Grounding Problem

hydrogen sufide

Yep. Sounds like attack from hydrogen sulfide or sulfur dioxide to me also. The corrosion of the exposed metal builds up the black layer, which will flake off as it thickens, to expose more metal. For small stranded wires, this can cause the wire to corrode completely. For larger power cables and bus bars, the problem is usually not enough to become a hazard. You can clean the corrosion off (de-energized), dry the surfaces, and apply a high dielectric strength varnish. The sulfur attack on the wires typically extends a few inches back under the insulation at the ends of the wires, and bleaches many of the insulation colors towards a tan. (This can be a real problem with instrumentation cables, because white and red all start to look the same.) Nickel-plated conductors (often used for 200ºC and higher temperature environments are usually immune to this type of corrosion; silver is not.

On your high-voltage wires, what is the condition of the stress cone-- has it been affected by the environment so it could arc-over?

--JMM

Thanks for you reply

The hv. Cables have not been terminated as yet it is dead front we will use inserts and load break elbows. How could I stop the reaction I suppose one could plug conduits with duct seal, one of testing labs suggested to use bleach to neutralize concentration I am not to sure by using bleach what might do to teck's outer jacket insulation?

In the transformer cable compartment the bottom is sand how one would go about to seal

Over the sand? Your comments would be greatly appreciated. Thanks

Welcome to CR4, Nick.

My experience includes meat rendering and sewage treatment plants, both of which have the type of corrosion you mention. I don't have experience on the high-voltage end. It sounds like the ground water is leaching the materials from the soil or fill in your location. This soil or fill could include slag or other materials which have a high sulfide content.

Try contacting a good 3M representative, in their division which works with electrical insulation materials. They may be able to suggest an appropriate grease or other coating material which would have the proper insulation characteristics and also resist the chemical attack on the bare metal and contact surfaces. They also would be able to advise you if the environment will have a deleterious effect on the cable's dielectric or on its stress cone (or recommend which stress cone materials to use).

If you had some way to ventilate this space, it sounds like the outside air is fairly clean while the enclosed space is the problem. Maybe you could lift the transformer 2-3 inches and place an appropriately screened ventilated support under it (suitable for its weight and temperature).

--JMM

actually, the corrosive effect only attacks zinc and zinc plated metals.

the same effect will also happen to lead.

Come-on people. I've been there and had to smell the fumes, change my clothes before entering my home, and deal with the wires which had corroded until they were actually falling off the terminals. I wouldn't be surprised if zinc (galvanizing) or lead are attacked, but I know that the copper sulfide does not form a stable coating on the surface of brass or copper. It tends to flake off, much like iron oxides do on all but COR-10 steel. Therefore, the long-term effect is reduction of conductor cross-section and eventual failure of the conductor or connector. (Often within 2 years for smaller gauge instrumentation or control conductors, and within a few months for the small brass springs in analog meter movements.) Nickel-plated conductors did not have a noticeable damage from sulfide attack in these environments, but they were significantly more expensive and difficult to obtain.

Well I have sent samples to the lab for testing and once I get results I will post them.

Next thing would be to fined solution how to clean the bus and wire.

Secondly talk to cable Manufacturer and as last have engineered solution

To remedy situation.

THANKS GUYS FOR YOUR HELP AND COMENTS, AS I HAVE PROMICED THIS ARE THE TEST RESULTS.

· 49.1 % copper (Cu),

· 47.6 % cuprite (Cu2O),

· 1.7 % Calcite (CaCO3),

· 1.6 % copper sulphide (Cu2S).