ABB RELION RET670, Applications Manual

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6.2.3.3 Scaling Factors for ANALOGREPORT channels
GUID-0DDAF6A9-8643-4FDD-97CF-9E35EF40AF7E v2
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 calefactor
offset
´
=
=
=
bit integer range
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:
• 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 504 163-UUS A
Section 6
Wide area measurement system
Transformer protection RET670 2.2 ANSI 121
Application manual