Breaker Trip?

[samir]

Hello,

I am working on a project still gathering all the information on it. In this the switchboard main breaker is fed from a Automatic Transfer Switch. The main breaker trips whenever there is a transition from Emergency to Normal. But the breaker does not trip when transition from Normal to Emergency.

Does anyone has run into a scenario like this. I am collecting opinions why and what could be the cause?

My concern is the load remains the same when transitioning on either side so it should either trip on either transition or not.

 

[hillbilly1]

Need more info, system voltage, ground fault protected? Loads served? just to name a few.

 

[david luchini]

If you have a large motor load, you may have an out-of-phase condition during retransfer to normal power, as the motors are coasting down.

Look into whether your ATS has a delayed transition feature for retransfer to normal.

 

[brian john]

If there are transformers downstream,l it is inrush current almost 99% guarantee. The generator cannot supply enough instantaneous current, but when you retransfer to utility the utility has an almost infinite bus in comparison to the generator.

Does the ATS have an in-phase-monitor?
Or is there a delay open transfer (delayed transistion)?
Does the circuit breaker that is tripping have adjustable instantaneous and/or short time?

 

[hillbilly1]

If there are transformers downstream,l it is inrush current almost 99% guarantee. The generator cannot supply enough instantaneous current, but when you retransfer to utility the utility has an almost infinite bus in comparison to the generator.

Does the ATS have an in-phase-monitor?
Or is there a delay open transfer (delayed transistion)?
Does the circuit breaker that is tripping have adjustable instantaneous and/or short time?

Yeah, that's the usual culprit. That's why we need more info.

 

[zog]

The main breaker trips whenever .

Trips on what function? What type of breaker, what trip unit? Need some clues.

 

[samir]

Here is more info:

It is in the attachment. All the breakers are Square D.The trip and type are mentioned on the one-line attached. The emergency side of the ATS-W is fed from the 1625 KVA transformer through a MJ 800 Amp breaker.

I am currently performing the coordination but still not sure whether this would resolve the issue. The issue is the when the ATS transition from Emergency to Normal takes place the breaker (005-01 trips) but it does not trip when transits from Normal to Emergency.

 

[samir]

If there are transformers downstream,l it is inrush current almost 99% guarantee. The generator cannot supply enough instantaneous current, but when you retransfer to utility the utility has an almost infinite bus in comparison to the generator.

Does the ATS have an in-phase-monitor?
Or is there a delay open transfer (delayed transistion)?
Does the circuit breaker that is tripping have adjustable instantaneous and/or short time?

I am not sure if the ATS has in-phase monitor. The services guy mentioned the transition is 50 to 70ms on either side. I have uploaded the part of the one-line with the breaker information. I working on coordination for now, hoping it works.

I think you are right I also thought generator being a weaker source cannot supply the inrush at once.

 

[hurk27]

Need more time transfering back to utility

 

[samir]

Need more time transfering back to utility

Is there any material I can read up about the collapsing field.

Also,I got an email from this forum with a different reply which had something to do with the wrong wiring CAB rather than ABC. Do you have any reference material to that where I can read up about it.

 

[brian john]

Need more time transfering back to utility

Usually by time they realize this the wrong ATS is installed, no delayed transition.

 

[hurk27]

Is there any material I can read up about the collapsing field.

Also,I got an email from this forum with a different reply which had something to do with the wrong wiring CAB rather than ABC. Do you have any reference material to that where I can read up about it.

I got crossed up in my mind and was thinking about the transition between two utility sources where utility 1 would be tied into the transfer switch as ABC, and utility 2 would be tied into the transfer switch as CAB, this would cause the collapsing field in the transformer to be transition back into the second utility 60? out of phase, even though the rotation is correct the phase rotation is offset by 120?.

A generator operating out of sync from the utility source will always have this problem at least 2/3rds of the time if the transition is too fast for the fields in the transformer to completely collapse, we had a 3kva single phase control transformer that exhibited this problem until we rotated the phases, At one time I thought this would apply to a generator as we had another lift station that again had a 3kw single phase transformer but this time it was fed from a generator for back up instead of dual utility sources, well as I found out it didn't work as unless the generator operated in sync the rotation of utility, the generator would always differ from the rotation of the utility, so our only solution was to add time for the transfer back into the utility to allow the field in the transformer to collapse.

Sorry for the confusion:ashamed1:

 

[brian john]

I
A generator operating out of sync from the utility source will always have this problem at least 2/3rds of the time if the transition is too fast for the fields in the transformer to completely collapse, we had a 3kva single phase control transformer that exhibited this problem until we rotated the phases, At one time I thought this would apply to a generator as we had another lift station that again had a 3kw single phase transformer but this time it was fed from a generator for back up instead of dual utility sources, well as I found out it didn't work as unless the generator operated in sync the rotation of utility, the generator would always differ from the rotation of the utility, so our only solution was to add time for the transfer back into the utility to allow the field in the transformer to collapse.

