# An example of calculating the technical losses of T&D lines

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## Introduction to Losses

There are two types of losses in transmission and distribution line.

1. Technical Losses and
2. Commercial Losses.

It’s necessary to calculate technical and commercial losses. Normally technical losses and commercial losses are calculated separately.

Transmission (technical) losses are directly effected on electrical tariff, but commercial losses are not implemented to all consumers.

Technical losses of the distribution line mostly depend upon electrical load, type and size of conductor, length of line etc.

Let’s try to calculate technical losses of one of following 11 KV distribution line ;)

### Example – 11 kV Distribution Line

11 KV distribution line have following parameters:

• Main length of 11 KV line is 6.18 km.
• Total number of distribution transformer on feeder:
25 KVA = 3 No.
63 KVA = 3 No.
100 KVA = 1 No.
• 25 KVA transformer:
– Iron losses = 100 W
– Copper losses = 720 W
– Average LT line loss = 63W
• 63KVA transformer:
– Iron losses = 200 W
– Copper losses = 1300 W
– Average LT line loss = 260W
• 100 KVA transformer:
– Iron losses = 290 W
– Copper losses = 1850 W
– LT line loss = 1380W
• Maximum amp is 12 Amps.
• Unit sent out during to feeder is 490335 Kwh
• Unit sold out during from feeder is 353592 Kwh
• Normative load diversity factor for urban feeder is 1.5 and for rural feeder is 2.0

## Calculation

#### Total connected load = No’s of connected transformers

Total connected load = (25×3) + (63×3) + (100×1) = 364 KVA

#### Peak load = 1.732 x Line voltage x Max. amp

Peak load = 264 / 1.732 x 11 x 12 = 228

#### Diversity factor (DF) = Connected load (in KVA) / Peak load

Diversity factor (DF) = 364 /228 = 1.15

#### Load factor (LF) = Unit sent out (in Kwh) / 1.732 x Line voltage x Max. amp. x P.F. x 8760

Load factor (LF) = 490335 / 1.732 x 11 x 12 x 0.8 × 8760 = 0.3060

#### Loss load factor (LLF) = (0.8 x LF x LF)+ (0.2 x LF)

Loss load factor (LLF) = (0.8 x 0.3060 x 0.3060) + (0.2 x 0.306) = 0.1361

### Calculation of iron losses

Total annual iron loss in KWh =
Iron losses in Watts x Nos of TC on the feeder x 8760 / 1000

Total annual iron loss (25 KVA TC) =
100 x 3 x 8760 / 1000 = 2628 KWh

Total annual iron loss (63 KVA TC) =
200 x 3 x 8760 / 1000 = 5256 KkWh

Total annual iron loss (100 KVA TC) =
290 x 3 x 8760 / 1000 = 2540 KWh

Total annual iron loss =
2628 + 5256 + 2540 = 10424 KWh

### Calculation of copper losses

Total annual copper loss in KWh =
Cu Loss in Watts x Nos of TC on the feeder LFX LF X8760 / 1000

Total annual copper loss (25 KVA TC) =
720 x 3 x 0.3 × 0.3 × 8760 / 1000 = 1771 KWh

Total annual copper loss (63 KVA TC) =
1300 x 3 x 0.3 × 0.3 × 8760 / 1000 = 3199 KWh

Total annual copper loss (100 KVA TC) =
1850 x 1 x 0.3 × 0.3 × 8760 / 1000 = 1458 KWh

Total annual copper loss =
1771 + 3199 + 1458 = 6490 KWh

#### HT line losses (Kwh) = 0.105 x (conn. load x 2) x Length x Resistance x LLF / (LDF x DF x DF x 2)

HT line losses = 1.05 x (265 × 2) x 6.18 x 0.54 x 0.1361 /1.5 x 1.15 x 1.15 x 2 = 831 KWh

#### Peak power losses = (3 x Total LT line losses) / (PPL x DF x DF x 1000)

Peak power losses = 3 x (3 × 63 + 3 × 260 + 1 × 1380) /1.15 x 1.15 x 1000 = 3.0

#### LT Line losses (KWh) = (PPL) x (LLF) x 8760

LT Line losses = 3 x 0.1361 x 8760 = 3315 KWh

#### Total technical losses = (HT Line losses + LT Line losses + Annual Cu losses + Annual iron losses)

Total technical losses = (831+ 3315 + 10424 + 6490) = 21061 KWh

#### % Technical loss = (Total losses) / (Unit sent out annually) x 100

% Technical loss = (21061 / 490335) x 100 = 4.30%

% Technical Loss = 4.30%

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#### Jignesh Parmar

Jignesh Parmar has completed M.Tech (Power System Control) ,B.E(Electrical). He is member of Institution of Engineers (MIE),India. Membership No:M-1473586.He has more than 13 years experience in Transmission -Distribution-Electrical Energy theft detection-Electrical Maintenance-Electrical Projects (Planning-Designing-Technical Review-coordination -Execution). He is Presently associate with one of the leading business group as a Deputy Manager at Ahmedabad,India. He has published numbers of Technical Articles in "Electrical Mirror", "Electrical India", "Lighting India", "Industrial Electrix"(Australian Power Publications) Magazines. He is Freelancer Programmer of Advance Excel and design useful Excel base Electrical Programs as per IS, NEC, IEC,IEEE codes. He is Technical Blogger and Familiar with English, Hindi, Gujarati, French languages. He wants to Share his experience & Knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics.

1. shozab
Jun 11, 2018

Dear Mr. Jignesh,

It is nice meeting you, i have gone thru your blogs and find certain excel calculation sheet, actually i m looking for the excel tool for Insulation Coordination as per IEC, IEEE, IS.

