3 Phase?

[New2Game]

TT System, 2 overhead lines, 3 incoming fuses providing 3phase supply. How is this with only 2 overhead cables?

 

[Gaz the Sparky]

any chance of a picture

 

[RF Lighting]

Are you sure it is a TP supply?

Could it just be three single phase supplies?

This is a 3no. SP supplies, yet it uses a TP head and meter

 

[New2Game]

How would i check if 3 single supplies? Why would it have three seperate supplies SP?

 

[RF Lighting]

The only way to know for sure is to test the voltage between phases.

If it is a TP supply then you will typically get a reading of between 400V & 440V (U) and between 230V & 250V (Uo)

Don't know why three SP supplies? Maybe a single 100A supply was not big enough, and the cost of upgrading the DNO transformer and wiring prohibited the installation of a TP supply?

 

[New2Game]

So would the two overhead lines be a phase and a neutral?

 

[RF Lighting]

That would be my guess. Are you sure there isn't another supply coming into the property from somewhere else?

Short of having a big transformer / invertor somewhere you can only have a single phase supply on two wires.

 

[New2Game]

It must be 3 SP! Is it just split into 3 different incoming fuses?

 

[Adam_151]

http://i69.photobucket.com/albums/i62/RFLighting/3spcutout.jpg

Is that neutral sized appropiately?

 

[RF Lighting]

I don't think it is personally. The DNO neutral appears to be 16.0mm² with potential to be carrying 300A

 

[Steve]

http://i69.photobucket.com/albums/i62/RFLighting/3spcutout.jpg

Is that neutral sized appropiately?

An issue i raised when he first posted that picture. IIRC, its in a nightclub in leeds.

 

[RF Lighting]

Well remembered!!

 

[Steve]

I remember the stupidest things.

 

[Spark123]

If there are only 2 wires then it can only really be a single phase supply. Wether or not the 2 wires are phase and neutral depends on the DNO setup, they may be 2 phases if they are feeding a transformer.
I must admit, I didn't like the look of RFs cutout the first time I saw it either.

 

[New2Game]

So would I be able to use a TP RCD incomer or would i have to use 3 SP RCDs?