On electric fields in belted cables and 3-phase gas insulated cables

Abstract

The electric field distribution in Belted Cables and 3-phase gas insulated cables (GIC) enclosed in a common ground enclosure is analyzed and presented in this paper. The electric fields in this type of GIC are analogous to those of 3-phase belted cables. Unlike 3-phase screened cables, the stress distribution in belted cables is not radial. With time varying voltages (power frequency voltage variations; quasi-static voltages) the stress distribution in the cable insulation changes, not being radial. The electric stress distribution is expected to show systematic, revolving effect. This revolving effect is important as the location of maximum stresses keep on shifting. Also, as a secondary effect, the revolving e-field results into electric-field-winds which can add to the particle movements in the gas insulated cables. The literature acknowledges that particle movements in the gas insulated system can have deleterious effect on the over all system insulation strength; which partly get impetus from e-field-winds. The stresses in such a cable are analyzed using open source software Finite Element Method Magnetics (FEMM). The results presented show that the field distribution over a cycle (of 50 Hz) at discrete time intervals are thought to be having a great educational value, giving a feel of electric field variation in (i) belted cables and (ii) GIC with common enclosure. The computed results of electric stress and potential distribution using FEMM are compared with available results based on CSM models to validate the present results where ever possible.