What are Distribution Transformers?

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Editorial Team - everything PE

Jun 25, 2024

A distribution transformer, also called a service transformer, performs the final voltage transformation in the electric power distribution system. It steps down the voltage from the distribution lines to the level required by residential, industrial and commercial customers.

Features of Distribution Transformers

  • High efficiency: Modern distribution transformers are carefully designed to achieve very high efficiency, of up to 97%, by minimizing no-load and full-load losses. This reduces energy wastage and keeps electricity costs low for consumers.
  • Reliability: Extreme quality control in design, raw materials and manufacturing results in highly reliable distribution transformers that provide trouble-free service for over 25 years.
  • Overload capability: Distribution transformers can handle short-term overloading above their rated capacity to account for occasional spikes in demand.
  • Protection features: Built-in devices like Buchholz relays, pressure relief valves, and temperature detectors protect distribution transformers from issues like overheating, voltage spikes, and short circuits.
  • Minimal maintenance: Robust sealed tanks with long-life insulating oil minimize maintenance requirements for distribution transformers.
  • Low environmental impact: Many modern distribution transformers use non-toxic, biodegradable vegetable-based insulating oils instead of mineral oils

Types of Distribution Transformer

  • Single Phase Distribution Transformer: These transformers are ideal for lower-capacity applications like residential complexes, commercial buildings, etc.
  • Three-Phase Distribution Transformer: These transformers are used in high-voltage power networks.
  • Pad-Mounted Distribution Transformer: These transformers are used in underground utility distribution lines and are used in urban and suburban areas to serve residential, commercial, and industrial customers.
  • Pole-Mounted Distribution Transformer: These transformers are installed on utility poles and typically serve residential and rural areas, ranging from 16 kVA to 100 kVA.   They are compact and are designed for outdoor use.

Comparison of Power Transformer and Distribution Transformer

Parameter                             Power Transformer                         Distribution Transformer

Type of Network

Transmission network of higher voltages

Distribution network of lower voltages

Voltage Rating

400 kV, 200 kV, 110 kV, 66 kV, 33 kV

11 kV, 6.6 kV, 3.3 kV, 440 V, 230 V

Power Rating

Greater than 200 MVA

Less than 200 MVA

Location

Generating station and transmission substations

Distribution stations near load centers

Function

Step-up or step-down voltage levels

Step-down voltage levels only

Operating Period

Full load operation

Light load operation during major parts of the day

Efficiency

Maximum efficiency at full load

Maximum efficiency at 60-70% load

Size

Larger size

Smaller size

Winding Configuration

Single primary and single secondary

Single primary and divided or tapped secondary

Purpose

Transmission of high-power electricity

Distribution of electricity to end-users

Applications

Transmission of power over long distances

Distribution of power to homes and businesses

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