Synchronization 1

[joan271273]

Could someone provide some insight on the difference between active and passive synchronization.

I have a project with closed transition were everything was designed around "pasive" synchronization and the Generator vendor is stating that they cannot do that and they only do "active" synchronization.

What are the differences?
Are there standard ways to bridge the gap or to make this work.

 

[joan271273]

Thanks for all the help, I will try to put everything together as to "suggest" some of the items pointed out within these posts, even tough I will have to tolerate statements like : I will not be liable, against the plan of record,etc. All of this when I have what I would call an incomplete design.

 

[JBinCA]

I have to agree with Waross. If you have a genset vendor that is already agreeing to provide an active synch solution, you shouldn't have any problem. It sounds like the parties involved simply don't understand each other (or one of them doesn't understand the operation of these systems).

The difference between active and passive synchronizing is whether there is a controller causing the two sources to become syncronized (active) or not (passive). A system that is intended to operate passive doesn't have any idea if there is a controller attempting to bring the two sources into synchronism or not, it only checks to see if they are (using a synch check relay instead of a synchronizer (25 vs 25A)) and then transfers. This could be done cheaply with a Basler BE3-25.

I think it would also help you to know that most "active synch" systems in industry do rely on a synch check relay (which is the defining component of "passive synch" systems) as a protective device anyway.

Regards

 

[rbulsara]

Joan:

The lesson to be learned is to hire the right professionals for the job. I wonder what was the basis of selection of engineers for this project?

 

[SilverArc]

Waross,

I would agree with idea of copying specifications. I had a complete different impression of consulting engineers buisness before I joined it. Most of the specs are already done and the job of the engineers is to change ratings and then thay ran into trouble.
My post about "regenerative power" is also result of this misundersting but we still have not bought the generator and it is in the bidding process.So I still have options.

The orginality is some thing that is very rare.
Anyways, I have seen, written many generator specs but ofcouse from the existing ones:

When ever the question has arised about the automatic transfer switch:
Only two things arise:
Open transition and Closed transition:
and the justification behind selection is that, if the sytem has large motors where magnetic field is drained during open transition, It will lead to very high inrush current for transformers and motors , which eventually might trip the main breaker. So, It is advisale to use a closed transition switch.

Now what I understand that an ATS, has nothing to do with the specification of generator. But this post seems to be creating a relation about a generator control system with a Automatic Transfer switch.

That means, we should ask the generator manufacturer if his generator is eligible for a typical closed transition or we might have to provided some extra hardwired control as you discussed above.

I had never heard of active and passive, I guess it is by default considered that an ATS will be compatible with generator.

Could you kindly elaborate on this issue.

Thanks

 

[waross]

Copying specifications. I don't have a problem with this, why re-invent the wheel. What gets expensive is when someone copies a spec that they don't understand. If the engineer doesn't understand the spec he may use a spec for the wrong application.
We installed a standby generator for a prison years ago. The spec was copied from another government installation which was off the grid. There were a few other mistakes. We installed a 500 KW when a 200 KW or 225 KW would have done the job.

I always recommend buying the transfer switch with the genset. The pricing is usually excellent. You also get compatibility most of the time.
The set I have just finished installing had the transfer switch bought with the set. It isn't directly compatible with the set. The drawing shows the ATS sending a start signal to the genset with a pair of volt-free contacts.
The genset has a voltage monitoring board which starts the set on the failure of the mains. It also monitors the genset voltage and sends an "OK to transfer" signal to the genset contactor in the ATS when the genset voltage stabilizes.
The drawing showed both these contacts connected together.
The mains voltage monitoring circuit in the genset controls was not wired.
The ATS had provision for the "OK to transfer" signal but as stated the drawing showed the wires connected to the wrong terminals.
The as soon as the genset control was put in automatic, it would start and run continuously. With the input to the voltage monitor not wired, it thought the power had failled.
When the power did fail, the ATS would not put the load on the genset because the "OK to transfer" circuit was wired to the "Start genset" circuit. Two sets of volt free contacts wired to each other.
I called the contractor and had an electrician install a small breaker and run two more conductors between the ATS and the genset. Ignored the manufacturers drawing and connected things properly and all is working well now.
What's the point?
Stuff happens, that's life. If you understand how your systems work and there is a problem or mistake, you deal with it (often quickly, easily and economically) and move on.
It's working well now.
I spec'ed a single phase set about two years ago. I got a quote from my favorite supplier and the customer got his own quote. Much lower than my price so he went with the set he found.
Came time to install the set and it was smaller then quoted. The salesman knew that a three phase set could be used for single phase, but didn't know that it had to be derated 1/3.
I had a few interesting conversations with the salesman and he referred me to the service manager who, the salesman said, would send me the proper circuit breaker to get the full output from the set. The service manager confirmed, by e-mail, that the set size was as I had said and the rating was as I had said. I gave the e-mail to the customer and he went back to the sales department. The vendor gave him a cash refund for the difference in price between the size of the set quoted and the size of the set supplied. The customer was happy, we arranged a couple of air conditioners to run only on the mains and not on the generator, and I considered the final installation as not perfect but pretty good.
My customer is happy with me and with the vendor and we will both be happy to deal with this vendor in the future.
respectfully

 

[SilverArc]

Waross,

Thanks for such an exhaustive description of events in real world. I would appreciate some comments on my this part of post:

"Should we ask the generator manufacturer if his generator is eligible for a typical closed transition or we might have to provided some extra hardwired control as you discussed above.
"

Thanks

 

[waross]

SilverArc
Do you have an Automatic Transfer Switch or will you be purchasing one? By all means ask the genset supplier for his comments. As strange as it may sound, a genset running at exactly the utility frequency is the most difficult for a passive transition. You have to change the frequency slightly to allow the set to drift into sync.
For large motor loads, I would suggest one of the following;
A slow open transition. The power would be off for long enough for the motor back EMF to decay or the motor starters to open for all large motors.
A closed transition.
A very fast open transition. This may not be available in large sizes. The only ones that I have seen were below 100 KVA and I don't know the upper limit of sizes available.
Note; Some standby sets come online in seconds and some motor installations take more seconds for the back EMF to decay. When going onto the standby set it is wise to survey your loads to insure that the generator power is not applied until the motors have had time to wind down or been disconnected. Be aware that during service work or trouble shooting, the generator may be running when an operator initiates a transfer to backup. Without transfer delay timers the transfer from utility to generator may be almost instantaneous. Because of the nature of standby sets and the need for starting time, closed transition is not used for going to backup.
By the way, I think you have a thread open on this. Let's continue in your thread or start a new one before you are taken to task for highjacking a thread.
respectfully