DC Components in the AC Networks Containing AC/DC Hybrid Transmission Lines

The use of hybrid AC/DC overhead transmission lines can help to increase the transport capacity of power lines. But the spatial proximity of DC and AC power circuits in the same right of way leads to the presence of additional DC components in the currents and voltages of the AC line. One of known effects caused by the presence of DC components in the AC networks is the DC saturation of transformers connected to the AC lines. The performance of power and instrument transformers under the influence of DC components may be altered. The influence of DC components on voltage and current transformers for a new planned AC/DC hybrid transmission line is considered in the paper. It is shown that the standard instrument transformers used in the AC power circuits are not significantly affected by the DC components caused by the operation of the DC line. The method for the estimation of the influence of the DC line operation on the instrtunent transformers in the AC power line is considered in the paper.