The Abu Dhabi Investment Authority (ADIA) is taking a 16.7% stake in a UK energy supplier.
SSE said it was selling the stake in Scotia Gas Networks (SGN) to ADIA for £621m (€694.7m).
The deal is expected to complete this month.
SSE will keep a 33.3% equity stake in SGN, which supplies gas to 6m properties in Scotland and the south of England.
A 50% stake in SGN was taken by SSE in 2005 for £505m.
SSE said that, following completion of the sale, SSE would have an ownership interest in five economically regulated energy networks with an estimated total value of more than £7bn.
A greater proportion of institutional investors are active in infrastructure, and most plan to raise allocations, according to recent research by IPE and IPE Real Estate.
The latest IPE Institutional Infrastructure Survey, launched last week in London, also suggests most investors no longer perceive the asset class to be expensive.