power system vs power grid

power system and power grid both are nouns.

Word	Noun	Adjective	Verb	Adverb
power system	Yes	No	No	No
power grid	Yes	No	No	No

As nouns, power system and power grid are synonyms defined as:

power system and power grid: a system of high tension cables by which electrical power is distributed throughout a region

Other synonyms of power system include grid.

power system (noun)	power grid (noun)
a system of high tension cables by which electrical power is distributed throughout a region	a system of high tension cables by which electrical power is distributed throughout a region