General Electric Co. yesterday announced it will acquire control of Kidder, Peabody & Co., Wall Street's 15th-largest brokerage firm, in a major expansion of GE's position in the financial services sector.

Although no price was announced, sources said GE will pay about $600 million in cash for 80 percent of Kidder Peabody, a privately held firm. Kidder Peabody's partners and future partners will own the remaining 20 percent, with the goal of retaining the kind of financial-compensation arrangements traditional in investment banking, the company's joint announcement said. The agreement was reached yesterday evening after a full day of negotiations. A formal announcement was scheduled for today.

The acquisition will take GE another long step toward an increasing concentration in the services and technology sectors, away from its historic base as a manufacturer of appliances and consumer electronics products.

In 1980, half of GE's earnings came from its basic manufacturing business. With the completion of the pending $6.2 billion acquisition of RCA Corp., anticipated later this year, 80 percent of GE's earnings will come from services and technology businesses.

Kidder Peabody will be added to a financial services group within GE that is expected to be its most profitable sector this year. Its core is General Electric Credit Corp., a major lender and leasing firm and the only nonbank among the nation's top 10 financial firms. GE Credit, with more than $20 billion in assets, contributed $377 million to GE's 1985 profit of $2.34 billion. Kidder Peabody will join a GE Employers Reinsurance Corp. subsidiary as the third part of the financial services network.

Kidder Peabody's total capital of $464 million at the end of March put it in the mid-ranks of the investment banking industry, behind the multibillion-dollar firms led by Salo mon Bros., Shearson Lehman Bros. and Merrill Lynch, Pierce, Fenner & Smith. Kidder Peabody has more than 6,000 employes in 74 offices.

Ralph D. DeNunzio, president of Kidder Peabody, said the partnership with GE will assure the firm of greater access to capital to expand its investment banking activities.

Although Kidder Peabody will be linked to GE's Financial Services subsidiary, it will be backed by the corporation, whose 1985 revenue exceeded $28 billion. "We believe that we have created a powerful business combination" of GE's capital and financial services strengths with Kidder Peabody's expertise as a 121-year-old Wall Street firm, DeNunzio said in a statement made yesterday with Robert C. Wright, president of GE Financial Services.

Reports of the acquisition had little impact on GE stock, which fell 62 1/2 cents yesterday to $78.25 in trading on the New York Stock Exchange.

The Kidder Peabody acquisition will extend GE's reach in new directions, continuing the ambitious corporate reorganization undertaken by GE Chairman John F. Welch Jr.

Although GE has invested heavily in capital spending to modernize its basic manufacturing businesses, under Welch it has steered toward a future in defense contracting, technology-based businesses and financial services.

To protect the company against the threat of import competition, GE's goal is to expand a base in services such as GE Credit or RCA's National Broadcasting Co., where the odds against successful foreign- based challenges are high.