128
Power Quality Analyzer PowerPad
®
IV Model 8345
20.8 TRANSIENT CAPTURE TRIGGERING MECHANISM
When a search for transients begins, each sample is compared to the sample
from the previous cycle. In standard IEC 61000-4-30, this monitoring method
is called the “sliding window method”. The previous cycle corresponds to the
middle of a virtual tube; it is used as the reference. When a sample deviates
from the tube, it is considered a triggering event; then, the instrument captures
the representation of the transient. The cycle that precedes the event and the
three cycles that follow it are stored in memory.
0
Reference cycle
(precedes monitored cycle)
Top of virtual reference tube
Cycle monitored
Bottom of virtual reference tube
Triggering event
The half-width of the virtual tube, for voltage or current, is equal to the threshold
programmed in the Transient mode’s configuration (see § 3.4.5).
20.9 CONDITIONS OF CAPTURE IN INRUSH CURRENT MODE
The capture is determined by a triggering event and a stop event. A capture will
stop automatically in any of the following cases:
■
The stop event occurs
■
The recording memory is full
■
The recording duration exceeds 10 minutes in RMS+WAVE mode
■
The recording duration exceeds 30 minutes in RMS mode
The capture stop threshold is calculated by the following formula:
[Stop threshold [A]] = [Triggering threshold [A]] x (100 - [stop hysteresis [ %]]) ÷ 100
The triggering and stop conditions of captures are below:
Filter
Triggering and stop conditions
A1
Triggering condition <=> [half-cycle RMS value of A1] > [Triggering threshold]
Stop condition <=> [half-cycle RMS value of A1] < [Stop; threshold]
A2
Triggering condition <=> [half-cycle RMS value of A2] > [Triggering threshold]
Stop condition <=> [half-cycle RMS value of A2] < [Stop; threshold]
A3
Triggering condition <=> [half-cycle RMS value of A3] > [Triggering threshold]
Stop condition <=> [half-cycle RMS value of A3] < [Stop; threshold]
3A
Triggering condition <=> [the half-cycle RMS value in one of the current]
channels > [Triggering threshold]
Stop condition <=> [the half-cycle RMS value in all of the current channels] <
[Stop threshold]