Voltage Drop Calculator

[kingpb]

Follow up to show difference between 1.0 and 0.85 power factor of load.

 

[Besoeker]

This seems to have got amazingly convoluted.
Our BS7671 (aka "The Regs") gives mV/A/m. Makes VD calcs very straightforward.
I'd be surprised if you guys don't have something similar.

 

[MyCleveland]

10 days of fretting over error in Z eff calculation.
Successfully did the programming to calculate the IEEE 141 "Actual VD". Ran a bunch of samples vs some known problems I was able to find on-line and all checked out.
Appears the %error was not worth the trouble, but it is done.
So I will stick by post #2, until proven incorrect.

Don's post #22 though I cannot explain. Not sure of the calculation method.
post #23 - match results

post #61 - NOT in agreement, 194' @ 0.85 PF

post # 77 & 78, what do these files do ?

posts #50 & 81, after PM, please post response for run at 3%, not 3 volts.

 

[mbrooke]

post # 77 & 78, what do these files do ?

77 calculates neutral current when IA, IB and IC values are plugged in.

78 calculates 3 phase currents for delta or wye connected loads.

Smart made about a dozen useful Excels. For a while I've been rooting on having them in some type of Sticky. He put a lot of effort into them and to be honest I like them more than some commercial software.

 

[kingpb]

posts #50 & 81, after PM, please post response for run at 3%, not 3 volts.

The voltage shown is the L-N voltage drop; in volts not in %.

 

[ramsy]

The voltage shown is the L-N voltage drop; in volts not in %.

208vac to neutral is a rare transformer used in older commercial & industrial buildings.

240V Split Phase Delta, or High Leg Delta, where #C Leg (Orange) of 208vac to Neutral is also called a Stinger leg.

While VD% changes dramatically between 3Ø 120vac vs 3Ø 208vac, both L-N calcs get 3.08 Volts @ pf 0.85 166ft.

Using 3 Volts, rather than 3% is Transformer independent.

 

[Besoeker]

Using 3 Volts, rather than 3% is Transformer independent.

That's what mV/A/m gives you.

 

[ramsy]

That's what mV/A/m gives you.

Can you share your work, so we can see how the variables are used?

 

[Besoeker]

Can you share your work, so we can see how the variables are used?

They are values given in BS7671.
For example 16mm^2 is 2.8mV/A/m.
You know the current, the length of run, so simple multiplication gives the voltage.

 

[ramsy]

They are values given in BS7671.
For example 16mm^2 is 2.8mV/A/m.
You know the current, the length of run, so simple multiplication gives the voltage.

For those less fortunate, without a copy of BS7671, can we see your work.

From NFPA-70 Table-8, American Wire Gauge #6 copper Stranded at 17mm^2, is nearest to your 16mm^2

Here's NEC Table 8. See 2nd column from left for mm^2 conversions of AWG
https://www.scribd.com/document/341061630/NEC-Table-8-Conductor-Properties

 

[mbrooke]

BS7671:


http://www.thailandlift.org/documents/BS7671-2008.pdf



Page 335 (334) I believe is where Besoeker is basing his values on- but he will have to confirm.

 

[Besoeker]

For those less fortunate, without a copy of BS7671, can we see your work.

As I said, I'd be surprised if you guys don't have something similar.
Anyway, there isn't much calculating. If your 16mm^2 was carring 10A it would be 2.8mV/m etc.
Simple innit?.............

And you can get conversions on the internet.
Convert gives you a wide range of choices.

 

[Ingenieur]

mV/A per m is no different than the NEC table, exactly the same
mV/A = V/A x 10e-3 = Ohm x 10e-3

so
Ohm x 10e-3 / m = Ohm / km, the primary NEC table value (secondary is Ohm/1000')

unit analysis
BS7671
mV / A / m x A = mV / m = V / km or v drop/length

NEC
Ohm / km x A = V / km or v drop/length

to get drop per specific length
BS7671
mV / A / m x A x m = mV

NEC
Ohm / km x A x km = V

there is no difference

 

[Ingenieur]

As I said, I'd be surprised if you guys don't have something similar.
Anyway, there isn't much calculating. If your 16mm^2 was carring 10A it would be 2.8mV/m etc.
Simple innit?.............

And you can get conversions on the internet.
Convert gives you a wide range of choices.

if our #12 (1.7 Ohm/th ft) were carrying 10 A
v drop = 17 V/th ft

we do have something similar
the NEC table

 

[kingpb]

208vac to neutral is a rare transformer used in older commercial & industrial buildings.

240V Split Phase Delta, or High Leg Delta, where #C Leg (Orange) of 208vac to Neutral is also called a Stinger leg.

While VD% changes dramatically between 3Ø 120vac vs 3Ø 208vac, both L-N calcs get 3.08 Volts @ pf 0.85 166ft.

Using 3 Volts, rather than 3% is Transformer independent.

Not quite sure what the reference to all the different voltages are related too. I was simply responding to a PM that asked if the voltage shown on the drawing was % or V.

The 208V on the diagram is a 208Y/120V system, for some reason ETAP displays the VD as L-N voltage.

 

[Besoeker]

if our #12 (1.7 Ohm/th ft) were carrying 10 A
v drop = 17 V/th ft

we do have something similar
the NEC table

I thought you must.
And simpler than your last post.

 

[Ingenieur]

I thought you must.
And simpler than your last post.

simpler is not better, this case in point
the last post was based on it (as most posts in this thread are)
my last post was showing the equvilency which seems lost on some
it is not 'similar', it is EXACTLY the same
the BS is not simpler, nor is the NEC, they are IDENTICAL

it only applies for a fixed temperature, conductor qty, pf

 

[Besoeker]

the BS is not simpler, nor is the NEC, they are IDENTICAL

I think most of our members would have understood that.
Identical other than the units of measurement, of course

 

[Ingenieur]

I think most of our members would have understood that.

not sure about that
you implied they were different and the BS std was simpler

it becomes clear when one sees V/I = Z
in some ways the nec may be clearer, simpler, since it expresses Z in Ohm (the std) vs volt/ampere

 

[Besoeker]

not sure about that
you implied they were different and the BS std was simpler

You may have inferred that. Incorrectly if I may say so.
It certainly didn't require 90 or so convoluted posts to get there.