Also Line loss calculation using UG cable at HV (33kV and 11kV)

You are requested to kindly post the blog on it electrical section or reply to me with returning email. It will be helpful. Alsot kindly let me the buying charges of these.

May 23, 2018

Thank you for your guide on calculating technical loss, however please I need clarification on 0.2 value used in loss load factor calculation and 0.105 used in calculating HT line losses(Kwh). Thank you

3. Rajesh kumar
Mar 05, 2018

Respected sir please provide the information of 8760

4. batuhan alkan
Dec 18, 2017

Ht line losses, peak powe losses and lt line losses calculation has to much calculation mistake can you explain how are you finding 831- 3.0 – 3315

5. Dhrumit
Jun 13, 2017

In Uganda my company get form Umeme 33kv. After line loss I get 28 -29 kg And my transformer set on step 5 last stape but I am not geting 415 volt. So what should I do. Please give me solution if you have.

6. Ramprabha
May 22, 2017

Thank you sir for giving this information. Plz clear. In load factor it’s mentioned 8760. How, what constant.

7. RAJESH JAIN
Jan 11, 2017

Two Distribution transformers of 630 KVA are installed in a residential group housing society. In summer they have 60% loading and in winter they have only 30-35% loading.I want to know in winter if all load will run at one Transformer and one transformer take in idle position , how much losses we can save. LT cables will be same ,only one Transformer will be in idle position for winter period.

8. sathish
Dec 03, 2016

hi friends any buddy have IEC and other standard codes and definition

9. WILIBALDO TORO
Oct 17, 2016

Dear Sir, do you have this article corrected? the question is because I have the same doubts with respect the ecuations and his results.

10. Jeffery B. Ballah
Jun 06, 2016

Dear Sir. Thanks for your opportunity provided me to read EEP materials on line. I’m praying that one day I can get a job that will enable me subscribe as a member so that I may be able to download and read these materials daily to improve my skills as a student reading Electrical Engineering in a war ravish country Liberia where there is no research lab and internets But thanks to EEP I’m fighting hard to be myself in this my chosen career.

Best regards.

11. Saif ur Rehman
Apr 08, 2016

Dear sir
I want to know that, how to include line losses in grid extension feasibility study please reply

12. Hafidz
Apr 03, 2016

Sir, what refrence for Book of this formula ? is there from iec,ieee,or etc?

13. vicku
Aug 18, 2015

1st of all tell me about max’m Ampere i.e u have taken max’m amp as 12amps , I don’t understand that that max’m ampere is of Line Conductor or Transformer..
how max’m Ampere Will be Calculated if NOT GIVEN.

14. Aliyu Mustapha Rufau
Aug 14, 2015

Thanks for the calculations

15. Temitope
Aug 10, 2015

Sir, your materials seem helpful. In your calculation of HT line losses where did the constants 0.105 from and it later transformed to 1.05. please am not too clear on this. what is the name of the constant? or is the constant meant feeder. and if its for 33kv feeder, how what will be the constant

16. ashoka r
May 13, 2015

sir i have very lack of knowledge about reactve power so kindly i request u to send some basic details regarding i hope u do the same.

17. ashoka r
May 13, 2015

dear sir i have very lack of knowledge about reactive power (kvar) so pls teach me about it ,
i am looking forward for ur valuable reply

18. Aye San Dar
Mar 08, 2015

Dear Sir,
let me know one thing from your technical losses calculation that what is the meaning of No of TC on the feeder??

19. Ashit Kumar Ray
Mar 07, 2015

Sir,i want to know the loss calculation in replacement of ab cable in distribution transformer sub station.Plz give an example with % of loss.
thanking you,
Ashit Kumar Ray,CESU,Odisha.

20. ulaganathan
Feb 24, 2015

Sir
I m working as a electrical engineer in transmission line field about 33kv and 220 kv.I have a doubt about line loss per km at both 33&220kv line and how to calculate them.I need your valuable prescription.

21. Sumit
Feb 04, 2015

There seems to be many calculation errors or formula errors. Also please provide clear definition of all the constants. I am very confused.

22. Dharmin joshi
Jan 07, 2015

how to find out line current for 33kv overhead transmission line for 3Km? if my power plant is 2mw.
pl mail me

23. Rajasekar
Oct 13, 2014

Sir,
What is 0.105 constant in line loss calculation and while calculating it shows as 1.05 and also the loss while calculating it is not 831 KWh How?

24. zaffar
Oct 11, 2014

264÷1.732x11x12=228 how

25. gaurav kumar goswami
Aug 06, 2014

hi ur providing a free and very helpfull guidline for elect engg …thanx for that sir

26. yeanling
Jun 11, 2014

364 /228 = 1.15 ? not 1.6 ?

and

HT line losses = 1.05 x (265 × 2) x 6.18 x 0.54 x 0.1361 /1.5 x 1.15 x 1.15 x 2 = 831 KWh

265× 2, where it is from?

27. ankit
Apr 30, 2014

if cable size is more than actual cable (depend on rated current) so what is loss?

28. Ali BY
Apr 28, 2014

I’m working on a project to reduce the losses in distribution lines of the city of Casablanca (Morocco). I need the methodology used in this example to perform the calculations. Thanks to send me the required elements. (aliby25@gmail.com)

29. Ayoyinka Muritala
Apr 25, 2014

Please, kindly assist and furnish me with the extensive list of test adopted universally performed on Power Transformers.

30. Moh'd alqasem
Apr 25, 2014

Thank you