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banny

@94.182.192.x

how do i prevent the ground loop?

we have two collocated shelter that feed from on generator and spaced from each other about 200 meter.all equipment are sensitive and need to be earthed so i have to ground both side,but its not practical bonding them together in result of an earth ground system.i want to use one Y/Y transformer to break the path of ground loop.should one side of the transformer earthed or both sides?is any body have comment on that?



mb

join:2000-07-23
Washington, NJ
Reviews:
·Comcast
·Verizon Online DSL

1 edit

More information is needed on what type of power, how you plan to distribute it from the generator to the two locations, and the type and power requirements of the equipment being supplied. In theory, transformers at the generator would isolate the locations from each other and the source, but depending on the power requirements of the equipment and the type of power supplies utilized at each piece, ( eg/12vdc ) total isolation from the mains may be attainable at the individual locations.



leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
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reply to banny

I agree with mb See Profile that more information is needed.

Since both shelters are fed from the same generator you most likely will have to bond the grounds together (even if it isn't "practical") for safety and code compliance reasons.

Where is the generator located relative to the two equipment shelters ?
Is all power locally generated all the time or is there also a utility grid connection with a transfer switch for the generator ?

Most importantly, what is the nature of the problem you are trying to solve ? The bonding of electric safety grounds is a completely different subject then ground loops on communication links.
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TheMG
Premium
join:2007-09-04
Canada
kudos:3
reply to banny

What exactly is the ground loop problem? Are you getting 60Hz hum induced into audio/signal lines between the shelters?



banny

@94.182.192.x
reply to mb

there are 2 shelters which are spaced from each other about 250 meter and there is a 40KVA generator that is located beside the shelter one.the generator neutral grounded within the shelter one and its feeds both shelters by cables.there is another data link between two shelters.my problem is data links and power link,both individually can complete the loop ground path which would be cause of circular currents.i know that using data isolator or fiber cable in data links can be a solution but for power line...already not



banny

@94.182.192.x
reply to leibold

ground bonding its impractical cause the space between the shelters are great and its fancy.all the electronic modules are powered by single phase supply.



alphapointe
Don't Touch Me
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join:2002-02-10
Columbia, MO
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reply to banny

I have no idea what electrical codes in Iran are like, but here in the US, ground bonding is required by code (and common sense...). Why is running a ground bond wire along with the electrical service to the second shelter a problem? (600 feet / 200 meters of cable is cheaper than having equipment fried or someone injured/killed...)
--
"When the hammer drops, the bullshit stops"



banny

@94.182.192.x

because the shelters are portable somehow.you imagine that if they want to change the shelters place,its not easy to do all this bonding together again!
I read us code before but there wasn't any sensible answer for this situation.



leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
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reply to alphapointe

I completely agree.

In order to use Y/Y transformers you would need to run power cables with a minimum of 4 conductors (3 phases plus neutral) if you omit the safety ground. Including the safety ground you need 5 conductors.

To do it properly you could use delta wiring between generator and shelter and even with safety ground still only need 4 conductors. You would then use the more common delta/Y transformers at the shelter.

Including the safety ground in plug connected power cables doesn't meet the strict guidelines for bonding within permanent structures but you are talking about a mobile / portable system.

In one such mobile / portable setup that I have worked with we had 2 generators (synchronized and interconnected) and up to 6 connected loads. Each generator and each load had its own temporary ground connection (mostly screw-type reusable rods) and all the grounds were "bonded" together through the 4 conductor power cables. There is absolutely nothing impractical in doing it right and safely.

P.S.: some of our loads were also connected with shielded (grounded) communication cables which meant that there was a 2nd (or 3rd if you count the earth grounding) ground connection between those loads. We never had any issues that were in any way related to ground loops.
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TheMG
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Canada
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reply to banny

said by banny :

my problem is data links and power link,both individually can complete the loop ground path which would be cause of circular currents.i know that using data isolator or fiber cable in data links can be a solution but for power line...already not

The power line... should run a ground between the two shelters.

As for the data cabling, yes, isolating it would be the proper way of doing things. We have hundreds of equipment shelters in various locations and in pretty much all cases there is some form of isolation on all data and audio circuits. Most often in the form of a balanced isolation transformer in the equipment itself, but sometimes as an external add-on. For some things, optoisolators or relays are used and in rare cases fiber.

Ground loops have very rarely been a problem, except in rare cases where a communications circuit becomes unbalanced.

banny

join:2014-08-19
iran, islami

what about using Y/Y transformer to cut the physical contact and loop path in power line?


banny

join:2014-08-19
iran, islami
reply to banny

hey Lei Bold,
thanks for elaboration.
how far were the loads from each other(in setup that u worked)?



leibold
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join:2002-07-09
Sunnyvale, CA
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The design was intended for a 250 meter radius around the master node. This means a theoretical maximum distance between any two loads would have been 500 meters but in all the exercises I participated in we never stretched out that far. My guess is that we may have gotten up to 100 meters between master and slave nodes with perhaps 150 to 200 meters between the two most distant slave nodes (since the slave nodes were rarely distributed over a full circle).
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TheMG
Premium
join:2007-09-04
Canada
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reply to leibold

OP: you still haven't mentioned what type of data/signal interfaces you are having ground loop problems with.

This would be very helpful in providing recommendations to solve the problem, which could turn out to be much easier and cheaper than getting fancy with the power distribution.

Quite often much easier to make the communications wiring immune to ground loops, instead of trying to eliminate the ground loops entirely (which could be possible with a small portable setup, but nearly impossible in larger permanent installations).

Expand your moderator at work

banny

join:2014-08-19
iran, islami
reply to banny

Re: how do i prevent the ground loop?

hey TheMG
there are two line RG213 (RF and trig) and one LAN cable.



John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:8
reply to banny

What and how many conductors are in the cable connecting the two portable buildings?



SmokChsr
Who let the magic smoke out?
Premium
join:2006-03-17
Saint Augustine, FL
reply to banny

The more times I read this, it looks more and more like you need to work at the ground loop from the signal cable side. I'd think that by using transformers to isolate the buildings you may actually make the loop worse. By isolating the electrical the only ground path from one building to the other will be through the signal lines. If the Neutral/ground from both buildings are already bonded at the generator, there shouldn't be very much of a ground potential difference. Also I'd recommend that the RF cables are protected at each end as well as placing surge protection on each end of the data cable. You may also want to consider placing "sacrificial" switches in each end of the data line as well.


banny

join:2014-08-19
iran, islami
reply to John Galt

thre are 4 power cable and two RG213 cable


banny

join:2014-08-19
iran, islami
reply to SmokChsr

yeah your right but as i wrote above we would use Isolator on data cables too.my problem is on the power lines,and of course any other solution from you guys would be warmly welcomed