 FIVE ENERGY companies have joined forces to plan a power cable of between 1,200 and 2,000 megawatts to connect Scotland and Norway by 2020.  Britain's Scottish and Southern Energy (SSE), Norway's agder Energi, E-CO and Lyse, and the Swedish company Vattenfall have created NorthConnect to study laying an underwater power interconnector between Scotland and Norway. The Scottish European Green Energy Centre - an not-for-profit organisation which supports renewable energy projects - has contributed Euro 50,000 (?43,000) to find the best route.  Sweden's Vattenfall said the cable will allow the two regions to link Norway's flexible hydroelectricity production with Scotland's intermittent wind power and help reduce reliance on fossil fuels.  "Scotland and Norway have rich and diverse natural resources from which to produce large amounts of electricity, and an interconnector could allow the potential of those complementary resources to be fulfilled," SSE's chief executive Ian Marchant said.  Britain's power market is connected to France and Ireland; a new 1,000 megawatt cable to the Netherlands will open on 1 april.