Electroendosmosis

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bphgravity

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Section 310.13 FPN states, "Thermoplastic insulation, where used on dc circuits in wet locations, may result in electroendosmosis between conductor and insulation."

I looked up the term electroendosmosis which is, "the effect of an electric field on the diffusion of water through or into a membrane or gel."

I assume this all means that the integrity of the insulation is compromised by this process? I have not been able to find a good explanation of this phenomenon. What exactly is this?
 
Re: Electroendosmosis

The first two sites I looked at had exactly the definition you posted. So I suppose you already did a search. :confused:

One site had it as medical if that helps.
 
Re: Electroendosmosis

Well, I never knew it had a name but yes, it's well known in telecommunications. Plastic insulated cables were introduced to replace the paper insulated cables and their problems when water got into them. It was soon discovered that PIC was not immune to moisture either. Funny thing is that you can take a faulty pair out of service and after awhile it will test OK. Put it back in service with voltage on it and it will again fail after awhile .

-Hal
 
Re: Electroendosmosis

I borrowed my co-worker?s scientific encyclopedia. It defines ?Electroendosmosis? as ?Electrophoresis in which the solid is stationary and the water phase is displaced and migrates towards the electrode.? That did not help much, so I looked up ?Electrophoresis.? There were two full pages on that topic. It is the study of the migration of charged particles through conducting solutions. The discussion was primarily related to medical research. The research techniques are over 50 years old.

From what I read, I infer that the issue is that the electric field of a wire conducting an DC current will be constant in direction and magnitude. This is as opposed to an AC circuit, for which any electric field created by the charged particles would vary in direction and magnitude. The distinction is important, as the constant presence of a constant electric field will constantly drive charged particles in solution either towards the wire or away from the wire (i.e., towards any nearby grounded surfaces). The ?charged particles in solution? would be impurities in the water that surrounds the wire (i.e., from the wet environment). The migration of these particles would be through the insulation system.

The bottom line:
Originally posted by bphgravity: I assume this all means that the integrity of the insulation is compromised by this process?
Click to expand...
I believe you are right.

ASIDE:
By the way, I almost always type my comments in Microsoft Word, before I post them. I was not at all surprised when Word did not recognize the word ?Electroendosmosis? (it was flagged by the automatic spell checker). However, I was astonished to discover that Word did recognize the word ?Electrophoresis.?
 
Re: Electroendosmosis

It's been a long time since I have looked it up, but I remember finding the answer to your question on one of the cable manufacturer's websites. If I remember correctly, it has to do with the breakdown of the ceramics used in thermoplastic insulation when the conductor is used in a wet location and is used in a dc circuit.
 
Re: Electroendosmosis

Ok, I found it! A definitive answer to the qustion of electroendosmosis, it's causes and its cures, can be found by going to www.Southwire.com, then clicking on "technical", then clicking "cable update". This has been the best information on the subject that I have been able to find; Quite clear and to the point.

[ January 31, 2005, 01:06 PM: Message edited by: don_resqcapt19 ]
 
Re: Electroendosmosis

That is a very good article. Thanks for the link. Now I can explain what that is when a student brings it up. :cool:
 
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