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## Calculation of voltage drop and cable size

• Calculate Voltage drop of Cable.
• Calculate  Size of Cable.
• Calculate Current Capacity of Cable.

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1. Peter
May 04, 2023

2. FRANK DICKSON
Oct 10, 2020

I have seen many question that i also want to know,where are the answers from author?

Mar 19, 2020

My own observation on above Volt drop formula am not ok with it.
I though the formula is like this….Vd=mvA x Load (I) x Length of cable.
But saw on the above cal the formula is like this..

.DATA:-
1.732 FOR THREE PHASE.
I = 160 AMPS.
L= 200 METERS.
PF= 0.85

FIRSTLY WE CALCULATE THE VOLTAGE DROP.
Vd = 1.732 x 160 x 200 x 0.85/(70 mm2 x 41.66)
= 16.1547 volts —————(1) for copper conductor.
Area(mm2)b= 1.732 x 160 x 200 x 0.85/(16.1547 x 41.66)
= 70 mm2 ———-(2) for copper conductor.

4. omar
Jan 18, 2020

Dear sir
what does it means (No. of Runs of selected cable)
thanks

• pooria
May 05, 2020

Dear friend its mean number of cable core for every phase

• Abzuar
Aug 25, 2022

Brother, Runs mean quantity of Cables per phase,

5. ucok tralala
Sep 03, 2019

thanks a lot for the program

6. Thomas Peter
Jun 22, 2018

Appreciate if you could reword “Cable laying on The Depth of ” to “Cable laying at The Depth of”.
Thanks.

7. brajesh
Jun 15, 2018

the cable resistance taken for calculation of voltage drop is having error
reference table showing more resistance for 3C X 16 Sq.mm cable then 3C X 10 Sq.mm, copper LT XLPE

8. haitham
Dec 28, 2017

THANK U SO MUCH

9. michael eaton
Mar 16, 2017

Some people criticizing the calculations. There are many packages on the market that will calculate your cable size, volt drop etc. but at the end of the day you need to know what your doing. Even the best packages will throw up errors in calculations and if using these packages, you need to be knowledgeable to validate the output.
This is a good tool to get you to the result you need, but you need to know what your looking at, not blame someone else for producing a tool that dumbs down what you should be competent in knowing.

10. Ganesh
Oct 30, 2015

11. hquocphu
Oct 14, 2015

SOMETHING WRONG IN DATASHEET:

PLPE resi
4cX4 5,53
4cX 6 3,7
4cX 10 2,29
4cX16 2,45
4cX 25 1,54
4cX35 1,11
4cX 50 0,082
4cX70 0,57
4cX 95 0,41
4cX 120 0,33
4cX 150 0,27
4cX 185 0,21
4cX 240 0,16
4cX 300 0,13
4cX 400 0,1
4cX 500 0,1
4cX 630 0,1

AND PVC

4cX4 8,89
4cX 6 5,53
4cX 10 3,7
4cX16 2,29
4cX 25 1,44
4cX35 1,04
4cX 50 0,77
4cX70 0,53
4cX 95 0,38
4cX 120 0,3
4cX 150 0,25
4cX 185 0,2
4cX 240 0,15
4cX 300 0,12
4cX 400 0,09
4cX 500 0,09
4cX 630 0,09

12. cahyo widodo
Oct 13, 2015

Please review bout voltage in your spreed sheet Mr. Jigness Parmar for the data in value cable if we implement type of cable Lt PVC arround of range cable size 4cX70 and 4cX95, the value of voltage drop so annoying me. The value of Voltage drop if we use 4cX95 should be smaller than we use 4cX70, but there is become bigger. i have put the value but i found the miss calculation i think, pardon me. Please review and give the your best development sir.

13. N M Venugopal
May 29, 2015

how do we size the cable when we have only load say 55 kW for a distribution board(3 pumps and lighting load) and at 415 v supply and a length of 400 m from source voltage to board.

14. M G Patel
Nov 08, 2014

Useful information

15. Parag Chamuah
Oct 13, 2014

Thanks for the work you have shared. I have few queries:
1.How do we know what is the phase value(φ)?
2.What is demand factor specifically?

16. bdthang
Jun 17, 2014

Very useful. It help me a lot!

17. kolumb
Jun 10, 2014

There is something wrong with the cable data – it’s impossible 3 different type cables with same Conductor Area, same matherial, to have 3 different Resistance (ohm/km).
Example – look first 3 cable types – PVC flexible, PVC insulated and XLPE insulated, for the same Conductor area (by example 1cX6), both Copper, resistance for the fist is 3.3ohm/km, for the second is 3,69ohm/km and the third is 1.53ohm/km.
May be the last one uses a super copper, twice better than first 2 :)

Apr 21, 2014

dear sir
I want to submit the formulas of cable sizing to those persons which are searching here and there.I appreciate of your current website which are publishing my cable sizing ideas.I am submiting another voltage drop and cable sizing formula.

