Scaling Factors For Analogreport Channels - ABB RES670 Applications Manual

Section 6
Wide area measurement system
6.1.3.3
94

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-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:
AnalogXRange =
3277.0
IECEQUATION2446 V1 EN-US
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2
Phasor measurement unit RES670 2.2 IEC
1MRK 511 407-UEN C
GUID-0DDAF6A9-8643-4FDD-97CF-9E35EF40AF7E v2
Application manual