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As the fault recording proceeds, TRIDENT sorts them according to the following table:
Current Fault
Conditions of fault termination
Conditions of passing from
dip to interruption
Rise
V < High Threshold - hysteresis
Dip
V > Dip Thr hysteresis
V < interruption Threshold
Interruption
V > Interruption Thr hys
REMARK:
if an interruption appears and/or disappears slowly, TRIDENT can record a dip,
then an interruption, then a sag before coming back to a normal value.
For the duration of the fault, every 2ms, the sum of the voltages for the calculation of the mean
value during the fault, and the peak value during the fault is updated.
At the end of the fault,
TRIDENT checks that its duration is greater than the fault duration
threshold programmed by the user. If not, TRIDENT ignores this fault.
Otherwise TRIDENT calculates the mean value of the voltage during the fault and archives the fault
parameters in memory (length, peak and mean values, type, phase).
Additionally, after the end of the fault, TRIDENT archives the mean values over 1s of the 3
voltages and the 3 currents following the end of the fault.
If it is an interruption, TRIDENT defines its type as long or brief according to its duration with
reference to the programmed discrimination threshold.
The memorization of the rapid variations is « circular », that is to say that when the memory is full,
the oldest recordings are replaced by the new.
5.4.3
Calculation of slow variations
Calculation of the mean voltages over 1 second :
The following formula is used :
V
V
Nb Ech
i
1
2
sec
_
Vi being the 1ms sample,
Nb_Ech the number of samples taken over the 1 second period.
The calculation of line voltages, currents and the active powers use similar formulas.
It is these values that are displayed in the section “
Direct Measurements”.