Back-to-back energization of a 60kV cable network - inrush currents phenomenon

On November 2008 the Danish government decided that all Danish transmission lines with a rated voltage equal to and below 150kV must be put underground, in order to reduce the visual pollution caused by Overhead Lines. This decision will lead to a massive use of underground cables in the Danish Network, and force a change in the approach used until now when planning, analyzing and operating electrical power systems. One problem that might arise is the energization of cables in parallel, as this operation may originate high inrush currents, which represent a risk to the circuit breakers connected to the cables. The Danish utility ENV plans to install a new cable on its 60kV network, which will be installed in parallel with other cables already installed in the network. This paper summarizes the study made to calculate the inrush currents during the cable´s energization, and its importance to the purchase of a new circuit breaker for the cable. A theoretical background of this phenomenon is also presented.