On Mon, 28 Jul 2014 14:20:17 +0100, Tim Watts wrote:

On 28/07/14 12:30, The Other Mike wrote:

How do you phase lock the French grid to the Belgian Grid to the Dutch Grid to
the German one to the Swiss one etc etc. It doesn't in the main involve DC and
at AC it is no real problem.

Are they phased locked? I don't know.

If they are, then they have relatively long borders which means lots of
interconnections.

You aren't going to hold 2 disparate grids in sync with one or two cross
channel links - National Grid has enough trouble holding the UK grid in
phase between Scotland and the South (they have (or had at Bankside at
least) a phase indicator colloquially known as the "scottish wobblemeter".

If it started oscillating, a certain amount of panic ensued...

Presumably you mean the old National Control, close to Bankside but round the
corner in the concrete bunker of Sumner Street / Park Street. That is almost
ancient history, they moved to the 'new place' well outside London in 1996.
Essentially everything now on very large screen monitors and consolidated to
just one level of control (nothing remaining at regional level) and just an on
site local backup and a bloke on a phone when all else fails.

Not sure how national control would ever be aware of any real time phase state
as the data supplied to them from across the UK and also from Scotland is just
digitised Voltage and Current Transformer values with a local refresh rate in
the order of seconds to tens of seconds, the transfer protocol used does not
permit any element of time / data synchronisation between sites or against any
time standard for these digitised analogue values.

While it's clearly nowhere near ideal a 60GW UK grid could be kept in sync with
what is around a 600GW Euro network with 3GW of AC interconnects, it wouldn't do
anything else in normal circumstances, it's a bit of wire just like the rest of
the system and with a series reactor and appropriate generator governor response
it would remove any dumbell effect, but what happens during a fault in on or
around the interconnects and the recovery post fault is, as always, more of an
issue. It still has the potential to go tits up very fast. A DC interconnect
remains by far the best solution for the UK to Europe despite the complexity.

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