What is the function of the Auxiliary Transformer in the Substation?

What is an Auxiliary Transformer?

Auxiliary transformers are static devices that function as step down transformers, transforming electricity from one alternating current circuit to another alternating current circuit at the same frequency.

These circuits are conductively disconnected yet magnetically related by a common time-varying magnetic field.

An auxiliary transformer is essential to the smooth running of a substation.

What are the Parts of Auxiliary Transformer?

Auxiliary transformer consists of the

  • Transformer oil,
  • Tap changer,
  • Conservator,
  • Breather,
  • Cooling tubes,
  • Buchholz relay,
  • Core,
  • Windings,
  • Insulating materials, and
  • Explosion vent.

It is basically a step-down transformer that converts the high voltage power going into the power station to a lower voltage suited for powering the facility’s many auxiliary systems, which are:

1). Providing Power for Auxiliary Systems

Auxiliary transformers supply the low voltage required to light the

  • Substation control room,
  • Switchyard, &
  • Other places.

This ensures adequate visibility for operators & maintenance people, especially at night.

2). Cooling Systems

During operation, large power transformers emit a lot of heat.

Auxiliary transformers supply the low voltage required to run the cooling fans & pumps that preserve these transformers operating safely.

3). Control and Safety Systems

Auxiliary transformers provide the low voltage required by the substation’s numerous control and protection systems.

These systems include

  • Relays,
  • Circuit Breakers, and
  • SCADA (Supervisory Control and Data Acquisition) systems,

which are critical for monitoring and managing the operation of the substation and assuring safety.

4). Source of Backup Power

In the case of a power outage, auxiliary transformers supply the low voltage required for charging the batteries that back up the substation’s DC systems.

These batteries are critical for maintaining the continuous operation of critical control & protection systems.

5). Auxiliary Motors

Many sub-station auxiliary motors, such as those used to operate

  • Disconnectors &
  • Tap changers,

depend on the low voltage produced by auxiliary transformers.

What is the purpose of the unit auxiliary transformer?

The Unit Auxiliary Transformer is the electricity Transformer that supplies electricity to the auxiliary equipment of a power producing plant during normal operation.

Application of an Auxiliary Transformer

The auxiliary transformers are used to:

  • Assist in isolating the high voltage & low voltage systems.
  • This improves safety by preventing electrical problems from spreading from one system to another.
  • Control the low voltage system’s voltage. This maintains the voltage provided to the auxiliary devices within acceptable limits.
  • Reduce the fault current.
  • Auxiliary transformers help to reduce the amount of current that can flow in the event of a fault by isolating the high voltage & low voltage systems. This serves to protect the equipment and prevent outages.
  • Auxiliary transformers are necessary components of any substation operations.
  • It performs an essential function in providing the power grid’s reliability and safety.

What is the difference between auxiliary transformer and station transformer?

Auxiliary Transformer Station Transformer
Provides power to auxiliary substation systems (such as lighting and control circuits). Makes simpler to transform voltage for primary distribution or transmission.
Operates with a lower voltage. Steps down for distribution or manages greater voltage levels for transmission.
Smaller capacity, used for supporting equipment. Greater capability, fulfilling the main roles of power distribution and transmission.

What is the auxiliary system in a substation?

Loads include

  • Transformer cooling,
  • Oil pumps,
  • Load tap changers,
  • Circuit breaker air compressors
  • Charging motors,
  • Outdoor device heaters,
  • Outdoor lights
  • Receptacles,
  • Motor-operated disconnecting switches
  • Control houses

are commonly supplied by substation AC auxiliary systems.