Poor power quality, same time every nite

[catchtwentytwo]

Interesting, it looks like the product is at end of life and now is supported by PowerWare. See http://www.powerware.com/Products/end_of_life_Manuals.asp?CX=3 I haven't totally digested the manual but it looks like the product is normally in the rectifier/battery/inverter path except when in static bypass.

Think of the UPS system as like a canary in a coal mine, it may provide a lot of clues when facing a PQ issue.

What KVA rating are they, that would help locate the official specifications on PowerWare's web site? The specs you linked to say [FONT=Verdana, Arial, Helvetica, sans-serif]"Input 5% or less; output maximum 3% linear load" but that's on a reseller's site. [/FONT]Can't understand the claim there is no rectifier, how would they charge the batteries?
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I'm guessing the UPS could be 8 years old. So the questions are:
[/FONT]

1. How well are they maintained and how old are the batteries?
2. Did they go on battery when the events occur?
3. Did they drop load or go to staic bypass (that could happen if the batteries were in poor condition see #1).
4. Is the environment where the UPS is located air conditioned and clean?
5. What size motors are being fed?

 

[catchtwentytwo]

Here's the user manual for the Unity 3-Phase UPS . There are sections on Alarms and Events that might show something at the times you are seeing the THD spike. Not clear how many and how long the events are retained so next time there's one of those events, some one should review them. Look for events just before the plant goes on generator.

 

[wirenut1980]

Thanks for the interest -- The units are Unity 3-phase, they are in a nearby building so I don't know what's going on during the spikes. What we do know, is that there has been only clean power since the utility changed took our plant off the feed we were on.

The plant tech said he didn't see anything on the control/display that indicated the units were disconnecting from supply.

Here is a product sheet:http://www.bomara.com/Best/unity1threephase_spec1_eu.htm

The product overview states "Unlike a double-conversion system, a UNITY/I Three-Phase system draws a clean sinusoidal current. With no rectifier to produce harmful input current distortion, this system requires no costly filtering.

The specs mention input harmonic distortion @ 5% or less.

Nice work, sounds like you nailed it. :smile:

 

[robbietan]

capacitors dont produce harmonics, they tend to 'draw in' harmonics to selves until they blow up. the harmonics could have come from the facility with the 'monster pumps' if those pumps use VFDs. the voltage THDs graphs you have show have high values for the 13th harmonic, which sound like the VFD have a 12 pulse rectifier. depending on how near your facility is to these 'monster pumps', I would suggest that you are being affected by this load. if the graph came from the primary side of your transformer (33000/480)

if the analyzer was connected to the transformer secondary, I would say that is your 12 pulse rectified UPS reacting to a voltage drop on the system caused by those 'monster pumps' starting.

I bet those electrotek guys would sure to have loved to be involved in this case

 

[zot64]

what is the price to expect on a meter like yours?