The Modbus measurands are located in the Modbus register area. The measurands are readable from both 3X and 4X areas from the same register addresses.
The Modbus measurands derive from the protection relay's internal, original IEC 61850 filtered measurand values. Modbus register values in this protection relay are always in integer format. Since the internal IEC 61850 values are often represented as decimal numbers, the Modbus stack needs to scale these values to integer format. Thus, there always exists a scale Factor and an offset parameter for each Modbus register value. The user can freely configure these parameters with Communication Management in PCM600.
The formula for calculating the Modbus register value is:
The range of the original IEC 61850 value can be seen in the Modbus memory map point list.
All frequently updated data are readable from a sequential data area. Additionally, there is a separate sequential data area for measurands and counters with a slow update rate.