Monitoring of 420 kV XLPE cable system in underground tunnel

This paper deals with continuous monitoring of components of a 400 kV XLPE cable system placed in an underground tunnel in South London. An advance concept to assess and monitor the condition of the insulation of cable system is described. Partial discharges are continuously monitored at all joints and terminations and at the same time the system performs measurement of oil pressure in 400 kV terminations as well as the condition of all sheath voltage limiters located in the joint bays. Special attention is given to the procedure of on-site acceptance of monitoring system and to the system maintenance strategy.