Short Answer:

Load Tap Changer (LTC) operation refers to the automatic adjustment of transformer tap positions while the transformer is under load, to maintain a constant output voltage. LTC allows changes in the number of transformer winding turns without interrupting power supply.

This operation helps the transformer respond to voltage drops or rises due to load variations. By shifting tap positions up or down, LTC ensures that the voltage delivered to consumers stays within safe and desired limits, making it essential for real-time voltage regulation in power systems.

Detailed Explanation:

Load tap changer operation

A Load Tap Changer (LTC) is an integral part of power transformers used in electrical power systems for continuous voltage regulation under varying load conditions. Unlike off-load tap changers, which require the transformer to be de-energized before switching taps, LTCs can adjust tap positions while the transformer is energized and supplying power. This feature ensures uninterrupted voltage control, making LTCs extremely valuable in substations, industrial networks, and grid transformers.

Working Principle of LTC:

1. Tap-Changing Mechanism:
   The LTC operates by changing the effective number of turns in the transformer winding, thereby altering the voltage ratio between the primary and secondary sides. A higher number of turns results in lower voltage and vice versa.
2. Operation Under Load:
   During LTC operation, the load remains connected, and the transition between tap positions must be smooth to avoid arcing or voltage disruption. This is achieved using make-before-break switching with resistors or reactors to momentarily share current between two taps during the transition.
3. Automatic Voltage Control:
   LTCs are typically controlled by voltage-sensing relays that continuously monitor the output voltage. When voltage deviates from a preset value, the controller signals the LTC to change its tap position, either increasing or decreasing the voltage.

Key Functions of LTC:

• Real-Time Voltage Regulation:
  Maintains stable voltage levels at the secondary side regardless of load fluctuations on the system.
• Supports Load Growth:
  Adapts to increasing demand without manual intervention, reducing the need for frequent transformer upgrades.
• Improves System Stability:
  Helps in balancing voltages across interconnected systems and prevents under-voltage or over-voltage conditions.
• Minimizes Power Losses:
  Optimal voltage regulation through LTC operation reduces the current flow required, minimizing I²R losses.

Types of Load Tap Changers:

1. Mechanical LTCs:
   Use mechanical switching devices and contacts for tap selection.
2. Electronic LTCs:
   Use power electronics and are faster, with less mechanical wear.
3. Reactor-Type and Resistor-Type LTCs:
   Use reactor or resistor components to limit circulating current during tap change.

Applications of LTCs:

• Power generation stations
• High-voltage substations
• Industrial facilities with fluctuating loads
• Renewable energy systems (e.g., wind, solar)
• Large urban distribution networks

Conclusion:

Load Tap Changer (LTC) operation is a vital process in transformer-based voltage regulation. It enables the transformer to adjust its voltage output without power interruption, ensuring stable delivery to consumers. By automatically responding to voltage deviations, LTCs improve system reliability, enhance power quality, and support the growing demands of modern electrical networks.