I need help determining cause of wave form distortion
I need help determining cause of wave form distortion
(OP)
The below wave forms where captured with a hioki 3196 attached to the load side of the service disconnect of a 300 amp service. The service feeds a lot of computer equipment 3 liebert units and a large Mitsubishi U.P. S system. The distortion occurs at irregular patterns 2 to 4 times an hour. Is the magnitude of the distortion something to be concerned about? Any help opinion or lead to a probable cause is greatly appreciated.






RE: I need help determining cause of wave form distortion
Hello.
It seems that some equipment was switched on phases 1 and 2 (red and green) making their respective phase currents almost in-phase with their respective phase voltages. The "blue" (phase 3) remained lagging its phase voltage.
Maybe power factor correction caps switching with the phase 3 cap not functioning well, or it' just my eyes!
Please try compare the peaks of the voltage waves with the respective current waves.
Others might have different takes on this, so just wait for a while.
RE: I need help determining cause of wave form distortion
The current waveforms show what looks like a >100A spike for each of these transients. The dI/dt looks quite dramatic, and the load tapers off from the peaks over the next few cycles. I would imagine it is one of your loads switching on. There appears to be a moderate amount of current THD both before and after the events.
burnt2x has quite admirably noticed the change of phasing alignments from before to after the events.
Of most concern is the actual amplitude of the load imposed, but an overall effect on the voltage waveform past the transient itself is not evident.
RE: I need help determining cause of wave form distortion
RE: I need help determining cause of wave form distortion
RE: I need help determining cause of wave form distortion
It seems to be a monitor problem.
Note that the voltages don't change when the currents increase. Is it a strong system?
Regards,
H. Bronzeado
RE: I need help determining cause of wave form distortion
RE: I need help determining cause of wave form distortion
Can you isolate the problem? If it occurs 2-4 times an hour, you could check each individual circuit being fed from the original monitoring point, and so on down the line until you find the problem.
RE: I need help determining cause of wave form distortion
For monitor problem I mean "instrument problem".
The suddenly change in the currents without a "response" in the voltages seems it may not be real, unless the short-circuit level at that point of measurement is very high in coparison with the load size (strong system).
H. Bronzeado
RE: I need help determining cause of wave form distortion
I totally agree with DanDel. Try isolate problem, on the first step don't think about reason.
Regards.
Slava
RE: I need help determining cause of wave form distortion
Where are the circuit boards in relation to the switched load? There is not much of a voltage spike at the point where you monitored the overall load, but if the circuit boards are at the end of the circuit where the switched load is, there might be a much larger voltage spike at that point because of the impedance of the circuit to the load.
RE: I need help determining cause of wave form distortion
RE: I need help determining cause of wave form distortion
The events are not voltage sags but occurrences of voltage distortions! The distortion value is approximately 20V or so. As far as I can remember, the possible causes of these phenomena are switching on of the following equipment:
- Operation of battery chargers
- Large computers
- Variable Speed Drives (VSD)
- Arc welders
- Fluorescent lighting with electronic ballasts
You may want to survey the area for these electrical equipment or initiate anti-distortion solutions (use of special circuit and grounding practices or install harmonic filters).RE: I need help determining cause of wave form distortion
This is odd.
RE: I need help determining cause of wave form distortion
RE: I need help determining cause of wave form distortion
RE: I need help determining cause of wave form distortion
The January issue is not on the EC&M website yet.