ABB rec670 Applications Manual

6.2.3.3 Scaling Factors for ANALOGREPORT channels
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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:
2
65535.0
0.0
65535.0 16
AnalogXRange
S c alefactor
offs et
´
=
=
= bit integer range
IECEQUATION2443 V1 EN-US
According to the IEEE C37.1
18.2 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:
1MRK 511 401-UUS A Section 6
Wide area measurement system
Bay control REC670 2.2 ANSI 113
Application manual

ABB rec670 Specifications

General

Brand	ABB
Model	rec670
Category	Control Unit
Language	English