Cable cars in hilly San Francisco are pulled along by an endless cable between the rails, which is driven by machinery in a centrally powerhouse
Cable cars in hilly San Francisco are pulled along by an endless cable between the rails, which are driven by machinery in a central powerhouse. 'Rails' is plural, so you use the plural verb 'are' for it. 'Central' is correct, rather than 'centrally'.
Cable cars in hilly San Francisco are pulled along by an endless cable between the rails, which is driven by machinery in(from) a central powerhouse If you use 'centrally', use should use 'located' along with it. Beacuse 'centrally' alone doesnot give you a complete sentence.
Cable cars in hilly San Francisco are pulled along by an endless cable between the rails, which is driven by machinery in a *central* powerhouse. As opposed to: The bank, grocery, and city hall are *centrally* located in the city.
Cable cars in hilly San Francisco are pulled along by an endless cable between the rails, which is driven by machinery in a central powerhouse Centrally is an adverb. You could use centrally located and the sentence would be fine. You want to use the word central which is an adjective. that describes powerhouse. Machinery is a noun and is fine.