GE Multilin 469 Relay - Nuisance Tripping

[adamscb]

Forum,

We have a lineup of GE Multilin 469 relays providing protection for five 1000hp, 4160v motors. We use auto-transformers to provide reduced voltage starting for all of these motors. The control method for this is accomplished by timers and contactors in the starter. To my knowledge, the protective relay plays no part in the auto-transformer reduced voltage starting, it is just used for overload/short circuit protection, and RTD temperature monitoring. There's been several instances where the Multilin trips out the motor on "Incomplete Sequence", both while it's going through it's start-up cycle, and also in other instances where it's running at full-voltage and then just trips it out. After looking in the manual, this does in fact have to do with reduced voltage starting, but the thing that gets me is all of the parameters associated with reduced voltage starting were at their default values - along with reduced voltage starting set to "Off". My question is if the Multilin has nothing to do with controlling/monitoring the soft-starting action, how can it nuisance trip on "Incomplete Sequence"?

P.S. - we got the motor to start back up successfully, these starters can be tested using "test power" (an external 120v control power that can test the starter even if the main 4160v breaker is down). It tested fine using test power, so we just reset the Multilin and started it back up. This is what I usually do when I see this nuisance trip.

Any help can be appreciated, this one has me stumped.

 

[rlundsrud]

Have you tried adjusting the averaging? This would help smooth out the current curve however it would increase the trip delay slightly (about 16ms).

 

[Jraef]

It detects incomplete sequencing by watching Current the current profile, so that can be explained, but the fact that you say that reduced voltage starting is Off is indeed puzzling. Could be that turning it off simply means it isn’t going to try to control the contactors, but the monitoring of the current profile still takes place. In that case, something is making your motor current look like that incomplete sequence profile.

 

[adamscb]

Disappointed that I didn't think of this earlier - I think I'll change the "Transition On" setting to "Current or Timer"...I believe that eliminates the possibility of an Incomplete Sequence Trip, if I'm reading the manual correctly.

 

[ATSman]

Disappointed that I didn't think of this earlier - I think I'll change the "Transition On" setting to "Current or Timer"...I believe that eliminates the possibility of an Incomplete Sequence Trip, if I'm reading the manual correctly.

It would be interesting to see if this solves the Incomplete Sequence (IS) tripping on startup. You stated that the same IS trip shows up even after the motor is up to full voltage which is puzzling. On page 79 of the manual it shows this relay monitors voltage as well as current. Could it be that the logic is confused and indicates IS trip when actually the line voltage is fluctuating beyond the threshold setpoints. Where are these settings (OV & UV) and can the volts or time delays be tweaked to compensate for these voltage changes?
Questions:
> Is this a new installation? If not, how long has it been happening.
> Is it just one motor tripping or random on others?
> What type of loads are the motors feeding and have you had problems with these loads?
> Are the loads identical?
> How stable is the line voltage and have you ever monitored it with a line disturbance analyzer?

 

[adamscb]

It would be interesting to see if this solves the Incomplete Sequence (IS) tripping on startup. You stated that the same IS trip shows up even after the motor is up to full voltage which is puzzling. On page 79 of the manual it shows this relay monitors voltage as well as current. Could it be that the logic is confused and indicates IS trip when actually the line voltage is fluctuating beyond the threshold setpoints. Where are these settings (OV & UV) and can the volts or time delays be tweaked to compensate for these voltage changes?
Questions:
> Is this a new installation? If not, how long has it been happening.
> Is it just one motor tripping or random on others?
> What type of loads are the motors feeding and have you had problems with these loads?
> Are the loads identical?
> How stable is the line voltage and have you ever monitored it with a line disturbance analyzer?

Old installation, old GE autotransformer 4160v starters.
It's pretty much random throughout all five, but three of them do it more often than others
These are vertical water pumps
All five loads are very similar, I wouldn't go as far as identical - all run in the 98A - 115A range
Not too sure about line voltage stability, seems pretty stable just by looking at voltage values on Multilin, no VFDs or other harmonic-inducing equipment is on the transformer feeding these.

I went ahead and changed the Multilin setting to "Current or Timer", the way I'm reading the manual it'll never cause an Incomplete Sequence Trip. I'm very confident now in saying that the 469 doesn't control any of the contactors - Auxiliary Relay 3 isn't wired to anything on any of these protective relays.