Power reliability scenario-Generator vs Commercial

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dschultz307

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I am in need of advice on the following scenario:

UPS battery plant has failed and UPS cannot carry critical load during an outage/transfer to secondary feeder or generator.

It will be at least a week until new UPS batteries are installed.

Mission critical facility.

Double ended switchgear (two feeds w/tie breaker; two generators, only one allowed to run at a time)

Facility less than six years old, about 100 hours on generator

Opinions on the following actions:

Leave it alone---The commercial power is more reliable than the generator.

Switchgear controller in AUTO, Turn off commercial feeds, allow switch gear to select one generator, transfer to other if a failure occurs.

Switchgear in MANUAL, Power facility on one generator.


I understand that a transfer to generator would result in a critical load outage under any circumstance.



Thanks,

Dave
 
I would say if this is a mission critical facility, the they could afford to run at least one generator in a stand by mode, which is ment "generator running and transfer on utility", most transfer switchs can still transfer fast enough to not loose power, but it will depend upon the type, fuel will have to be monitored unless NG is the source.

maybe others have a better idea
 
"Mission critical" - Spend some dollars and rent a "twinset" generator (both running, one on load, one in sync ready to take the load with no interruption). Pick a unit that can be paralelled with other sources, so disconnect your existing genset, connect the twinset, verify phasing, bring twinset on line, disconnect utility power, sleep easy for a week.

Twinsets are generally considered more reliable than utility power.

Make sure they dont run out of diesel... Don't laugh - it happens more often than one might think...
 
In the past we supported the entire critical load of a major financial market solely on generator while expanding the UPS systems (often for 18-20 hours at a time). We call that "diesel UPS system". But the facility had closed transition capability, 4 X 1500 KW generator plant, and 30,000 gallons of diesel fuel.

I'm not clear as to exactly how your generator plant operates, is it open or closed transition? Paralleling capabilities? And what configuration is the UPS system? Multiple modules? Parallel redundant?
 
Thanks for the replies.

Not sure what open or closed transition means.

The plant is designed to operate in the following sequence assuming all system are in AUTO:

switchgear fed by feed A
if feed A fails but B is OK switch to B
if A and B feeds fail start one generator and transfer load.
if generator 1 fails start generator 2 and transfer load.

This is all in the switch gear, there is no standalone ATS.

The switchgear is 1600A/208V Generator is a Cat Diesel Rated at 500KW Standy power.

The present load is about 220KW.

The UPS side of the plant is 2 130kVA modules parallel/redundant.
But the battery plant is unable to carry any load. So the UPS is now just one big filter.



Brings up another question:

A person informed me that running the generator at light load for too long will result in wet stacking. I would like to think the load I have would be more than enought to prevent wet stacking. Thoughts?
 
It sounds very much like an open transition system, and the UPS (when working) papers over the transitions.

Another thought is that it may be possible to rent batteries for your UPS. In the UK there is at least one specialist rental supplier (Backroom) who just deal in UPSs and distribution, and have a "we can solve your problem" attiude, and I'd have thought there should be similar companies in the USA.
 
Closed Transition switching is when one or more generators briefly parallel with the utility for a seamless transfer. Open Transition is a “break before make” switching. More info here.

I gather you have open transition and there is no way to not interrupt load when performing a planned transfer to generator. It now becomes an equation on how much risk can be endured.

1. Do nothing and hope there are now power events (storms, etc).
2. Perform a planned shutdown of the critical loads, open transition to generator and restore the loads. Once the batteries are replaced, you can switch back.

I wouldn’t worry about wet-stacking with the 220 KW load on a 500 KW generator. Even if you were running lightly loaded, that is a small risk versus dropping critical load. Full load banking by the generator service firm afterwards would help.

Are both UPS modules having battery problems? If not can one carry all critical loads?

With all due respect to UPS technicians, you should contact the battery manufacturer’s service organization or a firm that specializes in UPS battery plant service. They may be able to “jump out” bad cells and at least give you a reduced capacity capability or even have some sort of rental batteries.

Good luck and please let us know how this unfolds.
 
dbuckley said:
It sounds very much like an open transition system, and the UPS (when working) papers over the transitions.

Another thought is that it may be possible to rent batteries for your UPS. In the UK there is at least one specialist rental supplier (Backroom) who just deal in UPSs and distribution, and have a "we can solve your problem" attiude, and I'd have thought there should be similar companies in the USA.
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Excellent points!

dschultz307, where are you located?
 
I am in the Northern Virginia area.


The UPS technician looked over the batteries and didn't want to move batteries around because he felt the were all too weak. I wanted to see that happen but it was probably too labor intensive for the benefit.

We were prepared to perform a transfer to generator but our DPW/Maintenance staff recommended strongly against running on generator for 7 days. The statement was "There is much less risk on commercial power"
This seems against my experience in the past but they were the professionals on the scene and we went with their advice.
 
dschultz307 said:
I am in the Northern Virginia area.


