D.C. People's Counsel Brian Lederer yesterday urged federal regulators to turn down a utility industry plan to sell electricity to the owners of the Three Mile Island nuclear plant at cutrate prices.

The industry plan would force customers in the District of Columbia and elsewhere to subsidize indirectly the disabled nuclear plant, Lederer told the Federal Energy Regulatory Commission.

FERC is considering a proposal by members of the Pennsylvania-New Jersey-Maryland power pool to sell electricity to General Public Utilities Corp. for 10 percent more than it costs to produce. The rate is substantially lower than PJM members usually charge each other under wholesale rates that are regulated by FERC.

Lederer contends giving a discount on wholesale power sales to GPU would set a precedent for the next nuclear accident.Since the Three Mile Island plant was shut down more than a year ago, GPU has had to buy about 40 percent of its electricty from other companies.

Much of the power has been purchased from Potomac Electric Power Co. and the other members of the PJM pool, who buy and sell electricity from each other, under a long-standing agreement.

Lederer complained yesterday that PJM companies already are giving GPU a $30-million-a-year break on its purchases. The power pool agreement, he explained, requires each company in the group to have enough generating capacity in service to supply a specified portion of its needs; if a company is not able to provide the proper share of its own needs, it is supposed to pay the other companies more for its power.

Even though the TMI reactors have been shut down for more than a year, the power pool still considers them "in service," so GPU does not have to pay the higher rate, Lederer said.