MCY Mercury NZ ( MRP Mighty River Power)

[fish]

Turn to wikipaedia-
Manapouri is connected to the rest of the National Grid via two double-circuit 220 kV transmission lines. One line connects Manapouri to Tiwai Point via North Makarewa substation, north of Invercargill, while the other line connects Manapouri to Invercargill substation, with one circuit also connecting to North Makarewa substation. Another double-circuit 220 kV line connects Invercargill to Tiwai Point.[6]

but i am not sure why contact exclude Tiwai-is it because all of manapouri generation is contracted to tiwai ?

[Snoopy]

MRP relies on the Waikato river system for most of its generation-great when its wet but Waikato has a drought..
Taupo is nearly at its lowest limit.
I expect a prolonged period of high prices and I don't know how mrp will cope with this lack of generation and potentially having to buy power.
I know they coped last year-but taupo is near its low 2 months earlier this year

You wrote the above at the end of March, Fish.

Quoting from the Contact operational report for March (which nevertheless reports the state of the whole power market) on page 4.

"At 31 March, South Island storage was 79% of mean (28 February: 93%) and North Island storage was 52% of mean (28 February: 77%)"

Below that statement is a graph of Hydro storage. Within that graph is a line of actual storage and another comparative line of mean storage for any particular date you choose over a whole year. Look at the date of 31st March and you see something interesting.

Both North Island (substantially the Taupo catchment harnessed by MRP) and the South Island lakes are below their mean storage levels, as we already know.

The South Island storage was sitting at around 2200GWh as at 31st March.

The North Island Lakes were sitting at some 250GWh as at 31st March.

In absolute storage terms, the South Island storage capacity is an order of magnitude greater. So is a drought in the North Island catchment really an issue? I would argue not, because there is plenty of capacity in the south to 'flood the market' (sic) provided there is near to normal rainfall in the south. And if there is a drought in both islands, MRP now have a very substantial geothermal power reserve.

As an MRP shareholder, I suddenly feel a whole lot safer.

SNOOPY

PS

and rain looks unlikely to save them.

What a difference two weeks makes! From the same Contact March operational data:

"As at 14 April 2014, storage was:
– South Island: 69% of mean
– North Island: 61% of mean."

That represents a substantial inflow into the Taupo catchment in just a fortnight, with an equally substantial outflow in the south!

[fish]

I sure didn't expect so much rain.
glad you are feeling better about mrp
I am optimistic about population growth, I do like electric trains and cars and heat pumps.

[Marilyn Munroe]

T
The relevant point as I see it, is how does the Manapouri power get to the Benmore node? What Dr Patrick Strange said can still be entirely true, even if no link between Manapouri and Benmore currently exists.

SNOOPY

Benmore is connected to the South island grid by several AC transmission lines. These give the southern terminus of the HVDC link the ability to drag in power from other stations and send it north even if the Benmore Power Station is idle.

The line from Manapouri, which marches across the Christchurch Port Hills, stops off at the Twizel switchyard which itself has connections to Benmore. This is the most likely method of delivering electrons from Manapouri to the North Island via the HVDC link.

Boop boop de do
Marilyn

[Snoopy]

Benmore is connected to the South island grid by several AC transmission lines. These give the southern terminus of the HVDC link the ability to drag in power from other stations and send it north even if the Benmore Power Station is idle.

The line from Manapouri, which marches across the Christchurch Port Hills, stops off at the Twizel switchyard which itself has connections to Benmore. This is the most likely method of delivering electrons from Manapouri to the North Island via the HVDC link.

I guess I had a somewhat naïve impression of what the North South HVDC link was like.

From

http://new.abb.com/systems/hvdc/references/new-Zealand

we are told
"the DC link is a 610-km long inter-island HVDC transmission system, between Benmore substation on the South Island and Haywards substation north of Wellington."

