(Reuters) -German power utility RWE and U.S. investor Apollo Global Management ( APO ) said on Wednesday that they successfully closed their partnership transaction for a joint venture to fund power grid upgrades in Germany.

The new JV will help fund the expansion of the electricity transmission grid, with Apollo providing 3.2 billion euros ($3.7 billion) in financing.

The JV holds RWE's 25.1% stake in Amprion, one of four power grid operators in the country.

"RWE retains operational control of the JV and continues to manage the Amprion stake while consolidating the joint venture in its financial statements," RWE said in a statement.

Germany's electricity grid needs large investments to keep up with the growth of renewable energy and to help with the transition away from fossil fuels.

($1 = 0.8639 euros)

(Reporting by Simon Ferdinand Eibach, editing by Thomas Seythal)