Restraining devices to counter the migration of HV cables in duct

This paper deals with the development, testing and installation of special devices on Hydro-Quebec's underground high-voltage transmission system which limit the displacement of cables installed in individual ducts. The devices are installed in manholes at the exit and/or entrance to the cable duct. The principle of two inverted cones is used to create a progressive restraining force applied to an axially-shifting cable. Several laboratory cycling tests were used to validate the performance of such a solution before its use on a 120 kV line.