To ensure isolation of electrical equipment, which device provides a visible open point?

The correct answer, disconnect switches, are specifically designed to isolate electrical equipment from the power supply. They provide a visible open point between the power source and the electrical circuit, which is essential for maintenance and repair work.

These switches can be seen in their open position, indicating that the circuit is not energized, which enhances safety for personnel working on the equipment. This visibility ensures that workers can safely perform their tasks without the risk of electrocution or electrical hazards.

In contrast, circuit breakers are primarily protective devices that automatically shut off power in the event of a fault, but they do not always provide a visible open point and usually reset automatically once the issue is resolved. Arresters are used to protect equipment from voltage spikes, and relay protection systems monitor electrical parameters to act in case of faults, but neither of these options offers the clear, manual isolation feature that disconnect switches provide.