Three Washington banks have concluded a $8.6 million loan to an electric utility in Brazil - an international loan unusual for banks in this area.

James McComas, senior vice president of the riggs National Bank of Washington, one of the lenders, said the Brazilian financing was small enough that Washington banks could put it together here rather than requiring the foreign agency to go to banks in New York, as is normal.

The National Bank of Washington which arranged the loan, and Riggs each provided 15 percent of the loan, while the Export-Import Banks of the United States lent 55 percent. The First International Bank in Houston lent the remaining 15 percent.

The loan was made to Centrais Electricas do Sul do Brazil (Electrosul) to buy from Westinghouse two generators and auxiliary equipment to be installed in hydroelectric projects being constructed in Salto Santiago and Salto Osorio. The loan is guaranteed by the Republican of Brazil.

Attending a ceremony to sign the loan on Friday were McComas; Walton Sanderson, president of the National Bank of Washington: H.K. Allen, first vice president of the Export-Import Bank: Eduardo Aguirre Jr., vice president of the First International Bank; J.B. Pinheiro, ambassador from Brazil, and Fernando Marcondes, financial manager of Eletrosul.

Eletrosul is one of four subsidiary operating companies of Centrais Eletricas Brassileiras (Eletrobras), a government-owned holding company for Brazil's national power sector. Electrosul generates electricity for state electric companies in the southern most area of Brazil.