trip setting for ATS

[Lutfi]

quick and silly question:

who determines and how do you determine the trip setting for an ATS? The ATS already has been selected, sized and specified with the proper breaker rating.

This question came up during activation of the generator becasue the ATS tripped when certain procedures took place.

Regards

Lutfi

http://www.cdeco.com

 

[alehman]

I presume the ATS is made from a pair of circuit breakers? If the breakers trip one of the following may be the cause: (A) there is too much load, (B) there is a fault, (C) if the breakers have adjustable trip settings, the are set too low.

What "certain procedures" cause the trip? What other procedures do not cause a trip?

Can you be more specific about the installation, loads, ATS rating, configuration, etc.?

 

[rbulsara]

Is this closed transition type or open transition type ATS?

 

[rob46]

You may indicate the suggested ATS settings or require testing company to determine the settings. Delays in load starting (several steps) or several ATS in the system (like in hospitals) may affect the settings.
In case of one generator and one ATS you may consider the following:
"Start time delay: Three seconds (prevents nuisance generator set starts during momentary utility power variations). Transfer time delay: Three seconds (allows generator set to stabilize before load is applied). Retransfer time delay: Five minutes (prevents needless power interruption if return of utility power is momentary. Stop time delay: Five minutes (allows gradual generator set cool down) ".

 

[e5fornow]

Under normal conditions the ATS should not trip. All breakers should be set higher than the input feeder breakers from the Utility and Emergency.

If you have a close transition and during retransfer the ATS will often shunt a breaker if it is in parallel too long.

Usually this is done by shunt tripping the generator mounted breaker.

 

[EEJaime]

There could be many reasons for an ATS trip, any one of the over/under voltage or frequency sensors,etc... It could also depend on what your loads are and what your power sources are. We had a devil of a time with an ATS between a gas fired engine generator, (Waukesha), a chiller, (Trane), and the ATS, (Russellectric). It turns out that the Variable Frequency Drive on the Chiller was introducing so many harmonics into the system, the frequency safeties on the ATS would send it back to utility. Then the undervoltage sensors on the generator would trip if the chiller wasn't fully loaded and the VFD ramped down the chiller. The system was sold to a healthcare client of ours as a package, and the vendor assured them they had these installations "all over the country". As long as it took us to solve the problems, and as many times as they told us "it's not our equipment", it was obvious they hadn't done this before. We ended up disableing the safeties and tieing it into the Energy Management System to monitor all the pieces of equipment and maintain the operaton while still providing the equipment protection. As I said, it could be a lot of things.

Good luck with your project.