UPS going to Bypass Mode instead of supplying through Batteries. 2

[ArsalanKhan]

Background:

We operate a gas plant with a load of approximately 7 kW. Our power supply is provided by a substation, and we also have a backup generator connected to an Automatic Transfer Switch (ATS). This setup ensures that in the event of a power outage, the ATS switches to the generator. For critical loads, we have two UPS systems with Static Transfer Switches (STS) installed to guarantee uninterrupted power supply.

Issue:

Currently, we are encountering a problem where, during a power outage, the UPS effectively switches to battery power and maintains an uninterrupted supply to the critical load. However, when power is briefly restored and then interrupted again within a span of some seconds, the UPS switches to bypass mode instead of continuing to provide power from the batteries as it is designed to do. Can someone help us identify whether this issue is due to a fault in the UPS or the power supply?

 

[cranky108]

I'm on the western grid, not the eastern grid.

Likely a reason for not synchronizing would be voltage out of range, which can be measured and maybe fixed.

Then again, some UPS systems might be set up to manual transfer back, so the customer can predict the transition.

 

[crshears]

Re time error correction:

No problem, Bill.

FWIW I did come across some information suggesting that within ERCOT [ the Texas grid ] as well as within other global control areas, annual negative time errors of as much as ten minutes have been allowed to accumulate, without any attempt at correction.

Cranky wrote:

I don't have an exact date, but the major grid operators no longer keep the frequency at exactly 60Hz. This maybe because it cost them to pay larger plants to increase or decrease output in order to keep the frequency exact, and because of recent demands for lower cost electricity, this was one things of the past that was dropped.

Sort of like gold to backup the dollar. Doesn't happen anymore.

Given what I wrote above the quote, the post by cranky108 does have some validity; the EI still holds to a +/- ten [10] second time error tolerance, but this no longer necessarily applies to all the larger control areas worldwide, and clearly some have even abandoned maintaining a 50/60 Hz average.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[bacon4life]

Thanks for the clarification crshears. I had misunderstood that the withdrawal of BAL-004 did not actually mean the end of MTEC. I am confused what changed since NERC posted the BAL-004-0 White Paper Clean suggesting to terminate MTEC.

This image from the 2023_FRAA_Report_Final shows the typical frequency distribution for the major interconnections in North America.

 

[crshears]

Administratively I'm not sure whether all the eyes have been crossed and the tees have been dotted, which also confuses me, bacon . . . but paperwork doesn't always comport with reality, at least in my experience.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[crshears]

Hey all,

Last month I contacted the IESO here in Ontario, Canada, trying to get some information about system time error correction in the Eastern Interconnection.

They got back to me today.

This

https://naesb.org/pdf4/weq_bps062520w1.pdf

is the link to a public document published by NERC that in my view spells out in great detail the North American practices and particulars of this topic.

Hope this helps.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[waross]

Thanks CR

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[crshears]

NP;MP! [No problem; my pleasure!]

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]