802A Parallel operation ???

[cuad4u]

I emailed a former EE professor and a friend who designs generator systems for Cummins. Both watched the youtube video and both are vaguely familiar with the 002A and 003A gens. Both said it was a very good video that showed in simple terms that the two gens were sync'ed. What we did not see in the video is watching the light bulb and the oscilloscope display under varying loads to verify that the two gens remained in sync under varying loads. I wish it had shown that. However my two friends said it MAY work like shown in the video.

However as TurboJoe posted paralleling two 002A or 003A generators without auxillary controls MAY work but there MAY be problems, which MAY let some smoke out of the gens or out of the load, especially if the load needs a good pure 60Hz sine wave.

I have several 002A and 003A gens. In my case I will not try it. It will be interesting if somebody does try it for a long term application and lets us know how it works.

I for one am waiting on the actual results.

 

[TurboJoe]

AH... TurboJoe, what does that sync relay thingy cost?... and where can I get one?

I do not want to tread on the rules here, and I was going to post a competitors link. However in this case the product we have off the shelf is the best and most economical solution. You can also buy it on Amazon and that is NOT me for full disclosure. So I'm not trying to make money off the board with out being a vendor.

That being said here is a link to a very nice product that has a display, built in relay and control contacts for auto scync if you want. The picture is the old model, the new model is black, with better looking buttons. Cost is in the $150 range.

http://www.pc-s.com/pdf/ds_DKG 117_synchroscope and check synch relay.pdf

Good article on synchronizing.

http://www.o-t-s.com/synchronizing.htm
When reading the above link, the light bulb is used as a cheap way to represent phase angle. Just for a fun story, in an extreme example I have heard stories of 12 cylinder 2 Megawatt diesel generators ripping out of their floor mounts when closed into a system at the wrong phase angle. It instantly makes the weaker system match the stronger one. Imagine trying to instantly stop 3k horsepower.


Now, with the 117 I linked above, some auto genset controls, a PLC, and some cheap contactors, you could very well automate the transition form one generator, to two, to house or shop relatively easily. Its just control logic.

Edit: PS, how well the generators will work in parallel is still a crap shoot. All depending on the governors.

 

[CDR]

Wow that's cool

 

[CDR]

I do not want to tread on the rules here, and I was going to post a competitors link. However in this case the product we have off the shelf is the best and most economical solution. You can also buy it on Amazon and that is NOT me for full disclosure. So I'm not trying to make money off the board with out being a vendor.

That being said here is a link to a very nice product that has a display, built in relay and control contacts for auto scync if you want. The picture is the old model, the new model is black, with better looking buttons. Cost is in the $150 range.

http://www.pc-s.com/pdf/ds_DKG 117_synchroscope and check synch relay.pdf

Good article on synchronizing.

http://www.o-t-s.com/synchronizing.htm
When reading the above link, the light bulb is used as a cheap way to represent phase angle. Just for a fun story, in an extreme example I have heard stories of 12 cylinder 2 Megawatt diesel generators ripping out of their floor mounts when closed into a system at the wrong phase angle. It instantly makes the weaker system match the stronger one. Imagine trying to instantly stop 3k horsepower.


Now, with the 117 I linked above, some auto genset controls, a PLC, and some cheap contactors, you could very well automate the transition form one generator, to two, to house or shop relatively easily. Its just control logic.

Edit: PS, how well the generators will work in parallel is still a crap shoot. All depending on the governors.

Would you hook generator 2 to the bus and the load as well?

 

[TurboJoe]

In this case "bus" is the initial generator that would be up an running. The relay would monitor the second generator, or Gen in the diagram and send the command to close it's contactor when the requirements were met. That command would have to be integrated to open and close the gen contactor.

Very important obvious note: Never, ever parallel with the utility. The solar and wind systems that do have inverters that isolate them and have many grid tie safeguards built in, such as shutting down on loss of grid power.


Edit: To clear this up even more: The "bus" is any operating system. In this case the first generator, and includes the load. The second gen is hooked up to the bus (load) as normal, except the generator contactor would be off. You would use the relay to trigger when to close that contactor into the bus (load). Make sense?

 

[storeman]

Peapvp, Sewerzuk
Engineers are in the room. Where are you?
Jerry

 

[CDR]

In this case "bus" is the initial generator that would be up an running. The relay would monitor the second generator, or Gen in the diagram and send the command to close it's contactor when the requirements were met. That command would have to be integrated to open and close the gen contactor.