1- Vd = 1.732 x I X L X PF/ (Area mm2 x conductivity of copper) ———-FORMULA 1
2- Area(mm2) = 1.732 x I X LX PF/(Vd x conductivity of copper) ———–FORMULA 2

WHERE:-
1.732 FOR THREE PHASE.
2 FOR SINGLE PHASE.
L= LENGTH OF CABLE.
PF= POWER FACTOR.
Vd= VOLTAGE DROP.
CONDUCTIVITY OF COPPER AT 90 DEG.C = 41.66
CONDUCTIVITY OF ALUMINUM AT 90 DEG.C =25.64

DATA:-
1.732 FOR THREE PHASE.
I = 160 AMPS.
L= 200 METERS.
PF= 0.85

FIRSTLY WE CALCULATE THE VOLTAGE DROP.
Vd = 1.732 x 160 x 200 x 0.85/(70 mm2 x 41.66)
= 16.1547 volts —————(1) for copper conductor.
Area(mm2)b= 1.732 x 160 x 200 x 0.85/(16.1547 x 41.66)
= 70 mm2 ———-(2) for copper conductor.

if you want to use Aluminum conductor, apply conductivity of Akuminum which is above said.ABOVE CALCULATIONS ONLY FOR THREE PHASE.

FROM
M.SC.ENGG.MIEE(UK)

• Ramkumar M
Mar 07, 2015

How you get Area size 70mm2 ?

• jan
Apr 30, 2015

i dont have a voltage drop and sq.mm.i have only amps how did we calc the sqmm

• Ch. Khalid Parvez Akhtar
Jul 28, 2015

Its a wonderful working.I must compliment you for this great work. Congratulations
Regards
Ch. Khalid Parvez Akhtar
Jalalpur Jattan
Gujrat
Pakistan

19. thiru
Apr 19, 2014

calc is wrong.Diff cable size should apear for Al & Cu.

• m daley
Nov 20, 2015

can you give me the formula for calculating cable sizes please

20. osman
Jan 04, 2014

21. Kingsley
Jan 01, 2014

Very useful, Thanks.

22. [email protected]
Nov 14, 2013

Sir,
I have a query in cable designing excel spread sheet Ver.22.8.12, I would be much thankful If would get it clarified.
In sizing of cable for motor feeder, The “KW” entry is mentioned what? It is the mechanical output or electrical input. If it is the mechanical output, the actual electrical load consumed must be output/efficiency and the actual input current is
Full load ampere = Output power/(1.732*P.F*V*Eff)
If “KW” Entry is actual input power then Full load ampere = Input power/ (1.732*P.F*V), Efficiency is not required in this case.
But, in your case, the “KW” entry is multiplied with efficiency to obtain actual load consumed (May be the mechanical power output which is less than “KW” entry) and the motor amperage is calculated from the actual load consumed. In such a case loses may not be able to feed to obtain desired full load output.

As far as demand factor concerned it (Load factor) is okay.Please clarify.
T.Sankar

23. Accesstel
Sep 22, 2013

Hi guys please let me know if we can buy these tools if they are not downloadable. I have invested 4 hours now with no success.

24. Rajesh SV
Sep 07, 2013

25. Jonesy
Aug 09, 2013

26. Arnon
Jul 27, 2013

Nice !!!!!!

27. Donie
Jul 23, 2013

Useful! :)

28. wnirut
Jul 02, 2013

thank you

29. engele
Jun 18, 2013

Hi there,

would appreciate it if you could send a copy of the excel file to [email protected] thanks

30. gabrielovskys
Jun 17, 2013

31. celebrationcometh
Jun 17, 2013

32. celebrationcometh
Jun 17, 2013

Jun 05, 2013

hello
i want to know the logics so please provide me password for this cable designsheet

34. sam atlantis
May 28, 2013

• Edvard
May 28, 2013

Hi,

Make sure to enable cookies in your browser. If cookes aren’t enabled, browser doesn’t know when you’re logged in.

Hope you will make it!

35. neeraj tiwari
Apr 25, 2013

36. neeraj tiwari
Apr 25, 2013

i m not able to download excel sheet suggest me for same.

37. GnMvP
Dec 23, 2012

No DC cables?

Mar 30, 2012

very good program

39. Veeraraghavan VS
Jan 07, 2012

Dear Edvard,

I tried the cable selection excel sheet. It is very good. I am giving below my observations.

1. Why there are 2 PFs? C9 and C10 are OK. Why C15?
2. Once a 3 Ph motor is selected, all single core and 3.5core cables may disappear from the list for selection.
3. In the results, Starting voltage drop as % will be helpful to refer.
4. It may be better if the TDF (Total Derating Factor) considered in selection is displayed.
5. As a case study, i considered a 55KV, 433V, 3Ph motor. DOL Start, 0.85 Running PF, 0.3 Starting PF, 85% efficiency, 600m length, LT XLPE Al cable, 3 trays, 6 cable per tray, cables touching each other. According to my earlier calculation 3cx50 cable is not suitable – 10.23% Running voltage drop and 24.41% starting voltage drop. But this sheet is showing OK with 1.95% running voltage drop.

The TDF considered by me is 0.674. Of course, the resistance and reactance data are from Indian cable manufacturers.
Please let me know your opinion / observation. 3cx50 al cable for a 55KW motor in DOL starting for 600m distance – please check.

40. Pedro Abarca
Oct 12, 2011

My coment is that I need a electrical software

• jm010809
Oct 16, 2012

I use manual calculations since not all form of installation is covered on this spread sheet….