🚀 go-pugleaf

Phil Allison wrote:
> "Stupider than Anyone  Else"
> 
>> I have to phases of power supply to my house - so three power lines, two 
>> phases plus neutral.
>>
>> I've on occasion wondered what would happen if we lost the neutral line. 
>> It seems to me that we'd then have the voltage between the two phases 
>> across two sets of appliances, one set attached to one phase, and the 
>> other set attached to the other phase, with the two sets in series as a 
>> result of their common connection to the neutral wire. Since the two sets 
>> are unlikely to represent equal loads, the net result would be a large 
>> overvoltage on one set of appliances.
>>
>> My electrician says it's not an issue, but I can't see why.
> 
> 
> ** Loss of the neutral conductor in a 3 phase ( or 2 phase) AC supply system 
> can easily be a DISASTROUS  event.
> 
> For example:
> 
> In the live entertainment productions -  high powered lighting and sound 
> systems operate from 3 phase outlets via a hefty 5 pin plug and socket.  If, 
> due to wear and tear or damage to the plug or socket, one of the phases 
> drops out  -  that is an annoyance but not a disaster.
> 
> However, if the pin carrying the neutral fails to connect or as is often the 
> case *disconnects* during a show because of overheating   -  ALL HELL 
> BREAKS  LOOSE !!
> 
> Typically, some of the lamps will glow very brightly for a second or two and 
> fail, then other previously dim lamps will follow suit.  The AC fuses in 
> amplifiers will pop instantly and some equipment will be seriously damaged 
> when the PSU sections are destroyed. It all happens in a few seconds, while 
> the operators stand there with their mouths open  !!!
> 
> The MEN system:
> 
> In Australia, AC power delivery uses a system called " Multiple Earth 
> Neutral "  -  which requires that the neutral conductors in a premises be 
> connected to the plumbing system at the distribution board (ie power box). 
> It also requires that an earth stake be installed for the same purpose, but 
> some older premises may not have this.

If as you say, neutral has to be tied to Earth at the premises, then I 
can indeed see that the situation might not be so bad.

On the face of it, having significant current flowing from neutral to 
Earth would have to indicate a fault. It would be nice for the breakers 
to trip in such a situation, but I can't see that they will.

Sylvia.