Moody's affirmed Amprion GmbH's A3 issuer rating and revised the outlook to negative from stable. Amprion is one of the four German electricity transmission network companies.

"The outlook change to negative from stable reflects Moody's expectation that Amprion's key credit metrics could fall below the rating agency's guidance for the existing A3 rating," Moody's said in a July 31 research note.

The rating agency sees Amprion's strong financial profile weakening on lower allowed equity return in the current 2019-2023 regulatory period and increasing leverage due to further increases in planned investments over the next decade.