ABB Relion 670 Series Applications Manual page 97

1MRK 511 407-UUS Rev. J
6.1.3.3 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.
If the AnalogDataType is selected as Float , then these settings are ignored.
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:
• 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 =
IECEQUATION2446 V1 EN-US
The scale factor is calculated as follows:
sc alefactor
IECEQUATION2447 V1 EN-US
The scale factor will be sent as 1 on configuration frame 2, and 0.1 on configuration frame 3. The
range of analog values that can be transmitted in this case is
Phasor measurement unit RES670
Application manual
-AnalogXRange and +AnalogXRange . The resulting scale factor will be applied to
´
AnalogXRange 2
=
65535.0
=
0.0
=
16 bit integer range
3277.0
´
(3277.0 2.0 )
= =
0.1 a nd
65535.0
© Copyright 2017 Hitachi Power Grids. All rights reserved
AnalogDataType ) as Integer , there will be a down-
=
offse t 0.0
-0.1 to -3276.8 and +0.1 to +3276.7 .
Section 6
Wide area measurement system
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