(Adds comment, updates prices)
MELBOURNE, Sept 7 (Reuters) - London copper slipped from three-year highs on Thursday as traders locked in profits ahead of the outcome of a European monetary policy meeting later in the day, however a brighter outlook for global manufacturing growth cushioned losses.
"Stronger than expected PMI numbers (both official and Caixin) are constructive to the copper demand outlook in China," said analyst Helen Lau of Hong Kong-based broker Argonaut.
Investment in China's power grid for the first seven months of 2017 has grown by 10 percent on the year, while production of air conditioners has increased at the fastest pace in years, up by 19 percent, Argonaut said.
"Only property investment and production of autos are slowing. So overall copper demand is still healthy in our view."
* LME COPPER: London Metal Exchange copper had edged down 0.5 percent to $6,871 a tonne by 0712 GMT, having closed flat in the previous session. Prices on Tuesday hit the highest since September 2014 at $6,970 a tonne amid a global expansion in manufacturing activity.
* A trader said that prices fell through key support at $6,880 a tonne, which soured sentiment and fueled selling.
* SHFE COPPER: Shanghai Futures Exchange copper slipped 0.7 percent to 52,720 yuan ($8,091) a tonne.
* ECB: European Central Bank policymakers hold a widely anticipated meeting later on Thursday, amid speculation the central bank wants to wind down its extraordinary bond-buying monetary stimulus soon.
* US POLICY: U.S. Federal Reserve Vice Chair Stanley Fischer, a veteran central banker, will step down from his position in mid-October, potentially accelerating President Donald Trump's opportunity to reshape the direction of the central bank.
* SHFE NICKEL: Lower trading fees for nickel and tin traded on the Shanghai Futures Exchange come into force on Thursday, which could boost trading volumes and add to volatility in the contracts.
* STEEL: Iron ore and steel were down more than 1 percent, suggesting that input materials zinc and nickel may come under pressure.
* LME REFORM: The London Metal Exchange is due to release the findings of a major reform plan later in the session that is expected to include a reduction in trading fees for short-dated trades.
* LME UPGRADE: The LME is also set to announce an upgrade to its electronic trading system after falling volumes and user complaints about outages and poor functionality.
* US ECONOMY: U.S. services sector activity accelerated in August amid strong gains in new orders and employment, suggesting that a slowdown in job growth last month was probably temporary.
* BAUXITE: China agreed on Wednesday to loan Guinea $20 billion over almost 20 years in exchange for concessions on bauxite, an ore of aluminum which the West African country has in abundance, the mines minister said.
* COMING UP: European Central Bank interest rate decision and news conference from 1145 GMT
Three month LME copper
Most active ShFE copper
Three month LME aluminum
Most active ShFE aluminum
Three month LME zinc
Most active ShFE zinc
Three month LME lead
Most active ShFE lead
Three month LME nickel
Most active ShFE nickel
Three month LME tin
Most active ShFE tin
ARBS ($1 = 6.5160 Chinese yuan renminbi)
(Reporting by Melanie Burton; Editing by Richard Pullin and Joseph Radford)