Grid officials warn of strain as the region competes with European countries for shipments of liquefied natural gasNew England power producers are preparing for potential strain on the grid this winter as a surge in natural-gas demand abroad threatens to reduce supplies they need to generate electricity. New England, which relies on natural-gas imports to bridge winter supply gaps, is now competing with European countries for shipments of liquefied natural gas, following Russia’s halt of most pipeline gas to the continent. Severe cold spells in the Northeast could reduce the amount of gas available to generate electricity as more of...