Calculate Technical Losses of Transmission / Distribution Line:


  • There are two types of Losses in transmission and distribution Line.
  • (1) Technical Losses and
  • (2) Commercial Losses.
  • It is 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


  • 11 KV Distribution Line have following parameter.
  • Main length of 11 KV Line is 6.18 Kms.
  • Total nos. of Distribution Transformer on Feeder 25 KVA= 3 No, 63 KVA =3 No,100KVA=1No.
  • 25KVA 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.
  • 100KVA Transformer Iron Losses = 290 W, Copper Losses= 1850 W, LT Line Loss= 1380W.
  • Maximum Amp is12 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


Total Connected Load=No’s of Connected Transformer.

  • Total Connected Load= (25×3) + (63×3) + (100×1).
  • Total Connected Load=364 KVA.

 Peak Load = 1.732 x Line Voltage x Max Amp

  • Peak Load = 1.732x11x12
  • Peak Load =228 KVA.

 Diversity Factor (DF) = Connected Load (In KVA) / Peak Load.

  • Diversity Factor (DF) = 364 /228
  • Diversity Factor (DF) =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 / 1.732x11x12x0.8×8760
  • Load Factor (LF)=0.3060

 Loss Load Factor (LLF)= (0.8 x LFx LF)+ (0.2 x LF)

  • Loss Load Factor (LLF)= ( 0.8 x 0.3060 x 0.3060 ) + (0.2 x 0.306)
  • Loss Load Factor (LLF)= 0.1361

 Calculation of Iron losses:

  • Total Annual Iron loss in Kwh =Iron Loss in Watts X Nos of TC on the feeder X8760 / 1000
  • Total Annual Iron loss (25KVA TC)=100x3x8760 /1000 =2628 Kwh
  • Total Annual Iron loss (63KVA TC)=200x3x8760 /1000 =5256 Kwh
  • Total Annual Iron loss (100KVA TC)=290x3x8760 /1000 =2540 Kwh
  • Total Annual Iron loss =2628+5256+2540 =10424Kwh

 Calculation of Copper losses:

  • Total Annual Copper loss in Kwh =Cu Loss in Watts XNos of TC on the feeder LFX LF X8760 / 1000
  • Total Annual Copper loss (25KVA TC)=720x3x0.3×0.3×8760 /1000 =1771 Kwh
  • Total Annual Copper loss (63KVA TC)=1300x3x0.3×0.3×8760 /1000 =3199 Kwh
  • Total Annual Copper loss (100KVA TC)=1850x1x0.3×0.3×8760 /1000 =1458 Kwh
  • Total Annual Copper loss =1771+3199+1458=6490Kwh

 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 x1.15 x 2
  • HT Line Losses = 831 Kwh

 Peak Power Losses= (3 x Total LT Line Losses) / (PPLxDFxDFx 1000)

  • Peak Power Losses= 3 x (3×63+3×260+1×1380) /1.15 x 1.15 x 1000
  • Peak Power Losses= 3.0

 LT Line Losses (Kwh)= (PPL.) x (LLF) x 8760

  • LT Line Losses = 3 x 0.1361 x 8760
  • LT Line Losses = 3315 Kwh

 Total Technical Losses= (HT Line Losses + LT Line Losses + Annual Cu Losses + Annual Iron Losses)

  • Total Technical Losses = ( 831+ 3315 + 10424 + 6490)
  • Total Technical Losses = 21061 Kwh

% Technical Loss= (Total Losses) / (Unit Sent Out Annually) x 100

  • % Technical Loss= (21061/490335) x100= 4.30%

% Technical Loss=4.30%


About Jignesh.Parmar
Jignesh Parmar has completed M.Tech (Power System Control), B.E(Electrical). He is member of Institution of Engineers (MIE) and CEng,India. Membership No:M-1473586.He has more than 16 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”,”Smart Energy”, “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.

23 Responses to Calculate Technical Losses of Transmission / Distribution Line:

  1. gustavo rafael faquira soto says:


    • joe c. says:

      Total Connected Load=364 KVA.

      Peak Load = 264 / 1.732x11x12
      Peak Load =228
      I think there is a mistake in the above if Total connected load =364KVA
      But peak load is calculated with 264KVA?
      please explain.

