Underground Mine Grounding

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Just hardrock gold, no ignition hazard, but it is in Canada so M421 applies. I’m not sure how to accomplish that level of separation without crazy amount of insulated wire running all over the place. There are many surface infrastructure buildings all around the two shafts (each has an independent feeder going down).

Might need to message you the layout for some tips!
 
Bigjabe said:
Just hardrock gold, no ignition hazard, but it is in Canada so M421 applies. I’m not sure how to accomplish that level of separation without crazy amount of insulated wire running all over the place. There are many surface infrastructure buildings all around the two shafts (each has an independent feeder going down).

Might need to message you the layout for some tips!
Click to expand...

do the feeders to the buildings have a ground from a source isolated from the mine power?
if that is tied to the station bed you should be good (on a wye sec)
 
Ingenieur said:
do the feeders to the buildings have a ground from a source isolated from the mine power?
if that is tied to the station bed you should be good (on a wye sec)
Click to expand...

The underground surface infrastructure is isolated from the main plant - so no GPR issues from utility tie sub. However, current design is all underground surface infrastructure is tied to same ground bed as Underground feeder NGRs and also surface equipment. Lightning is the only problem... with all the pipes going underground and steel structures at the underground surface area I’m not sure how we can isolate?

Note this isn’t built yet so still time to fix.

Edit: to make it clearer... the underground portal area is isolated from the main plant. Current design is the underground portal area (including feeders to underground) is fed from isolation substations (with substation ground tied to main plant ground) with NGRs tied to portal area ground to prevent utility ground fault GPR from transferring to the underground mine.

Maybe we can tie overhead line shield wire and phase LAs on the overhead line feeding the portal area back to main plant ground..? That still won’t help if portal surface equipment is hit by lightning.:
 
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do you have a single line?

is surface power and mine power on the same xfmr?

are you saying the hoist structures (and other surface structures like fans, etc) are tied to the ngr?
or bypass it straight to the ground bed?

for your application you may be compliant
as far as the pipes and other steel entering the mine is it all bonded to a ground bed?
again may not be an issue

we use plastic pipe or rubber flex joints to isolate
since there is no explosion hazard you do not require the same level of isolation
 
Ingenieur said:
do you have a single line?

is surface power and mine power on the same xfmr?

are you saying the hoist structures (and other surface structures like fans, etc) are tied to the ngr?
or bypass it straight to the ground bed?

for your application you may be compliant
as far as the pipes and other steel entering the mine is it all bonded to a ground bed?
again may not be an issue

we use plastic pipe or rubber flex joints to isolate
since there is no explosion hazard you do not require the same level of isolation
Click to expand...

I agree it may be compliant, M421 only discusses GPR due to faults. Nevertheless, it's still a concern. I made a sketch of the layout to hopefully understand - the file is too big to post here though, can you PM me your email?
 
Bigjabe said:
I agree it may be compliant, M421 only discusses GPR due to faults. Nevertheless, it's still a concern. I made a sketch of the layout to hopefully understand - the file is too big to post here though, can you PM me your email?
Click to expand...

Unless the file contains info that you wish to remain undisclosed, I am willing to PM my email address and attempt to upload for you.
 
eta: the free software I used for this only does one pic/hour, so if someone wants to resize and rotate it for clarity, it would be much appreciated.

jumper asked me to post a file here, here we go:

pdf file is too big, converted it to jpeg. also rotated it 90*:

which also wont download. let me d/l it elsewhere... brb



20180121_DT_000013.jpg
 
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Thank you 480. Weird, at first I saw my pic full size on this thread, now it's thumbnail size, and it doesnt appear a mod edited my post. anyway, hope the pic helps y'all.
 
I'll print it at work tomorrow
lot of lines lol

I would strongly recommend to have it cad'ed up
request a meeting with the government inspector/engineer to review

one thing re:dwg
the feeders at the btm left connect to the isol subs 1 & 2 at the top right
correct?
 
Ingenieur said:
I'll print it at work tomorrow
lot of lines lol

I would strongly recommend to have it cad'ed up
request a meeting with the government inspector/engineer to review

one thing re:dwg
the feeders at the btm left connect to the isol subs 1 & 2 at the top right
correct?
Click to expand...

Thanks guys!! Jeez, I had no idea it would be such an ordeal!! Sorry!

The left half of the sketch is an SLD, the right side is the layout... the ISOL subs are shown higher up on the SLD.

The drawings are all CAD'd, I didn't want to post those details here so I just hand sketched the basic idea. The red lines indicate ground connections. The main point is everything on the surface in the vicinity of the U/G portals (including the NGR ground terminals) are connected to the same ground bed.
 
took a quick look on my iphone
looks good
we would not put the fan and shops on ug power, but in your case that may be legal
verify that

I do not like the la's tied to the mine bed
I would move them to the isol sub end and tie them to the main sub bed

is the ngr buried cable to the x0 insulated?
buried is good
needs to be insulated
if you have gnd fault that returns to the bed it may travel via earth to that conductor and bypass the ngr if earth R < ngr R

are isol subs 1 & 2 secondaries bused together/paralled? ph and x0?
or completly isolated?
are the ug mine drops paralled in the mine?
if they are you have parallel gf rtn thru the ngr's so their R is halved
if they are you only need one ngr that is tied to BOTH x0
I would locate that at the subs
 
Ingenieur said:
took a quick look on my iphone
looks good
we would not put the fan and shops on ug power, but in your case that may be legal
verify that

I do not like the la's tied to the mine bed
I would move them to the isol sub end and tie them to the main sub bed
Click to expand...

that would be extremely difficult given the distance.. I’m thinking about tying the LA’s to their own ground bed, 50’ from the mine ground bed, via overhead line, any comments?


Ingenieur said:
is the ngr buried cable to the x0 insulated?
buried is good
needs to be insulated
if you have gnd fault that returns to the bed it may travel via earth to that conductor and bypass the ngr if earth R < ngr R
Click to expand...

yes, 15kV armoured TECK cable. Shields, armour and ground wire isolated at isol sub end, tied to mine ground end.

Ingenieur said:
are isol subs 1 & 2 secondaries bused together/paralled? ph and x0?
or completly isolated?
are the ug mine drops paralled in the mine?
if they are you have parallel gf rtn thru the ngr's so their R is halved
if they are you only need one ngr that is tied to BOTH x0
I would locate that at the subs
Click to expand...

The isol subs 1 and 2 secondaries go down borholes and form a ring main underground. Interlocking will prevent them from ever paralleling. They are isolated from each other, but if one feed fails the other can pick up the entire underground power.
 
physically move the la's
put them on the pole near the isol subs
I did not mean run a wire from their shown location

a seperate bed may work
let me look at some stuff tomorrow and see what the recommended practice is
iirc we just put them on the output of the sub cb

if they take a hit where they are now the whole mine frame ground will be elevated

how are the isol subs bonded to the main sub?
oh w/the phases?
a buried copper conductor?
what kind of swgr is at the isol subs?
perhaps the la's can be bonded to the isol sub frames?
 
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