Video problems potentially caused by a earth grounding problem in commercial building?

Discussion in 'Power Electronics' started by Randy 7140, Sep 13, 2016.

  1. Randy 7140

    Thread Starter Member

    Jun 17, 2015
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    I would like to get everyones opinion on the attached picture of a earth ground schematic of a commercial building.

    I've been troubleshooting intermittent problems with a 4K video projection system with 4K video players that randomly fails for over 2 months. (6) 4K Digital projection units ran with a quad HDSDI line. The failures that occur can range from blacked out quadrants (loss of signal) on random projectors. All steps have been taken to troubleshoot this problem from replacement of video cable (1694A Belden) , replacement of video players, etc. Basically every step has been taken to troubleshoot from an A/V stand point of view. I'm now thinking it may be a ground fault in the buildings electrical system.

    Noticing that this facility is also having other major equipment issues (also randomly) as well as frequent power outages, I thought that the commonality between that and the equipment I am troubleshooting is AC power. I decided to look at the grounds of the entire building a found multiple major earth grounds corroded. This building is only one year old, but here is the catch. I cannot disclose what or where this facility is, I can say however that the building is basically a large refrigerator that moisture and water build up is a big issue. The copper grounds are pretty much always exposed to water and ground minerals.

    I do not have the equipment to do an impedance test at this time, although I know that this is the next step. The picture shows some really high leakage currents on ground that I preformed with a simple clamp meter. The fact that the generator ground is very low, it makes me think that there is a problem with the "Service entrance grounding conductor" potentially floating. I also attached a few pictures of the corroded grounds. I would love anyones thoughts on this.

    Thanks! Grounds SCHEM.jpg

    Randy
     
  2. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    First step might be to determine if leakage current is at fundamental or harmonic.
    Then determine source of leakage by scheduling shut down of building electrical, one section at a time.
     
  3. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,282
    1,235
    Seems like quite a bit, but then again it also sounds like a lot of equipment. Based on the ground current it looks like maybe the middle room.
    Why isn't the 60 Hz. stable?
     
  4. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
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    Well, you can tell there's a bunch of swimming pools, so a hotel, resort are possibilities. That much you can tell from the drawings.

    60 Hz may not be stable because of severe ground loops. This place probably should have had an Uffer ground and ground systems that transmitters and hospitals would use. You have a fault ground and reference ground which means two different bus bars for ground and isolated outlets for critical stuff.

    I think a fix for you might be to run isolated ground receptacles to your own box for the 4K system. You'd likely need two grounds in the box, one being isolated.

    You could consider fiber. You can distribute 4K video over fiber. See: http://auroramultimedia.com/news/ipbaset-4k-video-compression-latency-ip-distribution/

    Fiber distribution might solve your problem by itself.

    Grounds going haywire cause all sorts of issues. Intermittant grounds really nasty. They didn't really like it when I discovered that
    potentially 420 120 Volt outlets in a building were defective. I developed a test for them too. If you inserted two plugs in a defective outlet and wiggled one of them, one of the grounds would let go. The ground in the outlets was just pressure and depended on the tolerences of the outlet itself. You saw the evidence of sparks when you disassembled the outlets.

    Some were replaced no matter what. Others were tested and replaced. Still others were tested when critical equipment was added like computers.

    One issue I had was an outlet strip where a ground let go and destroyed a computer.

    Another issue I had was an X-ray set knocking out the RS232 drivers on a regular basis. Isolated drivers cured that.

    Finally, I invested about a $1000 USD on a oneac conditioner and a ISOBAR surge supressor for critical equipment where one part was a computer (pre IBM PC) that I repaired using a replace/exchange fixed fee repair per module. When i did that all repairs were 8" floppy drives and power supply. Later, when one of the systems was xferred to a Macintosh based computer system. 17 years later the system was still running with the same hard drive with only dust issues and one floppy drive issue. After 17 years, it was time for another upgrade. This time PC based.

    There were actually two different systems that got the conditioning. In the third upgrade process, one system was somewhat duplicated in a potable fashion and also got the conditioning. I doubt the reliability was even noticed by management.

