Failure of DCS FTA cards during Lightning

arjun_athi

Member
Location
SAUDI ARABIA
Dear Teams,

It has been observed that some of the FTA cards in the ABB DCS panels are getting damaged whenever the lightning occurs.
The 0V reference for the 24 V regulator has been connected to FTA through MCB and 0V reference has been connected directly from 0V bus.
whereas the 0V reference is grounded with chassis and chassis has been connected to Protection ground and not connected to Instrument ground.
As on date more than 80 FTA cards has been damaged during lightning.
Kindly advice on how to protect the FTA cards from damaged by Lightning.

Regards,

Arjun
 

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tom baker

First Chief Moderator
Staff member
Do you use the NEC for your wiring standard? My replies are based on the NEC.
First you need good Surge protection devices (SPD) at the service entrance, branch panels, and for your control panels. Any low voltage lines going outside should have SPDs. Under the NEC, you need a single point ground.
Lightning protection is a different standard, NFPA 790, its way beyond the scope of what I know.
For SPDS, what Mike Holt once said, "more is better, you get what you pay for"
Thats my advice and I am sticking to it.
 
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tom baker

First Chief Moderator
Staff member
And do you use the NEC for your wiring standard?
What is a DCS?
Looking at your pictures it looks like some kind of IEC wiring that I am not familiar with, but start with SPD and a lightning protection system.
 
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GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Where does it say that in the code? you can have as many ground rods as you want wherever you want.
You can only have ground-neutral bond, which may be what Tom was thinking of. Within the GES it is good design to to have one common point to which all the ground electrodes connect and from which all EGCs diverge, but I do not think that NEC mandates that.

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don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Bond the two grounding systems together at a single point.

We had that exact same issue with DCS where the manufacturer insisted on the two grounding systems being isolated. In the summer, with nearby lighting storms, they would lose I/O cards. They asked us to prove that the grounding systems were isolated, and we would, but at the same time we were telling them that the isolation was causing the problems. After the 3rd summer with the same issues, they let us bond the two grounding systems together, and no more problems with losing IO cards with nearby lightning storms.
 

arjun_athi

Member
Location
SAUDI ARABIA
Can you repost without the abbrevations?
Dear Mr. Tom Baker,

Good Day,

Thank you for your prompt reply,

My main concern in the DCS panel power supply common 0 V which is connected to Panel ground but it is supposed to connected to Instrument ground...

My concern is the 0V ground is connected to panel ground which is leading to damage to the FTA cards during lightning.
 

tom baker

First Chief Moderator
Staff member
Do you have a lightning protection system and surge supression?
I don't understand you instrumentation grounding system, under the nec we have a single point in the control cabinet for grounds.
 

paulengr

Senior Member
Do you have a lightning protection system and surge supression?
I don't understand you instrumentation grounding system, under the nec we have a single point in the control cabinet for grounds.
First thing to do is get a clamp on ground meter, understand how to use it, and start checking building/equipment grounds following NFPA 780 for instance. Most frequently what I’ve found is that the equipment grounding is poor/not installed properly. Things like say a poly tank with a level sensor sticking out on top with no air termination and the tank itself is not grounded. So this makes the control system the ground path for a strike anywhere near the tank.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
...
My concern is the 0V ground is connected to panel ground which is leading to damage to the FTA cards during lightning.
To help prevent that, both grounding systems must be connected together at a single point. Where you have two grounding systems connected to earth separately without bonding, the lightning storms set up potentials between the two grounding systems and that often results in damage to the electronic equipment.
 

arjun_athi

Member
Location
SAUDI ARABIA
Do you have a lightning protection system and surge supression?
I don't understand you instrumentation grounding system, under the nec we have a single point in the control cabinet for grounds.
Mr. Tom,
they have lightning protection system, but the damage is happening only for the FTA cards and other station equipment are same during lightning storm.
 
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