Power fluctuations and draw down

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I work at a ski resort and we are having a power fluctuation problems that has been present for the last 3-4 years. We have a ski lift located just outside our maintenance office building and whenever it is on, it starts affecting our surge protectors and battery backups for our computer system, enough to cause some battery backups to die completely. At our 480v panel downstairs, we have a 75KVA 480v - 208y/120v 150C rise transformer that is used to supply power to the whole building. The 480v panel also supplies the power to the ski lift that affects our system. Measured voltage fluctuations are 107v to 155v.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Electrical Engineer - Power Systems
What type and size is the drive on the ski lift motor?

How are your 'surge protector' being affected?

What type of UPSs do you have, inexpensive plug in the wall ones or ones with separate battery banks?

Are you using a true RMS meter when measuring your voltages?
 
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wirenut1980

Senior Member
Location
Plainfield, IN
Sounds like there are voltage sags to the building caused by the chair lift motor. The battery backups are probably switching to battery very often which drains the batteries quicker and wears out switching components of the UPS which eventually causes the UPS to fail.

First, I would try check if my battery backups have a sensitivity setting that can be switched from "high" to "medium." If you battery backup has a USB or serial port to connect it to your computer, you can usually make this type of settings change. If this does not solve the problem with your computer problems, or you can't make this change to the UPS, you may have to serve the building from a different transformer that does not have a chair lift on it.
 

G._S._Ohm

Senior Member
Location
DC area
a ski resort and we are having a power fluctuation problems that has been present for the last 3-4 years.

Measured voltage fluctuations are 107v to 155v.
Decades ago I read an article in the IEEE Spectrum magazine about a ski resort that had no problems until another resort opened 9 miles away, after which the breakers in the first ski resort began tripping. It was baffling.

An analysis showed that the inductance and capacitance of the interconnecting power lines were resonating but somehow this only caused the first resort problems.

I suppose the fix was to damp out these oscillations with some type of resistive load or maybe use mechanical damping or flywheels on the lift motors. In other words, the "Q" of the circuit was reduced.

Possibly you could confirm this theory by loading down your power lines with an enormous resistive load and look for a small or large change in the symptoms, hopefully in a good direction.

How often does the problem recur?
 
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Electric-Light

Senior Member
The common UPS, known as "standly" UPS are very sensitive. If I have my laser printer on the same circuit as my computer, it will hunt back and forth repeatedly from battery to line. They're very sensitive to notching.

One could use an online UPS(also called "double conversion"), but that's only isolating the computer from poor power quality and nothing else. It's available in a size as small as 750VA from TrippLite and multi kVA units are available from many manufacturers.

I would try to work it out with the utility. The medium voltage to 480v transformer may need to be oversized. Of course its possible to have 120/240 single phase or 208Y/120 fed from a different transformer right from medium voltage, but that may end up being having two separate billing meters.
 

brian john

Senior Member
Location
Leesburg, VA
What would be nice would be to utilize 2 power analyzers one at the service for the lift and one at your transformer that you can cross reference lift runs with voltage issues in the office. In lieu of this you could use two multi meters and two ampclamps (ALL TRUE RMS METERS), and two radios. Coordinate the operations.

SOME OF THIS HAS ALREADY BEEN COVERED ABOVE.

On line or off line UPS will not back a difference as the voltage fluctuations are causing the UPS's to go to battery too often with insufficient recharge time. In addition you have a limited amount of discharges for a battery.

Need to know what operates the lift motor Drive or what ever.

What is happening to the TVSS's
 

kwired

Electron manager
Location
NE Nebraska
I work at a ski resort and we are having a power fluctuation problems that has been present for the last 3-4 years. We have a ski lift located just outside our maintenance office building and whenever it is on, it starts affecting our surge protectors and battery backups for our computer system, enough to cause some battery backups to die completely. At our 480v panel downstairs, we have a 75KVA 480v - 208y/120v 150C rise transformer that is used to supply power to the whole building. The 480v panel also supplies the power to the ski lift that affects our system. Measured voltage fluctuations are 107v to 155v.
What is measured voltage at the 480 distribution panel when the 120/208 is experiencing the fluctuations? It may not be the ski lift itself but could be other loads on the 120/208 system that happen to operate when the lift is operating.

My first thought when you said 107-155 volt fluctuation is neutral problem on the 120/208 system. That is a big enough change in voltage that there is either something malfunctioning or was poorly designed and installed. If it once worked without this trouble something has failed someplace. Could be trouble with POCO equipment - that is why I ask what is readings in 480 volt panel. Also what is phase to phase voltage in 208 volt system when this is happening?
 

Electric-Light

Senior Member
I should have addressed this initially. If the problem is caused by the lift, the problem will be observable on the 480v side. Otherwise, I would start blaming downstream. Ski-resort? I don't know what you've got going on, but you mentioned UPS, so I'm guessing you've got computers. So, my first blame would be photocopy and laser printers.

My first thought when you said 107-155 volt fluctuation
The credibility of data is questionable if its the data reported by UPS. I have an APC SmartUPS standly UPS and when it switches back and forth between line and battery, it tends to capture the spikes from those events too.

A ski-lift is not like an air conditioner that starts many times an hour and I don't see it as being a fluctuating load.

Threadstarter,

Do you have a laser printer, or a photocopier, connected to the same circuit as the UPS? That will very likely upset the UPS.

