Final answer:
b) Circuit breaker. A circuit breaker senses and reduces abnormal current and voltage levels from fault conditions and transmits control signals to relays.
Step-by-step explanation:
The power system protection device that senses/reduces abnormal current and voltage levels from fault conditions and transmits control signals to relays is a circuit breaker.
Circuit breakers interrupt excessive currents to prevent thermal hazards and can be reset. They react much faster than fuses and are commonly used in electrical systems to protect equipment and prevent damage from fault conditions.
An example of a circuit breaker is a bimetallic strip that bends and breaks the electrical connection when overheated by an excessive current.