Very important obvious note: Never, ever parallel with the utility. The solar and wind systems that do have inverters that isolate them and have many grid tie safeguards built in, such as shutting down on loss of grid power.


Edit: To clear this up even more: The "bus" is any operating system. In this case the first generator, and includes the load. The second gen is hooked up to the bus (load) as normal, except the generator contactor would be off. You would use the relay to trigger when to close that contactor into the bus (load). Make sense?

Makes sense I would love to try this

 

[bohunk]

Thanks for that link TurbJoe... but now I have a question regarding the DKG-117. Perhaps I am misunderstanding what I read; but it would appear that the unit is single phase only OR could one assume if one of the 3 phases are matched the other two will be as well? Can you go into more detail regarding the additional controls and PLC stuff or should we take that off-line?

 

[Rapracing]

Just a dummy here but it sounds like not so good an idea to me. I'll just get a bigger generator if I need more

I just as soon not toast my electronics for the sake of an experiment

 

[TurboJoe]

Thanks for that link TurbJoe... but now I have a question regarding the DKG-117. Perhaps I am misunderstanding what I read; but it would appear that the unit is single phase only OR could one assume if one of the 3 phases are matched the other two will be as well?

The 117 monitors one line only. This works for single, or three phase. In a three phase system it is assumed ahead of time that your phase sequence is correct. Otherwise monitoring just one line is all you need. That tells you the voltage, phase angle, and frequency all you need to know.

Can you go into more detail regarding the additional controls and PLC stuff or should we take that off-line?

If you have each generator with its own automatic start control in however you choose to do that, and you have a transfer switch, and you have generator contactors then all you need is logic to coordinate what you want to do.

Now a days PLC's are inexpensive and software is usually free or also cheap.

A quick control scheme just thinking out loud and can be tuned or made better:

A plc constantly monitors load on your house. Big loads that are easily switched (AC, Water Heater) are on their own individual contactors controlled by the PLC, as well as feedback signals that tell the PLC when each device wants to turn on. (some higher end transfer switches can also do load control natively)

The house auto transfer switch detects loss of mains, and then does its thing to start up the generator and let it warm up before switching over. The same signal that fires up the generator also goes to the PLC (on a battery system). the PLC knows what loads were running, what loads want to run, and what can run on one generator.

The PLC controls what is on when the first generator comes online and gets connected to the house on the transfer switch. It makes sure that load isn't over 5kw.

At this point it would determine if it needs to fire up the second genertor, and if so does by sending a signal to the second generator.

Second generator comes online, warms up, and sends it signal that its ready to the 117. The 117 then connects both generators when they are in sync, then sends feedback to the PLC via the same contact.

PLC then switches the contactors of the additional loads to come online. Same process happens in reverse when loads shut off for x amount of time.

A quick, probably low estimate of costs off the top of my head: PLC ~400, dkg-117 150, auto start for mep802s ??, 30 amp contactors 45 -75 dollars each, PLC programming time ~5-6 hours at 150 an hour, then time to run all the low voltage wiring, enclosure for contactors, wiring for contactors, ect ect.


And now you see that its vastly simpler to just have a 10kw generator Though the neat factor is there, and learning how to progam plc's in ladder logic is fun. Then that also opens up a whole lot more, for instance home house power measurement, logging, alarms, ect. ect.

 

[TurboJoe]

We can also go to a higher end generator controller that has the built in logic for load control and paralleling. But thats not inexpensive either.

 

[CDR]

I wonder what would happen if you try to parallel a 002- and a 802a

 

[Ratch]

I think the same thing as a pair of 802's, though the 002 probably has a less accurate meter, so you'd be best off to set the governors using the same external frequency meter on each one. I'd think the 002 would handle more loading as the 802 started to fade, and cause weird stuff to happen if they couldn't break their link. The smoke might escape.

 

[Keith_J]

No, lightbulb synchronization does not show phase angle, it only shows voltage difference between legs. Phase angle is part of the power factor issue and that arises from inductive loads, like motors, transformers and some switched mode power supplies. Basically, it is the difference between the voltage and current. Normally, the two are the same and stay the same with pure resistive loads (toasters, light bulbs and space heaters). But motors and the like can cause current to lag behind voltage, this lagging is phase angle.

