Emergency Power causing starter issues

[snace]

Background
I am working on a renovation of a Sewage Pump Station were we upgraded the existing pumps and associated controls, but reused the existing service and generator. I have two new 75HP pumps with motors and a new control panel; by others. The control panel has individual starters (Siemens Sirius) with 150A CB's for each motor and the starters were programmed to limit the inrush. During testing, we found the starters would trip out and fail to across the line from poor power quality. We found that the pump station was at the end of a long utility feed and had voltage drop and poor power quality from local industrial loads. We installed a new utility pad mount transformer to improve the power quality and everything has been working great for a few months under normal or emergecny power.

Recently, the pump station was tested under emergency power and the starters are back to doing the same thing (but only under emergency loads). We are going to have the generator load bank tested to see if something has changed from a power quality standpoint.

Has anyone experienced this same issue with a genertor causing soft starters to trip out? Any suggestions as to what else could be happening? Thanks.

 

[GoldDigger]

Has anyone experienced this same issue with a genertor causing soft starters to trip out? Any suggestions as to what else could be happening? Thanks.

Not quite the same thing, but a full VFD with regenerative motor breaking could trip out when the motor is stopped when connected to a generator, since it could not absorb backfed power the way the grid could and let the voltage go above the programmed upper limit. But your are not using a VFD and pump motors do not need controlled braking.
If the soft starter were checking for a stable line frequency, it could fault if the generator slowed down momentarily under the load. That could happen because of mechanical governor problems or poor tuning of the prime mover engine. When load bank testing be sure to look at the response to a sudden load change as well as looking at maximum output capacity.

 

[eHunter]

Background
I am working on a renovation of a Sewage Pump Station were we upgraded the existing pumps and associated controls, but reused the existing service and generator. I have two new 75HP pumps with motors and a new control panel; by others. The control panel has individual starters (Siemens Sirius) with 150A CB's for each motor and the starters were programmed to limit the inrush. During testing, we found the starters would trip out and fail to across the line from poor power quality. We found that the pump station was at the end of a long utility feed and had voltage drop and poor power quality from local industrial loads. We installed a new utility pad mount transformer to improve the power quality and everything has been working great for a few months under normal or emergecny power.

Recently, the pump station was tested under emergency power and the starters are back to doing the same thing (but only under emergency loads). We are going to have the generator load bank tested to see if something has changed from a power quality standpoint.

Has anyone experienced this same issue with a genertor causing soft starters to trip out? Any suggestions as to what else could be happening? Thanks.

Need more info to form a targeted response.
Is this truly an NEC article 700 emergency power system generator that has to start and accept the full load within 10 seconds of utility failure?
Are the pump motors started as soon as the gensets are up to speed or delayed?
Do both of the pumps started at the same time or is one on a staggered/delayed start?
Are the new pump motors larger than the the older units?
What size genset is currently installed?
Have the motor breakers tripped on start?

During genset testing pay particular attention to sag, droop, voltage dip and the recovery, especially if it must accept the
full block loading in 10 seconds.