---
title: "T/F: % power loss affected by load factor"
subject: "Transmission and Distribution System Design"
chapter: 6
key: "semester_8/transmission_and_distribution_system_design:tf-power-loss-affected-load-factor"
source: https://www.bctengineer.com/q/semester_8/transmission_and_distribution_system_design/tf-power-loss-affected-load-factor
site: BCT Engineering
---

# T/F: % power loss affected by load factor

Transmission and Distribution System Design · Chapter 6: Electrical Load Characteristics and Load Forecast

- Asked in: 2068 Bhadra (old course), 5 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_8/transmission_and_distribution_system_design/tf-power-loss-affected-load-factor
- Whole chapter: https://www.bctengineer.com/md/semester_8/transmission_and_distribution_system_design/chapter-6

## Question

State whether the following statement is TRUE or FALSE and give reasons briefly: Percentage power loss of a particular load centre in a distribution system is affected from the load factor.

## Short answer

FALSE. Percentage power loss depends only on peak demand, voltage, power factor and resistance, not on how load varies with time. Load factor influences percentage energy loss, which equals % power loss multiplied by (0.3 + 0.7 × LF).

## Answer

**FALSE** (for percentage **power** loss); load factor affects the percentage **energy** loss.

**Reasons:**

- Power loss at any instant is $P_{loss} = 3I^2R$. The percentage power loss at peak is

$$
\%P_{loss} = \frac{3 I_{max}^2 R}{P_{max}} \times 100 = \frac{P_{max} R}{V^2 \cos^2\phi} \times 100
$$

  It depends only on the peak demand, voltage, power factor and resistance (conductor size and length). Load factor does not appear, so two load centres with the same peak but different load factors have the same % power loss.

- Load factor describes how the load varies with time. It therefore affects **energy** quantities:

$$
\%E_{loss} = \%P_{loss} \times \frac{LLF}{LF}, \quad LLF = 0.3LF + 0.7LF^2
$$

  so $\%E_{loss} = \%P_{loss}(0.3 + 0.7LF)$.

**Example:** % peak power loss = 8%.

| LF | % power loss | % energy loss |
|---|---|---|
| 0.3 | 8% | 8 × 0.51 = 4.08% |
| 0.6 | 8% | 8 × 0.72 = 5.76% |

The % power loss stays 8% for both, while the % energy loss changes with LF.

- Indirectly, if the **energy** consumption is fixed, a higher LF lowers the peak demand and hence the peak power loss. In that sense the planner sees load factor influencing losses, but for a load centre of given peak demand the percentage power loss is independent of load factor.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Is the percentage power loss of a load centre (at given peak) affected by load factor?
   A. Yes, directly
   B. No, it depends on peak demand, voltage, power factor and resistance
   C. Yes, through coincidence factor
   D. Only for long lines
   Answer: B. %P_loss = P_max R/(V^2 cos^2 phi) x 100 has no load factor term. (Key point: Verdict)

2. Which quantity does load factor affect?
   A. Peak power loss %
   B. Conductor resistance
   C. Percentage energy loss
   D. Voltage level
   Answer: C. %E_loss = %P_loss x (0.3 + 0.7 LF), which changes with LF. (Key point: What LF does affect)

3. With 8% peak power loss, % energy loss at LF = 0.6 is:
   A. 4.08%
   B. 8%
   C. 5.76%
   D. 4.8%
   Answer: C. 0.3 + 0.7(0.6) = 0.72, so 8 x 0.72 = 5.76%. (Key point: Example)

## Related in Transmission and Distribution System Design

- [T/F: LLF unity for constant power loss](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Atf-llf-unity-constant-loss) — Transmission and Distribution System Design, chapter 6
- [T/F: % power loss equals % energy loss](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Atf-power-loss-energy-loss-same) — Transmission and Distribution System Design, chapter 6
- [Percentage energy loss of 25 kVA transformer](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Atransformer-energy-loss-25kva) — Transmission and Distribution System Design, chapter 7
- [Define loss of load factor](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Adefine-loss-of-load-factor) — Transmission and Distribution System Design, chapter 6, asked 2×
- [Dependency of energy loss on load factor](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Aenergy-loss-load-factor-dependency) — Transmission and Distribution System Design, chapter 6
- [Reducing power loss in distribution systems](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Apower-loss-reduction-distribution) — Transmission and Distribution System Design, chapter 7, asked 2×

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