DC operated gas-insulated systems (GIS) play a key role in satisfying recent requirements of energy transmission. After energising, the initial electrostatic field is changing into the electric currents field, which is determined by conductivity processes based on charge carriers. Experimental results show the temperature-dependent effects of the changed field distribution under long-term DC stress and identify clear differences to calculations, which are solely based on conventional RC models. This work proves experimentally, what was exclusively calculated theoretically in literature so far: additional charge carriers, especially negative ions, accelerate the field transition after energising with DC.