I had the impression it was a single continuous cable poking out from Clifford Bay before striking shore near Petone before making the short leap to Haywards. But what you are saying Marilyn is that those power pylons marching across the port hills are in themselves part of the HVDC link?

SNOOPY

PS I see on further reading of my reference it answers my own question.

Length of DC submarine cables: 42 km
Length of DC overhead line: 575 km

[Marilyn Munroe]

But what you are saying Marilyn is that those power pylons marching across the port hills are in themselves part of the HVDC link?

No, the Port Hills transmission line is part of the AC South Island grid. This grid is also connected to the southern terminal of the HVDC link at Benmore. This gives the ability to use power produced at other South Island power stations to feed the HVDC link.

An example; Manapouri --> Twizel --> Benmore HVDC terminal -->(HVDC link) --> Heywards HVDC terminal --> North Island grid.

Boop boop de do
Marilyn

Definitions;
DC direct current
AC alternating current

[cyclist]

For those trying to get their head around the transmission network, the NIPS and SIPS diagrams on this page provide a single line diagram representation of the network: http://www.systemoperator.co.nz/docu...s-and-diagrams

And on this page you can find geographical representations of the transmission network: https://www.transpower.co.nz/resourc...s-and-diagrams

[Harvey Specter]

No, the Port Hills transmission line is part of the AC South Island grid. This grid is also connected to the southern terminal of the HVDC link at Benmore. This gives the ability to use power produced at other South Island power stations to feed the HVDC link.

An example; Manapouri --> Twizel --> Benmore HVDC terminal -->(HVDC link) --> Heywards HVDC terminal --> North Island grid.

Boop boop de do
Marilyn

Definitions;
DC direct current
AC alternating current

The lines are there but are they big enough to get the power (should Tiwai close) to where it needs to be?

[Snoopy]

For those trying to get their head around the transmission network, the NIPS and SIPS diagrams on this page provide a single line diagram representation of the network: http://www.systemoperator.co.nz/docu...s-and-diagrams

Thanks for this Cyclist. From the South Island map I can see the DC link in purple marching from Benmore north but inland and bypassing Christchurch by going west of Hororata. As you go north the line is still just west of Waipara before it forges east north of Culverdon.

This is the line that Transpower has recently upgraded is it not?

The question that Harvey Spector just put is, what about the lines that are north/south of the Benmore node that feed the power to that node? It is the lines south that must carry the power from Manapouri to Benmore.

I see two parallel 220kV lines, each with double circuit towers, coming from Manapouri and feeding into the node at North Makarewa and also into Invercargill. But all that power feeds into the same system as all the rest of the South Island hydro system. So while it may be correct to say that the 350kv DC line could feed the power from Manapouri north, can it do so at the same time as feeding power from those other South Island hydro stations north?
That is the question that needs answering here is it not?

SNOOPY

[cyclist]

Snoopy, I don't know for sure, but I suspect after recent upgrade work that the HVDC has the capability to take any available excess.

If you look at the maps, I think it is likely that the constraint is north of Roxborough. i.e. without Tiwai, the only remaining significant southern load centre is Dunedin. Any Manapouri generation that is not needed for lower South Island load, will add pressure to the network carrying Roxburough and Clyde generation (and those closer to Benmore) north to Benmore/Christchurch (and beyond).

In the Meridian prospectus, on page 55 it states:

"If the Tiwai Point aluminium smelter were to close, the current transmission system operated by Transpower has the capacity to allow Meridian to supply the majority of Manapōuri’s generation capacity to the national grid and the wholesale electricity market. Transpower has advised that the transmission network between Manapōuri and the rest of the South Island could be upgraded and it expects such an upgrade to take three years to implement from commencement of the project. In Meridian’s opinion, under normal market conditions this upgrade would allow Meridian to supply a significant majority of Manapōuri’s generation capacity to the national grid".

These guesses seem to be supported by this article: http://www.nbr.co.nz/article/if-tiwa...land-ck-138278

i.e. some constraint in the 220 kV AC network only, but nothing major.