Which device is considered a primary safety device in electrical systems?

A safety-operated switch is considered a primary safety device in electrical systems because it is designed to ensure safe operation by allowing the circuit to be manually or automatically opened in the event of a fault condition. This type of switch provides critical control over electrical circuits, significantly reducing the risk of electric shock or fire by ensuring that the circuit can be safely interrupted when necessary.

In contrast, other devices listed serve specific purposes within the electrical system. For instance, an automatic circuit breaker is primarily used for overload protection and to reset automatically after a fault is cleared, but it may not provide the same level of manual control that a safety-operated switch does. A ground fault interrupter protects against ground faults by quickly disconnecting power, but still relies on the presence of an intact circuit to function effectively. A fusible link provides a type of overcurrent protection that operates by melting and breaking the circuit when excessive current flows, but it needs to be replaced after activation and may not provide immediate operator control.

Thus, the safety-operated switch stands out as a fundamental device in ensuring safe electrical operations, making it a critical component in the design of safe electrical systems.