      • Dear Joe,

        It is typing mistake in peak load calculation
        connected load is 25KVA 3nos TC+ 63KVA 3NO TC + 100KVA 1No TC =25×3=63×3=100=364KVA
        and Peak Load is 1.732 x KV X Max.Amp=1.732x11x12 =228KVA
        Thanks for highlighting…

  2. PRASHANT SONI says:

    Thank you very very much for your valuable and noble help / service to other electrical engineers…

    As we know yyou have uploaded the article “11KV-415V OVERHEAD LINE SPECIFICATION (REC) ” That is very much useful and helpful to us…

    I kindly request oyu to upload an article like
    1) 66 kV – 11 kV OVERHEAD LINE SPECIFICATION (REC / CEA 2010 / IS STANDARDS / IE RULE1956) or GETCO specification

    We all hope for your kind support and help…

    Thanking you in anticipation,

    Thanks & regards,
    Prashant Soni

  3. PRASHANT SONI says:

    3) 66 kV – 11 kV SUB STATION SPECIFICATION (REC / CEA 2010 / IS STANDARDS / IE RULE1956) or GETCO specification

  4. PRASHANT SONI says:

    I would be glad to receive your affirmative response reply at your earliest possible convenience…

  5. shahbaaz says:

    may i know the technical loss on a 16 kms 11 kv double circuit feeder having dog conductor with a load of 10 mw transmitted direct on a bus bar of the grid station.. no distribution transformer installed in between sending point to receiving end i-e bus bar..hoping a positive response from your side.

    • Calculation method is already explain in detail…

      • UMAR HAYAT says:

        Dear sir, i want to calculate the OHL line losses for 33kV for the below detail so need you help
        Generation is 25MW and Single Circuit length is 26KM (21OHL + 5 underground cable) Voltage is 33kV, Conductor ACSR 400 Kundah, Resistance/kM 0.07311,

        what is the losses at 26KM line ?

  6. Hsu Mon Myint says:

    May I know the formula of finding HT losses (0.105 or 1.05).
    Now I m studying line loss reduction in distribution line.
    The above formulae are very useful for me.
    Thanks for ur sharing !

  7. M.Nanibabu says:

    Hello sir,
    I want tranmission loss of 1 km of overhaed line for 11KV, 33KV and 132KV with detailed explaination

    Yhank you.

  8. Ashit Kumar Ray says:

    Hello sir,
    Please tell iron loss & copper loss in 200 kva,250kva & 500 kva transformer
    thank you,

  9. E.LAKSHMANAN says:

    Sir,Calculate Technical Losses of Transmission / Distribution Line-HT & LT line losses are not matched with Formula’s,In my amply request you ,please explain step by step procedure calculation of T& D losses

  10. Nitin says:

    Kindly share the formula of LDF, as per REC it is Load Distribution Factor and you have mentioned it as Load Diversity Factor. As per REC formula LDF is (PxL)/(kVA-km) based on sample calculations of two or three representative feeders. Kindly clarify what is kVA in denominator.

  11. Akshay Manoj Gawade says:

    Dear Sir,
    can u tell me how the formula is derived for HT and LT line losses?

  12. Er. S S Walia Er.- in -Chief (Retd) says:

    For working out line losses, we can work out peak line losses in Kw/kM and then using the LLF ,line losses for the length of line (6.18 km) can be calculated. In this
    , the peak loss work out to 3x 12 x12x 0.54 =0.23328 kW/KM. Then using LLF, the line losses work out as under:-
    Annual energy loss/km 0.23328xLLFX8760
    =0.23328X 0.1361X8760
    =278.12 kWH
    Annual energy loss for 6.18 km of line = 278.12×6.18
    The HT Line losses worked out by you are 831. Please reconcile and comment.Formula used by you is not clear. On what basis factor 0.105 has been used . Please explain.

  13. Tanveer Haq says:

    Kindly tell how to find average LT line losses of 200,400,500 and 630kVA transformer?

  14. Reddy says:

    Hai sir my Query is why dont we use power factor for peak load calculation.& for resistance/Km For 2km we calculate HT-3ph(3-wire) =2*(3*R) or 2*(1*R).please clarify
    Thank You

  15. farooque ansari says:

    Sir colud u plzzz told me that how do i calculat losses between ht line and lt line

  16. jyotiska says:

    What is the procedure of calculating LT line losses:

  17. Good day sir, Our plant/ compound has a 3 units division plant each with a check meter for each individual meter reading and a primary meter (to total /sum up all meter reading for billing). At the end of the month , the total reading of 3 units is not the same with the primary meter, we had what we call a current loss/difference, Example: let say, total reading of 3 units meter( 20,000 + 15,000+ 5,000)=40,000 kwh , and the primary meter is = 44,000 a difference of 4,000kwh… Our problem is How can we fairly distribute current loss/difference to each 3 units/division.


    Mistake1- author have calculate by taking 1 number of 100 kva transformer but written 3 numbers

    Mistake2-HT line loss calculation what is .105 & 1.05

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