    I also mentioned to management that an in-house valve controller (about 4 of them) used ground in it;s neutral and they should be fixed because of safety, The reply i got was, they have worked for 20+ years. They were built with all yellow wire. Very annoying.

    Management had no idea when they speced power for some major equipment. So, 60 Amp 208 single phase got three wires instead of 4. The builders built an isolated pad by pouring it all and then chopping out the isolated area on then pouring it. they had two thermostats in the same room controlling two different heat pumps in the same room. they out 36 air to water heat-pumps on a timer. The building had really bad air infiltration. They tried to boost 90 degree water from the HVAC system to 80 PSI through a 3/8 tubing when the systems required 60 degree ground water to cool.
    One of the fun things was the layout of some of the labs never included the columns, so the techs sometimes inadvertently positioned their equipment in the middle of a column.

    Somebody had enough sense to do the machine shop mostly right with the panelboard located in the shop.

    The floor was entirely sealed cement except the administrative area which had tile and/or carpeting. The dust was horrendous. Lighting totally sucked except for the offices.

    We had to dump lots of water down the drain to cool equipment. The biggest consumers were refrigeration systems that replaced liquid nitrogen and diffusion pumps.

    See: http://ecmweb.com/content/basics-isolated-grounding-receptacles

    The power outages are bad for you too. Thus a UPS might be in order or even a "whole house" surge suporessor on your isolated ground circuits.

    Anyway you look at it, the solution will be expensive even if you fix your end of it.

    Renting a power line disturbance monitor might help.

    Yes, i think the grounding system is suspect and I think the building needs an isolated ground as well. Isolated means it will NEVER carry current.

    You don;t mention the distances. A oneac conditioner actually re-creates the ground, but you already likely have big loops because of the coax.

    Incidentally oneac is known now as Powerone and they don;t like the ISOBAR. When i saw the measured results at a show, I was sold.

    I think you should not have ground currents.

    Can you nail anybody by saying the equipment won;t function in say x to y degrees, RH z%, non-condensing?
     
    Last edited: Sep 14, 2016
  5. Randy 7140

    Thread Starter Member

    Jun 17, 2015
    32
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    Thanks INWO. I believe it's harmonic based on the unstable frequency I'm measuring. Instead of a solid 60Hz, its varying from 20Hz to 280Hz. Shutting down equipment individually is a great idea, they would just have to shut the entire building down to perform that test. They actually might not have any choice but to do just that. Thanks again!
     
  6. Randy 7140

    Thread Starter Member

    Jun 17, 2015
    32
    6
    Hi Rony, I'm not sure why its not stable. I imagine there is a piece of equipment introducing this noise into those lines that are ultimately inducing it into the shielding of my coaxial cables. Its varying from 20Hz to 280Hz....There are quite a few motors, compressors etc. connected to the same circuits so most likely its being introduced somewhere in that area. The highest leakage current is from the ground of the generator transfer switch in the right room of the drawing. Thanks for your thoughts.
     
  7. Randy 7140

    Thread Starter Member

    Jun 17, 2015
    32
    6
    Funny you say that. When the building was originally built and designed they requested our own isolated ground for all AV equipment. This did not happen.

    I'm working with the electrical engineers and contractor who put the system in today to determine what's going on with this. It's definitely a ground potential issue. I measured the eye and jitter of the HDSDI signals wth a scope and the signal is really noisy. Pretty much exactly like the example in the specs of this video isolation transformer...

    http://www.markertek.com/Attachments/Specifications/ALLEN/HD-VIT-75-Specifications.pdf

    I know I could probably get a couple of those and it would probably fix the issue, but were not going to spend money fixing our system if its an electrical problem with their building. Distances of the HDSDI cable are exactly 140ft which are well within spec of the cable and signal we are using according to Belden. We do have a UPS just for our video servers but nothing else.

    Thanks for your thoughts and input on this.
     
  8. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
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    And the proposed fixes will likely fix your stuff. It says nothing about the systemic building problem and the problems that may occur with other equipment.

    I have another story which sorta fits. We had a scientific instrument (A multi-channel analyzer) which would pop a $1500 USD board every so often. We had the schematics of the instrument and there was zero surge suppressing stuff in it. The company basically said, your not supplying it with 120 V 60 Hz power as specified, therefore it's not our problem.

