Final answer:
The purpose of the safety or protective relay is to disconnect the generator's field circuit in the case of control unit failures, protecting the equipment from damage and preventing electrical hazards.
Step-by-step explanation:
The purpose of the safety or protective relay is to open the field circuit of the generator should a failure of the controlling units occur. This is an essential component in the power generation sector, in both residential and industrial applications, as its function safeguards the generator from potential damage due to system failures. The protective relay senses the fault conditions and performs the necessary action to break the circuit, thereby preventing the flow of current which could otherwise lead to equipment failure or electrical hazards.