Rural transformer connections where 3-phase not available

us_sparkey · Feb 14, 2025

Greeting again, I am curious how earthing is (or was) done in rural areas of the UK where no-three phase is available say for just one house or a farm? Or perhaps a small village?
I imagine it would be a something like a 11kv - 230V single phase transformer grounded on one end of the secondary side like this:

Would you ever have a setup where the secondary of the transformer is center tapped for earthing? Or a 230 - 0 - 230 setup ? Like these?

Thanks

Andy™ · Feb 14, 2025

230 0 230 split phase is common in rural areas. which also creates a problem with many DBs etc since they are usually rated to 400v and not 460...

you won't get a 230v single phase supply with an earthed mid point

us_sparkey · Feb 14, 2025

Interesting thanks, do they ever use the 460V for large motors or anything?

Andy™ · Feb 15, 2025

3 phase 400v normally, larger will use 3 phase 690 but I've never worked on any that voltage. alrger again will use higher voltages

the 460v is simply cost saving by running 2 phases to the transformer instead of 3... only ever seen it in rural areas

poni · Feb 15, 2025

at my place we have motors from 110V to 11KVA

Phoenix · Feb 16, 2025

us_sparkey said:
Interesting thanks, do they ever use the 460V for large motors or anything?

Never seen it, and I don't really think two phases 180 deg apart would be give much of an advantage over a standard single phase motor, plus no one is likely to produce much kit for 460v as the market is likely to be limited even if it was provided, the DDNO are probably allowed to take it away and replace with two phases from a 3ph system if they had to upgrade the network for another customer. Only ever seen it used for two lots of 230v loads to manage loading. I.e. your normal loads on one side, and night store heaters on the other, and if there is another farmhouse off the same Tx then that might be the same but using opposite sides of the supply.

Thankfully we seem to have less varying supply systems than the yanks, who generally take 240v split phase to domestic properties to give 120v legs for power and lighting and 240v for things like cookers, aircon, heating, EV charging, etc, but if you live in an apartment building they bring a three phase transformer in, and every apartment gets two phases, your line to neutral is still 120v, but line to line is only 208v. And lets not forget when they have a system with a transformer having 240v secondary windings delta connected, with the earth placed midway along one, so your L1/L3 are like your split phase domestic system, and you get 240v between any two lines, but L2 to neutral gets you 277v which they call the 'wild leg'

Thank **** I'm British!