Introduction to Losses
There are two types of losses in transmission and distribution line.
- Technical Losses and
- Commercial Losses.
It’s necessary to calculate technical and commercial losses. Normally technical losses and commercial losses are calculated separately.
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%
Related electrical guides & articles
Can you provide the reference of the formulae used here? And what is the purpose of 1.05 factor taken in calculation of HT Line Loss?
Well done sir.
Please explain how you arrived at 12Amps Maximum Amp. and the values for the LT Line loss.
Thanks.
how did you get average LT line losses as 63W ,260W and 290W
how to solve it to get optimum distance ?
are the losses purely active power losses or a there is reactive power loss present as well?
Thanjks very much engineer Permer. Your case study of Distribution feeder loss calculation is very helpful. Thank you very much once again.
May I please ask for some clarifications, as follows?
1. Some calculations seems needs checking as the results does not reflect the figures calculated. Example, diversity factor calculated as 1.15 seems to be like 1.59 if correctly calculated and some more.
2. Where is the factor of 0.105 or 1.05 obtained in calculating HT line loss? Which figure is correct? 0.105 or 1.05?
3. Why is 8760 not used in calculating HT (and possibly LT line) losses to convert it to KWh?
Thanks so much for the good effort, hoping that you clarify these issues, please.
1.05 is correct. Considering line sag as 5% of total length
The actual Formula for calculating annual HT Line Loss
0.105 x(P^2 x RxLLF/(2xLDFxDF^2)
Yes, this is the actual formula.
Sir,
How to calculate the 1600KVA transformer line losses (11KV/433V), please send the step by by formulas.
what is the reason for huge transmission losses in 132kV underground cable system
please give answer in 11 kv line per meter line loss load is 7000 Amp Lt