GE Multilin D30 Line Distance Protection System D-1APPENDIX D D.1 IEC 60870-5-103DAPPENDIX D IEC 60870-5-103 COMMUNICATIONSD.1IEC 60870-5-103 D.1.1 OVERVIEWIEC 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 or19200 baud.This manual assumes basic knowledge of the IEC 60870-5-103 protocol and the standard IEC 60870 documents relating tothe 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 guidelinesAn 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 60870-5-103address space. This data is recognized by any IEC 60870-5-103 master.D.1.2 FACTOR AND OFFSET CALCULATION TO TRANSMIT MEASURANDThe general formula for the transmitted value is Xt = a * X + bwhere 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)SoXt = 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) * Xa = 4096/Xmaxb = 02)If Xmin = 0 (only positive values)Xt = (8191/Xmax) * X - 4096a = 2 * 4096/Xmaxb = -4096To calculate Xmax, one needs to know the rated value for the specific type of measurand.Xmax = 2.4 * Xrated
