Scaling Factors For Analogreport Channels - ABB RELION 670 SERIES Applications Manual

1MRK 506 369-UUS -
6.2.3.3
Line distance protection REL670 2.2 ANSI
Application manual

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 (AnalogDataType) as Integer, there
will be a down-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 -AnalogXRange and +AnalogXRange. The
resulting scale factor will be applied to the reported analog data where applicable.
If the AnalogDataType is selected as Float, then these settings are ignored.
The analog scaling in the IED is calculated using the equation:
AnalogXRange
=
S calefactor
65535.0
=
offset 0.0
=
65535.0 16 bit integer range
IECEQUATION2443 V1 EN
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:
• CFG-2 frame: The field ANUNIT (4 bytes) specifies the conversion factor as a
signed 24 bit word for user defined scaling. Since it is a 24 bit integer, in order to
support the floating point scale factor, the scale factor itself is multiplied in 10, so that
a minimum of 0.1 scale factor can be sent over the CFG-2 frame. The resulting scale
factor is rounded to the nearest decimal value. The clients receiving the Analog scale
factor over CFG-2 should divide the received scale factor by 10 and then apply it to
the corresponding analog data value.
• CFG-3 frame: The field ANSCALE (8 bytes) specifies the conversion factor as X'
= M * X + B where; M is magnitude scaling in 32 bit floating point (first 4 bytes) and
B is the offset in 32 bit floating point (last 4 bytes).
The server uses CFG-3 scale factor to scale the analog data values. As a result, the clients
which use scale factors in CFG-3 in order to recalculate analog values, will get a better
resolution than using the scale factors in CFG-2.
The following examples show how the scale factor is calculated.
Example 1:
Wide area measurement system
´
2
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