What is the main reason of communication lose problem when we connect PLC or DCS to RTU?

The main problem of losing our connections especially when we connect to any devices is that about the weather. Bad weather reallys affects our signals.

the main reason it should not be interferiance with High voltage transmision line if the wireless communication have been used 

Not familiar with these technical issues 

the main reason it should not be interferiance with High voltage transmision line if the wireless communication have been used 

or if we lost power supply from one side RTU side or PLC/DCS 

finally we have more reason to lose comunication between them .

there is no main reason. if you have comminucation failure 1. the installation EMC values are high. 2.new hardware downlaod with new firmware.3 cable fault. 

1. Direct interface means physical connection may cause problem.

2. Hardware problem may occur.

I would like to know your answer for the question, because I’m beginner in this field.