IEC regulations - earth power and earth signal separation

[DYV1973]

LS,

We were confronted by a customer that IEC regulations (we don't have an answer about which one) require that distance between power earth (220 VAC) and signal earth (4-20 mA) should be at least 1 meter. Can somebody confirm that this regulation exists, or is there somewhere a misinterpretation.

Thanks,
DYV

 

[VEBill]

Are you referring to connections to earth, i.e. ground rods?

 

[zappedagain]

I've been going through the IEC specs for hazardous locations (60079-##) and I haven't seen anything about separation that large.

NFPA Article 504.30 states that intrinsically safe wiring needs to be separated from non-intrinsically safe wiring by 2" (50 mm). I haven't seen any larger distances defined, so you can use that as a ballpark.

John D

 

[DYV1973]

@VE1BLL: Correct.

@zappedagain: thanks, and in my case it is even a non-hazardous location.

 

[VEBill]

I can't speak to the IEC regulations, but the concept of a single point common ground allows all the systems to rise and fall as if on a tide during a lightning strike. By providing separate grounds, then a differential voltage may occur during a lightning strike and cause equipment damage.

Back in the real world, using very long wires to reach a single point common ground can cause their own problems during lightning strikes. Metal building can help reduce this effect.

 

[peebee]

I suspect your client may be thinking of EIA/TIA or BICSI requirements to separate power wiring from communications wiring.

However, that should NOT be confused with or misinterpreted as a requirement to separate/isolate the power & signal grounding systems. It would be unsafe to do so and detrimental to the signals that he is presumably concerned about. Moreover, this would be a code violation in the US -- and I'm pretty sure in IEC-land too.

 

[peebee]

I found the BICSI requirement I was referring to, in the BICSI CO-OSP Design Manual. It states that the required clearances between signal and power conduits indicated (which are 3, 4 & 12 inches for concrete, masonry & earth respectively) are required by NESC.

Hope that helps.

 

[itsmoked]

What is a BISCI?

Keith Cress
kcress -

http://www.flaminsystems.com