For branch circuits over 150V to ground, the ground-fault protection shall not exceed _____ mA.

The correct answer is that for branch circuits over 150V to ground, the ground-fault protection shall not exceed 30 mA. This requirement is outlined in the National Electrical Code (NEC), specifically in NEC Article 680, which deals with the electrical safety of swimming pools, spas, and other similar installations.

Ground-fault protection is critical in these environments due to the increased risk of electric shock in wet conditions. A 30 mA limit for ground-fault protection is established as an appropriate threshold to effectively minimize the risk of severe injury or electrocution. It strikes a balance between adequate protection and minimizing unnecessary tripping of the circuit under normal conditions.

Design specifications, including the 30 mA requirement, are determined through safety considerations and the recognition of the unique hazards present in areas such as swimming pools and spas, where water can facilitate the conduction of electricity.

The other options represent values for ground-fault protection that may be appropriate in different contexts or for specific conditions, but they do not meet the NEC requirements for branch circuits operating above 150 volts to ground. Therefore, 30 mA is the specified maximum to ensure safety in these high-risk environments.