Arcing Horn Design inquiry? 1

[highvoltage1]

Material selection and compatibility for arcing horn design.
More specifically, the use of all Stainless-Steel material, or all Copper material used.

Any standards or codes for designing such electrical components?
Common types of materials used for arcing horns?
Any combination of materials used? S.S. with copper, S.S. with aluminum?

High voltage (15kV-34.5kV) applications with current ratings of 2000A.

 

[prc]

Arcing horns are rarely used nowadays at least for substation equipment accessory like bushings. These were necessary when surge arresters with gapped silicon carbide pieces were used in surge arresters. With metal oxide arresters, arcing horns are no more essential.
Since arcing horns have to handle only surge currents, any conducting ferrous or non-ferrous material is suitable for arcing horns. Of course corrosion aspects are to be considered during the selection.

 

[jwatty]

prc, I believe what you're talking about could be called a spark gap as well; My read of the question is arcing horns associated with switches. Most utilities I see now adays order switches with arcing horns as a default accessory. These are typically rated to interrupt around 2A of primary current, and are meant as a sacrificial device to protect the main contacts of the switch. They can be used to de-energize a transformer, for example. I believe these are typically made of galvanized steel. I'm not sure about the 2000A rating - typically arcing horns are not meant to carry any substantial current, they are used as a sacrificial piece when opening. This is different than load break devices on switches, like vacuum bottles, which can squelch currents in the 2000A range. I'm not aware of standards for these; if what you're referring to is what prc is talking about, the IEEE PES Surge Protection Devices Committee may have a standard (2771?). See the PES-SPDC website.

 

[Gr8blu]

Did you look for earlier posts on the topic - such as the one below?

https://www.eng-tips.com/viewthread.cfm?qid=284957

Converting energy to motion for more than half a century

 

[highvoltage1]

JWATTY, thank you for making the distinction between the primary current and load breaking.
The arcing horn (AH) being designed will mount to the blade of an air switch. This AH will make contact against a stationary arcing horn found on the live part of an air switch. As the switch opens, the actuating AH will lift the pick-up arm of a vacuum interrupter.

The challenge is that the actuating AH (Copper) and the Interrupter pick up arm (Stainless steel) are welding together before the pick-up arm on the interrupter triggers the interruption of current. Some potential alternative combinations include Copper with Copper and silicon bronze hardware, Stainless steel with Aluminum. It is unknown if Copper Tungsten, Copper Graphite, or titanium are better suited materials for this type of application.

Given that Copper and stainless steel are dissimilar metals, most resources warn of corrosion between the two when submerged and exposed to an electrolyte. In this case, there is no submerging, just exposed to the open air. It's unclear if the air is considered the "electrolyte" or solution in this situation. Either way, using similar materials will hopefully resolve the welding that is occuring.