MI 2892 Power Master
Theory and internal operation
169
Table 5.6: Alarm signatures
Date
Date when selected alarm has occurred
Start
Alarm start time - when first value cross threshold.
Phase
Phase on which alarm occurred
Level
Minimal or maximal value in alarm
Duration
Alarm duration
5.1.15
Rapid voltage changes (RVC)
Standard compliance: IEC 61000-4-30 Class A (Section 5.11)
Rapid Voltage Change (RVC) is generally speaking an abrupt transition between two “steady state” RMS
voltage levels. It is considered as event, (similar to dip or swell) with start time and duration between
steady state levels. However, those steady state levels does not exceed dip or swell threshold.
RVC event detection
Instrument RVC event detection implementation strictly follows IEC 61000-4-30 standard requirements.
It begins with finding a voltage steady-state. RMS voltage is in a steady-state condition if 100/120
U
Rms(1/2)
values remain within an RVC threshold (this value is set by the user in MEASUREMENT SETUP
RVC Setup screen) from the arithmetic mean of those 100/120 U
Rms(1/2)
values. Every time a new U
Rms(1/2)
value is available, the arithmetic mean of the previous 100/120 U
Rms(1/2)
values, including the new value,
is calculated. If a new U
Rms(1/2)
value crosses RVC threshold, RVC event is detected. After detection
instruments wait for 100/120 half cycles, before searching for next voltage steady-state.
If a voltage dip or voltage swell is detected during an RVC event, then the RVC event is discarded
because the event is not an RVC event.
RVC event characterisation
An RVC event is characterized by four parameters: start time, duration, ∆Umax and ∆Uss.
RVC Threshold
Arithmetic mean
of the previous
100/120 U
RMS(½)
values
DIP Threshold
RVC threshold
with 50% hysteresis
U
RMS(½)
values
ΔUss
ΔUmax
Time
V
o
lt
ag
e
U
RM
S
RVC event duration
100/120
U
RMS(½)
Figure 5.15: RVC event description
Start time of an RVC event is time stamp when U
Rms(1/2)
value cross RVC threshold level
RVC event duration is 100/120 half cycles shorter than the duration between adjacent steady
states voltages.
