How does load tap changer work?

The purpose of a tap changer is to regulate the output voltage of a transformer. It does this by altering the number of turns in one winding and thereby changing the turns ratio of the transformer. An OLTC varies the transformer ratio while the transformer is energized and carrying load.

What is an on load tap changer?

On-load tap changer (OLTC), also known as On-circuit tap changer (OCTC), is a tap changer in applications where a supply interruption during a tap change is unacceptable, the transformer is often fitted with a more expensive and complex on load tap changing mechanism.

What happens when off-load tap changer operated on load?

If the Off-Load Tap Changer is used while the Transformer is energized, heavy sparking will take place which will damage the winding and insulation.

Why tap changer is connected on the HV side?

on HV side voltage is high but current is less but in the LV side voltage is less and current is high. If we connect Tap changer on the LV side then sparking will take place. The HV winding generally wound over LV winding hence it is easier to access the HV winding turns instead of LV winding.

How is tap changing achieved?

Tap changing may be achieved by three conditions. Explanation: Tapping can be done to either primary or secondary sides. The taps may be placed on the primary or secondary side which depends on construction. Tapping is thus so useful for various applications.

Why OLTCs on load tap changer are used?

On-load tap-changers (OLTCs) are indispensable in regulating power transformers used in electrical en- ergy networks and industrial applications. OLTCs enable voltage regulation and/or phase shifting by varying the transformer ratio under load without interruption.

Which side is tap changer used and why?

On load tap changer is preferred on High Voltage Side: Mostly the power transformer is used for both step up and step down action. In that, the power transformer’s turns are in the high voltage side is higher than the low voltage side.

What is difference between on load tap changer and off load tap changer?

In a dry-type transformer, the cooling phenomenon takes place mainly with natural air. Unlike in on-load tap changing where the arc quenching is limited by oil when the transformer is on-load, the tapping with an off-load tap changer is only carried out when the transformer is in OFF-Switch condition.

Why OLTCs on-load tap changer are used?

In which up the tap changing transformer is used?

Off load tap changing is normally provided in low power, low voltage transformers. It is the cheapest method of tap changing. The tap changing is done manually though hand wheel provided in the cover. In some transformers arrangements to change the taps by simply operating the mechanical switches are also provided.

Where is tap changer located?

Tap changer can be located on primary side or secondary side. However it will be placed on high voltage winding side.

What is the principle of on load tap changer?

Principle of On Load Tap Changer. A tap changer designed to operate while the Transformer is charged is called On Load Tap Changer (OLTC). On Load Tap Changer, OLTC is Make Before Break type which ensures that no sparking will take place while operating OLTC. On Load Tap Changer (OLTC) is used for short period or daily voltage regulation.

When to use a tap changer in a transformer?

On load tap changers are used to change the turns ratio without disconnecting the load from it. Tap changing can be done even when the transformer is delivering load. On load tap changers considerable increases the efficiency of the system.

How does an oil type tap changer work?

In oil-type OLTCs there are two types of switching principles used, the diverter which consists of an arcing switch and a tap selector, and the selector which consists of an arcing tap switch. Diverter type OLTCs change taps in two steps: “First, the next tap is pre-selected by the tap selector at no load (Figure

Why does a load changer have an impedance?

This results in short circuit between the adjacent taps. The short circuit current must be limited by including resistor or reactor. Hence all forms of on load tap changer are provided with an impedance to limit short circuit current during tap changing operation. The impedance may be resistance or a center tapped reactance.