On-Load & De-Energised Tap-Changers (OLTC/DETC)

Standards: IEC 60214

Ratio regulation under load or off-circuit, vacuum/oil diverter options, motor drives and replacement gears.

On-Load Tap-Changer (OLTC)

Changes ratio under load; vacuum or oil diverter, motor-driven.

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De-Energised Tap-Changer (DETC)

Off-circuit ratio adjustment, rotary or linear, padlockable.

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Motor Drive Units

Drives, position transmitters and controllers for OLTCs.

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OLTC Oil Filter Units

Keeps diverter oil clean, extends maintenance intervals.

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Frequently asked

What is the difference between OLTC and DETC?

An on-load tap-changer (OLTC) changes the tap position under load without interrupting supply; a de-energised tap-changer (DETC) only changes ratio off-circuit.

What does a tap-changer do?

It steps the transformer turns ratio up or down to hold the secondary voltage within limits as the load and system voltage vary.

What is the most common tap-changer failure?

Contact and diverter wear — often detected by acetylene in the oil, which is why OLTC oil tests and condition monitoring are routine.

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