Overvoltage studies for the St. Lawrence river 500-kV DC cable crossing

An exclusive insulation coordination study has been conducted for the 500 kV DC cables that will be installed in a tunnel under the Saint Lawrence river. These cables will be part of the Radisson-Nicolet section of the Quebec-New England HVDC line. The authors provide an overview of the studies and the phenomena that will cause decisive overvoltage stresses on the cable insulation. The basic assumptions and the simulations of these phenomena with the Electromagnetic Transients Program (EMTP) are also discussed. Finally, the results of the overvoltage studies and the specified insulation levels for the DC cables are presented