With the increase in length there always occurs a voltage drop in the cable. Refer the attachment for voltage drop values, according to cable sizes and nominal current.
So you have to consider the size and length of the cable as per the values and load consumption of UVR/MN module.
Standard recommendation is that the voltage supplied to UVR/MN should not be less than 5% of rated voltage, even if the MN can operate down to 0.85Un.
Time Delay UVR/MN module of 230V AC and Cable size 2.5 sq. mm considered for this example.
Nominal current is pick-up current that is 200VA/230V = 0.9A.
With 2.5sq. mm/1A, voltage drop is 0.8% for 100 meter (as per table attached). This means that one can go up to 625 meter without any problems.
It could be more but keep in mind that minimum supply voltage cannot be less than 0.85Un.