Riding through POCO events.

[11bgrunt]

On Monday I will be part of a group visiting a plant where styrofoam plates and food packaging are made.
The principal controls reported are Yaskawa A1000 VFDs https://software.yaskawa.eu.com/en/...he-high-performance-drive/specifications.html and Siemens PLC S7-1500 CPU (PLC) Part number 6ES7-515-2AM01-0AB0 https://mall.industry.siemens.com/mall/en/WW/Catalog/Product/6ES7515-2AM01-0AB0
Service is provided by the POCO's 4200kVA, three phase transformer, 480/277Y.
This plant uses an extrusion process to create their product.

The problem is this plant's process cannot ride through a utility substation breaker operation. The reclose time on the POCO's first operation is 1 second.

We have heard stories that if there is a significant voltage sag to their equipment, they have similar problems. These sags are typically caused by primary faults on the POCO's lines that sag their power transformer voltage at the substation for the time it takes their OCPD to clear that fault.

What options are available that will allow this plant to ride through these types of events?
We have talked about UPS and similar high cost options. This plant peaks above 3MVA. Our role is to look at their equipment, gather information and make recommendations.

 

[zbang]

(written more for readers who haven't been down this road before, sound like you have)

First thing is to figure out which parts of the overall can gracefully handle a power event an which can't. Large heaters- they probably don't even notice a few second outage, PLCs and computers do (those should at least be on conditioned power, if not UPS, already). Cooling fans & pumps? A couple of seconds is probably OK it they restart properly. How do the various processes react to a momentary stop in product movement and how well do they restart (and what's the wastage). How long does it take to clear and restart the line? (the cost?)

Once you get all of that, then look at how to manage power. Any computer/controls/SCADA/etc should already be on conditioned power. If product movement is the key, maybe that part needs to be on a UPS of some sort (rotary?). A full-plant UPS is probably out of the question, but a bunch of individual UPS, both online w/ batteries, and rotary, might fit the bill. In some cases, just adding a flywheel to a machine might do the job, does make startup slower, though.

IIRC, this is how the general co-gen trend started in the 70's(?), factories that found it more reliable/cost-effective to generate their own power than to lose product and restart the production lines. (ISTR reading about glass factory in NJ.)

 

[Jraef]

I agree that the most cost effective solution is to identify and mitigate the equipment that is most sensitive. But also, it's best to start with data collection to know exactly what you are dealing with in terms of the depth, duration and occurrence (frequency) of events. Spending mega dollars to address something that happens once per year is often not cost effective compared to spending far less to mitigate things that happen every week. I always recommend starting off with connection of some sort of recording system, preferably for as long as they can put up with waiting for the solution. A year is best, but often people don't want to wait that long so as many months as possible is better than weeks or days.

Here is one I did for a customer that represents 9 months of monitoring (entire facility, 400A service)

What you can see here is that there was only one event that was over about 2 seconds (left, bottom, 0 volts for about 1200 seconds/20 minutes). So a full blown UPS would have only been needed for that single event. Most of the rest could have been dealt with by something that could provide just 2 seconds of hold-up time. They were being sold a $250k UPS system that was only necessary for that one event and even then, it would have only held them up for 10 minutes, not the full 20. They bought a solid state device that provided that, it was less than half the cost. In this case they insisted on protecting the entire facility (a hard drive manufacturing facility), but normally I would have put the recorder on more specific equipment that was critical and sensitive.

 

[ATSman]

Jraef,
Are you sure you didn't mean a 4000A (typo?) service for the entire facility?

 

[Jraef]

No. It’s one small building (clean room) housing specific machinery. These places are being built modular now so that when technology changes and whatever they were making becomes obsolete overnight, they just give up the building(s).

 

[ATSman]

Got it