Re: Help w/ Chokes

>From: Wallace Edward Brand <webrand-at-dgs.dgsys-dot-com>
>>My 16 kV, 10 kVA pole pig has a test specification called B.I.L. 
>>which I believe stands for Basic Impulse Level.  The nameplate says
>>BIL 120,000 volts.  
>>Happy Coiling! rwstephens
>Dear Jim:  If you are looking for the BIL (basic impulse insulation levels)
>for distribution transformers, they appear in Tables 3 and 4 for
>Oil-Immersed and dry distribution transformers respectively. 
> discharged to a zero or
>practically zero level as a result of a flashover at an external lightning
>arrester or some other protective device.  
>  I hope this is more useful than my earlier post.
> Wallace Edward Brand

[another response included]
> This 
>is a design standard which is apparently specified by the National 
>Electric Safety Code to permit power distribution equipment to be 
>"coordinated" with protective equipment (such as lightning/surge 
>arresters or the transformer bushings themselves) in such a manner that 
>the LAST thing to break down will be the transformer's windings. 
>In the presence of a switching or lightning-induced voltage surge, a 
>nearby arrester should fire first. If that fails, then the transformer 
>bushings or an internal spark gap should fire next, thereby preventing 
>the transformer windings from "seeing" a surge of sufficient magnitude to 
>cause internal breakdown and damage.
>As can be seen, pole pigs are built to withstand punishing voltage 
>surges, a fraction of which would cause even 15 KV neons to whimper and 
>go "belly up"
> Bert

	Bert, Robert, and Wallace,

	Thank you! It does explain why 'pole pigs' are so much more
robust that mere neons!

	Regards always,