Now, on these small gensets. As long as voltage between the legs is zero (no light bulb flashing), the breakers connecting the two to the load can be closed. What will happen is the load will be shared between the two, the running genset will slightly increase in RPM(freq) due to the drop in load while the new addition genset will sag a bit from the load. This sagging will cause some electromotive force transfer from the running to the new until their respective loads balance.

Furthermore, with two identical sets, the operator should see the load decrease by about 50%. If not, the engine governor may be adjusted to do so. This will complete the paralleling.

Now, why? Well, back when I was PFC Beetle Bailey, I ran the generator section on FTXs. I had the TOC, motor pool, PLL, RTO and even the mess hall demanding power. If I needed to refuel (gasoline sets), I had to shut down which meant every single customer had to be notified of outage. I lacked switch gear in the TOE so every cable had to be removed and connected to another. So I dreamt of parallel operation.

 

[TurboJoe]

No, lightbulb synchronization does not show phase angle, it only shows voltage difference between legs. Phase angle is part of the power factor issue and that arises from inductive loads, like motors, transformers and some switched mode power supplies. Basically, it is the difference between the voltage and current. Normally, the two are the same and stay the same with pure resistive loads (toasters, light bulbs and space heaters). But motors and the like can cause current to lag behind voltage, this lagging is phase angle.

When your talking about the same power source, you are right about your definition of power factor/phase angle. However, when you have two independent sources (generators not yet paralleled) there can be a phase angle difference between the two. This phase angle difference will also create a potential difference, in much the same way 240V is derived from one line being at 180 degrees and the other line being at -180 degrees. That would mean that voltage is present (light bulb on) until the phase angles match. This is a very critical part of syncing generators, more critical then voltage being slightly different, and a ton more critical then frequency being off. This is also what synchroscopes show,and part of the paralleling relay logic.

We actually did a job for a big power company, they used to have old mechanical synchroscopes that their operators watched to speed up or slow down one of the systems to get them in sync. If both systems are at the exact same frequency the phase angle difference between the two will never change. So one system must move faster or slower until the phase angles become the same. They then replaced everything to digital systems and lost the visual indication of phase sycn to know how much or little they need to speed up the system. We wound up doing some custom 15 inch HMI monitors to replicate the old mechanical meters. This way they had a visual clue of the systems to get them close enough for the relays to close into the load.

 

[Keith_J]

There can be phase angle difference only if the load is inductive. Still, the breakers can handle this. And the difference is halved when the second generator is brought online.

Big difference between commercial grid and two 5-20 kW generators.

 

[TurboJoe]

Again,you are absolutely correct about the phase angle variance cause by inductive load on a generator. However, even if there is no load on either generator there can also be a phase difference between them. That is what I'm pointing out. That is what is important in the paralleling question.

If you look at it mechanically, both generators have to be at the same exact rotational position to be inline. What are the chances of this happening with out any connection. If you try to connect them when they are not the in the same spot, bad things happen because of the difference in voltage induced by the difference in phase angle between the two sets. That lightbulb also shows this.

Big grids, little grids, fundamentals are the same. The only differences is the results of getting things wrong.

 

[CDR]

Again,you are absolutely correct about the phase angle variance cause by inductive load on a generator. However, even if there is no load on either generator there can also be a phase difference between them. That is what I'm pointing out. That is what is important in the paralleling question.

If you look at it mechanically, both generators have to be at the same exact rotational position to be inline. What are the chances of this happening with out any connection. If you try to connect them when they are not the in the same spot, bad things happen because of the difference in voltage induced by the difference in phase angle between the two sets. That lightbulb also shows this.

Big grids, little grids, fundamentals are the same. The only differences is the results of getting things wrong.

And this seems to be the question on my mind still with no load will they stay synced? The way I see I I think they will. If one of the motors stops will the other generator keep spinning it over?

 

[TurboJoe]

If the generators are electrically connected after syncing then yes, they will stay connected and in sync with no load. To prevent one generator from spinning a dead one, you would also need a reverse power relay. This will disconnect the sync signal if it sees reverse power over a pre-set threshold.

IMO if you wanted to parallel two sets, use a sycn check relay, and a reverse power relay if you want to be really safe, and control the second set and associated loads manually. This avoids all of the control logic and cost. Plus you would only need one auto start kit for the 5kw backup. Though you do need to be careful an auto switch won't drop 8+ KW of load onto one running set.

 

[TurboJoe]

Actually, depending on how the Mep802 behaves if the diesel engine stops it may open up the main contactor and disconnect itself.