The UPS technician looked over the batteries and didn't want to move batteries around because he felt the were all too weak. I wanted to see that happen but it was probably too labor intensive for the benefit.

We were prepared to perform a transfer to generator but our DPW/Maintenance staff recommended strongly against running on generator for 7 days. The statement was "There is much less risk on commercial power"
This seems against my experience in the past but they were the professionals on the scene and we went with their advice.
Click to expand...

Unless you can find records of the voltage measurement of each individual battery, it sounds like no one has been doing serious maintenance on the batteries. I'm going to Private Message you two reliable firms that specialize in battery maintenance.
 
Am I understanding correctly that this is main-tie-main ? If so, i'm curious as to how critical the facility is if a substantial portion of the local grid were to fail ? also, what is the history of both mains failing ? (just curiosity) (We have worked live on stupid stuff because people claimed their satcom could not go down or lives would be at risk, and while I am sure there are other "mission critical" operations, I often think that some are overstated so it perks my curiosity)
 
nakulak said:
................. (We have worked live on stupid stuff because people claimed their satcom could not go down or lives would be at risk, and while I am sure there are other "mission critical" operations, I often think that some are overstated so it perks my curiosity)
Click to expand...

Logical.:grin: I'd die if I missed "Desperate Housewives" As you say, it is always amazing how the power can not be shut off yet they mange the next time lightning takes out the power.
 
nakulak said:
Am I understanding correctly that this is main-tie-main ? If so, i'm curious as to how critical the facility is if a substantial portion of the local grid were to fail ? also, what is the history of both mains failing ? (just curiosity) (We have worked live on stupid stuff because people claimed their satcom could not go down or lives would be at risk, and while I am sure there are other "mission critical" operations, I often think that some are overstated so it perks my curiosity)
Click to expand...

I suppose you could call it main-tie-main. Only one main is on at a time.

The UPS powers all the critical loads that are not -48VDC. The plant has been up for 6 years and we only have about 100 hours on the generators so I imagine there has been plenty of times we have just switched to the other main.

mission critical in the impact to our customers and the trouble to restore services after an outage. We have done well until the UPS batteries were forgotten and died.

I just have heartburn about the DPW opting not to run the generator.

Dave
 
As others suggest, the best option is probably either a hired twinset generator, or a hired battery.

If finance or logistics prevent these options, then I would run on grid power which is normally more reliable than a single generator.
Although the installation has two generators, this does not help without a working UPS. There appears to be no provision for running the two generators synchronised and load sharing.
Any transfer from one generator to the other would result in power loss, albeit briefly to the critical load.

Since it is stated that the battery is defective, but the UPS itself is believed to be in order, two other possibilities exist to support the critical load.

Hire or buy a very large DC power supply with a 50/52 volt output and sufficient output current to run the inverter in place of the battery.
Connect this in place of the defective battery, the UPS wont "know" if it is connected to a large DC power supply or to a 48 volt battery.
The line voltage input to the power supply must be from an already running generator, or from the other of the two grid supplies.
Any failure of the primary grid supply would then result in the inverter in the UPS supplying the critical load from the DC supply, which is obtained from the generator or the standby grid supply.

The other option is to enquire of an extremly experienced UPS engineer, as to the chances of the defective battery being able to supply the load very short term, for just long enough for open transition switching.
The UPS will be fitted with a "deep discharge protection facility" This disconects the battery when the battery voltage drops too low, in order to protect the battery against harm from over discharge.
For a 48 volt nominal battery I would expect disconection at about 43/44 volts.
It may be possible to defeat or bypass this facility, so as to allow operation at a lower battery voltage, that the defective battery may be able to supply for at least the few seconds that generator starting takes.
 
Mission critical so "mission critical" and the batteries were "forgotten about".


Buy your new bank, build a new room, I guess, switch 'em quick.....

Or run on Gen and hope. I don't know how "mission critical" this is......

It sounds like financial critical. You wouldn't have this problem, if.......You spent some of your "financial" a few years ago.

"Mission Critical" in some circles is MUCH different than in others. The earlier poster that staed they worked on LIVE stuff because they were told is was "mission critical" and lives would be lost,( YEAH, YOURS) is an Idiot.

( Ibet there was BIG money in it though, right?)

I have ONE critical mission: GO HOME at the end of a safe day. If some architect, engineer or CFO, decides something is too expensive to do a certain ( read RIGHT) way, then too bad, your mission goes down the crapper with your money.

I see it every day, even in this economy, I'm good enough to walk off unsafe jobs and still have a dozen waiting. Maybe if some people would stop doing stupid stuff, it'd change alittle. But the CFO/CEO's KNOW that thy'll find someone who'll do it hot for enough money.

And I'd bet this mission critical place tries the SAME THING. We can save $200,000 by paying this fool $10,000. Do it, if he gets whacked, I still get to go home, and it's only 5% over budget. He's the qualified one, right?

I'm too good to risk my life for stupid people.....


Watch the news............



KEN
 
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