Clarification Shielded or non shielded 5KV cable

[bilwei]

We have a 4160 volt motor that we are going to replace the feeder wire. According local plant knowledge - supposed operating voltage is; Phase to phase is 4160 volts, phase to ground is 2400 volts. We cannot confirm the actual voltage at this point. The existing wire is non shielded. In applying the NEC 310.6 for shielded and non shielded cable; I am some what confused. Do I apply article 310.6 based upon the phase to phase voltage or phase to ground voltage? If I divide 4160 by the square root of 3 to get the phase to ground voltage it equals 2401.77. Acception to 310.6 allows non shieled cable up to 2400 volts. So do I use shielded or non shielded cable?

 

[K8MHZ]

We have a 4160 volt motor that we are going to replace the feeder wire. According local plant knowledge - supposed operating voltage is; Phase to phase is 4160 volts, phase to ground is 2400 volts. We cannot confirm the actual voltage at this point. The existing wire is non shielded. In applying the NEC 310.6 for shielded and non shielded cable; I am some what confused. Do I apply article 310.6 based upon the phase to phase voltage or phase to ground voltage? If I divide 4160 by the square root of 3 to get the phase to ground voltage it equals 2401.77. Acception to 310.6 allows non shieled cable up to 2400 volts. So do I use shielded or non shielded cable?

Hmm....

That section starts out, 'Solid dielectric insulated conductors operated above 2000 volts.....'

So...does that not apply to stranded conductors????

 

[K8MHZ]

So far, the only conductor type I could find for over 2001 volts is Type MV, Article 328. It also specifies solid conductors.

I have pulled lots of large (350) 5000 volt cable and it was all stranded and all shielded. So, was that not Type MV???

 

[K8MHZ]

Oh, and the voltage you need to consider (from Article 100) is the greatest rms difference of potential between any two circuit conductors, so the attempt at the 2400 volt exemption would be moot. The voltage of your circuit is 4160.

 

[don_resqcapt19]

Guys, it doesn't say the conductors are solid...it says it has a "solid dielectric", that is the insulation is solid.

 

[don_resqcapt19]

In older codes the non-shield cables were permitted for use in dry locations. There has been some changes in this section for the 2011 code that will permit the use of non-shielded cables for 5kV systems in some cases.

(E) Shielding.​

Non-shielded, ozone-resistant insulated conductors with a maximum phase-to-phase voltage of 5000 volts shall be permitted in Type MC cables in industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation. For other establishments, 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 connected to a grounding electrode conductor, a grounding busbar, an equipment grounding conductor, or a grounding electrode.​

There is also a new Exception #2.

Exception No. 2: Nonshielded insulated conductors listed by a qualified testing laboratory shall be permitted for use up to 5000 volts to replace existing nonshielded conductors

on existing equipment in industrial establishments only, under the following conditions:
(a) Where the condition of maintenance and supervision ensures that only qualified personnel install and service the installation.
(b) 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.
(c) Where used in wet locations, the insulated conductor(s) shall have an overall nonmetallic jacket or a continuous metallic sheath.​

(d) Insulation and jacket thicknesses shall be in accordance with Table 310.13(D).


Informational Note: Relocation or replacement of equipment may not comply with the term existing as related to this exception.​

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[bilwei]

Thanks for the input it is always enlightening. Shielded cable it is. Have a good day folks.