500 digatrp

[hawkeye23]

We have a 500 digatrip that has override discriminater light that is lite. Is the OD function the same as a instantainous setting? Would like to ask why that should be lite?
Thanks again.

 

[templdl]

We have a 500 digatrip that has override discriminater light that is lite. Is the OD function the same as a instantainous setting? Would like to ask why that should be lite?
Thanks again.

To illustrate the portion of the protection curve being adjusted, simulated Time-Current curves are pictured on the face of the trip unit. The particular setting to be adjusted is located in close proximity to its portion of the simulated Time-Current curve.
Should an automatic trip occur as a result of a fault current exceeding the pre-selected value in this portion of the Time Current curve, the red LED shown in this segment of the simulated Time-Current curve will turn "ON ".
To reset the trip unit there is a trip reset PB in the lower right hand corner and the IL should go out.

In your case you had a trip occur as a result of the instantaneous overriding your short time adjustment. If the short circuit incident is long enough is high enough in magnitude be trip unit will not wait for the short time to time out but will be overridden by the instantaneous resulting in your discriminator light being lit. No matter how the settings are adjusted the intent of the trip unit is always to protect the breaker first to assure that the breaker is always kept within its withstand rating in order to interrupt.