Closed Transiton ATS Switch

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Looking for the formula guru's & Persons familar with closed transition ATS units-
Connected load APX 320 Amperes System Voltage 480 3P4W ATS rated 600Amperes -
Normal and Generator OCPD 600 Ampere Frames, Draw Out Style Breakers with retrofited solid state trip units and fused protection. During routine testing of ATS unit. Nine units total with test consisitng of one sequentially operated ATS normal feed breaker being tripped to bring generator on line due to power loss with connected ATS transfering to generator with subsequent ATS units being exercised utilizing test button. Test button will force ATS to seek alternate source in closed or open transtion depending on unit setting - given this is a hospital all units set to closed transition. The actual problem, the worst possible ATS to have problem the Life Safety branch ATS attempts to close it closes out of phase angle blowing both the 600 ampere fuses for the breaker and the trigger fuse. Solid state trip records amperage reading of 7,000 amperes as well as the ATS unit.
The ATS units are a manufacturer's unit (Cummins) CPG - Model BTPC and fairly new for them given the mulitude of unrelated problems we encountered during commisioning process. But they remind me greatly of a Zenith unit which in my opinion makes an outstanding boat anchor - for what these cost, I could have purchased Russell and doubt very seriously I wpuld be making this post. Units meet specification intent, past that the customer nor myself or anywhere near happy with the units...customer has already started grumblings of wanting units changed out - it only took a year to get them installed between scheduling outages, equipment delay through submital processes, and them being retrofitted into a new 2 hour fire rated room to meet code.

Questions are as follows:
1. What formula will give me closed transiton connected time - 2 seperate sources normal and generator at 480V 3PH4W - number of cycles, connected out of phase to reflect the 7000A reading? I may have hammered that - but hopefully you get my intent.
2. Has anyone out there used this type switch or had this type problem with closed transiton switches.

ATS Service Tech was attempting to tell me yesterday, that they had nothing to do with breaker tripping and there may be a "parameters" issue to which I replied. I agree there is a parameters issue, why the hell is the unit not sensing correct phase alignment before closing out of phase - Oh and guess what happens when you buck phases...I believe it called a short, so yes the breaker is also on you.

Your input and experience is appreciated, have a great day all.


Steve
 

dbuckley

Senior Member
In the UPS world we use "wrap around bypass" switching which works in a similar manner to closed transition ATS, and as its a manual switching process the "both on" state lasts from several seconds upwards, depending on the enthusiasm of the engineer operating the switches. But it is a process not without risk, and several error and fault conditions can cause bad things to happen, any of which at least lead to loss of power to load, and some conditions are potentially destructive to switchgear and equipment.

Closed transition is always scary - it should not be possible for the transition to occur if there is phase shift for reasons you've examined first hand.

On the one occasion I've needed no-break power from possibly unsynced sources I've specified a static transfer switch (Cyberex DSTS) which is always an open transition switch, but works at semiconductor speed, so if the sources were in phase at the point of failure then the output is lost for much less than a cycle. For the data centre world I live in then a ragged changeover from non-synced sources is acceptable so the phase pattern "jumps", but I suspect that might be ugly on decent size motors :)

600A 480V static transfer switches are available but are rather more expensive than their non-semiconductor equivalents. But for safety critical it is probably a sound investment.
 

wirenut1980

Senior Member
Location
Plainfield, IN
Steve, the answer to your first question would involve having an accurate model of the system including source impedances, and loads and then changing the phase angles to try and get the 7,000 amps. However, I question the necessity of doing this. You already know what the issue is, so I think you just need to work with Cummins and try to find out why the generator is not in phase with the source...hmmm, I suppose the phase angle might provide a clue as to why the sources are not in phase. Such as looking for a small phase angle shift, or a 30 degree phase shift, or 120 degree phase shift...

Just thinking out loud, but maybe a quick and dirty way to estimate the phase angle difference would be to find out the line to line fault current at the transfer switch and then knowing that phase angle was originally 120 degrees, maybe you can calculate the phase angle to give you 7000 amps.

