GE Multilin B30 Bus Differential System D-1
APPENDIX D D.1 IEC 60870-5-103
D
APPENDIX D IEC 60870-5-103 COMMUNICATIONSD.1IEC 60870-5-103 D.1.1 OVERVIEW
IEC 60870-5-103 is defined as a companion standard for the informative element of the protection equipment. IEC 60870-
5-103 defines communication for a serial, unbalanced link only. Communication speeds are defined as either 9600 or
19200 baud.
This manual assumes basic knowledge of the IEC 60870-5-103 protocol and the standard IEC 60870 documents relating to
the protocol.
Standard IEC 60870 documents relating to IEC 60870-5-103:
• IEC 60870-5-1 Transmission frame formats
• IEC 60870-5-2 Link transmission procedures
• IEC 60870-5-3 General structure of application data
• IEC 60870-5-4 Definition and coding of application information elements
• IEC 60870-5-5 Basic application functions
• IEC 60870-5-6 Conformance testing guidelines
An IEC 60870-5-103 device is required to provide an interoperability table. Interoperability means that any required applica-
tion data in the device, which can be coded into an IEC 60870-5-103 data type, can be mapped into the IEC 60870-5-103
address space. This data is recognized by any IEC 60870-5-103 master.
D.1.2 FACTOR AND OFFSET CALCULATION TO TRANSMIT MEASURAND
The general formula for the transmitted value is Xt = a * X + b
where X is the measurand, a is the multiplication factor, b is the offset and Xt is the value transmitted.
The conditions for determining a and b, when the values exceed the range are:
4096 = a*Xmax + b (Xmax is the maximum value for the measurand)
-4095 =a*Xmin + b (Xmin is the minimum value for the measurand)
By solving the above system of equations for a and b, we find that:
a = 8191 / (Xmax - Xmin)
b = -4096 * (Xmax + Xmin) / (Xmax - Xmin)
So
Xt = 8191/(Xmax - Xmin)) * X - 4096 * (Xmax + Xmin) / (Xmax - Xmin)
We may further simplify the above formula for situations where:
1)
Xmin = -Xmax (positive and negative values) :
Xt = (8191/2*Xmax) * X
a = 4096/Xmax
b = 0
2)
If Xmin = 0 (only positive values)
Xt = (8191/Xmax) * X - 4096
a = 2 * 4096/Xmax
b = -4096
To calculate Xmax, one needs to know the rated value for the specific type of measurand.
Xmax = 2.4 * Xrated
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