cable depth 2

[vavanapoly]

hi every one i have a question about the HV and LT cables specifications
what is the standard depth for installation a HT and LT cables?
is there an equation to calculate that?
the HT cable voltages are 11 Kv 13.8Kv 33Kv and 400v ?
if there any site will help to understand that.

and always remember WHEN WORKING WITH ELECTRICITY SAFETY COMES FIRST
VAVANAPOLY

 

[alehman]

In the U.S., the National Electrical Code requires the following depths in inches:

up to 600V: direct bury=24, rigid metal conduit=6, plastic conduit=18
Under roads all depths must be at least 24.

up to 22kV: direct bury=30, rigid metal conduit=6, plastic conduit=18
up to 40kV: direct bury=36, rigid metal conduit=6, plastic conduit=24

These can be reduced by certain amounts if covered by concrete.

 

[mc5w]

Cinergy ( Cincinnati Energy ) requires primary distrubution lines to be buried with 36 inches ground cover over the TOP of the conduit or cable. The reasons for this are:

1. A possibility of upgrading to 19.92Y43.5 KV.

2. Secondary conductors can always be buried far enough above the primary conductors that hand digging around an existing padmount transformer is acceptable.

Remember, the National Electrical Code burial depth is to the TOP of the raceway or cable.

Mike Cole, mc5w@earthlink.net

 

[alehman]

36 inches minimum is a fairly common practice for primary voltages, even in conduit.

 

[cuky2000]

Underground cable depth could affect not only the cable ampacity but also the mechanical protection of the cable/duct bank assembly.

The ampacity of the cable is reduced with the burry depth. On the other hand, as deeper the cable is installed the mechanical strength is expected to improve.

Typical minimum vertical clearance requirements from the top of a duct bank use in utility environment is as follow:

a- Below pavement……………………………30 to 36 Inches.
b- Below finished ground grade………….24 to 30 Inches
c- Under sidewalk…………………………….18 to 24 Inches.

<sub>NOTES:
- Vertical clearances may be reduced 6 inches (~152 mm) for each 2 inches (~51 mm) of concrete or equivalent above the conductors.
- A minimum cover of 24 inches (~610 mm) is required for areas subject to heavy vehicular traffic such as driveways or parking areas.</sub>

The NESC (IEEE Std C2) suggest the top of duct bank to be installed 24 inches minimum below finished grade. On the other hand, the NEC allows under engineer supervision determine the cable ampacity for arrangements and environment conditions different to ones presented in the NEC