Short Answer:

Tap-changing transformers are special transformers that allow adjustment of the output voltage by changing the number of active turns in the winding. This is done through taps provided on the winding. They help maintain a constant voltage level even when the load or input voltage changes.

The main significance of tap-changing transformers is to regulate voltage in power systems. They are widely used in transmission and distribution networks to ensure stable voltage supply under different operating conditions. Without them, voltage levels might go too high or too low, which can damage electrical equipment.

Detailed Explanation:

Significance of tap-changing transformers

Tap-changing transformers play a crucial role in maintaining voltage stability in electrical power systems. Electrical loads keep changing throughout the day, and this affects the voltage level at different points in the system. If the voltage goes too low, equipment may not work properly. If it goes too high, it can damage devices. Tap-changing transformers solve this problem by allowing adjustment of the transformer’s turns ratio.

These transformers have taps on the winding, which are connection points that can be selected to increase or decrease the number of coil turns. Changing the number of active turns changes the output voltage. This tap selection can be done manually or automatically, and it helps keep the output voltage within safe limits.

Types of Tap-Changing Transformers:

1. Off-Load Tap Changer (OLTC):
   • The tap setting can be changed only when the transformer is not supplying power.
   • Used in applications where voltage variation is not frequent.
   • The transformer must be switched off to change the tap.
2. On-Load Tap Changer (OLTC):
   • Allows tap changing while the transformer is supplying power.
   • Commonly used in power transmission and distribution networks.
   • Automatically adjusts voltage without interrupting the supply.

Why Tap-Changing Transformers Are Important:

1. Voltage Regulation:
   They help maintain constant voltage at the consumer end, even if input voltage or load changes.
2. Improved Power Quality:
   Fluctuating voltage can affect the performance of sensitive equipment. Tap changers ensure smooth voltage supply.
3. System Stability:
   Helps stabilize the voltage across long transmission lines by compensating for voltage drops.
4. Flexibility in Operation:
   Utility companies can adjust voltage settings based on demand and network conditions without replacing transformers.
5. Protection of Equipment:
   Ensures that motors, machines, and other appliances receive voltage within their safe operating range.

Working Concept:

Tap changers work by changing the number of turns in the winding. Since the transformer’s output voltage depends on the ratio of primary to secondary turns, altering this ratio changes the output voltage. In OLTCs, switching is done with special mechanisms that avoid interruption or arcing during operation.

Modern transformers with OLTC are connected to automatic voltage control relays. These devices monitor the voltage and trigger tap changes when necessary. This automation is very helpful in substations and large power networks.

Applications:

• Electrical substations
• Power generation stations
• Industrial power systems
• Long-distance power transmission lines
• Voltage-sensitive areas like hospitals and data centers

Conclusion:

Tap-changing transformers are essential for voltage control in modern power systems. They provide a simple yet effective way to adjust transformer output voltage based on changing load or supply conditions. Their main significance lies in protecting equipment, improving power quality, and ensuring reliable electricity delivery without interruptions. Tap-changing capability makes transformers more flexible and efficient in real-world operations.