A power line from West Virginia to Connecticut could save New Englanders more than $2 billion over three decades, preserve up to 1,000 coal-mining jobs in the Midwest and reduce sulfur emissions by a half-million tons a year, according to an economic study released yesterday by New Hampshire Gov. John H. Sununu (R).

The study, prepared by the Center for Clean Air Policy, said that "the time appears ripe" for a major power transfer proposed two years ago by Sununu and West Virginia Gov. Arch A. Moore Jr. (R). The Washington-based research center was founded by a group of state governors in 1985.

Sununu, who outlined the proposal at a news conference here, said the 540-mile power line would carry 1,000 megawatts of electricity from the American Electric Power Co.'s coal-fired plants in Ohio and West Virginia, replacing expensive oil- and gas-generated electricity in New England.

In return, New England would pay for the power line and other transfer equipment, install flue-gas scrubbers on midwestern power plants generating up to 2,600 megawatts, and agree to build 1,200 megawatts of replacement generating capacity in West Virginia in the year 2000. New England customers would still save between $2 billion and $3.2 billion over 30 years.

The study said that the Midwest would primarily benefit through the protection of its high-sulfur coal industry. Most legislation to curb acid rain, which stems chiefly from sulfur emissions, is aimed at midwestern power plants. According to the study, the scrubbers paid for by New England would avert a switch to low-sulfur coal at the chosen plants and reduce sulfur emissions by 500,000 tons a year at no cost to midwestern power customers.

For purposes of estimating cost, the study assumed that the scrubbers would be installed on the 2,600-megawatt John Gavin plant in Ohio, the cheapest plant in the AEP system to retrofit. In 1980, the Gavin plant emitted about 376,000 tons of sulfur dioxide. The study did not explain how reductions of 500,000 tons a year could be expected.

The study acknowledged that finding a route for the power line would involve "significant political obstacles." About 80 miles of the line would require new right-of-way from West Virginia to Johnstown, Pa.; the rest would follow existing routes through Pennsylvania, New York and New Jersey.

"Constructing the line so that relatively inexpensive midwestern electricity might also be sold in these states is one option which might help facilitate their approval," it said.

The study also acknowledged that importing hydropower from Canada would be cheaper than transfering it from the Midwest. New England states have contracted to buy about 2,400 megawatts of hydropower from Canada by the year 2000.

But it concluded that Hydro Quebec, the main exporting utility, will "not be able to expand exports rapidly enough" to make a power line from West Virginia uneconomical.

Sununu, a former utility consultant, said New England's rising power demands will require more than Canada can supply. "This is not an alternative to purchases from Canada, it is in addition to those purchases," he said. "New England's problems go well beyond what we can get from Canada."