Setup

Monitoring location : 1-phase 2-wire, 100V circuit

Problem

Equipment has malfunctioned

Analysis

68 “Wave (voltage waveform distortion)” events were recorded during an 18-day measurement period using the following settings. All events are of the same type.

Next, the waveform of each “wave” event was checked, and 2 types of events were found.
Type 1: Not switched to a sine wave after the waveform noise
Type 2: Switched to a sine wave after the waveform noise
We can assume that the events classified as “switched to a sine wave after the waveform noise” were due to the switching to the UPS output (stand-by system).

It appears that Type 1 has a higher noise level and should be switched to the UPS output. However, Type 2 shows a bigger difference in the current waveform when the voltage waveform shows the noise. Therefore, we can assume that a transient overvoltage occurs simultaneously when this event occurs. Unfortunately, the transient overvoltage is not detected, because its threshold is set at 0.480kV (480V). It is recommended that the threshold be set at 0.07kV (equivalent to 1/2 of the wave peak value) for a 100Vrms circuit

Source : Guidebook for Power Quality Measurement, HIOKI E.E. Corporation