Boston Edison last week entered a suit in the state Supreme Judicial Court to overturn a city agency's approval last month of Harvard's $110 million Medical Area power plant project.

The Boston Redevelopment Authority (BRA) originally approved the project two years ago, but inadequacies in the plan--in engineering and environment quality considerations--led to a set of plan modifications that the BRA approved October 6.

Boston Edison argues in its suit that the modifications in the plan were fundamental change, and that the BRA should have followed the more time-consuming path of considering the modified plans as a completely new project.

If the BRA had examined the modified plans as representing a fundamental change in the power project, it might not have approved the project, it might not have approved the proved, John J. Murphy, public information director for Boston Edison, said yesterday.

Plan modifications included increased controls on air pollution, provisions for better backup equipment in case of failure, and an 85 per cent increase in the ground space that the plant will occupy.

Power Structure

Edward Lashman, University director of external projects, said yesterday the changes are not fundmental because the purpose of the construction project, to provide power, has not changed.

Boston Edison stands to lose about $4.5 million in electricity sales if the plant, now under construction, actually goes into service.

The Medical Area Total Energy Plant, as it is called is designed to provide steam, chilled water and electricity at a total savings of almost $2 million per year to the Medical School, affiliated hospitals and other Med Area institutions.

But Boston Edison has sharply contested Harvard planners' projections of cost savings.

In January 1976, after the BRA issued its approval of the original project plans, Boston Edison filed a suit claiming that the project did not constitute an urban renewal project for "public use and benefit."

The Suffolk Superior Court rejected the charges last year, but Boston Edison appealed the case to the state Supreme Judicial Court, which has not yet made any decision on the appeal.

Boston Edison's present suit also aruges that the decision of the BRA board was not valid because four of five board members are serving beyond the time limit of their original appointments, and the board's autonomy is undermined--so it is possible for Boston Mayor Kevin H. White to remove them at any time.

Charles Speliotis, counsel to the BRA, said yesterday the law setting up the board, states simply that board members shall serve until a successor is appointed.