ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Three Phase Supply

I was looking at overhead residential distribution cabling here in Ireland today a was just wondering exactly what's used. (Modern stuff would all be underground)

the poles carry 5 wires along the lowest one looks physically different cable from the other 4. Each house taps into one of the phases only and it seems to vary house to house to spread the load. Local shops etc seem to take connections from all 5 cables! for 3phase.

What's the 5th wire? system provided earth/ground?

The area's wiring would prob. date from the 40's / 50s some of it perhaps a lot older although im sure it's been upgraded over the years.

djk,
It wouldn't be some kind of a Pilot wire for a load control system, would it?.
Failing that, are you sure that it is not a wire for the streetlights control, as these are normally run off a different circuit from the distribution lines, this circuit is normally centrally-controlled, from a Daylight(photocell) switch.
Hope this helps.

Perhaps it is/was for controlling street lighting as it looks like a thinner cable

A fifth wire to operate contactors for street lights used to be quite common in some British towns and villages. I still sometimes see old poles where the control wire has been removed but the brackets that used to hold the insulators for the fifth wire are still there.

djk/Paul,
Pilot wires were used over here for years, in some places, they are still used.
I remember when I first started out as a Trainee Liney, you had to "Identify all conductors", in some places there were Pilots
for Hot Water, Street-lights, Load dumping relays, and a spare wire that was taken back to the control centre, all on the same pole as the normal 3p+N.
Pilots, killed a friend of mine, that I done my time with, there are 400V between all of them, they are never on the same Phase.

Trumpy,


Just found this post today!

Ya, send them on over (scan and E-mail), and I'll see they get placed in the reference section.

I have some EE manual schematics for KWH meters, plus KVAR meters.
When time allows I'll draw up a few.

Scott35 S.E.T.

Most of the controls for this sort of thing are done by sending short HF signals down the lines these days.

For years it was common practice for the "Economy 7" domestic night rate to be governed by a timeclock installed alongside each meter. The "Radio Teleswitch" is now common. No clocks to adjust, and the PoCo can adjust the times from a central control point if they need to.

Yeah Paul,
A lot our traditional Ripple supply signals,
are now sent by UHF and are injected at various points around our local Grid system,
saves having Pilot systems.
Another development over here, is the use of UHF (Almost like Packet Radio), to energise and de-energise certain parts of the HV and EHV systems, around here.
But good old Radio Telephones are still used to make sure that the Disconnection has actually happened, this will never be made obselete.
Don't trust this packet stuff, for this type of work though, what about Interference, but I am sure that they have got this figured into the equation.
Here's hoping!.