AI module burns while thundering


Thread Starter


Analog input module (Model no-6ES7 331-7KF02-0AB0, Siemens) is frequently burning during thundering. 06 inputs (MW from Mark V, Pressure transmitter, Temperature Transmitter) from different places have been connected to this module. We have checked the grounding of the respective panels, system and found ok. Even though we have tightened all the possible connections. The ground resistance of the system is less than 0.5 Ohm. Grounding shield of multi-core Control cable is grounded only on the side of Analog input module. Other side is kept open. The main thing is that 08 more modules are there in the same panel. But all remains healthy except that one of the same place. All modules are powered by same power supply.

What may be the probable cause for this problem and what should the remedy?

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David Wilson

> Analog input module (Model no-6ES7 331-7KF02-0AB0, Siemens) is frequently
> burning during thundering.

Is there an object near one of these remote devices that is the likely target of lightning? Often, the damage from lightning strikes is not direct, but induced current flow from the magnetic field from adjacent strikes. Read Tesla's patent application for his lightning protector. It is not a Franklin lightning rod with a point, it is rounded and looks like an umbrella with no sharp points. The Franklin lighting rod actually attracts lightning with its sharp point.

Is the wiring in conduit? Non-ferris conduit does not block magnetic fields. Assuming induced voltage, can the wiring be re-routed to change the cables' angle to the lightning strikes?

Try looping the input end of the cable thru a ferrite core. I have connected a high value resistor to ground, from the analog input, in order to shunt induced noise. You might try a couple of zener diodes with a 30 - 40 v piv.

Is the module's rail mounted on a painted back-plane? Make sure the rail is grounded.

How about a fibre-optic transmitter? I thought about wireless, but I see you have nuclear industry checked.

Curt Wuollet

I'd check just where those circuits go and the grounding of the items they are attached to.

Having a good ground on the PLC doesn't do much good if the system the sensors are attached to can be lifted to high potential. This happens frequently when you span two services or power systems. And lightning pretty much does what it pleases, you might even find something no longer has a ground wire.

Hi experts,

I like to join with you in this nice discussion.

The guy (who posted this thread) and me are in a same power plant. Following David Wilson's post (by the way- thank you very much) our answers are as follow:

1. Yes. There are 4 nos' of Exhaust chimney where lightening arrestors are used. As you said they might be the likely target of lightening. We checked proper grounding and they are fine.

2. Yes, wiring is conduit. Metal conduit with proper grounding is used.

3. No fiber optic transmitter. And this is not a Nuclear industry. It is a combine cycle power plant (with GE gas turbine and SIEMENS Steam turbine).

Last couple of days our findings are as follows:

1. We found one multicore cable shield (for instrument) was grounded in both side and 3 pair of instrument cables are used for 3 different signals. It may be the cause of damaging module by inducing loop current through current.

2. One signal 4-20 mA coming from GE (Speedtronic- TBQC) panel with 14 VDC. This signal is connected to S7 control panel Analog Input module which is 2 wired configured. How I'll isolate this voltage (Voltage GE Panel!!) from S7 panel (i mean only mA will come to S7 panel).
Thank you very much for your answer. Now replying answer of the question.

1. Yes, there are 04 exhaust chimney.

2. No, it is not conduit wiring. It is on the cable tray.

3. No, it is not painted back-plane. Module is mounted on female type rail.

4. Transmitter is not fiber optic. The industry is combined cycle power plant (Gas turbine based).