What are tap-changing transformers?

Short Answer:

Tap-changing transformers are transformers equipped with special switches called taps that allow changing the turns ratio without interrupting the load. This helps adjust the output voltage to desired levels even when input voltage or load conditions vary.

They are widely used in power systems to maintain voltage stability and improve power quality by compensating for voltage fluctuations during operation.

Detailed Explanation:

Tap-changing transformers

Introduction

Transformers are key devices for voltage conversion in electrical power systems. However, voltage levels can vary due to load changes or fluctuations in the supply network. To maintain stable voltage at the output, tap-changing transformers are used. These transformers have multiple taps on their windings, which can be switched to change the effective turns ratio, thereby adjusting the output voltage.

Tap-changing transformers are essential for improving voltage regulation and ensuring reliable power delivery.

Types of Tap-Changing Transformers

  1. No-Load Tap Changer (NLTC)
    • Operates only when the transformer is de-energized (no load connected).
    • The tap position is changed manually or automatically during no-load conditions.
    • Used mainly in distribution transformers where voltage adjustment is occasional.
  2. On-Load Tap Changer (OLTC)
    • Allows tap changing while the transformer is energized and supplying load.
    • Uses special switching mechanisms to avoid interruption or sparking.
    • Common in power transformers in transmission and large substations for continuous voltage regulation.

Working Principle

  • Transformer taps are connection points at intervals on the winding.
  • Changing taps effectively changes the number of active turns in the winding.
  • By increasing or decreasing the turns ratio, the output voltage can be raised or lowered as required.
  • OLTC uses diverter switches and transition resistors to switch taps smoothly without power interruption.

Applications

  • Maintaining constant voltage in transmission and distribution networks.
  • Compensating voltage drops due to load changes or line losses.
  • Supporting power system stability by controlling voltage levels.
  • Used in generators, large transformers, and distribution substations.

Advantages

  • Provides flexible and automatic voltage control.
  • Reduces voltage fluctuations and improves power quality.
  • Enhances system reliability and protects sensitive equipment.
  • Minimizes manual intervention and downtime.
Conclusion

Tap-changing transformers are specialized transformers with adjustable taps that help maintain desired voltage levels despite fluctuations in supply or load. They are crucial in power systems for voltage regulation and stability. On-load tap changers allow seamless voltage adjustment without interrupting power supply, making them highly valuable in modern electrical networks.