Self and mutual impedances of a finite length gas-insulated transmission line (GIL)

Starting from three-dimensional integral Freedholm's equation of the second kind with weakly singular kernel we obtain two equations for the complex voltage drops in the phase conductor and the enclosure, respectively. Self and mutual impedances appearing in these equations are expressed in the form of integral relations for any current density distribution. In case of a single-phase GIL of finite length we introduce equations determining these impedances without taking into account skin and proximity effects as well as taking them into consideration. For the case of a three-phase GIL we work out an analytical numerical method of determination of self and mutual impedances of GIL, which takes into account also the so-called ‘outside proximity effect’. We also describe the research post consisting of a single-phase GIL with a return copper plate built in GTH&MT laboratory of GEC ALSTHOM T&D in Villeurbane.