STRANGE NEUTRAL CURRENT !!!!

[FatAlan]

Anyone growing whacky baccy in the loft?

 

[David Prosser]

Old landlord didn't pay the bills ? Maybe trying to claw back some money from your mate. I've two ridiculously high bills in the past both of which were just a ruse to get me to ring the supplier and confirm details and to let them send a meter reader around. One was explained as they didn't believe the meter readings could be so low. It was a local cricket club that was hardly used through the winter. The other one was over a rented property where the previous tenant had skipped out without paying the last year or so electric. Two visits from the meter guys and new bills where issued.

 

[Lucien Nunes]

There seem to be some misunderstandings going on here. Ordinary meters measure energy used. They do not care which phase it is used from, or how well balanced the load is. You can use it all on one phase, or equally across three, the energy consumption will be what it is. They cannot charge you for energy you could have used on the other phases had they been loaded to the same current as the highest-loaded phase. The tariff might depend on your maximum demand, and half-hourly metering can report this, so there could be an incentive to manage the load both as far as size and timing of load peaks. That is reasonable and sensible, as spreading peak loads helps manage the energy networks.

Unbalanced loads create neutral current, as do certain harmonics in both single and 3-phase loads. Neutral currents themselves are of minimal importance to the customer, e.g. with a 100A TP+N supply it matters little whether the neutral current is 1A or 100A. There is a modest efficiency advantage for the supplier of the load is balanced due to lower cables losses, and they must manage the total neutral current so that it is not excessive in any distribution cable. But neutral current does not equate to 'energy paid for but unused' or any such thing. It's merely the algebraic difference between the line currents. If loads on different phases differ in power factor (e.g. lighting mainly on one phase, motors on another) then the neutral current calculations must take this into account. The most extreme cases, with phase angle controlled loads, can result in higher neutral current that any line current which can cause overheated neutrals, but this is truly rare and extreme. With the figures in the OP, there is no such hazard as the neutral current is less than the highest line, hence no reason to think something is going to be overloaded.

Low power factor causes higher currents than are truly necessary to deliver the amount of energy purchased. This increases cable and transformer losses, and hence costs the supplier, so there are incentives to keep the p.f. as high as possible. Again, this is a networks efficiency consideration, and while low metered p.f. might be reflected in a less favourable supply tariff, the supplier cannot charge for energy that would have been delivered at the same current had the p.f. been unity.

Going back to the OP, 269kWh per day is an average load of 11kW. I can produce that load by switching on the appliances I can see from where I am sitting, and that doesn't include any cooking equipment. It could result from being wasteful, growing tropical plants, even a miscalibrated meter. But it doesn't sound like anything that would make me fall off a bar stool or an indication there is anything amiss with the supply.

 

[static zap]

....... The tariff might depend on your maximum demand, and half-hourly metering can report this.............

So a high startup demand , may get you on less reasonable price per unit , or is it more of a equipment standing charge -=un-used capacity in hardware ?
(had heard about staggering run up of high demand
devices so the don't coincide)
Was penalty for a peak current , or power consumed ?
(or is this in-consistent across DNO / metering fitted)

 

[Marvo]

If his bill is in units of kWh then he's not being penalised for poor power factor, non-linear loads, harmonics etc and as Lucien says I've never seen a metering device that calculates consumption using the highest load phase current.....

 

[Marvo]

If you think the bill is wildly inaccurate from the evidence of consumption you can see then install a data logger or a temporary CT meter to check its accuracy.

If the metering turns out to be accurate then draw up a plan to make some easy savings such as converting halogen/filament lighting to LED, install timers on hot water cylinders and reduce water temperature, clean all the refrigeration condensors and check fridge door gaskets etc etc.

 

[HandySparks]

...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, your average measured currents give about 20kW at 240V. Multiply by 24h, gives 480kWh per day. So I doubt that the supplier's meter is over reading.

I agree with Lucien, there's no problem with the neutral current, given the unbalanced load.

 

[stevels4]

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

DNOs don't get involved in metering, the likes of Eon and Scottish Power are meter operators.