For circuits up to 5,000 volts, under what restrictive condition can non-shielded cables be used?

Using non-shielded cables in circuits up to 5,000 volts is permissible under specific guidelines, particularly when replacing an existing installation. This is because the existing infrastructure may have been designed and assessed to operate safely with non-shielded cables, making it acceptable to maintain consistency in the type of cabling used during replacement.

In the context of electrical safety, regulations often prioritize maintaining the same standards as previously established installations, assuming they complied with codes and best practices when first installed. This makes it crucial to justify the continued use of non-shielded cables based on their historical reliability in that specific application.

Other options may suggest conditions like newness or specific item types, but these do not address the ongoing need for safety and functionality in existing setups, which is a primary concern in electrical installations. Similarly, while insulation is important, merely having minimal insulation does not necessarily ensure safe operation, thus it is not a valid standalone condition for using non-shielded cables in any circuit.