Collectibles--General (Modern)/post


QUESTION: I have came across several post insulators many are broke.  What type of material are the silver disc and the round block that are inside of them.  If you need pics i can post

ANSWER: There are a number of different style post insulators - can you attach a picture

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id of post
id of post  

QUESTION: Here are the picts of the post insulators

Thanks for the pictures - they help.  These are actually not post insulators, but they are lightning arresters -- They are typically mounted no power poles and designed to safely conduct the high voltage to ground in a lightning strike to protect the rest of the system.  The cylinders are most likely made of a semi-conducting material such as zinc oxide or silicon carbide that provide a path to ground when the voltage exceeds the rating.  From the marking this is rated for 9-10KV so voltages above that would "jump the gap" through the semiconducting material to ground, protecting the rest of the circuit.  The silver disk may be just plated metal to help separate the cylinders.  Here is a similar complete unit on Ebay:

         Hope this helps!  Thanks, --Bob

Collectibles--General (Modern)

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Bob Berry


Questions related to collecting Glass Insulators and porcelain insulators - I can provide historical information as well as current collector values. I am also interested in purchasing insulators I need for my collection.


I have collected since the early 1970's and have much historical information, as well as knowledge of current insulator values.

National Insulator Association (

BS & MS in Electrical Engineering

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