Mats of insulating rubber must be provided for operators of live front switchboards where the voltage to ground exceeds what voltage?

Operators of live front switchboards must have insulating rubber mats in place when the voltage to ground exceeds 150 volts. This is a safety standard designed to protect the operators from electrical shock. The rationale behind this threshold is based on the increased risk of injury at voltages higher than this level.

At 150 volts and above, the potential for electrical shock becomes significant, and the insulating properties of rubber mats serve to reduce this risk by providing a barrier between the operator and the energized components. This safety measure is particularly crucial in environments where operators may be exposed to live electrical circuits, as it helps to ensure their protection while they work.

The choices reflecting lower voltages do not require insulating mats because the associated risk of serious electrical shock is considered manageable under those conditions. However, once the threshold of 150 volts is exceeded, additional precautions, like the use of rubber mats, are necessary to maintain safety standards in electrical work environments.