Hi Dear Experts ,


Recently i Found An Issue about Drawing and Designing Control System Grounding Document , I Use Emerson DeltaV MD PLUS Controller DCS and i have Some Different Method about Grounding Signal Cable Screens Presented By EMERSON :


1) Emerson has Presented a Grounding Manual and it is emphasized that we must Connect Cable Screens to Chassis Ground CG( or PE) and DO NOT Connect Cable Screens to DC Ground .(Attachment 1)


2)i have a Document Regarding to a Project has been Done BY EMERSON and they Connected Cable Screen Bars to IE (Instrument Earth ) and also they Have Connected DC Power Negative(-) Pole to IE . (Attachment 2)


Can Anyone Guide Me ,


With Best Regards


A.Ahmadi

 

Show us how you ground single loop transmitter wiring.

 

What I always do and follow: below 10kHz only ground on the computer/plc/dcs side, above 10kHz: ground on both sides. At Philips we made a clean "measurement ground" inside the control panel and that is the point where we also connected the - of all power supplies to.
Most frequency inverters work at higher frequencies than 10kHz, sometimes lower, but it makes sense to always use a screened cable from the inverter to the motor and earth it on both sides.

In rocky soil environments (Spain, Austria, Slovenia, Japan etc.) we drove a earth pin into the ground that touched ground water level, sometimes in Spain (above Madrid) we had to drive it 100m into the ground. This was absolutely necessary for our type S thermocouple measurements inside a 1450°C SiC rod electrically heated oven where all starts to radiate extremely above 1200°C.
Using EMC cable glands is mandatory of course, don't be the guy that strips the screen, turns it into a kind of worm (which is a COIL of a few uH that doesn't want the noise to pass) and connect that to PE. No, be the guy that uses the proper EMC cable gland to connect the screen of the cable to the cabinet.

 

In operating plants, field grounding of instrument cables is not recommended, due to ground faults that exist in all operating environments, leading to intermittent several hundred volts potential differences between the control room instrument ground and earth ground in the field.