At present, studies are promoted on the standard for high-voltage test techniques for UHV-class equipment. In the lightning impulse voltage test, discussions are made on the use of the relative overshoot magnitude evaluation method and waveform conversion method with k-factor which were adopted in the IEC 60060-1. However, since issues still remain in adopting these methods to UHV-class equipment, the present paper examined techniques which can evaluate the lightning impulse test waveforms reasonably. As a result, two techniques were newly established. The one is base curve extraction method and the other is new k-factor suitable for UHV-class equipment.