An electrical testing company will begin an inspection tomorrow of all 57 PCB transformers in Smithsonian Institution buildings to determine what repairs are needed to bring them to federal standards, Smithsonian officials said yesterday.

Smithsonian spokesman Alvin Rosenfeld said the first steps toward meeting the Environmental Protection Agency's orders to clean up and repair transformers leaking the cancer-causing chemical were completed yesterday as crews "mopped up" areas contaminated by the leaks.

After an emergency inspection Friday, the EPA gave the Smithsonian 48 hours to clean up the leaks and begin repairs of PCB transformers in the Museum of Natural History, Museum of American History and the National Portrait Gallery/Museum of American Art. The EPA said none of the polychlorinated biphenyl (PCB) leaks are in areas that are accessible to the public.

"We have initiated action according to the definition of EPA," Rosenfeld said about 24 hours after the agency released its report. "We have asked Substation Test Co. of Forestville to send a representative on Monday at 9 a.m. to walk through the entire electrical setup. All 57 transformers containing PCBs will be reinspected by Substation."

Based on that inspection, Rosenfeld said, a schedule for repairs will be determined. No estimates of the cost or the time it will take to make repairs were available yesterday. Other Smithsonian buildings with PCB transformers are the National Air and Space Museum, the Smithsonian castle, the Freer Gallery of Art and the Arts and Industry Building.

It is not known how repairs will affect the operations of the various museums, which attract a total of about 30 million visitors annually. Because many of the transformer repairs may cause the shutdown of power to portions of the buildings, Rosenfeld said, "We will have to establish a repair schedule" taking into consideration "the safety of the collections and the safety of people."

Smithsonian officials have traditionally opposed closing exhibition areas in the museums to allow for similar work. Testifying earlier this year before the Interior subcommittee of the House Appropriations Committee, Smithsonian officials said they were not asking for all the money they would need for advanced fire protection equipment because its installation would mean closing down large portions of the museums.

Most of the Smithsonian's PCB transformers were inspected earlier this year by Substation Test, and leaks were found in about two-thirds of them. The 23 PCB transformers in the Museum of American History are generally those in the worst condition, according to Substation's inspection report.

Leaks were found at gaskets and along welding seams in 16 of the museum's transformers, the report said. The leaks along welds are considered the most difficult and costly to repair, according to officials, because the PCB fluid must be drained from the transformer before resoldering to prevent burning PCBs, which give off other chemicals, including dioxins that are up to 1,000 times as deadly as PCBs.

The Hazardous Materials Unit of the D.C. Fire Department was seeking to determine the location of PCB transformers in the Smithsonian buildings June 27 when members discovered evidence of the leaks. Later in the visit, the firefighters were asked to leave the Museum of American History because they had not cleared the tour through Smithsonian fire prevention officials.

Fire Department spokesman Ray Alfred has said that the extreme dangers presented in fighting blazes involving PCBs include "the possibility of liver damage, the possibility of sterility, the possibility of birth defects and the possibility of cancer." He said firefighters would enter a building only to make rescues if there were a PCB blaze.

Because of the danger presented by fires in PCB transformers, the EPA last week issued new regulations that call for the phase-out of high-voltage PCB transformers in commercial and public buildings by 1990 and for enhanced electrical protection for lower-voltage PCB transformers.

The Substation report submitted in June to the Smithsonian recommended the replacement of 35 low-voltage circuit breakers in the Museum of American History, the Smithsonian castle and the Arts and Industry Building after 10 failed inspection.

William G. Welles, assistant director of the Smithsonian's Office of Plant Services, defended the electrical system, saying that some defects noted by Substation included flag signals that do not work properly and circuit breakers that trip too early. "The circuit breakers are protected downstream by other breakers," Welles said.

The Substation report states that six of the low-voltage circuit breakers in American History would not "trip," or interrupt the flow of electrical current, and noted that a breaker in Electrical Vaults 1 & 2 "is not safe for service."

"Should one serious fault occur on a circuit whose breaker trip protection is not functioning, the ensuing fire and smoke damage could be extensive," Substation's report said.

Three "bus bars," or high-voltage disconnection switches, in the Museum of American History are rusted in the closed position that permits electricity to flow through; they cannot be operated manually to cut off the current, according to Substation.

None of these defects has been corrected, according to sources familiar with the Smithsonian's electrical plant.