TRANSFER SWITCH SETTING

[puckman]

There is this generator that supplys back up power up to 2000amps in a power failure . Now during online test the gen starts like it should when it sees a loss of power during testing. When it sees utility power is restored the MCC main trys to close ,the main is controled by a plc . You can here the motor winding in the main breaker bucket trying to close and then opens again repeating this over and over again.. It also has a manual handle that charges the breaker, which we did at different times. The breaker for some reason always says spring discharged and some of the other cb in the switchgear are saying the same thing.
There is a transfer switch that someone played with that has a keyed switch " auto close" "auto open" " manual close" and maybe one more setting.
We are not sure where it should be. Any ideas where this switch should be set?
We turn off the gen and than have to close the main by a chicken switch . Thanks for your help.

 

[hillbilly1]

Were going to need more info, "maybe one more setting" is pretty vague. Sounds like something is broken, such as a cable or limit switch. What is the manufacture? Switch model?

 

[templdl]

Are you trying to do an instantaneous transfer from emergency to normal? If so are both sources in phase? If not, trying to close back to the normal source when the sources are not in phase results in a fault tripping the breaker instantaneously.
If you can't do an in phase transfer you are going to have to use a TDN (time delay neutral) which disconnects the emergency source of a brief moment allowing for any counter EFM loads to die down before connecting back to the normal sources.
Remember that you lost power in the first place making it necessary to stary the generator and then connect to the emergency source and as such a brief loss of power upon transfer from emergency to normal shouldn?t be a big issue.

 

[hillbilly1]

Are you trying to do an instantaneous transfer from emergency to normal? If so are both sources in phase? If not, trying to close back to the normal source when the sources are not in phase results in a fault tripping the breaker instantaneously.
If you can't do an in phase transfer you are going to have to use a TDN (time delay neutral) which disconnects the emergency source of a brief moment allowing for any counter EFM loads to die down before connecting back to the normal sources.
Remember that you lost power in the first place making it necessary to stary the generator and then connect to the emergency source and as such a brief loss of power upon transfer from emergency to normal shouldn?t be a big issue.

The OP was saying it was continually trying to transfer back, most of the breaker type transfer switches will lock out once the breaker is tripped, preventing a transfer into a fault. More info is needed.

 

[rcwilson]

It sounds like the breaker is trip free, either mechanically because an internal latch is not making up correctly or electrically from an outside control like the PLC sending a continuous trip signal.

You need someone with breakar maintenance experience to look at it.

Our expert Zog should have some ideas.

 

[puckman]

it is a asco 950 transfer panel. it has 3 keyed positions not sure what setting it should be in. this is a switch that says something like ' transtion switch to normal power'. The main cb motor sounds like it is trying to close than opening up repeatitly. the cb says 'spring discharged' and we would have to crank it and then press close switch remotely after turning gen off . these are ds westinghouse breakers. A person moved the setting and doesn't know where it should be put back to and either do i.. thanks again for your help.

 

[brian john]

Have you got the one line?

You need to determine what contact is open and why, often on systems like this there is a coil in the CB that will not allow the CB to close unless certain factors are satisfied.

The CB will trip free as you mentioned. Look in the CB there is most likely a shunt coil a closing coil and an coil that locks locks the CB out.

What type of CB, usually if this 3rd coil exist some where on the CB (usually on the bottom) there is a bypass for emergency closing of the CB...DO NOT USE THIS determine what is the issue.

The other issue is as noted a trip free that is the lubricant is binding the closing mechanism, this is simple to determine. Pull the CB rack it into the close positioned (out of the cubicle) and watch the operations.

I’d bet on the controls.

 

[puckman]

will check on the one line but we don;t place much hope on finding it.

We got another idea. We have a dual main and should alternate them and pull the faulty one and send it out for service [ no one remembers when there was service]. Then check operation of gen with other main cb . Both main cb have the kerk key setup. This might be the best way for us , we don't have expierence on repairs in this area. We were hoping it was that key selector switch on the transfer panel that was tampered with, everything worked fine until it was touched and moved.

Thanks to everyone for there input with this one .

 

[ATSman]

More Information Needed

More Information Needed

it is a asco 950 transfer panel. it has 3 keyed positions not sure what setting it should be in. this is a switch that says something like ' transtion switch to normal power'. The main cb motor sounds like it is trying to close than opening up repeatitly. the cb says 'spring discharged' and we would have to crank it and then press close switch remotely after turning gen off . these are ds westinghouse breakers. A person moved the setting and doesn't know where it should be put back to and either do i.. thanks again for your help.