Sorry for the confusion:ashamed1:

While an in-phase -monitor can minimize this issue, due to the speed of the newer ATS's this issue is very common when the load is comprised of step down transformers.

 

[hurk27]

While an in-phase -monitor can minimize this issue, due to the speed of the newer ATS's this issue is very common when the load is comprised of step down transformers.

The thing that gets me is many of the manufactures didn't even think of this problem for transfer switch's that are not being use for zero sequence transfers, while making the transfer faster in some cases so fast contactors don't even drop out, but without the generator being in phase with the utility and not just the same rotation but ABC to ABC, these transformers are getting hit sometimes as much as 180? out of phase, that is twice the energy of a bolted fault if you think about it, as a bolted fault is a short circuit of the voltage at the rating of the transformer, but two sources 180? out of phase connected together will have twice the energy going into that fault so for 2 480 volt sources that is 960 volts at the available current of both sources being put together, but we know that the transformer field energy will have some decay so its not quite that high but it still can't be good for the equipment or the contacts of the transfer switch.

When we had the field engineer from Kohler out on the site to commission the installation and we told him that we need to put in a 1 second delay when transitioning back to utility he had no idea about the problem, we had to show him the effect and it took 4 tries to get it to do it, this is because it only happens 2 out of 3 times as an average, but to get him to better wrap his mind around the problem it took me to use the transfer switch with the generator disconnected and the utility connected to both the utility input and the EMG input, but one was ABC and the other was CAB, and when the load which we only had the transformer in-line was transfered it blew the 30 amp fuse every time, he got this deer in the headlight look and said they never thought about when a transformer would be on the load side, he had to go back to Chicago and get another control board that allowed the delay to be changed as the one we had didn't allow it as it had a fixed resistor and the one he brought back had an adjustable one, so hopefully Kohler has ironed this problem out and now allows the delay to be changed on all of them.

Generac also has this problem as they also do not have an adjustable transfer delay when returning back to the utility.

 

[hillbilly1]

Generac also has this problem as they also do not have an adjustable transfer delay when returning back to the utility.

Generac has more problems than that with their Nexus controller.:roll:

 

[hurk27]

Generac has more problems than that with their Nexus controller.:roll:

What have you experienced, I have installed a few and other then transformer loads which I just use a delayed contactor on them I haven't had any problem with them in any other areas, other then the PITA of having to get the start up code to get it to run for the first time which installers who would not fill out the warranty card and send it in brought that on, and also it does some what deters theft as if some one steals it and you report it to Generac they can track down anyone trying to get the code again unless they are after just the scrap prices.

The oldest unit I installed with a Nexus controller was installed in 2008 and have not had one bit of problems with it?

Older units had problems with the batteries as they still were trying to use a trickle charger which does not shut off after the battery reaches float voltage and this had the effect of causing it to loose water which if it was allowed to run dry can cause a battery explosion, the problem was their engineers didn't think about the problem that we could no longer find maintenance type batteries that had removable fill caps that would allow the battery to be maintained, but after I wrote a lengthy letter to one of their engineers, they changed to float type chargers that shut off when float voltage is reached (14.2v) so maintenance free type batteries work just fine, when the Nexus controller was developed the battery charger was included on the mother board so no more trying to figure out where to put the wall wart charger.

I will agree that their alternators do not like to be over loaded for very many times, I have lost 3 alternators where in one case the home owner took it upon himself to add a hot tub that put the load just over the rating of the generator, he said it tripped the breaker on the generator just fine but after about 4 or 5 times the alternator lost one of the hots, in the windings, another case was an old 5kw unit that the owner kept connecting more loads to it till it smoked the alternator, so I can't totally blame Generac for it, but it still should not have burned up the alternator with the breaker protecting it working correctly, they handle bolted faults just fine as the breaker opens faster, but overloads that are right at the limit of the breaker are the ones that get the alternator as the breaker might hold for hours.

 

[hillbilly1]

What have you experienced, I have installed a few and other then transformer loads which I just use a delayed contactor on them I haven't had any problem with them in any other areas, other then the PITA of having to get the start up code to get it to run for the first time which installers who would not fill out the warranty card and send it in brought that on, and also it does some what deters theft as if some one steals it and you report it to Generac they can track down anyone trying to get the code again unless they are after just the scrap prices.

The oldest unit I installed with a Nexus controller was installed in 2008 and have not had one bit of problems with it?

Older units had problems with the batteries as they still were trying to use a trickle charger which does not shut off after the battery reaches float voltage and this had the effect of causing it to loose water which if it was allowed to run dry can cause a battery explosion, the problem was their engineers didn't think about the problem that we could no longer find maintenance type batteries that had removable fill caps that would allow the battery to be maintained, but after I wrote a lengthy letter to one of their engineers, they changed to float type chargers that shut off when float voltage is reached (14.2v) so maintenance free type batteries work just fine, when the Nexus controller was developed the battery charger was included on the mother board so no more trying to figure out where to put the wall wart charger.

