Plant Power Quality Checking - Page 1
Forum section: electronics / beginners

author: Tech_Monkey
author_rank: Contributor
timestamp: November 01, 2022, 05:20:41 pm
content: Hey folks. I guess this question isn't really "electronics" but I have a feeling I'm asking the right people..... We are having some issues in our plant that can really only (imo) be attributed to dirty power. (We've checked all the boxes to make sure its not processes) We have a mix of large and small equipment, old and new. Lots of old induction motors and pumps, and as time goes on we're adding more and more VFD equipment. We have very broad mix of machinery. We don't have any Cap banks or Filters, in fact we are paying a penalty for our Power factor every month so I do know that needs to be addressed.Anyways, I bought a fluke 190-504 series ii. I'm not planning on connecting to any of the main switch gear, I will wait on the licensed electrician to do all that along with the actual power study, but in the mean time, what kind of tests can I do just to see where we're at today. For example, just checking the voltage waveform on a 480 socket that's not in use is a connection I can safely make. Same with our 230 rail.... but is looking at those wave forms all I can safely do without an electrician?I had extensive electrical training in the airforce so I do have a good understanding what I'm getting into, I just don't have any background with plant power systems and what to really look for that causes issues with equipment. I know how to handle electricity safely so I'm just interested in growing my skillset mainly, and also be able to point to something to the owner and say "this is an issue and you need to get the power guys in here to do more thorough testing"thanks for you help

author: Tech_Monkey
author_rank: Contributor
timestamp: November 02, 2022, 08:57:23 pm
content: I posted this in a more appropriate forum and got some good answers. Thanks anyways folks!

author: bdunham7
author_rank: Super Contributor
timestamp: November 02, 2022, 09:16:14 pm
content: I've been through sorting out these issues in a small-ish industrial setting with old wiring and a huge variety of equipment and without giving you an exhaustive list of things to look at--which you probably have already gotten elsewhere--I'll just give you three tips I found helpful.First, make sure if you have separate service entrances or panels or different voltage systems that they are not interconnected in some way, including neutrals.Second, use all 4 channels of your scope (8 would be even handier so you could use current transformers, but that's another story) and use the 4th channel to measure neutral-to-ground. On most of my problem circuits--split phase or three-phase or high-leg delta, I could observe transient abnormal voltages on neutrals. The causes were widely varied, but that always seemed to be there.Third, your power company will come out and monitor your power and then tell you that it is within specifications on their end. Before you even bother them, make sure you have identified something concrete that is out of spec. Don't think about power as 'dirty', identify specific issues.

author: CaptDon
author_rank: Super Contributor
timestamp: November 03, 2022, 08:19:14 pm
content: There are a multitude of 'Power Analyzers' available that can be rented from the test equipment rental houses. All different capacities among the analyzers including printouts of min/max parameters and even graphic printouts of transients. If you suspect poor power as your culprit the investigation will be extensive and extreme transients your probable bandit.

author: nightfire
author_rank: Frequent Contributor
timestamp: November 05, 2022, 02:01:16 pm
content: I agree- some Fluke 435 or similar would be the right course of action.The difficulty is that sometimes it is hard to get to the voltages safely, especially in big distribution cabinets.A trick that I used with my last employer to connect my Fluke 435 on:Installed a simple box on a fused outlet /fused with 2A Neozed or the lowest value of NH fuses), that has 4mm lab jacks installed (attention: They have to be rated for CAT III/IV, depending where you are measuring)- in those you can then safely plug in your testgear)Classical issues in big plants (My last employer was a datacenter, so we had lots of capacitive load going on with the PSU of the servers)- dirty mains input provided from the power company. Not uncommon these days- Switching Power supplies causing mains feedback- Switching of big motors etc. also causing some feedback or harmonics- Lighting (electronic ballasts) causing mains feedback (11,13,15 harmonics)- TN-C portions on old installations causing LOTS of stray currentsHere it is also a simple thing to measure the PE with a current clamp that is also able to capture higher frequencies, or measure some hot input wires (no PE) with a clamp, so the difference would be PE current- compare that with the PE of that line, and you get an idea what/if stray currents are roaming through your installation.