OHST Practice Exam

A double insulated hand tool does not require an equipment grounding conductor because it is designed with insulation that protects against electrical shock. This type of equipment is constructed to prevent any live parts from being exposed, minimizing the risk of electrical faults that could lead to shock or injury. The design typically involves two layers of insulation or isolation between the user and any live electrical components. As a result, these tools are considered to be inherently safe, reducing the need for an additional grounding conductor.

In contrast, the other options all involve scenarios where grounding is necessary to ensure safety. For instance, equipment connected to a double revers delta system or a wye connected transformer might require grounding to manage fault currents safely. Additionally, circuits protected with circuit breakers still necessitate grounding for effective fault protection, ensuring that any accidental leakage current is directed safely to the ground.