MV switchgear - bottom cable working clearance

[power2020]

Dear Folks,
Here is one more.
We have 11KV indoor Switchgear (indoor) with total of 14 feeders/vacuum circuit breaker switchboards (including incomers).
Total Switchboard dimension: 14000mm length x 1800mm width x 2200 height.

All switchboards are bottom cable entry (No Bus Ducts)

Now my query is.
1) I am proposing 1-meter (depth) x 1-meter (width) cable trench as my client is not given any specific guidelines.
Is that enough to pull these cables (11KV 300SQMM) and to work confortably for cable termination.

Any Practical experiences / problems faced by anybody.

Please give your valuable suggestions..

Thanks

 

[controlsdude]

NEC is very clear on wire bending radius where it comes to enclosures and terminations.

Where ever you have to terminate you need that specific space around it to bend that specific size wire in the enclosure or trench

Article 110 talks specifically to wire bending radius and connections and the spacing required.

As a point their are 200 references in the NEC to this info, you probably need NEC book or PDF doc and search for this info.

 

[urjaengrs]

i think the clerence you cinsidered is fare enough.. if it is 1200 mm or more that wud b better. ofcourse, as suggested by JMOUNCE, please refe some guidelines baout bending requirements of HV cable

 

[power2020]

Thanks Guys,
Unfortunately i dont have access to NEC docs, but IEC.
Mr.urjaengrs (Electrical), I feel now 1500mm depth is required as 1000mm bending radius is required (as per cable manufacurer).

However, i still feel why should not we go for complete cable vault (with complete bottom opening like cable basement area) for this substation, as this building is going to be with MV switchgear panel (14000mm length x 1800mm width x 2200 height) and LV switchgear panel (15000mm anlength x 1800mm width x 2000 height)and other distribution panels. Offcourse cost will increase.,,

Still i need our experts suggestions..

Thanks

 

[Electic]

You have several options and I have seen all of these in practice:

1) a proper sized conduit may be routed up beneath the terminating space, using wide radius bend.

2) a trench as you describe may be built, with dimensions expanded for cable bend radius. Note that installation will be easier if you enlarge the dimensions.

3) A larger trench may be installed under the entire termination space of the switchgear. This may include racks or brackets along the walls to suspend the cables and it is recommended to include more cable length than minimum. This allows circuits to be rearranged in the future if loads are changed.

4) a full basement beneath the switchgear, with cable tray to hold the cables, and small floor penetrations only beneath switchgear terminating compartments. This makes installation easiest and allows future changes, but also is more expensive.