Short Description: An OLTC is an automatic or remotely controlled device that adjusts the transformer's voltage ratio while it is energized and carrying current. It is essential for grids where stopping power to adjust voltage is not possible.
Description: OLTCs are typically installed on the high-voltage (HV) side because the current is lower, which reduces arcing.
- Mechanism: It uses a "make-before-break" contact sequence. Before disconnecting from the current tap, it connects to the next one through a transition resistor or reactor to prevent short-circuiting the winding turns while ensuring a continuous current path.
- Components: Key parts include a selector switch (to choose the tap), a diverter switch (to handle the load transfer), and a motor drive mechanism.
- Applications: Found in main power transformers at substations and industrial facilities with varying load demands