Here is what my laser printer does to the circuit. The level of fluctuation isn't so great, but it is very fast, and many UPSs have so called high change of rate over time tripping. Sort of like driving on drift notification bumps on freeway shoulder. The height change is low, but very fast. My UPS will go back and forth between battery and line. The change is within limits, but the rate of change is high enough that UPS trips out.

 
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kwired

Electron manager
Location
NE Nebraska
I should have addressed this initially. If the problem is caused by the lift, the problem will be observable on the 480v side. Otherwise, I would start blaming downstream. Ski-resort? I don't know what you've got going on, but you mentioned UPS, so I'm guessing you've got computers. So, my first blame would be photocopy and laser printers.



The credibility of data is questionable if its the data reported by UPS. I have an APC SmartUPS standly UPS and when it switches back and forth between line and battery, it tends to capture the spikes from those events too.

A ski-lift is not like an air conditioner that starts many times an hour and I don't see it as being a fluctuating load.

Threadstarter,

Do you have a laser printer, or a photocopier, connected to the same circuit as the UPS? That will very likely upset the UPS.

Here is what my laser printer does to the circuit. The level of fluctuation isn't so great, but it is very fast, and many UPSs have so called high change of rate over time tripping. Sort of like driving on drift notification bumps on freeway shoulder. The height change is low, but very fast. My UPS will go back and forth between battery and line. The change is within limits, but the rate of change is high enough that UPS trips out.

I did not think of reported voltage being reported by the UPS. That would make some sense if that is where voltage reading is originating. The other thing that complicates this is the fact that the OP indicated that this is a problem when the lift is running, but the observed problem is on the other side of a transformer from what the lift is connected to. He does not mention any trouble anyplace else besides the UPS.

I kind of have an idea that maybe the lift has a VFD and is introducing harmonics that the UPS does not like.

I don't know all the ins and outs on harmonics but think this is a direction that maybe the investigation should go assuming that the 480 volt and 120/208 volt measurements appear normal when the fluctuations are happening and if there is a VFD driving the lift.

If the 120/208 system did have the kind of fluctuation that the OP mentioned then the problem would not be limited to just the UPS, they would have a lot of lighting problems and other noticeable troubles.
 

Electric-Light

Senior Member
If the 120/208 system did have the kind of fluctuation that the OP mentioned then the problem would not be limited to just the UPS, they would have a lot of lighting problems and other noticeable troubles.
That's why I suspect laser printer or a photocopier with a rapidly switched fuser control, which is very often connected together as a computer peripheral, often on the same power strip as the computer when it really shoud be, in my opinion, connected to a dedicated branch as an appliance.

The laser printer causes enough notches to visibly disturb lighting. Your eyes are quite sensitive just like UPS events that cause UPS to click would very likely cause a noticeable flicker.

Inkjet printers are costly to maintain, so I know that in commercial use, laser dominates the market share. Laser printers go in idle, but it will continue this disturbing abrupt draws for 5min to one hour to reduce warm up time. The duration depends on settings or firmware.

Since this is a commercial building, the lighting is not going to be sharing circuits with outlets like in homes. The light maybe on 120 or 277, but if the lift was the cause, I'm fairly confident that they will flicker enough to be noticeable.
 
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Speedskater

Senior Member
Location
Cleveland, Ohio
Haven ridden many ski-lifts, they do stop several times each hour!

I would suspect the ski-lift's regenerative braking from an "E" stop when someone falls off a chair when loading or unloading.
 

kwired

Electron manager
Location
NE Nebraska
That's why I suspect laser printer or a photocopier with a rapidly switched fuser control, which is very often connected together as a computer peripheral, often on the same power strip as the computer when it really shoud be, in my opinion, connected to a dedicated branch as an appliance.

The laser printer causes enough notches to visibly disturb lighting. Your eyes are quite sensitive just like UPS events that cause UPS to click would very likely cause a noticeable flicker.

Inkjet printers are costly to maintain, so I know that in commercial use, laser dominates the market share. Laser printers go in idle, but it will continue this disturbing abrupt draws for 5min to one hour to reduce warm up time. The duration depends on settings or firmware.

Since this is a commercial building, the lighting is not going to be sharing circuits with outlets like in homes. The light maybe on 120 or 277, but if the lift was the cause, I'm fairly confident that they will flicker enough to be noticeable.
I understand that but how will it relate to only happening if the ski lift is in operation?
 

kwired

Electron manager
Location
NE Nebraska
Haven ridden many ski-lifts, they do stop several times each hour!

I would suspect the ski-lift's regenerative braking from an "E" stop when someone falls off a chair when loading or unloading.
That statement would indicate that there is likely an electronic drive controlling the lift. Across the line starting and stopping should not have such an impact in a separate building on the other side of a transformer plus only effect a somewhat more sensitive load. Across the line starting will not introduce anything into the supply when stopping other than a slight increase in system voltage when the load is removed unless there is some undersized equipment or conductor issues.
 

obm2010

Member
kindly check your transformer in bank, by the help of your nearest commercial power cooperative. voltage drop from your commercial power is only on single phase., this the other factor of your problem. the transformer in bank will be adjusted only by the authorized personnel of your nearest electrical cooperative
 

obm2010

Member
sir, check your transformer in bank by the help of your nearest electrical cooperative., because one of the possible cause of your problem is that your transformer is in single phase and same of the mechanical parameters in your transformer will be adjusted by the said personnel.
 
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