True or False.....

[Guest123]

So, got a call this morning from local authority saying that a number of houses on a site we had worked on had "lost" power. Ok says I, I'll shoot straight over, no worries.


Turns up to about 17 ressies all standing on their doorsteps with pitchforks and torches in hand, waiting for me as it turns out.

What's up says I......come and smell my telly says one of them!!!!

To cut a long story short, it turns out that no less than 18 television sets had totally burned out....due to a SUPPLIERS problem, felt the relief I did.

So I'm chatting to the DNO guys assuming there was a surge of some kind on that particular line. no no says the chap.....we lost a neutral.

Lost a neutral......are you sure??? definately he says.

Now it may be me but would a loss of suppliers neutral really cause 18 T.V's to flombay themselves.....opinions please gents.

 

[acvc]

Earthing system PME?

 

[Guest123]

No Sir, TN-S.

Should have stated that really as it is the basis of my Q.

 

[pennywise]

It's an insurance job a well organized one, they all want new 50in plasmas by kick off tomorrow.

 

[davelerave]

could be overvoltage or undervoltage - DSO lost the 'star'(neutral) point on the 3-phase trafo

 

[pmac10]

from the mouth of a linesman i know from NIE, reverse polarity will take out every TV on a street.

 

[8145keith]

Hi there,

Just TVs out sounds like lightning to me.
regards kj

 

[xraytek]

Hi,
Definately true as we lost the main neutral at work and it resulted in every piece of equipment one of the phases smoking.

The way I visualise it is to imagine equal single phase loads on a 3 phase board.
If the neutral to the board was lost then equipment will still operate due to a return path through another load on a different phase as they are joined by the neutral rail.
The equal loads will mean that the voltage across each load will remain the same.
If the loads were not equal then you will get voltage rise on one load and voltage drop on the other.

If you had 2 resistors of equal value in series across a 24 v supply you will measure 12v across each resistor.
If the resistor values were different then the voltage across each resistor will also be different.

 

[Des 56]

Clutching at straws here perhaps but, maybe someone from the suppliers cross conneted an outgoing phase with a neutral on an item of switchgear or a cable joint that resulted in a 2 phase supply instead of phase- neutral

Why only televisions though ?

I thought BT were the biggest culprits for frying electronic equipment, with lightning strikes on their phone lines, when questiioned they say " Not us GuV"

 

[UNG]

It may have taken out the TV's but other appliances could have been damaged but have not failed yet.

About 10 years ago got called to an intruder alarm fault in a hospital it was quite a big system with multiple power supplies most had failed as the sub station earthing / neutral had failed and the resulting floating neutral caused one phase to have 300+ volts on it