Understanding Transformer Tap Changers: Types, Functions, and Applications

A large white electrical box against a blue sky. Image representing transformer tap changers and their types, functions, and applications.

Understanding Transformer Tap Changers: Types, Functions, and Applications

Substation and distribution transformers play a crucial role in the electrical power distribution system, stepping up or down voltage levels to ensure efficient transmission and distribution of electricity. To enhance the adaptability and efficiency of these transformers, they are often equipped with tap changers. In this blog post, we will dive into the world of substation transformer tap changers, exploring their types, functions, and applications in the electrical power industry.

Types of Tap Changers

1. On-Load Tap Changers (OLTC)

On-load tap changers, also known as OLTCs, are designed to change the transformer’s tap settings while it is energized and under load. OLTCs use various mechanisms, such as diverter switches and selector switches, to alter the transformer’s winding connections. This allows for voltage adjustments to compensate for fluctuations in the power grid, ensuring a steady supply of electricity.

OLTCs are commonly found in substation transformers, where voltage adjustments are frequently required to accommodate changing loads and voltage profiles.

2. De-Energized Tap Changers (DETC)

De-Energized Tap Changers (DETC)

 Unlike OLTCs, de-energized tap changers are designed to switch the transformer’s taps when it is de-energized or offline. They do not require complex switching mechanisms since they operate under no load conditions.

DETCs are used in substation, pad mounted, and pole mounted transformers (distribution transformers). They are ideal for making tap changes during scheduled maintenance or when the transformer is out of service. 

Functions of Tap Changers

1. Voltage Regulation

The primary function of a tap changer is to regulate the output voltage of transformers. Voltage fluctuations in the power grid can impact the quality of electricity supplied to consumers. Tap changers allow transformers to adapt and maintain a constant output voltage, ensuring a stable and reliable power supply.

2. Grid Stability

Tap changers play a critical role in maintaining the stability of the electrical grid. They respond to voltage changes and load variations promptly, reducing the risk of voltage sags or surges that can disrupt the power supply.

Applications of Tap Changers

1. Distribution Transformers

Tap changers in distribution transformers are vital for supplying electricity to homes, businesses, and industries. They ensure that voltage levels remain within acceptable limits, regardless of load fluctuations or grid disturbances.

2. Substation Transformers

Power transformers in substations often use tap changers to regulate voltage levels in high-voltage transmission networks. This is crucial for efficient long-distance power transmission and grid synchronization.

3. Renewable Energy Integration

With the growing integration of renewable energy sources like wind and solar, tap changers are essential for accommodating the variable power output from these sources. They help maintain grid stability when renewable generation fluctuates.

4. Industrial Applications

Industries with sensitive equipment rely on tap changers to provide consistent voltage levels, safeguarding their operations from voltage-related disruptions.


Tap changers are heroes of the electrical power grid, ensuring that voltage levels remain stable and suitable for various applications. Understanding the types, functions, and applications of tap changers is essential for maintaining a reliable and efficient power supply, especially in a world that increasingly relies on electricity for daily life and industrial processes. These devices continue to evolve and adapt to the changing demands of the power grid, making them an indispensable component in our quest for a more sustainable and electrified future.

UTB sells a variety of transformers including substation transformers with taps. Whether you need OLTC or DETC we’ve got you covered! If you are in need of a quote, feel free to contact our sales team either by calling in at 855-214-0975 or emailing us at [email protected]