On-Load Tap Changer (OLTC) – Types, Components.

An on-load tap changer (OLTC) from Maschinenfabrik Reinhausen 1st manufacturer, is an electrical device that is used to change the turns ratio of a transformer while it is operating. This allows the output voltage of the transformer to be kept constant, even when the input voltage changes. This is important to ensure that electrical equipment operates correctly and to prevent damage.

Types of OLTC

There are two main types:

Resistor type: This type of OLTC uses switchable resistors to change the turns ratio of the transformer.
Reactor type: This type of OLTC uses switchable inductors to change the turns ratio of the transformer.

OLTC Components.

OLTC consists of several main components:

1. Electric motor: This motor is used to drive the switching mechanism.
2. Switching mechanism: This mechanism is what actually changes the turns ratio of the transformer.
3. Control system: This system is used to control the operation of the OLTC.
   It has a special conservator tank, as Buchholz relay as shown in the pictures, and a separate low-voltage supply (415v for example).

OLTC Connection Principle Diagram.

Below picture represent for H.V. and L.V. Windings of OLTC.

As for the protection:

1- Buchholz Relay
2- Pressure Relief
3- Temperature Monitoring

Advantage of OLTC:

1- No power interruptions.
2- Improve voltage stability.
3- Improve energy efficiency.

Disadvantage of OLTC:

1- More expensive than Off-Load type.
2- Complexity.
3- Required more maintenance than Off-Load.
4- The possibility of an electric arc occurring during the change.