| Author |
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sphealey
Guest
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 Posted:
Fri Aug 12, 2005 12:20 am Post subject:
Grounding rack for sheathed fiber optic cable |
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We are going to be routing 12 metallic-sheathed fiber optic cables
across our plant floor (usual mix of 480V, welding, etc) and into the
datacomm room. It seems to me that the metallic sheath should be
grounded at the point where the cables enter the room, to drain off any
induced voltages on the sheath.
In the dim past I used IBM Type 1 cable, and the termination racks had
a tower that the cable would run through. You would strip off 1 cm of
the insulation at the point where the cable ran through the tower and
crimp a tab on the tower onto the metallic shield, then ground the
tower. I would think this should work for the fiber cables also.
However, I can no longer locate any such part. Any suggestions?
Thanks.
sPh |
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Alexander Burke
Guest
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| Posted:
Fri Aug 12, 2005 8:20 am Post subject:
Re: Grounding rack for sheathed fiber optic cable |
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Fiber optic cabling makes no use of electromagnetic signals, and is
therefore immune to even incredibly-high levels of electromagnetic
interference.
Solid heavy metallic conduit should protect the cables nicely from
physical impact, welding sparks, etc.
No grounding is necessary from a data point of view. |
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sphealey
Guest
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| Posted:
Fri Aug 12, 2005 4:20 pm Post subject:
Re: Grounding rack for sheathed fiber optic cable |
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| Quote: | Fiber optic cabling makes no use of electromagnetic signals, and is
therefore immune to even incredibly-high levels of electromagnetic
interference.
|
Indeed.
[...]
| Quote: | Solid heavy metallic conduit should protect the cables nicely from
physical impact, welding sparks, etc.
|
Unfortunately, from a life-safety and equipment damage point of view
fiber optic cables with metallic sheaths and/or metallic strength
members, such as the indoor/outdoor armoured cable we are using for
this application, can develop voltages and current flows from induction
on the sheath or leakages from power cables that it may cross or
parallel. Corning Cable Systems has a white paper on their site
discussing this.
In the specific case, besides the usual plant induction and leakage
possibilites, one run will be passing through a 24kV
transformer/switchgear enclosure so the possibility for induction is
high.
I was fortune enough on my first fiber optic project many years ago to
be teamed up with a power systems electrical engineer who walked me
through all this, so it has been a bit of an obsession of mine since!
sPh
No grounding is necessary from a data point of view. |
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Jgolan
Guest
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| Posted:
Wed Sep 07, 2005 4:20 pm Post subject:
Re: Grounding rack for sheathed fiber optic cable |
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You are absolutely coprrect that the metalic portion of the cable needs to
be grounded. If this is a BX or greenfield type construction of tyhe
cable, the easest way is to use groundable connectors made of BX or
Greenfield and then run a grounding conductor from the connector to a
ground bar.
Joe Golan, RCDD
-------------------------------------
sphealey wrote:
| Quote: | Fiber optic cabling makes no use of electromagnetic signals, and
is
therefore immune to even incredibly-high levels of electromagnetic
interference.
Indeed.
[...]
Solid heavy metallic conduit should protect the cables nicely from
physical impact, welding sparks, etc.
Unfortunately, from a life-safety and equipment damage point of view
fiber optic cables with metallic sheaths and/or metallic strength
members, such as the indoor/outdoor armoured cable we are using for
this application, can develop voltages and current flows from induction
on the sheath or leakages from power cables that it may cross or
parallel. Corning Cable Systems has a white paper on their site
discussing this.
In the specific case, besides the usual plant induction and leakage
possibilites, one run will be passing through a 24kV
transformer/switchgear enclosure so the possibility for induction is
high.
I was fortune enough on my first fiber optic project many years ago to
be teamed up with a power systems electrical engineer who walked me
through all this, so it has been a bit of an obsession of mine since!
sPh
No grounding is necessary from a data point of view.
|
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Watson A.Name - \"Watt Su
Guest
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| Posted:
Sat Sep 10, 2005 4:41 pm Post subject:
Re: Grounding rack for sheathed fiber optic cable |
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"Jgolan" <jpgolan_at_earthlink_dot_net@foo.com> wrote in message
news:38DTe.214016$Jd.15223@fe11.news.easynews.com...
[snip]
| Quote: | In the specific case, besides the usual plant induction and leakage
possibilites, one run will be passing through a 24kV
transformer/switchgear enclosure so the possibility for induction is
high.
|
Q: You have signal cables running thru two different electrical
enclosures. One enclosure has a 24kV electrical cable carrying ten
amps. The other enclosure has 240VAC at 100 amps. Which of the signal
cables is going to get the most induced current?
A: Since the 24kV cable is shielded, there is going to be very little
electrostatic induction from it (we have 4160 VAC cables underground,
and they are shielded, too). The signal cable will have little
electromagnetic induction from the ten amps of the 24kV cable. But the
signal cable in the 240VAC, 100A enclosure will have up to 10 times as
much electromagnetic induction as the 24kV enclosure. |
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