Hope this helps, sorry if it does not.:smile:
 

ATSman

ATSman
Location
San Francisco Bay Area
Occupation
Electrical Engineer/ Electrical Testing & Controls
CT Theory

CT Theory

Looking for the formula guru's & Persons familar with closed transition ATS units-
Connected load APX 320 Amperes System Voltage 480 3P4W ATS rated 600Amperes -
Normal and Generator OCPD 600 Ampere Frames, Draw Out Style Breakers with retrofited solid state trip units and fused protection. During routine testing of ATS unit. Nine units total with test consisitng of one sequentially operated ATS normal feed breaker being tripped to bring generator on line due to power loss with connected ATS transfering to generator with subsequent ATS units being exercised utilizing test button. Test button will force ATS to seek alternate source in closed or open transtion depending on unit setting - given this is a hospital all units set to closed transition. The actual problem, the worst possible ATS to have problem the Life Safety branch ATS attempts to close it closes out of phase angle blowing both the 600 ampere fuses for the breaker and the trigger fuse. Solid state trip records amperage reading of 7,000 amperes as well as the ATS unit.
The ATS units are a manufacturer's unit (Cummins) CPG - Model BTPC and fairly new for them given the mulitude of unrelated problems we encountered during commisioning process. But they remind me greatly of a Zenith unit which in my opinion makes an outstanding boat anchor - for what these cost, I could have purchased Russell and doubt very seriously I wpuld be making this post. Units meet specification intent, past that the customer nor myself or anywhere near happy with the units...customer has already started grumblings of wanting units changed out - it only took a year to get them installed between scheduling outages, equipment delay through submital processes, and them being retrofitted into a new 2 hour fire rated room to meet code.

Questions are as follows:
1. What formula will give me closed transiton connected time - 2 seperate sources normal and generator at 480V 3PH4W - number of cycles, connected out of phase to reflect the 7000A reading? I may have hammered that - but hopefully you get my intent.
2. Has anyone out there used this type switch or had this type problem with closed transiton switches.

ATS Service Tech was attempting to tell me yesterday, that they had nothing to do with breaker tripping and there may be a "parameters" issue to which I replied. I agree there is a parameters issue, why the hell is the unit not sensing correct phase alignment before closing out of phase - Oh and guess what happens when you buck phases...I believe it called a short, so yes the breaker is also on you.

Your input and experience is appreciated, have a great day all.


Steve

Steve,
I am a service rep for GE-Zenith Controls (the "Boat Anchor" people:roll:) on the west coast. I have done startup and commissioning on several of their CT units but have never encountered anything like this so, like you, I am going in cold. There is a Failed to Disconnect feature on ATS's with CT that could have prevented this disaster wich I will explain later. Most of the problems I find have to do with the units failing to transfer to generator within the 1 minute synch window and lock themselves out (the emer contacts never close.) This is caused by the genset freq being set to close to 60HZ (the CAT guys are famous for this:cool:) which does not allow the two sine waves to cross and synch in enough time. The solution is to adjust the gen F to either > 60.2HZ or < 59.8HZ (0.2HZ differental.) This produces a faster sweep time.

Let's talk about what you have. Cummins Power Generation (Onan design) BTPC with the Power Command microprocessor. This is make before break contact operation. The test switch is operated and on transfer to emer the way it works is a timer starts when the emer contacts close (sources paralleled) and after 100 millisec. (same as for Zenith.) the micro sends a signal to open the normal contacts and the transfer is complete.
With the Zenith MX250 micro, if the signal from the micro does not open the normal side contacts in 100ms then after 325ms a signal is sent to shunt trip the emer source breaker and an alarm is sounded and the ATS is locked out untill the problem is corrected. On the Onan unit it is called the Failed to Disconnect alarm and functions the same way.

From what I gather, a proper startup has been performed on these units and they were transferring ok at some point (is that correct?) If not I would definetely do a point to point wiring check. Two crossed voltage sensing wires on either source could have caused this.

I recommend the following:

1. Set the problem unit to function as open transition and test with the Test
Switch. This will verify that thetransfer mechanism and solenoids are good.
2. Take the schematics that came with the unit and identify the shunt trip
terminals on the back of the micro. to confirm if this wiring is in place. If it
is then apply a test voltage to the breaker shunt trip terminals to prove it
trip the breaker.
3. If all the wiring (shunt trip, voltage sensing, power cabled, phasing, etc.)
looks good then it's possible that part of the logic circuit that opens the
normal source has failed and the micro needs to be replaced.
4. Check the wiring on all the other units to prevent this from happening to
them.
The part# for the service manual is 0962-0519 and can be purchased from your local Cummins Dealer.
Hope this helps and keep us updated on your progress as I am very curious to know the cause.:)

Tony
 
So Far With CT ATS

So Far With CT ATS

This evening we shall be meeting with the Cummins representives, (several and various) but including a design engineer, two specialty techincians and a vice president. The purpose is to find (not tweak setting) but find the cause for the event. I thank you for your responses and shall keep you in the loop regarding outcome.

Have a great day all!

