Dear all,
In one of my project, I find one PLC control panel near to the 33KV main power line, (only 70cm far), my system did not start yet, but the question is:
Is that power line going to affect my panel work, if yes, what is the solution?

CPU inside the panel is TWIDO, communication through RS-485 modbus line into main Premium PLC which it 300 meters far from this panel.

A control panel 70 cm away from a 33KV power line? That's an odd choice of placement, why so close? Are the 33KV lines sheilded or no? That will probably make all the difference in whether or not it will effect the communication. Also, that will be a nightmare for people that have to troubleshoot the panel especially if the lines are unshielded, that is a huge safety issue. I wouldn't want to troubleshoot that panel.

If the power line is only 70cm away I assume that it is an insulated cable (or group of single cables) and it is either contained within a duct or buried. In terms of interference with the PLC high voltage cables are generally less of a problem than low voltage because the currents are so much smaller and the cables are screened as a matter of course (for safety rather than EMC reasons). It is not unusual to have PLC's mounted within HV switchboards (or MV in US terminology) where they are mounted much closer than 70cm to enclosed busbars. The level of electromagnetic interference is a factor of current rather than voltage.

Not really a problem. Safety wise, most gear these days is metal clad at that voltage. Metal enclosed is still around but the cost adder for metal clad isn't that much. You said 70 cm and that's just about the required distance between the conductors and the casing on this kind of gear, so I'm assuming that you're either talking about the gear or the cable. The cable definitely should be the shielded variety (with a ground) for safety reasons. That's what you normally get when you buy medium voltage cable these days. Either way, I wouldn't recommend stepping on them but I work around 23kV, 7.2kV, and 4160V cables all day long. Never seen any problems with the electronic gear either. 70 cm is just about the distance that I'd normally expect to see for electronic gear around 33 kV switch gear such as protective relaying, power metering, and so forth. That stuff is not built to any different standards than standard PLC gear.

If it's not insulated or shielded, then the old rule of thumb would be at least 10 feet of separation between the conductor and yourself, vehicles, and so forth. I can't remember whether the distance is still 10 feet or goes up for a 33.5 kV system under the current IEEE recommendations and NFPA 70E. The 10 foot rule is for safety.