---
title: "Define distribution transformer"
subject: "Transmission and Distribution System Design"
chapter: 5
key: "semester_8/transmission_and_distribution_system_design:define-distribution-transformer"
source: https://www.bctengineer.com/q/semester_8/transmission_and_distribution_system_design/define-distribution-transformer
site: BCT Engineering
---

# Define distribution transformer

Transmission and Distribution System Design · Chapter 5: Electric Power Distribution

- Asked in: 2080 Chaitra, 1 marks
- Video: [Distribution Transformers 1](https://www.youtube.com/watch?v=PnwGTPPnTd4) — Susan Blaser
- 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/define-distribution-transformer
- Whole chapter: https://www.bctengineer.com/md/semester_8/transmission_and_distribution_system_design/chapter-5

## Question

With respect to a distribution system, define distribution transformer.

## Short answer

A distribution transformer steps down the primary distribution voltage (11 kV or 33 kV) to the consumer utilization voltage (400/230 V). It is usually pole- or plinth-mounted, rated 25–500 kVA, and designed for low core losses and high all-day efficiency as it remains continuously connected.

## Answer

A **distribution transformer** is the step-down transformer that converts the primary distribution voltage (11 kV or 33 kV in Nepal) to the consumer utilization voltage (400/230 V). It supplies the secondary (LT) network.

It is usually pole-mounted or plinth-mounted, rated about 25–500 kVA (for example 11/0.4 kV, 100 kVA, Dyn11). It is connected all the time, so it is designed for **low core (no-load) losses** and high all-day efficiency.

## Check yourself

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

1. What does a distribution transformer do?
   A. Steps down 11 or 33 kV to 400/230 V for the LT network
   B. Steps up generator voltage
   C. Connects two grids
   D. Measures energy
   Answer: A. It supplies the secondary network at consumer voltage. (Key point: Function)

2. Why is low core loss important?
   A. It is a high-voltage device
   B. It is connected all the time, so no-load loss runs continuously
   C. It is overloaded
   D. It has no copper loss
   Answer: B. Continuous energisation makes core loss costly, so all-day efficiency is the aim. (Key point: Design emphasis)

## Related in Transmission and Distribution System Design

- [Selecting distribution transformer size and location](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Atransformer-size-and-location) — Transmission and Distribution System Design, chapter 7, asked 2×
- [Single phase vs 3-phase distribution transformer](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Asingle-vs-three-phase-transformer) — Transmission and Distribution System Design, chapter 7, asked 2×
- [T/F: under-loaded distribution transformer losses](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Atf-underloaded-distribution-transformer) — Transmission and Distribution System Design, chapter 7
- [Radial vs loop distribution system](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Aradial-vs-loop-distribution) — Transmission and Distribution System Design, chapter 5, asked 2×
- [T/F: lightning overvoltage in distribution system](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Atf-lightning-distribution-vs-transmission) — Transmission and Distribution System Design, chapter 3
- [Distribution system used in INPS](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Ainps-distribution-system-type) — Transmission and Distribution System Design, chapter 5

## Related in other subjects

- [Design: 150 kVA 6600/400 V distribution transformer](https://www.bctengineer.com/question.md?key=semester_5%2Felectric_machine_design%3Adesign-150kva-6600-400-regulation) — Electric Machine Design, chapter 3, asked 5×
- [Design: 100 kVA 4000/433 V distribution transformer](https://www.bctengineer.com/question.md?key=semester_5%2Felectric_machine_design%3Adesign-100kva-4000-433) — Electric Machine Design, chapter 3, asked 4×
- [Selecting distribution transformer size using Ku and Ks](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Atransformer-size-ku-ks) — Industrial Power Distribution and Illumination, chapter 4, asked 3×
- [Power versus distribution transformer](https://www.bctengineer.com/question.md?key=semester_5%2Felectric_machine_design%3Apower-vs-distribution-transformer) — Electric Machine Design, chapter 3, asked 3×