ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Ring Main Circuits

I always wonderd why the UK insist in using the "Ring Main Circuit" for domestic sockets and industry use "Radial" circuits. Until I came across this intresting artical Origin of ring main circuits

How common are ring circuits outside of the UK?

Thanks for the link!

Ring mains of this type are rare outside the UK. It is used in British influenced countries (including Ireland is influenced by the Brits).

Ring mains for distribution of power (in the street, on poles etc.) has found use in other places too, but I don't know how common it is. It makes a lot of econmical sense, since you can make long cable runs with limited voltage drop in the case of moving loads. Ehhh... Let me rephrase that: If you have a bunch of houses, the odds are that the cooker and the water heater is only on in a couple of houses at the same time. Then a ring is great.

Good call C-H,
While the NZ block system here could be called a Ring Main,it is a 3 phase one, fused at every "take-off" point at single phase or 3 phases, depending upon the load.
As I've said before here, the real use for Ring Mains in NZ are for Caravan Parks.
With Neutral-Screened cables and an RCD at each socket on the system and an earth electrode at every 2nd or third box, (depending on the size of the park).
Things are a Faultsman's worst nightmare, drunken tourists with no power.
Worst ones are Kiwi's from just down the bloody road, that wanted to try out their new campervan.

Thanks Kenbo for that link.
Interesting reading.

In the old 1987 NZ regulations the ring main circuit was discussed and allowed although it never took off exept in camping grounds as Mike already said.

[This message has been edited by RODALCO (edited 07-29-2006).]

I think the answer to that is "Not very." In the U.S., the NEC rules about parallel conductors would not allow them.

I don't think it's any secret around ECN that I'm not a fan of the ring circuit. Here are a couple of threads from the past:

Ring circuits UK style.

Ring circuits revisited

Some GDR documents indicate the use of 2.5mm2 aluminum ring circuits for sockets, but they were fused 10A, so I can't really tell their purpose.

I'm not sure about the blowing characteristics of the fuses in BS1363 plugs to be quite honest.

Just to give you a few examples:

my Iron recently had a short circuit. The 16A MCB tripped and the RCD tripped very quickly. The BS1363 fuse remained fully intact.

More worryingly, I've seen the same happen with 20A diazed fuses. i.e. there was an overcurrent fault on a kettle and the plug fuse remained intact while the 20A diazed popped.

Ireland permits Ring Circuits but, they're generally not used very widely. You'll find, almost with out exception, that we tend to use 16A and 20A radials (in Ireland that is)

[This message has been edited by djk (edited 07-30-2006).]

djk,
You more or less expect an MCB to trip before a BS1363 plug fuse on short circuit, considering the Time-Current Characteristic of MCB's.
It takes time to heat up a piece of tinned copper wire (albeit short), the mechanism in the MCB works by magnetism caused by the fault current on the circuit, these are pretty much instant in their action.
Also, with the diazed fuse, if they are anything like an HRC fuse, there are 7 strands of finer silver wire leading through tubes in the fuse body, this means that the fuse will blow at a lower aggregrate(sp?) fault current.
It's also done like that to ensure the fuse runs cooler.

All Diazed fuses I've ever taken apart (up to 25A) had a single strand of wire.

I guess the BS1363 fuses are more an overload protection than a short circuit protection. But then on the other hand they only make sense in the plugs of let's say outlet strips/multi taps. I always thought that system was less than ideal...

I've certainly seen a 20A BS3036 rewireable fuse blow before a BS1363 13A fuse.

Edit: Make that BS1362. 1363 is the plug/socket standard, 1362 the fuse standard.


[This message has been edited by pauluk (edited 07-31-2006).]