Steve
 

brian john

Senior Member
Location
Leesburg, VA
Have you placed a scope or meter across both sources to verify when the transfers occur?

The ATS and phase relays either work or do not. There is a design spec for the ATS, it either meets this spec or does not.

In a hospital I would go Russell all the way......................Man those things are built tough.
 
ATS Continued Story

ATS Continued Story

The mega-minds of Combined Cummins Technicians meet Monday evening and shotgunned the problem by pulling circuit boards to send back to the factory for inspection, found no obvious smoking gun, but definate signs of the fire, normal and generator contacts on A-C phases are toast for the most part. Closing a circuit out of phase tends to do that. I will keep you appraised of the battle action as it unwinds.

Brian John, I agree with you WHOLE HEARTEDLY on the Russell's - I've had some problems with Russells on occassion but nothing of this magnitude!!! I didn't put this project together - I got saddled with riding it out, start to finish and it has been a long painful ride - 9 ATS units - cut first unit in Mid-Feburary and last one in first week of June working through customers (VA) scheduling as they felt our submitted schedule (required by specifications was entirely too aggressive at two per week.

Have a great day ALL !

Steve
 
Results to Date on ATS

Results to Date on ATS

Since removing the control and logic circuit boards from the ATS - over a week ago, we are still no closer to resolution. I absolutely HATE to think what a HUGE pain in the rear it would be to have to replace these units with any other switch - given it is government, I could see that happening should Cummins fail to provide remedy. The swirling will continue, regardless and in the meantime it is quickly going to become very ugly for Cummins as extended overheads at miniumum and replacement of units with another manufacter at a maximum will be chunk of change to swallow.

Have a good day all!

Steve
 

ATSman

ATSman
Location
San Francisco Bay Area
Occupation
Electrical Engineer/ Electrical Testing & Controls
Since removing the control and logic circuit boards from the ATS - over a week ago, we are still no closer to resolution. I absolutely HATE to think what a HUGE pain in the rear it would be to have to replace these units with any other switch - given it is government, I could see that happening should Cummins fail to provide remedy. The swirling will continue, regardless and in the meantime it is quickly going to become very ugly for Cummins as extended overheads at miniumum and replacement of units with another manufacter at a maximum will be chunk of change to swallow.

Have a good day all!

Steve

Steve,
Please read and respond to post #4 or give it to one of the Cummins engineers to respond.

Tony
 
Tony I did as you asked (The first time)

Tony I did as you asked (The first time)

Tony,
I read and forwarded your post to the Cummins Techicians, preliminary results found nothing wrong with components. From Cummins this morning "The factory has evaluated the boards and have not found your "smoking gun." As we have committed we are not stopping there with out a defined failure component. Currently the factory is going through the firmware code line by line to discover any potential errors in the code or that the logic could have provided. Cummins is committed to assure that the equipment furnished does and will continue to operate as specified without fail."

Thanks
Steve
 

ATSman

ATSman
Location
San Francisco Bay Area
Occupation
Electrical Engineer/ Electrical Testing & Controls
PProcess of Elimination

PProcess of Elimination

Tony,
I read and forwarded your post to the Cummins Techicians, preliminary results found nothing wrong with components. From Cummins this morning "The factory has evaluated the boards and have not found your "smoking gun." As we have committed we are not stopping there with out a defined failure component. Currently the factory is going through the firmware code line by line to discover any potential errors in the code or that the logic could have provided. Cummins is committed to assure that the equipment furnished does and will continue to operate as specified without fail."

Thanks
Steve

Ok, if the components check ok then the question is has the unit ever transferred properly in the past? If not then a point to point wiring check needs to be done on the ATS internal wiring. One crossed wire will do it.
Also, you did not answer whether the unit has the failsafe shunt trip feature
I mentioned to prevent this catastrophe. If so why didn't it function? That wiring needs to be checked.

Tony
 
Tony

Tony

I shall put the question regarding shunt trip to them. In answer to your question regarding unit operation the unit was pre-commissioned (tested) without load attached, once passing the pre-commisioning testing - the load was connected - normal power was failed to the unit, generator cranked, normall power restored, generator power failed to see that unit was seeking source and it transfered as it should have. This was done for two more operations BEFORE starting to switch unit using test switch and was done in both open and closed transtion.
Failure occured during a rountine testing for the ATS units whereby a selected ATS unit normal power was killed and the test button on the remaining eight were operated (All in closed transition except for fire pump which was in open transition. When this unit attempted to close to generator power from normal power it must have been almost 180 degrees out judging from the contacts inspected after the fact on both the normal and generator side of circuits. Pipe and conductors were rattling and the recorded was 7,500A on the fault.

