Waveform Examples for Subcycle (Transient) Events

Subcycle or Transient Event

A Subcycle (or Transient) Event will be triggered (and a waveform consequently captured) when a transient event occurs that causes a larger than expected excursion from the nominal AC waveform. Noise, spikes, and other transients that are higher in frequency than the mains (higher than 50Hz or 60Hz normally) frequency, and cause deviations in the nominal sine wave, can trigger the Subcycle Event.

Triggering is controlled by the Sub-Cycle Event Trigger. The Sub-Cycle Event Trigger is a feature unique to the TEALwatch® power monitor. The Sub-Cycle Event Trigger (SCET) is a very flexible set of algorithms that effectively track the AC waveform and trigger an event when there is an unexpected sub-cycle excursion from the nominal AC voltage waveform. Refer to the Users Manual, section 3.6 for more details.

Several examples of a Subcycle Event waveform signature are shown below.

Example of a Subcycle Event, showing a fairly large, intermediate frequency
(1kHz - 2kHz), subcycle transient, mainly on phases A and B. The Subcycle Event
on phase A causes a higher than normal peak and RMS voltage to appear,
and can be particularly damaging and disruptive to sensitive electronics.

Example of a Subcycle Event, showing a fairly large, intermediate frequency
(1kHz - 2kHz), subcycle transient, mainly on phases A and B. The Subcycle
Event on phase B has multiple zero-crossing points during the event,
and can be particularly damaging and disruptive to sensitive electronics.

Example of a Subcycle Event, showing a fairly large, intermediate frequency
(1kHz - 2kHz), subcycle transient, mainly on phases A and B. The Subcycle Event
on phase A causes a higher than normal peak and RMS voltage to appear,
and can be particularly damaging and disruptive to sensitive electronics.

Example of a Subcycle Event, showing a fairly large, intermediate frequency
(1kHz - 2kHz), subcycle transient, on all 3 phases. The Subcycle
Event on phase A has multiple zero-crossing points during the event,
and can be particularly damaging and disruptive to sensitive electronics.

How Do I Adjust The Trigger Thresholds?

To adjust the set-points of the event triggers, please refer to the Users Manual, section 3.6.

How Do I Eliminate These Kinds of Events?

To reduce or eliminate these kinds of power events, you may need to increase the level of your power conditioning to a Voltage Regulator or a UPS. For more information, visit our Additional Power Conditioning web-pages.

For a sampling of various Case Studies that describe various power quality issues and their causes, please visit our Case Studies webpage.

For more information, please contact the TEAL Marketing Department.