By Kate Abnett BRUSSELS (Reuters) – Investments of more than half a trillion euros will be needed to modernise Europe’s energy grid this decade, if countries are to succeed in ramping up wind and solar power to break free from Russian gas, a draft EU document showed. The European Commission is set to publish next week a plan to “digitalise” Europe’s energy system, as well as laying out new emergency measures to tame sky-high gas prices and help cash-strapped energy firms this winter. The draft plan, seen by Reuters, said electricity grid investments of 584 billion euros are needed until 2030, …