MV cable in LV Duct Bank 2

[mikeengurs]

We have a situation where we have to route MV (4160v) cable in a LV duct Bank. Routing will involve Man Holes where LV and MV will be exiting PVC conduits and entering others as they head to their destination. MV cables are all shielded, with shields grounded on both sides. My question is, when MV cables exit PVC duct bank conduits (in destination and/or Man Holes), Per NEC, do they need to be routed in conduits so that they are separated from LV cables? Do they have to be grounded? Thanks in advance!

 

[Elecband]

I am not aware of NEC much. But it is a good practice to physically separate cables of different voltages. You mentioned MV cable shields are grounded.

 

[hdp]

Per the 2011 version of the NEC, Article 300.3C(2)(c) Over 600V...
"In manholes, if the conductors of each system are permanently and effectively separated from the conductors of the other systems and securely fastened to racks, insulators, or other approved supports, conductors of different voltage ratings shall be permitted.

Conductors having nonshielded insulation and operating at different voltage levels shall not occupy the same enclosure, cable or raceway."

This section specifically applies to conductors over 600V sharing an occupancy with conductors rated at 600V or less.

 

[mikeengurs]

Thanks a lot hdp, and Elecband!

 

[7anoter4]

According to NEC 300.37 "Aboveground Wiring Methods" a conduit has to protect the cable above the Ground.
According to NEC 300.50 C the conduit has to protect the cable up to 2.5m above the Ground.
300.3 C (2) c and d:
(c) Excitation, control, relay, and ammeter conductors
used in connection with any individual motor or starter
shall be permitted to occupy the same enclosure as the
motor-circuit conductors.
(d) In motors, switchgear and control assemblies, and
similar equipment, conductors of different voltage ratings
shall be permitted.
That means you may use the same conduit for main MV cable and LV heater or RTD or bearing thermocouple.
But I think if the distance from manhole to supplied equipment[motor, transformer or switchgear] it is more than 20 ft.[6 m]
it is better to separate the instrument or control cable in another metallic conduit.
If the conduit it is a metallic conduit [steel rigid conduit or else ] according to NEC 250.11(5) it has to be grounded.