What is the acceptable range for a voltage rating on switchboards?

The acceptable range for a voltage rating on switchboards is at least equal to the system voltage but can be higher to ensure safety and operational flexibility. This means that switchboards are designed to handle fluctuations in voltage and can accommodate situations where the system voltage may be subjected to surges. By having a voltage rating that is at least equal to the system voltage, the switchboard can operate effectively within the expected electrical conditions without risk of failure or hazards.

This also takes into consideration safety regulations and standards which emphasize that equipment must be rated for voltage levels that may exceed normal operating conditions. It allows for the possibility of future expansion or changes to the system that may require higher voltage ratings.

Regarding the other options, a rating that is only higher than the system voltage does not account for the need for equipment to match the nominal system voltage at a minimum. Similarly, stating that the rating should be exactly equal limits flexibility and does not account for potential voltage increases that may occur. Lastly, a rating lower than the system voltage poses a safety risk, as it can lead to equipment failure or unsafe operational conditions when voltage levels exceed the equipment's capabilities.