ABB RELION REF615R Technical Manual page 432

Section 8
Power quality measurement functions
426
Generally, no event detection is done if both the magnitude and duration requirements are
not fulfilled. For example, the dip event does not indicate if the TRMS voltage magnitude
remains between Voltage dip set 3 and Voltage dip set 2 for a period shorter than VVa dip
time 3 before rising back above Voltage dip set 3.
The event indication ends and possible detection is done when the TRMS voltage returns
above (for dip and interruption) or below (for swell) the activation pickup limit. For
example, after an instantaneous dip, the event indication when the voltage magnitude
exceeds Voltage dip set 1 is not detected (and recorded) immediately but only if no longer
dip indication for the same dip variation takes place and the maximum duration time for
dip variation is not exceeded before the signal magnitude rises above Voltage dip set 3.
There is a small hysteresis for all these limits to avoid the oscillation of the output
activation. No drop-off approach is applied here due to the hysteresis.
Consequently, only one event detection and recording of the same variation type can take
place for one voltage variation, so the longest indicated variation of each variation type is
detected. Furthermore, it is possible that another instantaneous dip event replaces the one
already indicated if the magnitude again undershoots Voltage dip set 1 for the set time after
the first detection and the signal magnitude or time requirement is again fulfilled. Another
possibility is that if the time condition is not fulfilled for an instantaneous dip detection but
the signal rises above Voltage dip set 1, the already elapsed time is included in the
momentary dip timer. Especially the interruption time is included in the dip time. If the
signal does not exceed Voltage dip set 2 before the timer VVa dip time 2 has elapsed when
the momentary dip timer is also started after the magnitude undershooting Voltage dip set
2, the momentary dip event instead is detected. Consequently, the same dip occurrence
with a changing variation depth can result in several dip event indications but only one
detection. For example, if the magnitude has undershot Voltage dip set 1 but remained
above Voltage Intr set for a shorter time than the value of VVa dip time 1 but the signal rises
between Voltage dip set 1 and Voltage dip set 2 so that the total duration of the dip
activation is longer than VVa dip time 2 and the maximum time is not overshot, this is
detected as a momentary dip even though a short instantaneous dip period has been
included. In text, the terms "deeper" and "higher" are used for referring to dip or
interruption.
Although examples are given for dip events, the same rules can be applied to the swell and
interruption functionality too. For swell indication, "deeper" means that the signal rises
even more and "higher" means that the signal magnitude becomes lower respectively.
The adjustable voltage thresholds adhere to the relationships:
VVa dip time 1 ≤ VVa dip time 2 ≤ VVa dip time 3.
VVa swell time 1 ≤ VVa swell time 2 ≤ VVa swell time 3.
VVa Int time 1 ≤ VVa Int time 2 ≤ VVa Int time 3.
1MRS240050-IB C
REF615R
Technical Manual