I want to select the HV connector f

[bahram]

I want to select the HV connector for a 145kV current transformer.
The CT terminals are tinned copper. Can I allowed to use Aluminum bolted connector or I shall use a bi-metal plate in contact surface between terminal pad and connector pad?

 

[busbar]

Bellevilles are handy for bolted connotations with hex cap screws for copper-to-aluminium joints.

http://www.fciconnect.com/pdffiles/brochures/MC02_Section_L-Hardware.pdf

 

[scottf]

You can use aluminum in contact with plated copper. That's the whole purpose of the plating.

 

[jbartos]

Suggestion: Not every plating on the copper is suitable for aluminum interface. The plated copper hardware has to specifically say that it admits aluminum. Often, it is advertised as Al/Cu hardware.

 

[bahram]

Thank for your support. I have to say that jbator and scottf have different Idea.

Let's look at the following data regarding the material's normal potential against hydrogen:

Al : -1.45 volt
Tin : -0.146
Cu : +0.35

If the Aluminum be in contact with Tin, the voltage difference will be 1.304 and if copper be in contact with Tin, the voltage difference will be 0.496. So these show that the corrosion will be higher if we connect Al clamp directly in contact with Tinned plate, than in the case if we use CUPAL.
Would you please advise me in this regard.

 

[scottf]

I'm not sure I follow jbartos and bahram's comments.

I can say this....I work for a HV electrical equipment manufacturer and it is quite common for us to ship tin-plated aluminum and nickel-plated terminals on our equipment. Almost all HV connectors are also plated. We commonly connect bare copper to tin-plated aluminum surfaces with no problem.

 

[jghrist]

It is also common to connect bare aluminum to tin-plated copper. If the proper compound is used between the pads, no electrolyte will be present so galvanic corrosion is not a consideration.

If bimetallic plates are used, the aluminum-copper joint permanently bonded to exclude electrolytes and oxidation.

It is important to use Belleville washers with enough depth of spring to allow for differential thermal expansion when the bolts are a different material than either pad. Consider the expansion of both pads and the bolts. Washers should not get completely flat or cold flow can occur.