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7
7.1 Phasor Measurement Unit (PMU)
53
Digital Fault Recorder, SIMEAS R-PMU, Manual
E50417-H1076-C360-A5, Release 10.2012
Data recording
The phase angle of signal X
m
is calculated in relation to a cosine function with the nominal
frequency that has been synchronized with the UTC time reference (UTC = Coordinated
Universal Time) (see figure 7-2).
Figure 7-2 Determining the phase angle
ϕ
of the measuring signal X
m
with regard to the cosine function
The reporting rate (see Page 54) defines the number of phasors transferred per second. If the
defined sampling interval T
0
is unequal to the integer multiple of the measuring signal cycle
duration T
m
, the phasor's length remains constant, however, the phase angle is changed (see
figure 7-3).
Figure 7-3 Sampling of the signal X
m
; T
m
unequal T
0
If the sampling interval T
0
corresponds to the integer multiple of the measuring signal X
m
cycle
duration, a constant phasor is determined during every sampling instant.
UTC
Time
Sync
ϕ
Δ ϕ
= -90 degrees
ϕ
Δ
Cosine function
Measuring
Signal
X
m
ϕ
0
0
ϕ
1
ϕ
3
ϕ
2
ϕ
4
Measuring signal X
m
Sampling instants
Tm
ϕ
T
0
2 T
0
3 T
0
4 T
0
5 T
0