According to the Wikipedia article on the Orlan space suit, all models of the suit after and including the Orlan-DM were designed to be self-sustaining:
The first Orlan suits were attached to the spacecraft by an umbilical tether that supplied power and communications links. The Orlan-DM, and all models since, were designed to be self-sustaining.
A spacewalker in an Orlan-DMA suit.
However, it seems that there are many advantages to using an umbilical - you could stay outside much longer, for one. Could the suit use an umbilical if needed?