OLTC dry type transformer can manually or automatically adjust the step voltage with non-power off which can meet the projects that have high requirement on voltage stability quality or frequency voltage fluctuation. Presently, the OLTC transformers are all step voltage regulation. For 10kV and 35kV, normally the adjusting range is -10%~+10% of rated voltage and generally, there are 9 steps. The adjusting range of voltage can also be designed according to customer requirement, but the maximum adjusting range is no more than 20%.

The differences between OLTC transformer with common transformer are mainly as followed:

1. The voltage adjusting taps from high-voltage coil shall be set according to voltage regulation range. The numbers of taps of OLTC transformer are more than common transformer.

2. Presently, the voltage regulation is realized through turns adjust so that there will be one on-load tap changer equipped to realize safe regulation.

3. The on-load tap changer is equipped with controller through which voltage regulation operation is realized which can be set in manual or automatic ways.