Borehole HV Cable Installation

[OhioAviator]

Hi All,
I have been given the task of installing 15kV power via a 50 ft long borehole, six inches in diameter, from the surface down into an underground limestone mine. The power cable down the borehole is estimated to be a 500 MCM three-conductor cable plus ground. I have never installed a borehole cable nor have I ever seen it done. I am looking for any technical help and advice anyone can give. Some questions I have are:
1. Does the cable need to be steel wire armored, or can I use PVC jacketed armored cable similar to what is used in industrial plants?
2. Can the cable be suspended from one single point at the surface, or do I need to attach one or more steel messenger cables to the borehole cable to distribute the weight of the borehole cable along its length?
3. What kind of clamping arrangement should I use if single-point suspension is employed, and where can I obtain the necessary clamping hardware?
4. Do I need to employ some sort of 'deadman' arrangement, or other method of taking the weight of the borehole cable up on the surface?

If anyone can direct me to some technical resources or to some companies who specialize in borehole cable installation, that would be most appreciated.

Kind Regards,


John

Galatians 2:20

 

[cuky2000]

See the videos in the links below:
1. Does the cable need to be steel wire armored, or can I use PVC jacketed armored cable similar to what is used in industrial plants? Regular solid dielectric cable with PVC jacket could be used for this application.

2. Can the cable be suspended from one single point at the surface, or do I need to attach one or more steel messenger cables to the borehole cable to distribute the weight of the borehole cable along its length? I am under the impression that the described installation is with an encase pipe with multiple conductor. Encasing could be PVC, HMPE, Steel or sometime with bundle polymer conduit without encasing. This will be determine by the geotech side data and other specific conditions.

3. What kind of clamping arrangement should I use if single-point suspension is employed, and where can I obtain the necessary clamping hardware? Could you provide some sketch or more info on this

4. Do I need to employ some sort of 'deadman' arrangement, or other method of taking the weight of the borehole cable up on the surface? See above

https://www.youtube.com/watch?v=nIh593k0rF8

 

[OhioAviator]

Hello cuky2000,

Thanks for your advice. I haven't gotten into this far enough to make a beer napkin or whiteboard engineering drawing yet. I was thinking that since the total suspended length of the cable will be around 85 ft, I could use a single 4 ft long chinese finger cable grip to support the cable at the surface. In addition to the chinese finger grip, the cable would emerge out of the borehole at the surface and travel vertically to a fixed 'D'-Ring where it would wrap around the D-Ring (and be clamped to it) down to a small horizontal cable tray. From there it would travel along the cable tray a few feet over to the utility pole where it would then radius upward and go up the pole to the cable terminators at the top of the pole. I hope that explanation was clear in the absence of a sketch. If you or anyone have any other ideas or suggestions I would certainly appreciate hearing about them.

I am unable to watch YouTube videos here at work as my employer has YouTube blocked for everyone.

Thanks!


John

Galatians 2:20

 

[7anoter4]

In my opinion, it is about a cable run as in attached sketch.

It could be?