Have a great day!
Steve
 
Final Report & Remedy

Final Report & Remedy

1. Tony, no they don't have shunt breaker in these units.
Following is from Cummins
Cummins Atlantic is attaching a report from our factory on the events that you experienced on your ATS-1. You will see from the information that after an exhaustive testing and analysis process we have identified that the switch did in fact close out of phase due to the closed transition synchronizer not being activated to provide a synch check function. The other item was due to system communication delays that did not provide the required updates within the timeframe required and locked out the control.

The factory has performed over 20 additional validation test sequences and have not been able to make the board or software from your switch ATS-1 re-create the failure event. The factory is going to replace your complete switch assembly with a new replacement switch. Your switch will be sent back to the factory for additional destructive tests to make the system failure occur as you experienced. Currently, the factory has the switch in the build process and are looking at the first week of September for a delivery. I will be in the factory on Wednesday and Thursday this week and I will have an update on the delivery schedule for you while I am at the factory.

We do apologize for the issues and loss of confidence that this malfunction has caused each of you. Cummins is looking to regain your confidence and prove to you that you have a very strong and reliable system for many more years of operation. Cummins Atlantic is prepared to "do what ever it takes" to earn this level of confidence from the VA staff, Gregory Electric and the engineers/ designers of this system.

Should you have any questions concerning this information or require any additional information, please do not hesitate to contact me directly.
Sincerely,

"I would inculde the test file info but it would not up load.

Thanks for the good feedback and responses and continue to keep safety in the front of you mind, so you don't lose more than your mind.

Steve
 

ATSman

ATSman
Location
San Francisco Bay Area
Occupation
Electrical Engineer/ Electrical Testing & Controls
Root Cause Not Identified

Root Cause Not Identified

1. Tony, no they don't have shunt breaker in these units.
Following is from Cummins
Cummins Atlantic is attaching a report from our factory on the events that you experienced on your ATS-1. You will see from the information that after an exhaustive testing and analysis process we have identified that the switch did in fact close out of phase due to the closed transition synchronizer not being activated to provide a synch check function. The other item was due to system communication delays that did not provide the required updates within the timeframe required and locked out the control.

The factory has performed over 20 additional validation test sequences and have not been able to make the board or software from your switch ATS-1 re-create the failure event. The factory is going to replace your complete switch assembly with a new replacement switch. Your switch will be sent back to the factory for additional destructive tests to make the system failure occur as you experienced. Currently, the factory has the switch in the build process and are looking at the first week of September for a delivery. I will be in the factory on Wednesday and Thursday this week and I will have an update on the delivery schedule for you while I am at the factory.

We do apologize for the issues and loss of confidence that this malfunction has caused each of you. Cummins is looking to regain your confidence and prove to you that you have a very strong and reliable system for many more years of operation. Cummins Atlantic is prepared to "do what ever it takes" to earn this level of confidence from the VA staff, Gregory Electric and the engineers/ designers of this system.

Should you have any questions concerning this information or require any additional information, please do not hesitate to contact me directly.
Sincerely,

"I would inculde the test file info but it would not up load.

Thanks for the good feedback and responses and continue to keep safety in the front of you mind, so you don't lose more than your mind.

Steve

Steve,
I am not sure what Cummins means by the "CT synchronizer not being activated." Although I have found that manufacturers, although they don't lie, have a way of not telling the whole story in order to protect the reputation of their products.
In any case I applaud them in stepping up to the plate and agreeing to replace the unit. Does that also include the labor to remove & install the new one??? ;)
Thanks for the post!

Tony
 
The Final Saga of the ATS from Hell

The Final Saga of the ATS from Hell

The factory after two months of testing the defective unit components, delivered this not totally unexpected news. The issue was internal timing supposedly although they were unable to duplicate the fault at the factory. Vendor did step up to the plate and offer to replace the entire unit. I however had to explain, that I had absolutely no problems with the enclosure it was built like a rock, besides for us to remove would have taken an act of congress and more money than they wanted to spend as the ceiling height in the room containing the ATS units would not allow for tipping the unit over (3 Hour fire rated with a header in the way at that) after I dollarized the decision for them they decided to change all the interior components and unit has been working fine for three months now. I do still don't feel warm and fuzzy but hopefully I will get through the next nine monthes. All in all a horrible experinence.

Have a good day all!

Steve
 

mayanees

Senior Member
Location
Westminster, MD
Occupation
Electrical Engineer and Master Electrician
Thanks for closing the loop Steve.
Always appreciate learning from the experience of others.
John M
 
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