Connection of the Dinorwic pumped storage station in Snowdonia to the 400 kV supergrid is to be made by two 400 kV cable circuits rather than by overhead lines because of the outstanding natural beauty of the area. The cables have 2500 mm2 copper conductors, oil-filled paper insulation and aluminium sheaths and will be cooled by circulating water in high density polyethylene pipes laid with the ca...