Shieled cable requirements

[posttoasties]

It is my understanding that under NEC requirements you must use shielded cable when running above 2400V. Someone also told me that if you have a transformer that has a voltage tap above 2400V you must use shielded cable whether or not you are using the tap or not. For example if I have a transformer that has a 2000V tap and 5000V tap, they claim that I need to run shielded cable coming out of the transformer no matter which tap I am using because the transformer has at least one tap that is rated greater than 2400V. I have not been able to find any code to support this claim and was hoping someone had some information, thanks.

 

[dcspector]

All I know is 400.31(B)

 

[RUWired]

. I have not been able to find any code to support this claim and was hoping someone had some information, thanks.

Try 310.6

310.6 Shielding
Solid dielectric insulated conductors operated above 2000 volts in permanent installations shall have ozone-resistant insulation and shall be shielded. All metallic insulation shields shall be grounded through an effective grounding path meeting the requirements of 250.4(A)(5) or 250.4(B)(4). Shielding shall be for the purpose of confining the voltage stresses to the insulation.
Exception: Nonshielded insulated conductors listed by a qualified testing laboratory shall be permitted for use up to 2400 volts under the following conditions:
(a) Conductors shall have insulation resistant to electric discharge and surface tracking, or the insulated conductor(s) shall be covered with a material resistant to ozone, electric discharge, and surface tracking.
(b) Where used in wet locations, the insulated conductor(s) shall have an overall nonmetallic jacket or a continuous metallic sheath.
(c) Insulation and jacket thicknesses shall be in accordance with Table 310.63.