Is it necessary to install a grounded conductor at each service disconnecting means in an AC system operating over 1,000 volts?

In an AC system operating over 1,000 volts, it is indeed necessary to install a grounded conductor at each service disconnecting means. This requirement is rooted in safety regulations and standards aimed at ensuring that electrical systems can operate safely and reduce the risk of electric shock or equipment damage.

The presence of a grounded conductor provides a path for fault currents to safely return to the ground, which helps to clear faults through the operation of protective devices such as circuit breakers or fuses. This is vital in high-voltage systems where the risk of severe injury or equipment failure is significantly increased.

In addition, NEC (National Electrical Code) guidelines specifically stipulate requirements for grounding in various voltage systems, reinforcing the necessity to maintain consistent grounding practices throughout the electrical installation. The intent is to promote a uniform safety standard that protects both equipment and personnel effectively.

The other options do not align with the established codes and standards for high-voltage systems. They suggest circumstances where grounding might not be required, which is inconsistent with safety practices in electrical engineering.