why is volt drop important???

[bobbybrown]

whats the reason we worry about volt drop?
It cant be because of the design of fittings etc.. because the actual voltage can be 230v +10% -6% percent,
i believe if there is a voltdrop then the current will increase as per ohms law
maybe its something to do with potential differences e.g 230 at one end and 236.9 at the other (3%) however i dont understand why would that cause concern????

 

[mayfair]

so as current increases the cable would in as simple a term possible get hotter and probably beyond its specs. Sure someone else will explain it in a lot more depth. btw the current should not increase just because the voltage drops. I think im right

 

[bobbybrown]

true but a mcb provides protection for over-current

 

[mayfair]

So you want it to trip all the time ? i think not so in your design you allow for voltage drop, your allowed 5%

true but a mcb provides protection for over-current

 

[sparkiegaz]

maybe machines and controls need to be kept within certain voltages to operate correctly ,,,

 

[telectrix]

try running fluorescent lighting at 205v. it flickers more than a 1920's movie.

 

[mayfair]

is it not supposed to flicker like ..........must be that 100m a speaker cable i used and to think i paid 6 quid for the roll

try running fluorescent lighting at 205v. it flickers more than a 1920's movie.

 

[lewlec]

try running fluorescent lighting at 205v. it flickers more than a 1920's movie.

very true, i have a customer which is down on voltage during milking time and its like a disco each time the milk pump start up.
.

 

[andyb]

The current will not increase because the resistance of the circuit stays the same, so the current will reduce.

The reason is as eluded to in the op, for the satisfactory operation of any connected equipment.

 

[pushrod]

whats the reason we worry about volt drop?
It cant be because of the design of fittings etc.. because the actual voltage can be 230v +10% -6% percent,
i believe if there is a voltdrop then the current will increase as per ohms law
maybe its something to do with potential differences e.g 230 at one end and 236.9 at the other (3%) however i dont understand why would that cause concern????

Not true - are you thinking of transformers?

If you reduce the voltage you will reduce the current and so reduce the power


edit - great minds andyb

 

[bobbybrown]

"So you want it to trip all the time ? i think not so in your design you allow for voltage drop, your allowed 5%"
errrr you lost me why would it trip all the time??

just want to know why its 3% on lighting and 5% on other, and why this would matter if the nominal voltage is 230 +10 - 6???

 

[Des 56]

Operating electrical equipment below its acceptable voltage rating can lead to premature failure and hazardous situations.
Inductive loads, such as motors and ballasts can overheat, shortening equipment life and increasing energy consumption.
If operated below their rated voltage, resistive loads, such as heaters, simply won't provide the desired output.
A 10% reduction of voltage reduces the power output by 19%, because power output reduces as the square of voltage.
Reduced circuit voltage can cause lights to flicker when other appliances or equipment cycle on.

 

[pushrod]

"So you want it to trip all the time ? i think not so in your design you allow for voltage drop, your allowed 5%"
errrr you lost me why would it trip all the time??

just want to know why its 3% on lighting and 5% on other, and why this would matter if the nominal voltage is 230 +10 - 6???

because some lighting is very sensitive to reduced voltage. The 230 +10 -6 figures are only what the DNOs guarantee lose more than 3% on 224V and fluorescent lighting is going to really struggle.

EDIT : and for a really good answer read the one above!

 

[bobbybrown]

cheers guys thats cleared that up

was getting a bit confused with the dno guarantee

 

[bobbybrown]

just another quick question regrading volt drop, the 3 percent rule on lighting, is that 3 percent on the actual measured voltage or 3 percent on 230v?

imo it would make sense to be based on 230v and not measured voltage . e.g if your supply was 1 percent over 230v then you should be allowed up to 4 percent volt drop

i know the further you are away from the substation the lower your measured voltage will be, out of interest does it drop much or will it still be nearly at 230v?

 

[pushrod]

just another quick question regrading volt drop, the 3 percent rule on lighting, is that 3 percent on the actual measured voltage or 3 percent on 230v?

imo it would make sense to be based on 230v and not measured voltage . e.g if your supply was 1 percent over 230v then you should be allowed up to 4 percent volt drop

i know the further you are away from the substation the lower your measured voltage will be, out of interest does it drop much or will it still be nearly at 230v?

the 3% figure is on 230 V as that is what you should expect even though reality is that it will often be more. So for lighting you calculate for Vd to not exceed 6.9volts

edit: in my experience supply voltage has always exceeded 230V