What is a requirement for electrical equipment installed in ungrounded systems?

Limiting voltage from lightning is a critical requirement for electrical equipment installed in ungrounded systems. This is essential because ungrounded systems operate without a direct connection to ground, which can increase the risk of voltage surges from external factors like lightning strikes. By requiring equipment that can mitigate these surges, the safety and functionality of the electrical system can be preserved, preventing potential damage to equipment and reducing risks of electrical shock or fire.

Other choices, such as creating a high-voltage output or including complex circuitry, do not directly relate to the specific safety needs of ungrounded systems. Moreover, the requirement that equipment be made from renewable materials is not standard for electrical installations, particularly with respect to grounding and bonding practices. Therefore, focusing on limiting voltage from lightning is integral to maintaining system integrity and safety in ungrounded electrical setups.