Electricity Interconnectors

[Merle Haggard]

HVDC links are between 100 kV to 800 kV with the current UK links ranging from 200 kV to 600 kV.

The Chinese have a 1,100 kV UHVDC link stretching 2,046 miles to transfer 12 GW.

Thank you for the reply.

Yes, one of the 4 units in Cruachan pumped hydro scheme is now contracted as inertia rather than generation. So rather than providing power, the turbine is powered to 600rpm.

Thank you, interesting.
Is that possibly because of the large amount of renewable energy sites in the Highlands and offshore, and lack of other revolving generators makes it necessary?

 

[Bald Rick]

Yes, one of the 4 units in Cruachan pumped hydro scheme is now contracted as inertia rather than generation. So rather than providing power, the turbine is powered to 600rpm.

Thank you, interesting.
Is that possibly because of the large amount of renewable energy sites in the Highlands and offshore, and lack of other revolving generators makes it necessary?

It’s all rather confidential, but AIUI it is to supply power to a secret Empire base.…

 

[mbonwick]

Thank you, interesting.
Is that possibly because of the large amount of renewable energy sites in the Highlands and offshore, and lack of other revolving generators makes it necessary?

It's a combination of things - the lack of large, rotating mass with most renewable forms of generation is what creates the need. (Wind tubines aren't directly coupled to the grid, so can't be used for this)

The location is helpful but not the main reason - mostly its just that Cruachan has large installed turbines which won't be being removed any time soon, and is already connected and configured to take power from the grid (more conventionally during overnight off-peak to pump water up from Loch Awe, and absorb the nuclear baseload) - so didn't need much in the way of expensive recontrolling.
Dinorwig in Wales does a similar thing, keeping turbines spinning in air but mainly for the purpose of meeting peak loads/ short term reserves (c.16 seconds from drawing power to full generating load is mental!)

 

[Ediswan]

Yes, one of the 4 units in Cruachan pumped hydro scheme is now contracted as inertia rather than generation. So rather than providing power, the turbine is powered to 600rpm.

A not-too-technical description here:
https://www.drax.com/uk/power-generation/why-spin-a-turbine-without-generating-power/

The National Grid ESO is taking a new approach to this aspect of grid stability by using what are called synchronous condensers. These complicated-sounding pieces of machinery are actually quite straightforward in their concept: they provide inertia to the grid without generating unnecessary power.

Cruachan Power Station is already capable of running its units in synchronous condenser mode

It is a nifty application of an established technology.