Overcurrent Relay

Discussion in 'General Electronics Chat' started by qitara, Apr 7, 2014.

  1. qitara

    Thread Starter Member

    Jan 18, 2013
    Hi guys

    I am trying configuring these Siprotec protection relays from siemens and after going trough the manual on how to configure them i couldn't understand something, when configuring the relay to trip a CB that lets say run a motor, you cant program the current directly into the relay you have to use a formula which is I/In= (The value which is to be programmed in the relay) where (I) is the current that the relay should trip the breaker on and the (In) is the rated current of the protection device in this case it would be the SIPROTEC 7SJ6005 that i am using, the question is, why not just allow the user to set the current directly instead of using a formula that is trip current divided by the protection device rated current ? what is the purpose of this ?

    Thanks in Advance guys