Feb 10 - Microsoft is exploring using superconducting power lines in its data centers, which could potentially accelerate its massive U.S. build-out of the server warehouses by making them more energy-efficient, the company said on Tuesday. Big Tech's effort to swiftly build and electrify giant data centers across the U.S. to expand technologies like artificial intelligence has been slowed by the country's aging power system and constrained electricity supplies. Microsoft said recent tests of