* Busch likely to get CEO job after being named deputy CEO
* Michael Sen named as head of standalone energy business
* Kaeser could leave Siemens by middle of next year
* Busch's technical background seen as positive
* (Adds union comments, sources)
By John Revill and Alexander Hübner
ZURICH, Sept 18 (Reuters) - Siemens promoted Chief Operating Officer Roland Busch to become deputy chief executive, it said on Wednesday, putting the 54-year-old in pole position to eventually replace Joe Kaeser as head of the German engineering group.
Siemens said its supervisory board would decide in the summer of next year on a successor to Kaeser, whose contract is due to run until early 2021.
In his new role, Busch will be responsible for implementing Siemens's 2020+ strategy which will see the trains-to-turbines maker focusing on factory automation and smart buildings as the core of its business.
"By appointing Roland Busch Deputy CEO, we're emphasizing the importance of the industrial digitalization of the company for the next generation," supervisory board Chairman Jim Hagemann Snabe said in a statement.
Siemens declined to say whether Busch's promotion meant he would automatically be named chief executive to replace Kaeser, who has led Siemens since 2013.
But the new role meant Busch, who is also Siemens chief technology officer, would now have time to prove he was capable of being CEO and if he was successful he would most likely get the top job, a source close to the board told Reuters.
He will take up his new role on Oct. 1.
Another source told Reuters that Busch, with his technical background, was the right man to lead Siemens, while it was possible that Kaeser could step down as early as the middle of next year.
It was highly unlikely that Kaeser's contract would be extended beyond January 2021, unless Busch proved to be a disaster, the source said.
"The new Siemens needs a technician again as boss," a board source told Reuters. "Busch would be the right solution.
"Kaeser has been Siemens' top salesman, negotiating large power plant and train contracts with politicians," the source added. "The future Siemens with smart infrastructure and digital industries no longer needs another type of CEO. You need a technician again."
Siemens on Wednesday also named managing board member Michael Sen as the head of its standalone gas and power business which it plans to list in September 2020.
The 50-year-old executive was the favorite for the job, Reuters wrote last week, and his appointment could remove him as a candidate to eventually replace Kaeser.
Siemens is spinning off the 30 billion euro ($33.18 billion) business after years of falling sales and profit as the rise of renewable power triggered a collapse in demand.
Sen will work as co-chief executive alongside Lisa Davis, the current head of gas and power business from Oct. 1. Davis will stay with the unit until January 2020, and stay with Siemens until her contract expires at the end of October 2020.
Snabe said Sen's experience in the power industry put him in a good position to lead the new company. Before returning to Siemens in 2017, Sen spent two years as chief financial officer at German utility E.On.
Union leaders said Sen was a suitable candidate for the energy company job, while Busch had the background to succeed as deputy chief executive of Siemens.
Busch, with his many years of experience as chief technology officer and strategist, has the best qualifications to develop Siemens in future, said Birgit Steinborn, chairwoman of the Siemens works council and first deputy chairwoman of Siemens's supervisory board. (Reporting by John Revill Editing by Edward Taylor and Lisa Shumaker)