69 kV Buried Cable

[sobeys81]

Hi,

I am an industrial consulting engineer and don't work in a utility but we have a client who has a substation at 69 kV that needs some buried cable work at 69 kV. It is in Alberta and client does not this cable to be armoured.

Is it possible to be a unarmoured cable to be direct buried. I would appreciate some comments.

 

[alehman]

The NEC does not required it to be armored.

 

[sobeys81]

Thanks Aleham.

In Canada, utilities are not supposed to abide by Code. Electrical Safety authority has no say over their way of doing things. But I being a consultant has to go by the rules of safety. So Let me just jot it down;

1. A 69 kV cable can be unarmoured and direct buried so what possible protection mechanism would be in place to
for any eventuality.

I would appreciate if any one has some literature available on this design.

Thanks

 

[dpc]

You can put it in conduit.

"An 'expert' is someone who has made every possible mistake in a very narrow field of study." -- Edward Teller

 

[alehman]

You said you don't work in the utility, so I assumed this is an industrial client.

Some unarmored cables are approved for direct burial. If you want protection, you can put it in conduit, install warning marker tape or concrete planks above the cable.

 

[jghrist]

Unarmored 69 kV direct burial cable is common. I'd suggest talking to some cable manufacturers.

 

[WhiteyWhitey]

Just for my own information,

Is an unarmoured cable different to a cable with no metallic sheath?
What would the reason for requiring an un armoured cable be?

For mechanical protection you may consider things like encasing the cable in Conduits, concrete, covering with steel plates, marker tapes etc or a combination of these.

Thanks,
Andrew

 

[alehman]

No. The sheath or shield is required for electric field control on all high voltage cable. The armor is a separate outer layer of physical protection.

 

[benlanz]

Most 69kV cable is not armored. A concentric wire design is plenty good enough for the typical utility application. I recommend that you contact one of the major manufacturer's. If you need high level application engineering contacts, I would be glad to help.

Benjamin Lanz
Past Chair of IEEE 400
Sr. Application Engineer
IMCORP- Power Cable Reliability Consultants