Day 3 - So what's that bit for?

[Moley]

Well, this wasn't going to be my day 3 subject but today has been a long day and time is short.

At power stations electricity is generated at one voltage then stepped up for distribution. The generator output is usually around 21kV. National Grid distribute at either 275kV or 400kV. DNOs go up to a maximum of 132kV. So, the generated voltage has to be stepped up to the distribution voltage. This is done via a (bloody big) transformer. So, how does then generator connect to the transformer? Big busbars! As I hadn't planned this post I'm a bit short on good pictures but this is a busbar :-
To give an idea of size those supports are around a foot long.
How do these connect to the transformer? Flexible braids :-

All those connections have to be cleaned, Contact grease (known as baby ----) applied, torqued and then ductored. Each joint must have a resistance of 10 micro ohms or less.
Well, that's just the basics. Time is getting on so I'll end it here for now. I'll take some better photos and carry on with this thread soon.

 

[davesparks]

How often do they have to go through that process, is it a routine thing or a one off at time of connection?

 

[Moley]

Different companies have different time scales for major maintenance on their GSUs (Generator StepUp Transformers) but every few years the transformer has to be disconnected totally and testing carried out to see if there are any issues. Both HV and LV sides are disconnected (I know technically the LV is not LV but that's how it's refered to) totally. If testing carries over two or more days then just a single braid is reconnected at the end of the day just to maintain an earth overnight.

 

[littlespark]

And it’s your job to make sure all this hex bolt heads are perfectly aligned…. Like all domestic accessory faceplate screws must be vertical.

 

[Moley]

Bugger that. They end up in whatever position they want