Secondary protection is typically required for a 3-phase transformer rated 600 volts or less to comply with which sections?

Secondary protection is typically required for a 3-phase transformer rated 600 volts or less to comply with which sections?

• A. 240.21/ 408.36
• B. 240.21/ 408.35
• C. 240.20/ 408.36
• D. 240.22/ 408.37

Answer: (A)

Secondary protection for a three-phase transformer rated at 600 volts or less is addressed by combining the general rules for overcurrent protection with the specific requirement that protection be provided on the transformer's secondary side. The general overcurrent protection framework is found in the section that covers how overcurrent devices are sized and applied to conductors. The transformer-specific requirement, which mandates protection on the transformer’s secondary when it feeds a panel or similar load, is in the section dedicated to transformer and panelboard protection. Put together, these two sections establish that, for a transformer of this size, there must be secondary protection in place and indicate where to find the exact requirements. This pairing is why the correct answer points to the general overcurrent protection section along with the transformer secondary protection section. The other pairings reference sections that deal with different topics or aspects of protection and do not specifically address the transformer secondary protection requirement for a 3-phase transformer of this rating.

Secondary protection for a three-phase transformer rated at 600 volts or less is addressed by combining the general rules for overcurrent protection with the specific requirement that protection be provided on the transformer's secondary side. The general overcurrent protection framework is found in the section that covers how overcurrent devices are sized and applied to conductors. The transformer-specific requirement, which mandates protection on the transformer’s secondary when it feeds a panel or similar load, is in the section dedicated to transformer and panelboard protection. Put together, these two sections establish that, for a transformer of this size, there must be secondary protection in place and indicate where to find the exact requirements.

This pairing is why the correct answer points to the general overcurrent protection section along with the transformer secondary protection section. The other pairings reference sections that deal with different topics or aspects of protection and do not specifically address the transformer secondary protection requirement for a 3-phase transformer of this rating.