Critical Point on an OC relay

[Js20981]

What determines the critical point of an OC relay? We already have a curve value for the relay and TD setting and are able to determine the time value for different magnitudes in sec. current. Why is the critical point necessary?

[Kalbi_Rob]

What determines the critical point of an OC relay? We already have a curve value for the relay and TD setting and are able to determine the time value for different magnitudes in sec. current. Why is the critical point necessary?

In what relation are you talking about the critical point of an OC relay? Typically critical points are determined during the coordination of Zone-2 and OC relays to determine the optimal tripping time. In this regard, I would recommend reaching out to your local PE for producing your relay settings.