Complex sentence: Protection relays respond to such conditions as over-current, over-voltage, reverse power flow, over- and under-frequency, and even distance relays that would trip for faults up to a certain distance away from a substation but not beyond that point.
Split into simpler sentences: Protection relays respond to such conditions as over-current, over-voltage, reverse power flow, over- and under-frequency. Distance relays trip for faults up to a certain distance away from a substation but not beyond that point.