Over current relay

[panthripu]

Hi
Now a days i am trying to understand overcurrent relays operation. I would like to know what is the difference between I>,I>> and I>>>. Also difference between inverse,very inverse and ext. inverse.
I want to replace old overcurrent relay (7sj5111) with 7sj6001. Setting the parameters is once of the confusing job . What should be the right approach for it?

 

[ron]

This is a great resource. It also helps realize how big a question you asked.
http://www.geindustrial.com/pm/notes/artsci/artsci.pdf

 

[T.M.Haja Sahib]

Hi


What should be the right approach for it?

The right kind of approach depends on what kind of person you are.Do you learn by studying concepts,or by seeing others how they do it or trying it out by yourself or by challenges through others etc.,?Better,you may take a Briggs-Meyers Personality test for your own design of a 'right approach'.

 

[richxtlc]

The definite-time overcurrent protectionfor the 3 phase currents has a low-setovercurrent element (I >), a high-setovercurrent element (I >>) and a high-setinstantaneous-tripping element (I >>>).
The difference between inv, very inverse, etc, is the slope of the curve. Protective systems engineers use these characteristics to coordinate tripping between the primary relaying and the backup relaying.