On-site measurements for voltage unbalance studies associated with the AC railway operation: Objectives, methodology and monitoring results

Monitoring voltage and currents in electric power systems can provide valuable information about the performance of the network as a whole and/or locally for specific areas and consumers. Furthermore, measurement data can be of great assistance to the validation and assessment of simulation models developed for power system studies. Lately, the noticeable increase of non-conventional types of loads, such as the AC railway, has raised concerns regarding the secure operation of power transmission networks. This renders the monitoring and reporting of various aspects of system's power quality even more necessary. For the Danish transmission grid, in particular, the relevance of voltage unbalance with regards to traction loads has been augmented since the decision to expand the electric railway. Towards this direction, and on the occasion of a newly built electrified line, voltage unbalance measurements were carried out and are presented in this paper. The information from the extracted data is intended to be used at a later stage for voltage unbalance studies associated with the Danish AC railway operation.