A federal judge has ordered officials of Maryland's beleaguered prison system to transfer 100 inmates to federal institutions, a move that gives the state more breathing space in its long-running efforts to end overcrowding.

Maryland has been under federal court orders since May 1978 to end what was turned unconstitutional overcrowding in its two largest prisons. But one of those facilities, the reception wing of the century-old Maryland Penitentiary in Baltimore, is still 320 inmates over capacity.

The order this week by U.S. District Court Judge Alexander Harvey for federal transfers appeared to come as a relief to state officials, including Gov. Harry Hughes, who said through a spokesman that this approach "enabled the state to meet the court requirements without jeopardizing public safety."

Two weeks ago Hughes had asserted that he was prepared to violate the court order against overcrowding by moving hundreds of inmates now in minimum security settings back to more secure prisons.

That assertion came in the wake of the resignation of the state's top prison official and Hughes' assessment that the system was plagued by mismanagement and the transfer of violent prisoners to minimum-security settings.

The prison system has been under siege for years in three lawsuits that ended with orders from the court or promises from the state to end overcrowding. In each case, however, the state has received numerous deadline extensions and still has failed to comply.

In Baltimore this week, Judge Harvey directed the state to identify for transfer 50 state inmates who are also facing federal prison terms and 50 others who would volunteer to serve part of their state sentences in federal facilities.

Harvey set no deadline for the transfers, but scheduled another hearing in the case for May 29.

Under Harvey's directive, the state would be required to pay federal authorities about $25 a day to house each inmate volunteer who did not have a federal sentence, according to Stephen Minnich, the Division of Correction overcrowding coordinator. That would add up to a tab of more than $37,000 a month for 50 volunteers.

Minnich said the state is preparing a list of prisoners with federal convictions and will seek other volunteers. But Minnich added that "it would be an administrative nightmare to scatter 100 people through the federal system."

Minnich said that Thomas Schmidt, the state's acting Secretary of Public Safety, is preparing a comprehensive plan to deal with the overcrowding problem.

Minnich said the plan is likely to include a program to transfer some minimum-security inmates back to more secure settings, the building of temporary facilities to house inmates and the conversion of some unused state space to prison housing.

The state is also looking to the June 1 opening of the long-awaited medium-security annex to the Maryland House of Correction at Jessup to ease the overcrowding situation. That prison will have 512 beds.

However, the state is also under orders to ease overcrowding at its medium-security institution in Hagerstown, which is now 310 inmates over capacity. In the federal lawsuit involving that institution, the judge has indicated that he is leaning strongly to finding the state in contempt of court if it does not comply by May 18, according to Minnich.

As to Judge Harvey's order in the penitentiary case, Richard Seligman, the lawyer representing the penitentiary inmates, said it was a "positive move. It will provide some relief, but I don't think it will accomplish the goal."