UDR register value manipulation - Arc protection - Auto synchronization - Bay control and measurement - Merging unit - Transformer protection - 2 winding - Feeder protection - Voltage regulation - Capacitor bank protection - Petersen Coil control - Grid automation - Busbar differential protection (high impedance) - Back-up protection - Motor protection - Busbar protection (voltage and frequency) - Transformer protection - 3 winding - Interconnection protection - Generator protection - Power management/Load shedding - Modbus Communication Manual - REX640 Protection and control - PCL4 - IEC - ANSI

Additional rescaling of the source data value

There are three possibilities for UDR rescaling of the Modbus source register value.

Multiplicative and divisor scaling are similar operations. The defined scale factor can in both cases be a decimal value. For example, multiplicative scaling by 0.25 is the same as divisor scaling by 4.

Ratio scaling can be used in the same manner as multiplicative or divisor scaling, but including an offset. Additionally, it is possible to define new limit ranges for the resulting register value. Value then saturates (stops) at the defined min. and max. values. This may be needed for retrofit purposes, in case the relay value must emulate exactly the same value range as the value from the replaced unit.

For multiplicative and divisor scaling, the register value always saturates at the min. and max. values for the register type in question. The value does not roll over.

Swapping high and low words within a 32-bit register

32-bit registers do not exist in the Modbus standard. A 32-bit register consists of two consecutive 16-bit registers that together form the 32-bit value. There is no official definition for the low-high word order in a 32-bit register. Most vendors, including this relay's, use the order high-low (high word on lower address) as default. If the word order is incorrect, for example in a retrofit case, it is possible to change it.

Specific retrofit UDR manipulations

Swapping of the byte order within a register word
Redefining the register bit size. Less than 16 bits are used for the value. The used bits can additionally be left or right justified within the register, that is, they can appear on either the most significant or least significant side of the register.

Table 1. UDR scaling alternatives
Scaling alternative	Setting	Description
No scaling		No change is made to the sourceValue
Ratio scaling	UDRScaleArg1 = Min in	Uses all 4 scaling arguments UDRScaleArg1... UDRScaleArg4.
	UDRScaleArg2 = Max in
	UDRScaleArg3 = Min out
	UDRScaleArg4 = Max out
Multiplicative scaling	UDRScaleArg1 = Multiplicand	Uses the argument UDRScaleArg1 (Min in)
Divisor scaling	UDRScaleArg1 = Divisor	Uses the argument UDRScaleArg1 (Min in)

Ratio scaling operation

The sourceValue is to be checked for saturation. If it is less than "Min in", the UDR result value is equal to "Min out". If it is greater than "Max in", the UDR result value is "Max out". Otherwise the UDR result value is calculated as

X = (MaxOut-MinOut)/(MaxIn-MinIn)
UDR_ResultValue = X × sourceValue + (MinOut - X × MinIn)

Multiplicative scaling operation

UDR_resultValue = sourceValue × multiplicand

Divisior scaling operation

UDR_resultValue = sourceValue/Divisor