Feasibility of DSR applications in transmission grid operation—Control of power flow and imbalanced voltage

•In meshed transmission networks the capacity of high voltage lines is underutilized.•DSRs can be used to push power toward high voltage lines.•Unsymmetrical operation of DSRs is more beneficial than symmetrical DSR operation.•Unsymmetrical operation of DSRs can reduce voltage imbalance at the receiving end.

Distributed Series Reactors (DSRs) can be used to control power flow to more fully utilize the capacity of a transmission network, delaying investment in new transmission lines. In this paper the IEEE 39 bus standard test system is modified to a 3-phase, unbalanced model consisting of 230 kV, 345 kV and 500 kV lines, where lines of different voltage run in parallel. This model is used to study load growth and the effect of adding DSRs to alleviate resulting overloads, and in particular to alleviate overloads on lines of different voltage running in parallel. The economic benefit of adding DSRs to the network is compared to the addition of new transmission lines in the network. In the second part of the paper the effect of unsymmetrical operation of DSRs on a single transmission line is studied and compared to the symmetrical operation of DSRs. It is found that unsymmetrical operation of DSRs is more economical. Finally the unsymmetrical operation of DSRs to reduce voltage imbalance in the network is considered.