Perpustakaan Digital ITB

Hybrid overhead lines are a promising concept to increase transmission capacity without building new overhead lines. By utilizing an existing double circuit AC overhead line and turning it into a bipolar AC-DC hybrid overhead line the power delivery capability can be increased significantly. However, mutual electromagnetic coupling will occur on hybrid OHL between the AC and DC circuits. Fundamentally, three coupling phenomena exist between the AC and DC conductors, which are capacitive, inductive and ohmic coupling. The coupling mechanisms will influence the conductor surface gradients. Therefore, capacitive and inductive coupling have the most dominant effects on the DC side. Ideally, the surface gradient on a DC circuit is of constant value over time. However, due to the coupling with the AC circuit, the field components at the DC circuit will be superimposed with an AC ripple. The changes of the surface gradient will affect the DC conductor’s corona phenomena, which often appear in foul weather conditions. Corona discharges cause losses and audible noise on DC circuits. In this master thesis, calculations regarding capacitive and inductive coupling affecting the surface gradients of the DC circuit of a fictive Austrian 420 kV and an Indonesian 500 kV hybrid OHL are presented. Furthermore, laboratory AN measurements were carried out to investigate how an AC ripple affects AN of a DC circuit on hybrid OHL. The results show that the AC ripple increases AN, especially for positive DC polarity, and that the effectiveness of noise reducing conductor surface treatments is reduced noticeably. Additionally, the gathered results were used to carry out AN and CL predictions for the analyzed OHL models.