From: "Nick Rouse" <[email protected]> To: <[email protected]> Sent: Saturday, October 07, 2000 7:44 PM Subject: Re: Overcurrent Protection: One or Both Sides?
Hello Richard No, there is only one fuse in the standard BS1363 mains plug . It is in the live side and the plug is not reversible. The neutral of UK low voltage distribution systems is earthed at the local distribution transformer (and sometimes at additional points). In all but remote rural areas the three phases are distributed along the road together with the neutral and one phase and the neutral fed to each house so that every third house is on the same phase. The purpose of the fuse is to not to protect the house wireing or the appliance but to protect the mains cord between the plug and the appliance. This is required because nearly all houses are wired on the ring main system. All sockets on the same floor are connected to a ring of heavy cable. This ring is protected by a fuse or circuit breaker with a rating appropriate to the heavy cable. The lower rated mains cord therefore needs separate protection. This system has the advantage that low powered appliances can be fitted with cheaper and less clumbsy power cords and be safe plugged into and socket. Damaged or overloaded mains cords are a common source of hazards and not always well dealt with in other systems Fuseing the neutral is stongly frowned on in UK safety circles. For UK use, you can afford it use two pole circuit breaker, else fuse only the live side. Nick Rouse > > ----- Original Message ----- > From: <[email protected]> > To: <[email protected]> > Sent: Friday, October 06, 2000 8:59 PM > Subject: RE: Overcurrent Protection: One or Both Sides? > > You are correct that fuse protection in the British cord is for fault > protection of the building wiring. I could be wrong, but I thought that > there were two fuses in the plug. Perhaps others can comment on this. > > Fusing of the neutral is a messy issue. If you use only one fuse, it > cannot > be in the neutral. If you use a fuse in the line and a fuse in the > neutral, > the warnings you indicated must be present. > > Richard Woods > > ---------- > From: [email protected] [SMTP:[email protected]] > Sent: Friday, October 06, 2000 3:15 PM > To: [email protected] > Cc: [email protected] > Subject: RE: Overcurrent Protection: One or Both Sides? > > > Richard, > > To prevent unexpected hazards to service persons, that fuse may > not be > place in an identified neutral line. > > It is permitted to place a fuse in an identified neutral line > provided that > the "live" side is fused + special information/marking is given > > Having said that, the UK and some other parts of the world have a > power > mains setup that allows for heavy earth fault currents from either > pole. So > they use dual fused power cords. > > Could you give an example of "dual fused" power cord? The British AC > plug > is equipped with just one fuse connected to the "L" side. But as I > understand this "system" is used to protect their unique building > wiring, > not the equipment. > > John Radomski > Compliance Engineer > Clare Corp. > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
