volt drop calcs and 230 v

[jackhammerJIM]

why do we have to do the calcs to 230v when the supply never is 230v

measured voltage at source is 248 volts at the site i am on at the moment ,

can somebody shed some logic on the idea before i start engineering an 18 volt drop into my cable sizes

( a joke of course but why not ? ) :ihih:

 

[Marvo]

230v is a nominal figure. In real life products rated at this nominal figure already have extra capabilities or tolerances engineered into their design which makes acceptable variations from the nominal figure acceptable.

 

[ChrisElectrical88]

I always use measured voltage, shhhhh ;-)

 

[Guest55]

230 is the nominal single phase voltage the dno's must provide as set out by the EU electrotecnical conformity commitee.

but as you say , i dont think i've ever seen less than 236-238v.

you could use the actual measured voltage for calculations as it would give you more favourable parameters to work with , although some may warn that a change in the network supply could see that voltage drop , thus leaving your cable assessments up sh*t creek.

but it will never happen in reality , the high voltage goons will just crank up the tappings at the sub-station ;-)

 

[ChrisElectrical88]

Using the nominal could leave you up **** creek. I did a install at 223V once! DNO informed, DNO not arsed!

 

[Jabbajaws]

Using the nominal could leave you up **** creek. I did a install at 223V once! DNO informed, DNO not arsed!

What do the IET expect to happen where this occurs? Im a little confused here. If l listen to my maths teachers from sparky college, he said that a voltage drop can cause a circuit to overload.

Is that whats happening here, at the transformer perhaps? Ive no idea personally and would love to know the answer as ive never seen 223V anywhere before. Always been 236-253V...

 

[jackhammerJIM]

do the transformers have to be de energised to change taps or do they bang it live ?

 

[Marvo]

Don't even think about it.....

 

[Jabbajaws]

Im pretty sure that the minimum is 216V for tolerances allowable if l remember correctly. Please put me right if im talking piggie-excrement. I think its nominal voltage 230 -6%=13.8V which is 216.2V to +10%=23V which is 253V...

 

[markc123]

Jabberjaw was the name of my first pet goldfish when i was a little nipper!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Sorry, procede with the thread ...

 

[markc123]

Im pretty sure that the minimum is 216V for tolerances allowable if l remember correctly. Please put me right if im talking piggie-excrement. I think its nominal voltage 230 -6%=13.8V which is 216.2V to +10%=23V which is 253V...

Aye, it states that in the documentation somewhere. Can't remember where ive read it, GN3 maybe...Don't get me to quote page, because that sir - i cannot.

 

[jackhammerJIM]

hahaha , im curious marvo but not that daring

they all seem to be padlocked anyhow

 

[Guest55]

do the transformers have to be de energised to change taps or do they bang it live ?

its done live.

 

[Guest55]

Aye, it states that in the documentation somewhere. Can't remember where ive read it, GN3 maybe...Don't get me to quote page, because that sir - i cannot.

ESQCRegs.

 

[markc123]

ESQCRegs.

Was wondering when your next correction was going to be - it seems to long biff haha.

Can guarantee you wrote that with a massive grin on your face.

 

[Guest55]

i'm watching.
always.

;-)

 

[snowhead]

why do we have to do the calcs to 230v when the supply never is 230v

measured voltage at source is 248 volts at the site i am on at the moment ,

can somebody shed some logic on the idea before i start engineering an 18 volt drop into my cable sizes

( a joke of course but why not ? ) :ihih:

It may be 248v today, 235v tomorrow, 224v next week on that site.
Which voltage are YOU going to use?

 

[HandySparks]

Another consideration is that high voltage drop in a circuit implies high circuit impedance. So variations in load will produce large changes in voltage. I suspect that this is one reason for the lower permitted VD where lighting is present, as changes in voltage, and therefore light output, are particularly noticeable with traditional lighting types. Of course, with LEDs supplied by regulated drivers, this isn't an issue.

 

[Tiny Spark]

its done live.

Well I cant comment on all trannys and my HV experience is limited but ime pretty sure ours has a sign on the side saying it has to be done dead?

Either way I stay well clear of the damned thing LOL

 

[Engineer54]

its done live.

Rarely done live Biff, local DNO TX's are just not that sophisticated!! lol!! Going further upstream on the network, is where you'll generally find the on line and auto tap change facilities....