I am reinstalling an existing 220 V pool pump and have found that the equipment ground is a bare copper wire, not insulated as per current code requirements . A new home run to the panel is about 100 ' and not practical . Will introducing a gfi breaker in either a spa panel downstream from the main panel or a gfi breaker in the main panel bring the circuit up to standard ?
No, it wouldn't bring it up to standard
Pool pumps need to be grounded (using an insulated ground wire when the wiring run is in a corrosive environment) and GFCI protected, so adding the GFCI won't make up for a lack of grounding, unlike the situation with ungrounded receptacles, where GFCI protection can be used to bring an ungrounded receptacle up to Code.