    So, if your contract specified an isolated ground, there was a breach of contract and whatever you promised, you can't deliver it.
     
  9. Randy 7140

    Thread Starter Member

    Jun 17, 2015
    32
    6
    Thanks KeepItSimple! I agree.

    Problem is, it was more of a request that was not taken seriously and not done...It was not listed in a contract (Although it probably should have been). I agree with you, no manufacturer is going to support any piece of their equipment that is not being supplied the correct voltage and frequency.

    I found an interesting piece of info today. The main transfer switch that receives the incoming 3 phase circuit from the power company is reading 5 amps on the neutral and 2.5 amps on the ground. I know some current should be there, but how much is too much?

    Thanks again for your thoughts.
     
  10. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
    1,142
    201
    Do you know the feed voltage and/or type? e.g. Y, Delta or hi-leg delta?

    If there is 208 and 277 in the building, It's likely Y.

    Remember, that there should only be one place where ground and Neutral tie together and the generator complicates things.

    I don't think those currents should be there. Common in the uk (I'm in the US) is RCD's or our GFCI's except in the uk they put it on the entire house. See: http://wiki.diyfaq.org.uk/index.php?title=RCD

    Potential differences bother me more because of the 149 foot length and the ground of say the TV and the Coax does not originate from the same place.

    What devices, if any, have 3-prong cords that don;t return to your equipment rack? Can they form a ground loop with the coax?

    Something to look for at your end is say a stray coupler/splitter that is touching the building girders/aluminum studs etc. You have to isolate those from the building.
     
    Last edited: Sep 14, 2016
  11. Randy 7140

    Thread Starter Member

    Jun 17, 2015
    32
    6
    Yes, there is 208 and 277 so its a Wye system. I'm to the point where I cannot proceed as I do not have the proper test gear, tools or safety gear needed.

    I've raised the red flag and there is an electrical contractor coming out to inspect and they are also going to monitor the power for 24 hours. As well as the power company that is going to check the connections at their transformer feeding the building.

    There are way too many devices to list. I believe its a problem at the projector side that has a different ground potential. I'm thinking ground noise and current drain is draining to the equipment rack (4K video players) causing the random dropouts. Not only all that, but the video cables are run through metal conduits grounded to the same noisy ground. I'm sure video cables inside of a piece of this conduit with current present would definitely cause some induction.

    Im going to add an additional copper grounding conductor from the equipment rack to a lower noise bus bar tomorrow to see if it at least temporarily will help.

    Thanks again Simple!
     
  12. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
    1,142
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    A place with cameras was having a sync issue and it turned out to be a splice was touching the building, essentially somewhere in the middle of the run.

    Look at 3 prong devices and a coax that isn't in your rack.

    I'm sure you can also pull a cable and look at the voltage between the now unconnected shield (from your rack) to the nearest ground at the far end.

    i now need to ask, just how you got an RG6/U cable from a to b? I'm sure your going through firewalls in the process and that's the main reason for your conduit. Not all conduits can be used as the grounded conductor. Maybe none.

    I did a safety system and had to penetrate a firewall with a bunch of fire rated PTFE cables. THEY really wanted to use a big hole filled with fire stop and I said NO. I also had to do some separations because the signals from the H2 detectors were very low. The conduit terminated in a large J-box and then a cord connector transitioned each cable across the firewall into Plenum space. Basically, stuff could be added with ease. it was nice. I told the electricians what i wanted and they ran the cables/conduits/enclosures etc. and left everything mostly unterminated. I also had issues keeping the wires class II out of conduit. The system received a signal from the fire alarm and sourced two fire alarm signals.

    At home I had an interesting issue; A Romex ground was only twisted and not attached to well to a metal box in a daisy chained outlet configuration. So, the outlet ground came from the end of the coax some 75 feet away in the attic. The antenna should see the same ground as the distribution amp (Some 52 db amp) since the Antenna is grounded and the distribution amp is grounded through 4 taps and the third prong. When the distribution amp ground became high Z, there were definately issues.
     
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