Kai Hansen left Helloween in 1989 because, as he saw it, the band was straying from its roots in high-speed yet melodic, British-derived metal.
His refusal to bow to trends and stick to the style he clearly loves is admirable, but on the other hand, it doesn't allow for much growth or evolution.
Power Plant is more of the same from Gamma Ray, inarguably well done, but hard to differentiate from their many other albums in this particular metal style.