Hi,
We have a ESD system in one of our several plant locations that has reported Noise/ Interference several times in past two months in Safety Control System Digital Output modules and IO Bus (internal bus to connect and communicate Control System IO Racks). It also reported module faults which we replaced with new ones. When we checked these faulty modules in other less critical system spare slots, we found them working without problem after keeping them under observation of more than a week. In parallel, the Tech. support team of Safety System manufacturer was contacted and they have been very supportive. So far we have replaced several DO, AI modules, one AC/DC Power supply and one rack bus module.
Since, this ESD system is very critical for plant operation, it can't be shutdown for detailed investigation. We are suspecting interference is playing a major role here and causing modules capacitor to glitch and making them go to fault state. We are planning to execute some tests in Online system to find root cause and need your review and advise on the same.
i) Performing ground test on AC incomer and DC power supplies by using multimeter.
ii) Performing ground test to make sure all field instrument cables shield are connected to Instrument Earth plate on one side.
iii) Performing integrity/continuity test on field instruments shield cables by using jumper on Junction box side to short two shield cables and measuring on system side.
iv) Radio interference measurement using RF meter (need to check if Telecom team has the tool)
v) Static charge test?? (advise needed)
vi) Interference measurement using oscilloscope?? (advise needed)
vii) Any other test suggestion?
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