how are houses connected to the substation transformer

[calum63]

hi there, probably not the best site for this question but here goes. I live in an estate with approximately 250 modern houses. there is transformer in our street in a large grey box. so with nothing better to do on the weekend I had a wee peak (obviously I did not go inside it). Anyway I will describe what I a saw in the substation as best as I can in absence of a picture. On one side there were 2 large red cables ( I'm guessing the 11kv feed in and out from other substations?), a bare metal rod thing (earth mat underneath the substation), and finally 2 largish black cables on the other side of the transformer (415/240v) output?.

any I back to the question how are all these houses connected to this transformer?. Will those 2 black cable support all these houses?.

sorry if its confusing but thanks

 

[calum63]

must be too technical for this site. I will try elsewhere.

 

[Jackrae]

Answer (a) by 1P+n connected to the 3P+N cable buried in the street

Answer (b) yes

Or are those too simplistic

 

[calum63]

so in this case would it be around 40 houses per phase?. so as the cable leaves the transformer it splits up in junction boxes. sorry if appeared rude it was just no one answered so I assumed they didn't know.

 

[westie101]

Yes you are right on the red coloured cables.

The various boxes will be HV switchgear, transformer and LB cabinet.
Which as you noticed has 2 large black cables coming out to the various streets.
These are 3 phase cables of up to 300mm2 per phase, the size dependent on load and voltdrop calculations
From these, single phase services will them go to each property, jointed usually in the footway outside the property.

Load will be determined by average usage, for example a gas heated house with a choice of cooking would be given an ADMD (After Diversity Maximum Demand) of usually 2kW.

So for the size of the estate probably a 500kVA transformer.
This will give an LV fuse size of up to 400A to provide discrimination with the HV protection of the transformer.

(Been out enjoying ourselves riding trains all day)

 

[calum63]

thanks thats very clear . hope you had a good day. just one thing is it just a simple joint per house to main cable or do the joints have multiple cables leaving it?. I'm just very curious thanks.

 

[westie101]

just one thing is it just a simple joint per house to main cable or do the joints have multiple cables leaving it?. I'm just very curious icon_lol.gif thanks.

It can be either, most joints can be for up to 4 separate service cables, also in some areas one service can go into a house then another service cable can be looped out of there to a property next door.
The loop is done on the bottom side of the DNO cut-out

 

[calum63]

thanks , you learn something new everyday.

 

[bernardgreen]

A typical junction of a domestic supply to the 3 phase and neutral cable running along the street.

Untitled

• bernardgreen
• 9 May 2015
• 1