Trip vs. Unlatch Trip
Trip vs. Unlatch Trip
(OP)
Can someone explain the difference between "Trip conditions" and "Unlatch Trip conditions" for relay logic?
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RE: Trip vs. Unlatch Trip
Where did you find these terms - any chance of the full text?
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RE: Trip vs. Unlatch Trip
TR = Trip Conditoins
ULTR - Unlatch Trip Conditions
I could not upload the file due to size, but it can be found from SEL website or google.
RE: Trip vs. Unlatch Trip
RE: Trip vs. Unlatch Trip
RE: Trip vs. Unlatch Trip
RE: Trip vs. Unlatch Trip
However, there may be circumstances where you need to 'latch' the output to 'sustain' a trip until other requirements are met.
Maybe you want to wait until a motor operator opens a switch, then a limit switch contact in the switch control reports back that the switch is open (although this might be handled better by 'seal in' logic in the motor circuit). Once the switch contact reports 'open', you can 'stop tripping'.
Maybe you have an old external reclosing relay that has to go through a timed logic cycle after the 1st relay sends a 'trip', etc.
A lot of SCADA systems only like to send a short term (~0.5s) control output, and you may need to 'seal in' the relay's trip function for a longer period. Establishing necessary conditions for the trip signal to drop out may be more trustworthy than relying on a simple timer and assuming whatever it is has finished.