STRANGE NEUTRAL CURRENT !!!!

[simon rogers]

Morning fellow practicioners of the dark art we call ELEKTRICKARY , I have recently been ask by a close freind if i thought his electric bill seemed "A SLIGHTLY BIT HIGH!!!". So he showed me it and I nearly fell off my bar stool (forgot to say he is a publican),his usage breakdown has come back at 269KWH now wait for it ..........per day . Now i admit i am no expert on metering rates etc , but i am 47 and started my apprenticeship when i was 16 , so have a few years under my belt , have been self employed from 21 till now and have run / designed/tested jobs from an extra socket to 20/30 million £ new builds and refits. So i am throwing myself out there to see if i am missing something bloody stupid . I have calculated his total load from fridges etc info plates lights by counting and added about another 30A on top , and it comes to 119A total . Now this is spread over a 415V 3 phase supply , which i have clamp metered up and monitered the indivdual cores which average out Brown/red- 23A , black/yellow- 19A & Grey/blue - 42A , oh and the neutral comes back with 38A on it.This obviuosly is nowhere near 269KWH , and was thinking this rouge N current must be from a dodgy connection on supply side ? It is also obviously a potential overheating risk i would have thought ? So does anyone have any thoughts to help me out PLEASE . thanks for reading my bumbbling thought train Simon

 

[Deleted member 26818]

As far as I am aware, meters do not measure neutral current.

 

[telectrix]

from the phase currents you quoted, the N current should be approx. 20A for that unbalanced load.

also,from another thread, it appears that your customer is billed on the phase with the highest current, i.e. 42A in this case.

 

[marc8]

from the phase currents you quoted, the N current should be approx. 20A for that unbalanced load.

also,from another thread, it appears that your customer is billed on the phase with the highest current, i.e. 42A in this case.

could you look at balancing the load slightly better this would then bring down the current on the highest phase & bring the other phases closer overall thus reducing the bill.

 

[The Ghost]

Is this an HH meter with remote monitoring. You have looked at his bills does it give a Kva figure on the top right corner?

 

[static zap]

Neutral currents are bad for the Bill ! ,
unbalanced , effectively paying for what you may not have used on 2 phases ,
(that' s the part of 3 PHASE that is a big down side)
....Has something got a bad power factor ?
Hence phases not cancelling as well as they should .
( Do they have propper central heating ? )

 

[The Ghost]

So the neutral is the overflow from the unbalanced phases. If I do a scaled triangle to get the neutral overload I get 30a on the neutral.

 

[UNG]

Have you looked back through the billing history and how it has changed over the last few months / years
Looking at the figures you have posted has someone got a decimal point in the wrong place or added a zero and it should really be 26.9KWH per day

 

[Wilko]

May have misunderstood, but 11kW continuously for 24hrs is 264kWh used. On a single phase 11kW is about 48A. So - is the load you measured continuous? I'd have thought it would average to maybe 10% of peak, perhaps. Which puts me back thinking @UNG is onto something

 

[simon rogers]

ok i will start answering from top down lol .Spinlondon a clamp meter will measure the current(if any) on anything you clamp it round. Telectrix not sure about the 20A and i think it depends on who and what tarrif it is on for billing .marc8 balancing the loads is my next step , not as easy as it should be due to nothing on the 30 way ancient ryfield board being labeled and multiple circuits coming out of at least half the fuses that are being/not being used.Vortigern not a HH meter just normal clamp meter monitered and recorded twice an hour for a day just to get an idea and didnt notice kva.UNG he is only in there a few months and the previous landlord hadnt paid any electric bills for god knows how long (about£ 34k long ) so no bills to compare it too ,but i had thought about the decimal point being wrong , its easily done if someone aint paying attention . Thanks all of you for the input and quick responces . I will hit it again later on and keep all of you posted to how it goes cheers sibo08

 

[static zap]

So the neutral is the overflow from the unbalanced phases. If I do a scaled triangle to get the neutral overload I get 30a on the neutral.

Using your 30 A graphically obtained , I get worst case 331kWh ... daily
(if exactly 2 phases -unused ...power factor may improve this !)
...2/3 of your bill is un-real (and i/j-joke) ...or NOT £
(my maths was lazy for- this one -interaction will probably make it 270)

 

[Simonslimline]

Any harmonics summing in the neutral?

 

[static zap]

...or it's just a pub full of old in-efficient things
old coolers / Halogen lighting , and electic heaters flat/accomodation
.. from era when electicity was cheap .... Breweries -are not generous !
Only need 16A per phase average to get there !
(got rid of old freezer -for this type of reason)

 

[The Ghost]

No harmonics on my part that is a straight equilateral calc/diagram

 

[buzzlightyear]

probably a faulty meter .on three phases. time to get DNO involved.