PI Ratio

[cvirgil467]

Anyone know what a miniumum PI value is for VPI dry type transformers (15kv - 480Y/277v).

The megohms values look good but when i look at the PI values, they don't look so good.

 

[jcormack]

Not sure what you mean by PI value ?

 

[engy]

3.14159???

 

[charlie b]

“Polarization Index." It is the ratio of the results of an Insulation Resistance (IR) test after ten minutes to the IR reading taken at one minute. Here is an ECM article from 2004:
http://ecmweb.com/mag/electric_review_polarization_index/

I do not, however, know what constitutes a good reading for the equipment you describe.

Edited to add: Here is a previous thread on the topic:
http://www.mikeholt.com/cgi-bin/codeforum/ultimatebb.cgi?ubb=get_topic;f=3;t=002477;p=

 

[brian john]

Virgil:

I am not in my office at this time, so I do not have my copy of NETA Specs. but you can check their web site.


http://www.netaworld.org/Category.cfm?CategoryID=3