ABB Relion 670 Series Applications Manual page 108

Section 6
Wide area measurement system
synchrophasor and frequency data which are included in the C37.118 synchrophasor streaming
data are filtered in order to suppress aliasing effects, as the rate of the C37.118 data is slower than
the data rate for internal processing. For this purpose, there is an anti-aliasing filter designed for
each reporting rate. The correct anti-aliasing filter will be automatically selected based on the
reporting rate and the performance class (P/M) settings. The filters are designed to attenuate all
aliasing frequencies to at least -40 dB (a gain of 0.01) at M class.
For example, when the synchrophasor measurement follows the fundamental frequency beyond
the fixed Nyquist limits in C37.118 standard, the anti-aliasing filter stopband moves with the
measured fundamental frequency. This has to be considered in connection with C37.118, where the
passband is defined relative to a fixed nominal frequency as shown in the equation 15.
F
s
f
±
0
2
IECEQUATION2418 V1 EN-US
where,
f
0
F
s
6.2.3.3 Scaling Factors for ANALOGREPORT channels
The internal calculation of analog values in the IED is based on 32 bit floating point. Therefore, if
the user selects to report the analog data (
conversion of a 32 bit floating value to a new 16 bit integer value. In such a case, in order to
optimize the resolution of the reported analog data, the user-defined analog scaling is
implemented in the IED.
The analog scaling in the IED is automatically calculated by use of the user-defined parameters
AnalogXRange for the respective analog channel X. The analog data value on the input X will have a
range between
the reported analog data where applicable.
AnalogDataType is selected as Float , then these settings are ignored.
If the
The analog scaling in the IED is calculated using the equation:
S calefactor
offset
65535.0
IECEQUATION2443 V1 EN-US
According to the IEEE C37.118.2 standard, the scale factors (conversion factor) for analog channels
are defined in configuration frame 2 (CFG-2) and configuration frame 3 (CFG-3) frames as follows:
102
The synchrophasor measurement is adaptive as it follows the fundamental
frequency over a wide range despite the reporting rate.
is the nominal frequency
is the reporting rate
-AnalogXRange and +AnalogXRange . The resulting scale factor will be applied to
´
AnalogXRange 2
=
65535.0
=
0.0
=
16 bit integer range
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AnalogDataType ) as Integer , there will be a down-
1MRK 511 401-UUS F
(Equation 15)
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