Given:A 120/208V, 3 phase service is fed with a single size 500KCMil, copper conductor for each phase. The main circuit breaker is rated at 300 amps.A copper grounding electrode conductor from the main service panel to the cold water pipeline must be ___?

Given:A 120/208V, 3 phase service is fed with a single size 500KCMil, copper conductor for each phase. The main circuit breaker is rated at 300 amps.A copper grounding electrode conductor from the main service panel to the cold water pipeline must be ___?