Siemens SENTRON PAC5200 - Page 28

4 Measurands and Recording
4.1 Measuring and Recording System
28 SENTRON PAC5100/5200, 7KM5212/5412, Device Manual
E50417-H1040-C568-A1, Edition 03.2015
Definition of the Measurands
Mains Voltage Level
• The measurement determines the RMS value of the mains voltage over a 10-period time interval for 50-
Hz distribution systems and over a 12-period time interval for 60-Hz distribution systems. All 10-/12-period
time intervals are measured without interruption and overlapping (the overlapping area excluded, see
Figure 4-1).
Undervoltage of the Mains Voltage
• The basic measurement of the RMS value V
rms
of an undervoltage is the determination of the RMS value
V
rms
(1/2) for each single measuring channel (see Figure 4-2). The limiting value for undervoltages is a
percentage value of Udin.
• The factory setting of the hysteresis is 2 % of Udin. It can be set from 1 % to 6 %.
• In multi-phase systems, all channels are independently synchronized in the zero point of the voltage.
• In 1-phase systems, undervoltage begins when the voltage V
rms
falls below the threshold of the
undervoltage. Undervoltage ends when the voltage V
rms
rises above the threshold value of the
undervoltage plus the hysteresis.
• In multi-phase systems, undervoltage begins when the voltage V
rms
falls below the threshold of the
undervoltage in one or more channels. Undervoltage ends when the voltage V
rms
rises above the
threshold value of the undervoltage plus the hysteresis in all measured channels.
• The undervoltage threshold value and the hysteresis are parameterized according to the measuring task.
• Undervoltage is characterized by the data pair residual voltage (V
res
) and duration (t):
The residual voltage is the smallest voltage value of V
rms
which is measured in a channel during
undervoltage.
Figure 4-2 Undervoltage Representation
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
V [V]
44,85 44,90 44,95
t [s]
V
rms
(1/2) :
RMS value over one period synchronized to the zero point of the fundamental
component , updated after each half period .
This value is only used to detect undervoltages , overvoltages and voltage
interruptions.
V
rms
n
n+1
n+2
n+3
n+4
n+5
n+6
n+7
n+8
n+ 9
n+10
V
rms
V
rms
V
rms V
rms V
rms
V
rms
V
rms
V
rms
V
rms
V
rms