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Associate

Join Date: May 2009
Posts: 41

Drain Wire Connection

05/02/2010 2:34 AM

In Junction box, there will be a drain wire from TXR (From single twisted pair cable) and there will be drain wire in multipair cable for each TXR (Analog signal). We will connect the drain wire of the multipair cable on the control panel or marshalling side to ground. What we should do the two drain wires in the Junction box for the TXR.

Please explain this, for analog cables and for digital cable too.

Thank you in advance.

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Join Date: Oct 2007
Posts: 29
Good Answers: 1
#1

Re: Drain Wire Connection

05/03/2010 12:23 AM

Hi,

You should connect the Drain Wire from Multicore cable from Marshalling Cabinet in Junction Box to a common bar to which all the drain/shield cables from transmitter cables will be connected. The transmitter cable shield/drain wire should be cut or isolated at Transmitter housing. Make sure that these drain wires/shield are connected to ONE END ONLY - preferable to Marshalling Cabinet side where from it will to a SOLID ground. The common Bar - a copper bar with multiple screws on it can be installed in JB, which can be used for multiple drain wire connections comming from all other field instruments.

Regards,

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Associate

Join Date: May 2009
Posts: 41
#2
In reply to #1

Re: Drain Wire Connection

05/03/2010 12:50 AM

Thank you for the information. You mean to say that to connect the individual drain wire from all field instruments and the drain wire of the respective multipair cabel to connect to the common bar inside the junction box, and to connect the other end of multipair cable drain wire to the safety ground at the control panel end.

Am I wright?

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Associate

Join Date: Oct 2007
Posts: 29
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#3
In reply to #2

Re: Drain Wire Connection

05/03/2010 2:36 AM

Yes thats right..... But then make sure that the drain wire of transmitter cable, at transmitter end, is NOT connected to anywhere. You may cut the DRAIN wire and insulate properly, in the transmitter housing.

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#4
In reply to #3

Re: Drain Wire Connection

05/03/2010 2:44 AM

Thank you for the reply. Can we use this type of grounding of drain wire for digital cable too.?

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Active Contributor

Join Date: Jan 2010
Location: I am at Chennai India. Retired Dy General Manager - Power Plant Automation
Posts: 23
#5

Re: Drain Wire Connection

05/03/2010 2:52 AM

This is only a protective earth hence it can be connected to protective earth line not to signal earth. Both the earths are ultimately connected to Electronic earth, not to station earth.

No double earthing is allowed for instrument cables if you use panel protective earthing the drain wire should not be connected to marshalling earth also. If marshaling earth is connected to electronic earth then it can be used but connection at the panel should be disconnected only one earthis allowed. It is same for both analog and digital cable.

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Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

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#6

Re: Drain Wire Connection

05/04/2010 3:33 AM

Follow the Cabling Standards in use at the installation.

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PWSlack (1); ravindran_52k3 (2); seethasub (1); srzambre (2)

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