800M 32mm SWA - could this cause increased electricity bills due to voltage loss

Assuming light bulbs come on at normal brightness, then voltage drop in the long cable is not part of it.

Now then, there are 365 * 24 = 8760 hours in a year


6000KHh annually  is equivalent to a steady load of 680 watts.

Think ten or eleven 60watt light bulbs on 24/7 (or twice that load half the time or any other equivalent)


What kind of site is this - domestic, industrial unit, farm shop ?


I'd be looking for a heater left on, lights or refrigeration equipment running non stop, or a rack of IT equipment,


How hot does this transformer run ?


With a friend looking at the meter and 2 mobile phones or walkie talkies, disconnect things and verify the meter comes to a stop.

Mike.

Yes an excessively long or undersized cable can add to electricity bills, though usually the increase is modest.

If the voltage at the appliance is lower than normal then it might either work less efectively and thereby require longer hours of use to achieve the desired result, or it might draw a greater current.


As regards the transformer, more detail is needed, idealy a photo of the unit and a close up photo of the rating plate. Some such transformers waste significant energy even when not loaded.


800 meters of 35 mm cable sounds too long to supply a home unless the load is improbably small. It might be worth having a larger cable installed, but we need more details to give proper advice.

Yes, two very good points in the  post preceding mine. How hot does the transformer get ? Heat represents wasted energy, unless it contributes to heating the premises. (and even then it is a total waste in warm weather and a partial waste even in winter if it displaces cheaper heat sources)

And yes, turn off everything and observe the meter, as described.


The calculated average load of 680 watts Might consist of say 180 watts lost in the cable (much more under heavy load) and 300 watts lost in the transformer, with only 200 watts on average being applied to any useful purpose.

Do have this right - you have half a mile of LV cable and a transformer on your side of the meter?


If that is the case then there would certainly be some losses - 800m of 35mm² would have a resistance of about 1.25mΩ/m so about 1Ω for 800m L & N. Looking at the case where your installation is drawing say 10A, I²R losses for the cable alone would be about 100W. Your 6000kWh suggests around a 3A load on average - so minimum losses in the cable would be around 9W (<80kWh/year). Drawing the same energy at higher power over shorter durations would increase the losses. Eg. drawing 20A for three hours a day (about 5000kWh/year) would mean cable losses of 400W or 1.2kWh/day or 438kWh/year. (But do check my maths!)


The transformer too will have losses - both constant and as a proportion of the load - but others here know much more transformers than me, so best wait for their suggestions.


An obvious check is to place some metering on the load side of the half-mile of cable and transformer - and compare the results with the supplier's meter - a clip-on energy monitor can be had for around £30 and should give you a first approximation quite easily.


   - Andy.

I have had a similar problem, but I have searched and searched and found no attic light left on.


Part of the problem was an old freezer which Mrs P refused to dispose of until eventually it died. I do not know how much all those things on standby use, but I am prepared to pay for the convenience, even though it troubles my environmental conscience.


I think that you are right to question the supply side, but also see if you have any appliances which are using more than you might wish.

This is more in the form of a general enquiry to all - how hard would it be to fit a step up/step down transformer on either end for a pretty small load?


How would that affect the metering at the origin - if the load went straight into a step up transformer - 800m down the 35mm 2 core - into a step down transformer and LV fuse that end to protect the transormer that end - and into the consumers DB? 


Are small step up/step down transformers readily available? (I guess I could google this, but am more interested in the replies)


How much bureaucracy would be involved? Would you need to register the cable run on some sort of national data base, (because its HV) and get council permission perhaps - but I assume this would mostly be on private land? If it was private land - could you just bury this cable anywhere? (Obviously it would be wise to get some reasonable depth, sand, cable tape, concrete top lid etc etc - but would you have to?

(because its HV)

It might not be - I gather 690V is a common choice for such applications (1/3rd the current, so 1/9th the cable losses) - and that would still be within LV limits.

   - Andy.


edit: OK not quite within LV limits (it would exceed 600V to Earth on a single phase system), but still within the simple 1000V limit for the scope of BS 7671.

Step up down transformers are worth doing for fixed loads. If the load is not there for much of the time, then the transformer losses get to you, and it may or may not be worth it. for small transformers 5% loss is typical, larger ones are better. Lightweight tool transformers are cut fine on the core performance and are quite a bit worse.


I remember Stuart Little doing something like this for fans at the far end of a chicken farm, where the load was on 24/7 and the current was well defined so  the transformers could be well sized. I think all up the transformers were more or less paid for by the saving on cable costs.

Disconnection times and ADS generally need some thought, you may end up breaking on the incoming 230V wich 'shunt trip' techniques but RCD style sensing on the 690 for earth faults.

mike.

Hi all,


So many replies and so quickly, thank you all.


OK here goes...

to clarify 

1 - Yes 800 meters of cable between the meter and the transformer

2 - Transformer is a OCVC 20H-S (manual attached)
Model-20OCVC-H-1P.pdf

3 - Its a domestic property, gas central heated only a single oven as the significant wattage utensil/item, no heaters.

4 - Been here a year now, and I have confirmed the usage over a few meter readings.


thanks

Rolf