Is it permissible to install high voltage in rigid non metallic conduit in a tunnel?

Answer for USA, Canada and countries running a 60 Hz supply service.

For permanently installed equipment in tunnels I find no special limitation on what can be used. I take this to mean that high voltage conductors in rigid non metallic conduit may be installed in a tunnel if other provisions of the code are followed, such as using schedule 80 PVC when the conduit may be subject to physical damage.

As for mobile or portable equipment, non metallic raceways may not be used in tunnels.

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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.