Siemens SIMEAS R-PMU, Руководство пользователя, Страница: 55 / 296

7
7.1 Phasor Measurement Unit (PMU)
55
Digital Fault Recorder, SIMEAS R-PMU, Manual
E50417-H1076-C360-A5, Release 10.2012
Total vector error (TVE)
The TVE describes the error between the actual and the measured value of the input signal. The
standard IEEE 37.118 - 2005 defines among others the maximum threshold of 120 % V
n
or I
n
.
Up to this threshold a TVE of 1 % must not be exceeded for steady signals. The standard defines
two levels the influencing factors may not exceed and a TVE of 1 % must not be exceeded. SIM-
EAS R-PMU complies with level 1 defining the following influencing factors for a TVE of 1 %:
−
Signal frequency (related to f
n
): ±5 Hz
−
Signal amplitude (related to 100 % nominal amplitude): 10 % to 120 %
−
Phase angle (related to 0°) ±
Π
−
harmonic distortions (related to <0,2 % (THD): 10 % of each harmonic up to 50th harmonic
The TVE is defined as follows:
where:
X
r(n)
= real part of measured signal X
r
= real part of input signal
X
i(n)
= imaginary part of measured signal X
i
= imaginary part of input signal
Values influencing the TVE:
‰
Amplitude error
‰
Phase error
‰
Synchronization accuracy (deviation from UTC)
The synchronization accuracy is influenced by the timer, e. g., the GPS timer, the correct setting
of the latency (see chapter 8.3) and the optimum installation of the GPS antenna.
TVE
X
r(n)
X
r
–
( )
2
X
i(n)
X
i
–
( )
2
+
X
r
2
X
i
2
+
------------------------------------------------------------------
=
Note
For currents higher than AC 7 A, SIMEAS R-PMU switches internally to the high current range
(AC 7 A to AC 400 A). For a current transformer with a transformation ratio 1000 A / 1 A or
1000 A / 5 A, this corresponds to a current of 700 % I
n
or 140 % I
n
. The high current range pro-
vides a lower measuring accuracy: Due to this fact, PMU data are marked as invalid in 16 bit
integer format for currents higher than AC 7 A. Normally, this are short term events, caused by
short circuits, for example. See chapter 16.1.4, current input (VCDAU or CDAU).