FAQs: Code and System Operator

This page lists questions, answers and feedback received about the HVDC project, the code and the System Operator (SO).

Feedback/questions Response
What will participants see in the WITS schedules with round power and in the market data-Constraints screen (please provide examples of both)? The existing HVDC component flow information will still be published, but also extended to cover the WDS. When in round power, participants will see non-zero flows on one “north” branch and one “south” branch for Pole 2 and Pole 3
When will Transpower provide the post pole 3 voltage stability constraint into Wellington with the STATCOM in place (following the recent constraint bindings participants are still seeing a significant south transfer risk)? The System Operator is responsible for the studies which will determine the new constraints. They are not able to do this until the HVDC Pole 3 changes will be available to them. This will be at least September for the first stage of the Pole 3 changes. The constraint changes related to the STATCOM in place will not be for some time. The STATCOM is not expected to be commissioned until late 2013/early 2014.
Will Transpower be constraining the market to achieve the required HVDC link transfers for the tests?

The Grid Owner will be including maximum transfer limits as part of its offer for both Pole 2 and Pole 3.  These are a normal part of the transmission offer and reflect the technical limitations (for example, proven capability of Pole 3 at a certain point in the commissioning programme) of each Pole, for a given test.

The Grid Owner will offer minimum branch constraints to Pole 3 in order to create the correct pole-sharing for some roundpower and bipole tests.  This will only impact economic dispatch to the extent that it affects transmission losses.

However, within that offered capability, the Grid Owner will not use minimum or maximum HVDC constraints in order to create the market conditions it requires for a test.  The Grid Owner will enter into market transactions in order to move the market (and therefore the scheduled HVDC link transfer) for some tests, but will not be constraining the market in the sense of moving away from economic dispatch.  Further, the System Operator will not be constraining generation on or off to achieve the tests. 

Will Pole 2 be treated as a secondary reserve risk during commissioning? While Pole 2 itself is well proven, once it starts operation via the new temporary interface to Pole 3 then the overall Pole 2 system may be unproven for a time. Until such time as the system is proven to the System Operators satisfaction then Pole 2 may be treated as a secondary risk. These issues are still being discussed with the System Operator.
Will Pole 3 be treated as a secondary reserve risk during commissioning? Until Pole 3 is proven to the system operator’s satisfaction it will be treated as a secondary reserve risk.  The system operator is working with the grid owner to determine the point in the test programme where Pole 3 will cease to be a secondary risk.
What impact will the EA’s proposed secondary reserve risk Code change have on Pole 3 commissioning? That Code change proposal is too early in its lifecycle to say anything definitive about it.  Transpower made a submission on the proposal (which we do not agree with) and we expect that to be made available on the EA website soon.
Will the grid owner be offering Pole 3 subject to minimum constraints for the tests? Yes.  It will be necessary to put minimum transfer constraints on Pole 3 to achieve some of the bipole and round power tests.  For some tests that will mean that the natural scheduled HVDC link transfer will be incompatible with the test, in which case we will move the market through market transactions to achieve a compatible transfer.
How will the cost of additional round power losses be allocated? Transpower consulted on this earlier in the year.  The industry consensus was that the cost should be allocated to all purchasers through market prices and the existing processes for setting them.  Transpower is proceeding on this basis.
What happened to the round power Code changes you consulted on? The Code changes we consulted on were designed to remove all doubt that constraints not necessarily related to capability could be placed on Pole 3 during commissioning (specifically, when the HVDC link is in round power mode).  This was to support the industry’s preference for the cost of additional losses from round power to be allocated to all purchasers through market prices.  The EA disagreed with the need for the Code change.  The EA is of the view that the Code already allows for all manner of minimum and maximum transfer constraints to be applied to Pole 3 during commissioning.  Transpower is proceeding on that basis.
What impact will FTRs have on commissioning for the later project stages? The final design of the FTR market is not yet complete.  Like everyone, Transpower will be watching carefully to see what impact FTRs have on market behaviour once they are introduced.
Is Transpower actively pursuing the regulatory alternatives? We believe that we can achieve the commissioning programme with commercial solutions and we have the industry’s support for this.