ASCO 950? Sure you don't mean model 940? Regardless, if it is a stand alone ATS then not sure why a PLC is controlling the normal source main breakers (DS) as you mentioned since all the transfer logic would be built into the ASCO microprocessor or relay logic. The "transition switch to normal" may be a feature on the ASCO that changes the ATS logic from open transition to closed transition.
I mention this because you stated that after turning off generator you are able to remotely close the DS breaker. It is possible that during retransfer the 2 sources are not synchronized and the PLC is sending a constant trip signal to the DS breaker (by external sych relay), then when you remove the emergency source you can remotely close the DS breaker. Try moving that switch from "closed transition" to "open Transition" and test the system. Based on all the info it sounds like the DS tripping free is caused by the shut trip being energized and not a breaker maintenance issue.
A single-line and interconnect control drawings would answer all these questions.

Tony

Try putting the mystery switch in the "auto open" position and test system. This may mean open transition and could solve your problem.

Tony

 

[puckman]

It is a 950 stand alone and it has a GE funac plc inside its enclosure. When the test is over and the switchgear senses power restored the cb sounds
as it is trying to close then opens againover and over , also the change handle starts to shake and we put the transition switch in the opposite setting and that stops the cb and charge handle from doing what i stated. After gen stops we must manually close cb otherwise cb doesnot close.
Also seen panel light up "device 47 trip". Thanks again.

 

[ATSman]

47 Relay

47 Relay

It is a 950 stand alone and it has a GE funac plc inside its enclosure. When the test is over and the switchgear senses power restored the cb sounds
as it is trying to close then opens againover and over , also the change handle starts to shake and we put the transition switch in the opposite setting and that stops the cb and charge handle from doing what i stated. After gen stops we must manually close cb otherwise cb doesnot close.
Also seen panel light up "device 47 trip". Thanks again.

You left out the important key to the mystery. The 47 device is a phase sequence/ voltage imbalance relay. It is monitoring the bus voltage on the generator and utility sources. Sounds like when it compares the two sources it senses either a phase sequence reversal or voltage imbalance beyond its threshold settings. Then signals the PLC to send a trip signal to the DS breaker preventing closing (tripping free.) When the generator shuts down, the PLC program is reset removing the descrepency and you are able to close the breaker.

I suggest you have a testing company come in and measure the bus voltages and phase rotation of both sources and compare readings. Then have the 47 relay tested to determining the trip threshold. If the source voltages look good then the relay settings are out of adjustment or the relay is defective and needs to be replaced.

 

[templdl]

That was my thought originally Tonytonon, they are attempting at doing an out of phase transfer where the emergancy and normal phase are not in sync. Either there must be a TDN to allow any counter EMF to dicipate or ther must be a means provided to assure that the emergancy and normal sources are synced before paralleling the sources.

 

[puckman]

Thanks for the help with this , I will take your advice and relay it to my bosses and have a testing company look at the system.
Thanks for your time and patience on this, great help.

 

[Jraef]

I think the others have moved you to the crux of the issue, but without being there to see everything this is about as far as we can help you.

But one thing I wanted to clear up for you though, the sound of the breaker motor is not the motor trying to close the breaker directly. The motor is just charging the spring, the spring closes and opens the breaker. The spring holds enough charge to both close and open the breaker once, so it only needs to recharge after opening. I say this because you are interpretting that the motor is trying to close the breaker when in fact if you hear the motor, that means it has already tripped and is recharging again to be ready for another close command. So as the others said, that breaker sounds like it is tripping instantly, further indicating that its sensing circuit is seeing, or not seeing, something that is incorrect.

 

[puckman]

Thanks for clearing that up jaref , it will help me explain our problem to management and the testing company.
I like to ask one more question if i could. When manually charging spring with handle and the handle has reached its limit should the charge indicator
say " spring charged " ?

 

[ATSman]

Thanks for clearing that up jaref , it will help me explain our problem to management and the testing company.
I like to ask one more question if i could. When manually charging spring with handle and the handle has reached its limit should the charge indicator
say " spring charged " ?

Yes.
In addition to what Jraef stated, most LV air frame CBs have 2 sets of springs: closing springs and opening springs. Also,
depending on the manufacturer, frame type and vintage (GE AK, Wave Pro, Westinghouse DB, DS, Magnum, ITE K frame, etc.) the closing springs will either charge after the breaker closes or after the breaker opens or trips.