR 220/110 project is complete in 2018)" "North Makerewa Capacitor Bank Intertrip Scheme" "This scheme minimises the rise of system voltage levels in the Southland area when there is significant loss of load at Tiwai." "This scheme trips capacitor banks at North Makarewa if there is significant loss of load at Tiwai." "Normally Disabled"

4 Wanganui AUVLS Comment added: "Also enabled for 110 kv circuit outages and outages where low postcontingent voltages will be apparent at WGN" Upper South Island AUVLS Comment added: "Scheme currently withdrawn" New AUVLS scheme "Hawera" "This scheme manages low voltages during BPE MTNWGN or HWASFD outages, or with all circuits in service and a tripping of either the HWA SFD circuit or Patea feeder during extreme load/generation scenarios." "Commissioned Aug 2017, but currently disabled. Awaiting final offer from Grid Owner." Arapuni South Bus runback scheme now commissioned Statement "to be commissioned in 2017" replaced with "Commissioned". Part C Section 2.2 Table 21 Table caption orphaned from the Formatted the caption to "Keep with next". table Part C Section 3.1 Incorrect section reference Changed "Section 2.4 of Part A discusses " to "Section 2.5 of Part A discusses ". All Multiple Minor formatting. Changes applied GZ01 GZ01 6. CONTINGENCIES UNDER PLANNED OUTAGES (N11) Step load at Albany Statement inserted: "A step in demand is forecast at the Albany 33 kv GXP by This may restrict the timing of the planned outages described in sections 8.2.3, and " GZ02 New upgrade: PEN T10 to be replaced with strategic spare. Statement "There are no committed projects in Grid Zone 2. " replaced with description that adds further detail to the entry in, Table 22. GZ02 GZ04 GZ04 5. CONTINGENCIES UNDER INTACT NETWORK CONDITIONS (N1) Step load at Wiri Statement inserted: "Wiri is forecast to experience a step increase in demand by 2019, but this additional loading is still below the variable line ratings." All Multiple Formatting, spelling, "crossreference errors". Table 21: Summary of WKM 220kV Hydro increasing to committed generation 120MW by 2019 Changes applied Inserted table entry to indicate committed 15MW step Without the variable line ratings a contingency of BOBWIROTA circuit 1 or 2 would overload the other circuit. This is the same as the entry in, Table 21. Simple powerflows were performed to confirm that existing operational measures can currently manage this increase.

5 GZ04 3. DEMAND AND GENERATION Table 31: Location, type, and capacity of generators in Grid Zone 4 WKM 220kV Hydro is now 105MW not 100MW Corrected the WKM 220kV Hydro table entry from 100MW to 105MW GZ06 GZ07 GZ07 GZ07 GZ08 Sections 2, 6, 8.2.1, 8.2.2, 8.2.3, CONTINGENCIES UNDER INTACT NETWORK CONDITIONS (N1) Table 21 and Body Text Table 21: Committed projects in Grid Zone 7 Table 21: Committed projects in Grid Zone 7 Table 51: Contingencies during intact network conditions The HWA bus upgrade is now complete. Several N11 planned outages have operational measures for before and after the upgrade. Broken table cross reference to Table 21 BPE T2 and T3 replacement and T1 decommissioning BPEHAY conductor upgrade not in this table Contingency HAYMLG 1 or 2 no longer a problem All Multiple Formatting, spelling, "crossreference errors". 1. GRID ZONE 10 AND 11 NETWORK OVERVIEW 4. ASSUMPTIONS AND BACKGROUND Figure 12: Schematic representation of Grid Zones 10 and 11 TIM interconnecting transformer upgrade Inserted the statement "Note: Hawera bus rebuild is now complete." in each of the sections listed Fixed crossreference This chapter will be completely revised and "before" operational measures removed at the next full SSF review. Fixed incorrect transformer unit numbers Same error as, Table 22 Inserted new table entry: "Conductor upgrade of the BunnythorpeHaywards A and B line to provide a moderate increase in rating." Deleted the table entry containing this entry Changes applied SLD updated Formatting Reformated the bullet list of upgrades as a table (i.e. Table 21) for clarity and also to match the format of other chapters Table 2 1: Committed projects in Grid Zone 10 & 11 Updated this table to match the new/revised upgrades reported in, Table 22 ISL SVC9 has been returned to full service of 75/+150MVAr from 75/+40 ahead of schedule New / revised upgrades: * BRY T5/T6 upgrade * ABY T2 upgrade * New TIM ICT Footnote 3 that described the derated capacity of SVC9 was rewritten to state that SVC9 is at full capacity. This upgrade is reported in, Table 22, but was not included here. This was an issue in the June 2015 SSF. It was removed from Dec 2016 SSF, Section 8.1, but not removed from this table. 5. CONTINGENCIES UNDER INTACT NETWORK CONDITIONS (N1) Table 5 1: Contingencies during intact network conditions The SSF only reports ASBTIM TWZ1 or kv circuit as overloading T5 (or T8). It does not report that it can cause voltage collapse as well. Added statements: "Voltage collapse in Timaru area and wider Ashburton area and USI" "Manage load below voltage stability limits: approx. 126 MW with no Tekapo A generation; approx. 135 MW with Tekapo A." Information taken from Transmission Planning Report 2017

