MEL - Meridian Energy

[Jantar]

Todays Press, Wednesday, 16 March 2016, front page, reports that the dairy farmers in the Ashburton Area use almost as much power as Tiwai Point. What now? All views welcome.

The South Island load profile has changed dramatically over the past few years. Summer time used to be a time of light demand for the south island. Now we see mid afternoon loads in summer approaching those of winter, and a totally different shape to the load profile. The big issue to Transpower is that this new demand is north of the lower South Island line constraints, and if Tiwai did close with only one years warning, then the extra power available in the lower South would be unable to be sent to where the demand is further north. It could take up to 5 years to complete a satisfactory upgrade to those lines.

[Harvey Specter]

Todays Press, Wednesday, 16 March 2016, front page, reports that the dairy farmers in the Ashburton Area use almost as much power as Tiwai Point. What now? All views welcome.

And people think water is free. Add in cost of electricity and the cost of the irrigation schemes (if you dont have a good bore) and the cost adds up. Less intense farming will reduce that power load a bit but will ramp up again if/when the milk price increases again.

I've talked to farmers and in some situations, they prefer irrigation to actual rain as they prefer the control.

[xafalcon]

I've talked to farmers and in some situations, they prefer irrigation to actual rain as they prefer the control.

Many farmers refer to rain as "money falling out of the sky"

Who wouldn't want to be in control of such a substance

If capital cost of irrigation wasn't an issue, there would be a lot more of it

Irrigation economics only stack up in a few areas of NZ which allow lower intensity dry stock land to become high intensity, or where consumer vegetables are cultivated

[xafalcon]

The South Island load profile has changed dramatically over the past few years. Summer time used to be a time of light demand for the south island. Now we see mid afternoon loads in summer approaching those of winter, and a totally different shape to the load profile. The big issue to Transpower is that this new demand is north of the lower South Island line constraints, and if Tiwai did close with only one years warning, then the extra power available in the lower South would be unable to be sent to where the demand is further north. It could take up to 5 years to complete a satisfactory upgrade to those lines.

I know you are in the industry, so can you please explain why getting power out of the lower SI is so tough (I understand the cook st cable limitations)

When I travel to Shanghai, I see pylons carrying bundles of 5 conductors below each insulator. In NZ the most I have seen is a pair, but generally only a single conductor. The height of the conductors and horizontal/vertical spacing between them seems the same in China & NZ.

So why can't more conductors be added to existing pylon insulators to quickly, simply and relatively cheaply increase capacity?

[dobby41]

I know you are in the industry, so can you please explain why getting power out of the lower SI is so tough (I understand the cook st cable limitations)

When I travel to Shanghai, I see pylons carrying bundles of 5 conductors below each insulator. In NZ the most I have seen is a pair, but generally only a single conductor. The height of the conductors and horizontal/vertical spacing between them seems the same in China & NZ.

So why can't more conductors be added to existing pylon insulators to quickly, simply and relatively cheaply increase capacity?

More could be added but that doesn't happen overnight.
Pylons might need upgrading (the cable is pretty heavy).
You don't build these things with 5 conductors when you only need 1 - waste of capital

[Harvey Specter]

Many farmers refer to rain as "money falling out of the sky"

True for some. It was a cropping farm I was talking to and the rain was creating major complications with his harvest. He wanted the rain the previous 2 months, not the current month.

[Jantar]

I know you are in the industry, so can you please explain why getting power out of the lower SI is so tough (I understand the cook st cable limitations)

When I travel to Shanghai, I see pylons carrying bundles of 5 conductors below each insulator. In NZ the most I have seen is a pair, but generally only a single conductor. The height of the conductors and horizontal/vertical spacing between them seems the same in China & NZ.

So why can't more conductors be added to existing pylon insulators to quickly, simply and relatively cheaply increase capacity?

Between the lower South Island and Waitaki River stations there are three circuits. Two of them are quite big with two conductors (called duplex) beneath each insulator, and one is quite small and only has a single conductor beneath each insulator. The meatier circuits connect Roxburgh to Clyde, Cromwell and on to Twizel, while the smaller one goes from Roxburgh to Livingston then to Waitaki, with a split off north to Islington.

The ROX-CYD-TWZ circuits were upgraded last year to help alleviate existing constraints, but not to allow for any new ones. If Tiwai was to close then a whole new double circuit, both duplexed, would be needed from Roxburgh to Waitaki and on to Islington.

Duplexing existing circuits isn't as easy as simply hanging another cable beneath the insulator. the towers need to be strengthened for increased wind and snow loading, the insulators need to heavier to cope with the extra weight, and the tension to get the correct sag needs to be adjusted.

[cyclist]

To help visualise what Jantar is saying, here is a map showing the geographical layout of the network: https://www.transpower.co.nz/sites/d...ion-map-nz.pdf

And here is a single line diagram showing the circuits and their ratings: https://www.systemoperator.co.nz/sit...0For%20Web.pdf

[xafalcon]

Thanks for the extra details guys. I'm always keen to learn from those more knowledgeable than I am.

[xafalcon]

Between the lower South Island and Waitaki River stations there are three circuits. Two of them are quite big with two conductors (called duplex) beneath each insulator, and one is quite small and only has a single conductor beneath each insulator. The meatier circuits connect Roxburgh to Clyde, Cromwell and on to Twizel, while the smaller one goes from Roxburgh to Livingston then to Waitaki, with a split off north to Islington.

The ROX-CYD-TWZ circuits were upgraded last year to help alleviate existing constraints, but not to allow for any new ones. If Tiwai was to close then a whole new double circuit, both duplexed, would be needed from Roxburgh to Waitaki and on to Islington.

Duplexing existing circuits isn't as easy as simply hanging another cable beneath the insulator. the towers need to be strengthened for increased wind and snow loading, the insulators need to heavier to cope with the extra weight, and the tension to get the correct sag needs to be adjusted.

What are the impediments and economics for adding another pole to the HVDC from Benmore to Haywards? I'm assuming it will be useful at some point in time regardless of Tiwai