High Voltage Clearance and Existing Steel Column - Concrete Encasement of Column?

[buening]

I'm still trying to get info on this cabinet (voltage), but I have a project that has an existing steel column where a high voltage electrical cabinet (20' long x 8' wide x 6' tall) is to be installed on the concrete slab in the vicinity of the column. The manufacturer of the cabinet states a 60" clearance shall be maintained from the cabinet to exposed steel, and we're around 30" right now. For those that have dealt with situations like this, couldn't we just encase the existing column in concrete to insulate the exposed steel from the electrical current? The cabinet is being installed adjacent to a concrete wall and atop concrete slab both with steel reinforcing, so I can't imagine it'd be much difference. The column is a W8x24, so nothing huge. Is there a reference or formula to determining how thick of concrete it'd need to be based on a certain voltage? Its a whole mess of steel above this column, so relocation would not be cheap so I was looking into ways of keeping the column as-is but insulate it from the electrical.

 

[Heaviside1925]

OP,
Also consider code minimum distances as well, you may address the manufacturer's requirements for exposed steel but still have issues with NEC or NESC required clearances. I had a similar issue with exposed steel on a past project and the cabinet manufacture recommended a barrier wall, which might be cheaper than concrete encasement. I'd reach out to the cabinet manufacture and see what their recommendations are.

 

[buening]

Thanks for the response! This area is in a pit of a manufacturing plant where floor space adjacent to the cabinets are a premium (and this is the only column in the pit), so building a separation wall may get in the way unless the wall doesn't have to be all that long. The column is 10' tall with access above it to where concrete could be poured in easily to encase the column. I'm just not sure if encasing would insulate it enough or what thickness (cover) of concrete would be needed. The alternative would be to pour a concrete column adjacent to the steel column and remove the steel column, but that'd be more expensive than encasing the column.

 

[Heaviside1925]

Insulation will be based on voltage. You mention high voltage in your post. Do you know the voltage? and what AHJ / code requirements are you under?

Bear in mind, concrete is not an insulator. Think of a an Ufer ground (concrete encase grounding system). Having a steel column this close to a high voltage (115-230kV) source then surrounding in concrete would give me pause since you could possibly be creating an unintentional circuit with your column becoming the sacrificial anode. Another situation way back in my career involved Very high voltage (these definitions are code defined, not just allegorically speaking). This was at a TV station and all the steel columns in the transmission room were required to be insulating cement encased with an embedded copper mesh connected to a grounding grid. Think of the concept of holding florescent bulbs under transmissions lines and they light up. I would be hesitant to be the responsible party in finding a workaround to the manufacture's clearance requirements. I would discuss this with the electrical gear manufacture since clearance issues are a common in these settings and see what their recommendations are. It may be simple as applying an insulating coating to the steel of a certain thickness, but I would rely on the gear manufacturers for recommendations.