6 Sections 6, 8.2.3, Tables and Body Text Planned Outage: "ASBTIMTWZ 1 or kv circuit Or TIM T5 or T8 220/110 kv interconnecting transformer". N11 of both T5 and T8 does not overload ISLLIV1 as claimed "ASBTIMTWZ 1 or kv circuit" and "TIM T5 or T8 220/110 kv interconnecting transformer" are now split into two separate planned outages In June 2015 SSF planned outages and were reported separately. In the Dec 2016 SSF these were combined into a single issue, which was difficult to understand and resulted in the incorrect statement that loss of T5 and T8 can overload ISLLIV1. The two issues have been reseparated for clarity. Section Table Loss of AshburtonTimaruTwizel 1 or kv circuit Section Loss of AshburtonTimaruTwizel 1 or kv circuit Section Loss of AshburtonTimaruTwizel 1 or kv circuit Added Statements: "or TIMT5 or T8 220/110 kv interconnecting transformer" "Voltage collapse risk during high load periods in the 110 kv Timaru area when the STU split is open." Added Statements: "When StudholmeTimaru kv circuit is open, load recently coming online in the Timaru 110 kv network." "Concerning voltage collapse,... The Timaru interconnecting transformer upgrade being commissioned in October 2018 will remove this risk." Deleted statement: "(or even higher if Tekapo A reactive support is not available, see section )" A full description of the voltage collapse problem is included and the TIM ICT upgrade is described as a measure to relieve this issue. Deleted because it refers to Section in the June 2015 SSF, which has since been deleted. Section was the N11 planned outage: Outage of AlburyTimaru kv Circuit and the Loss of AshburtonTimaruTwizel 1 or 2 Circuits (Tim T5 or Tim T8)" Planned Outage of AshburtonTimaru Twizel 1 or kv Circuit or Equivalent Timaru Transformer and Loss of Timaru AlburyTekapo1 110 kv Circuit or Tekapo A G1 Table Loss of Tekapo A can also cause problems during this planned outage. Voltage collapse can occur before transformer overloading occurs. Statements added to the summary table: "or Tekapo A G1" "Possible voltage collapse in Timaru 110 kv network during high Timaru, Temuka and Studholme load." "Avoid outage when 110kV Timaru area load is above 126 MW voltage stability limit."

7 GZ14 GZ Planned Outage of AshburtonTimaru Twizel 1 or kv Circuit or Equivalent Timaru Transformer and Loss of Timaru AlburyTekapo1 110 kv Circuit or Tekapo A G1 Loss of Tekapo A can also cause problems during this planned outage. Voltage collapse can occur before transformer overloading occurs. Paragraph added: "If the 110 kv Timaru area load is above the 126 MW voltage stability limit during any of these N1 1 contingencies, voltage collapse will occur before the Timaru interconnector overload protection scheme can trip any feeders (See section for details). The available operational measure is to not schedule this outage during high load periods until the Timaru interconnecting transformer upgrade in October 2018, which will resolve this voltage collapse risk." All Multiple Formatting Changes applied Table 2 1: Committed projects in Grid Zone 14 Updated this table to match the new/revised upgrades reported in, Table 22 New / revised upgrades: * Gore 220/110 kv Teeinterconnection and new Gore 110 kv bus configuration * HWB 110/33 kv supply transformer T1 and T2 replacement The following footnote is also included: "The 2017 Transmission Planning Report states that the voltage stability limit through one Timaru interconnecting transformer is 126 MW without Tekapo A generation and 135 MW with Tekapo A generation."