Regular Instant Voltage drop in a large warehouse facility! 1

[mjawhary]

I am working on a power failure issue at a big warehouse distribution facility in NY. I posted on the site a while ago regarding finding a solution for the power brownouts they have been having that caused the forklift chargers to fail. I recommended using the FLUKE 175 to record power parameters for a period of a week, the data results came back and it shows that they had one incident of a voltage drop on two phases from 277VRMS to 120VRMS, the drop was instantly and then came back to normal, this caused power failures and caused the current to spike. Other than this voltage fluctuation ranged from 275VRMS TO 288RMS max during that week and I think it is normal. I am trying to find the best and more economical solution for this matter, I called the power company before and they said that they didn't report any brownouts or power issues in that area!

Thank you ,

 

[jghrist]

Can you correlate the voltage drop to weather? Sometimes, a fault on the utility distribution system will cause an momentary interruption on the affected circuit but a voltage dip on all circuits connected to the utility distribution substation. This may not be recorded by the utility or may be recorded only on the circuit that tripped.

 

[mjawhary]

It keeps happening every month or two once or twice even at sunny morning day, so weather is not the problem!

 

[Skogsgurra]

How long were the dips? And were there any high voltage transients when they came back? Do you have any graphic representation? Or doesn't the 175 have graphics?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[rasevskii]

It may seem obvious, but has anyone checked the tightness of all the connectors and cable lugs, etc.? Perhaps a shutdown should be arranged and everything from the transformer secondaries should be tightened up, possibly. It could be also a bad primary fuse or fuseholder acting up. Your self and the power company together.

Especially if it an old installation where corrosion has occurred. Any copper to aluminum connectors in the circuits?

rasevskii

 

[itsmoked]

That sounds like a bad connection spasming to me too. Consider a thermal scan of all the panels and fuses that supply the location you monitored.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Could be that the chargers are failing shorted and then clearing. If you are measuring closer to the charger than to the transformer those readings may be realistic.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[mjawhary]

It happens less frequently than I mentioned, I would say on average once every two months. If it was a bad connection I would expect it to happen once a day or couple of days, also the dip was short exactly 3 seconds on phase'A' then it went back to normal?

 

[Skogsgurra]

Three seconds? How often does the 175 sample?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[waross]

How far from the service transformer to the main panel? How far from the main panel to the sub panel? how far from the sub panel to the chargers? Where on this system are you connecting your instrument? Does your instrument have a recording function or just a hold function?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jghrist]

You might want to rent a power quality meter that can record a waveform of the dip. If every dip is exactly 3 seconds and the voltage dips from a steady 277V to a steady 120V, then there is something strange going on with some equipment in the plant.

 

[musaUKPN]

I have seen this before. The reasons were found to be due to faults on any of the 11kV distribution feeders from the utility 132/11kV substation, but the dips were not of the range of 3 seconds!

When compared the date/ time of the dips recorded at customer's installation exactly co-related to the faults recorded on the utility main substation. The fault level on utility main substation was high enough and together with high impedance of transformers (as 3x 50MVA 132/11kV transformers were running parallel) a voltage dip observed upon occurance of a momentary and/or permanent fault. Those dips caused the customer's ACB's to trip to under voltage function as well.

As advised by others, please refer matter to utility and check the utility fault data against the dips at customer's installations.

musa UKPN

 

[Skogsgurra]

Not following you at all, mjawhary

Are you really using this Fluke 175?

http://www.fluke.com/fluke/usen/digital-multimeters/fluke-170.htm?PID=56027

Does it really record over weeks? Battery life seems to be only a few hundred hours and I see no recording possibility in the data sheets. Or do you use some other instrument?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[mjawhary]

I am using Fluke 175 and yes it measures and records all wave forms, it is a powerful instrument, I was able to view the event on the graphs. I ll check with the utility again and do some more research.
Thank you

 

[Skogsgurra]

Something doesn't compute here. How fast does your 175 sample?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[waross]

Have you left out any numbers in the meter model number? How far are you from salt water?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[mjawhary]

Sorry I meant FLUKE 1750 not 175. I am far away from salt water.

 

[Skogsgurra]

OK. That's better. You really need to be more careful.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[jraef]

One more possibility into the mix.

Large Wye Delta starters can cause this sometimes. There is a phase shift that takes place when they transition from Wye to Delta and depending on where the phase angle of the supply is at the moment of transition and the possibility of an incompete decay of the motor magnetic field, the combination can cause very severe transition spikes that are known to not only damage the motor, but cause seemingly random voltage dips and spikes in the system. The randomness stems from the combination of issues that it takes to cause this.

So to eliminate this possibility, check EVERY marge-ish motor in the warehouse, making sure you especially pay attention to any chiller compressors for the HVAC system (or refrigeration compressors if it's a cold storage warehouse). If you (or your neighbors) have absolutely no large Wye-Delta starters, then look elsewhere. But if you find one, put your recorder on that motor fpor a while.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[itsmoked]

Oh yeah, nice one Skogs! An excellent candidate for this scenario.

Keith Cress
kcress -

http://www.flaminsystems.com