I will agree that their alternators do not like to be over loaded for very many times, I have lost 3 alternators where in one case the home owner took it upon himself to add a hot tub that put the load just over the rating of the generator, he said it tripped the breaker on the generator just fine but after about 4 or 5 times the alternator lost one of the hots, in the windings, another case was an old 5kw unit that the owner kept connecting more loads to it till it smoked the alternator, so I can't totally blame Generac for it, but it still should not have burned up the alternator with the breaker protecting it working correctly, they handle bolted faults just fine as the breaker opens faster, but overloads that are right at the limit of the breaker are the ones that get the alternator as the breaker might hold for hours.

You cannot use them commercially other than optional standby systems, it takes way too long for the controller to recognize power loss, start generator, and transfer. There is no adjustment for this either. I have a 60 kw sitting in the warehouse we had to remove and replace with a Kohler. Generac said they could build a custom controller in about two months.

 

[brian john]

Generac has more problems than that with their Nexus controller.:roll:

Agreed.

 

[hurk27]

You cannot use them commercially other than optional standby systems, it takes way too long for the controller to recognize power loss, start generator, and transfer. There is no adjustment for this either. I have a 60 kw sitting in the warehouse we had to remove and replace with a Kohler. Generac said they could build a custom controller in about two months.

Depends on which unit level you purchase, their industrial units are designed for closed transition transfers as emergancy back up, startup and transfer can be set for very fast transfers as short as 5.1 seconds:

Generac Industral GTS transfer switchs

Utility Voltage
Dropout.........................................................................................................................75-95% (Adj.)
Pickup...........................................................................................................................85-95% (Adj.)
Line Interrupt...........................................................................................................0.1-10 Sec. (Adj.)
Engine Minimum Run............................................................................................................5-30 Min. (Adj.)
Engine Warmup..............................................................................................................5 Sec.-3 Min. (Adj.)
Return to Utility.....................................................................................................................1-30 Min. (Adj.)
Engine Cooldown..................................................................................................................1-30 Min. (Adj.)
Standby Voltage.......................................................................................................................85-95% (Adj.)
Standby Frequency..................................................................................................................80-90% (Adj.)
Time Delay Neutral.............................................................................................................0.1-10 Sec. (Adj.)
Transfer on Exercise.................................................................................................................On/Off Switch
Warmup Timer Bypass.............................................................................................................On/Off Switch
Time Delay Neutral Bypass.......................................................................................................On/Off Switch
Inphase Monitor.......................................................................................................................On/Off Switch
LOGIC CONTROL w / Inphase Monitor

Home and commercial units are more design for optional standby, the newer nexus transfer switch's are much faster then the older system as I can remember them having a 30 second delay then engine start up, then a 1 minute warm up, before transferring, then when power returns it had a 1 minute delay before transferring back to utility then a 1 minute cool down before the generator shuts down, it was really that bad, but now its way faster as you can see below:

Nexus Smart Switch™ 100-400 amps, Single Phase
?
Generac Power Systems, Inc. • S45 W29290 HWY. 59, Waukesha, WI 53189 • generac.com
?2011 Generac Power Systems, Inc. All rights reserved. All specifications are subject to change without notice. Bulletin 0186670SBY-E / Printed in U.S.A. 05/06/11

FUNCTIONS
All Timing and sensing functions originate in the generator controller

Utility voltage drop-out......<60%

Timer to generator start.........10 second factory set, adjustable between 10-30 seconds
Engine warm up del................5 seconds
Standby voltage sensor.........60% for 5 seconds
Utility voltage pickup...........>80%
Re-transfer time delay...........15 seconds
Engine cool-down timer..........60 seconds
Exerciser ............................12 minutes every 7 days

The transfer switch can be operated manually without power applied.

 

[hillbilly1]

Depends on which unit level you purchase, their industrial units are designed for closed transition transfers as emergancy back up, startup and transfer can be set for very fast transfers as short as 5.1 seconds:

Generac Industral GTS transfer switchs



Home and commercial units are more design for optional standby, the newer nexus transfer switch's are much faster then the older system as I can remember them having a 30 second delay then engine start up, then a 1 minute warm up, before transferring, then when power returns it had a 1 minute delay before transferring back to utility then a 1 minute cool down before the generator shuts down, it was really that bad, but now its way faster as you can see below:

They still take too long for anything but optional standby. That was the delay on ours, 10 seconds to start, 5 seconds to transfer. 5 seconds too long to pass Fire Marshal inspection. If you spring for the industrial unit, you might as well get a Kohler or Cat.