## 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.

**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 K kWh**

**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%**

Aye San Dar

Dear Sir,

I am very glad to have a chance sharing your knowledge.

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

I am looking forward for your valuable reply.

Ashit Kumar Ray

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.

ulaganathan

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.