Paralleling gear problems

[iamjohnmack]

Hello All,
Pertinent info; Three 200 KW Cat 3406B's with SR4 gensets(units 1-3). One 150KW 3306B CAt with SR4(unit4) Upgraded VR6 regulators to include upgraded droop cts 5amp. CTs are sized to genset amperage. #4 ct is original cat CT. Waiting on new CT from Flex Core. Will install once it arrives. All sets are self excited brushless. Manual voltage adjust 7C-2700 Cards and series boost modules on all sets. Remote voltage adjust pots in door of gear. Setup 480 volt(High Wye) outputs to run in an offshore Service Barge via paralleling switchgear built in the mid 80's. I think the gear was built by ConTech not sure not very much info availible.

Heres the rub. Had a difficult time getting these units to share inductive load. Power factor were a mess. After some very helful info from the Engtips community was able to work those issues out(for the most part). I still am having a very curious condition occur when wanting to sycronize automatically, in particular with the number 4 unit. When the manual/auto switch is placed in the "auto" position the voltage climbs to around 510 volts and it(sycronizer) will not send breaker close command. Sync scope is very slow to move(never makes the rotation) and sync lights stay on. When you bring the unit online manually it performs ok but is very slow to come around to allow breaker closure. I feel that I should mention that the sycronizer is setup with conacts to raise and lower voltage via a Woodward MOP. All units are wired identically and units 1-3 also have this curious voltage raise condition(although not to the degree that 4 does) but they seem to be able to sync automatically on their own.

I have had Cat Techs in on 1-3 but they did very little to the 2301a on 4. 4 is the electric start unit to build air pressure to start the other 3. I have benn reading resistive values for the remote voltage adjust pots. The value is around 3.69kohms at the regulators (all four) with the wires connected to the regulators and does not change when the switch is moved from manual to auto and back. When I lift the wires from the regulators I can "see" the 5Kohm values from each pot when the switch is moved. I feel that the 3.69kohm value is internal to the regulator but am confused by it. Any help in this would be greatly appreiciated!!! Why do the voltages climb? And, why will 4 not sync on its own? THANKS!!

 

[catserveng]

If you "auto" sync you must have a synchronizer in the switchgear? Do you have just one that is selected to adjust the oncoming unit or one for each generator? What kind of synchronizer? Maybe a Woodward SPM ro SPM-A? Do you know what the voltage match range of your synchronizer is? If it is a Woodward SPM-A it can be anywhere from 0.5% to 10%, is determined by the part number of the synchronizer.

Have you by any chance just started over and went back thru the startup for the synchronizer? I just finished a job where the outputs to the AVR MOP were backwwards, and have been for 10 years. For years the plant operator "fine tuned" the voltage before synchronizing, so it was always within the voltage match window and never tried to adjust, when he retired and the new guy let it do it in AUTO, it drove the voltage the wrong way.

As for the sync scope not moving around, almost sounds like the sync speed bias to the 2301 is not doing what it should.

If you can provide some more detail about which synchronizer you have and may be able to give you some better direction.

Mike L.

 

[catserveng]

One more thought, if these have Woodward SPM-A's. Has anyone messed with the Voltage Offset pots on the front of the synchronzer? Normally these don't need to be messed with, but as the synchronizers get older and drift a bit they could need a tweak. However I find most techs don't now what they are for and play with them, and one of the results is the SPM driving the voltage the wrong way.

If these are SPM's get a copy of Manual 82348 and give it a read.

Mike L.

 

[iamjohnmack]

Hey Mike! Good to hear from you again. I was hoping that you were still here on ENGTIPS. You actually helped me with the last problems I was having with this system. That all is working well. Thanks again for that.
As far as the sycronizer there is only one that is selectable for each set. It is a Basler Electric BE3-25A Style W2N. I have pulled the MOP's out and "bench" tested them to verify that they are indeed working. Two of the four were ok so I didnt go any further. I probably should just to be sure pull the other two. It is hard to see them moving to begin with. As far as verifying the correct raise lower signal I will do that. I am not sure what you mean by going back over and doing a start up. Is the any literature out there that may help me get a better understanding of how this works under normal operation? Any wisdom you may be able to provide would be extremly helpful. THANKS!!!!!

 

[IBRCAN]

I am not sure what you mean by going back over and doing a start up. Is the any literature out there that may help me get a better understanding of how this works under normal operation?

He means going back through the set-up procedure for the synchronizer, in case something was missed upon initial commissioning or someone has been fiddling with the pots. Manual for the synchronizer is available on Basler's website:

http://www.basler.com/php/download_page.php?section=protect#BE3.

There is also a technical paper there beside the BE3 manual that talks about synchronizing.

In first post you said "When you bring the unit online manually it performs ok but is very slow to come around to allow breaker closure." Can/did you adjust the speed pot to cause the oncoming unit to speed up (.1 Hz or so)?

 

[iamjohnmack]

IBRCAN, Thanks for the info! I'll definatley look through it. There is a pot on the front of the gear that I can adjust but based on the fact that the other units seem to parallel ok I just never considered it. I'll have to look through the print and verify that the pot is in play when trying to sync in auto.. to be honest I'm not sure. To be completly honest I'm still getting an education on all of this. ( In case that was'nt obvious) I apprieciate the info and anything else you can school me on...
John

 

[catserveng]

That Basler is a good synchronizer, just worked on a system with one last week.

Probably the toughest thing for you is to make sure you have good documentation on the selection circuits. Frankly I hate seeing a single synchronizer on multiple generator applications, find that later in their service life things don't work as they should and most of the time in in the logic to select the correct incoming unit sensing or speed/volt bias outputs. I know it saves money and space, and I shouldn't really complain because it generates a good deal of revenue for me.

First off, is it wired correctly for being a Woodard governor output and contact volts raise/lower per the manual?

Something to do as a good first check is to verify that the correct sensing is getting to the synchronizer, with the desired unit running, if you can manually adjust it's voltage up or down and make sure you're seeing the correct voltage at the synchroniser generator voltage input terminals.

If that's ok, next I would make sure the voltage adjust command is working as expected, one of the easiest ways is to just use a jumper and first go across the RVC and RVNO contacts and make sure the generator voltage goes up, then repeat for LVC and LVNO and make sure the voltage goes down. This would check the entire circuit from the synchronizer all the way to the generator votlage regulator thru whatever incoming generator selection logic you have installed.

Page 5-1 of the Basler Manual (thank you IBRCAN for the link) has the intial setup procedure using the TEST/OPERATE switch, I would go thru that procedure and make sure all the speed and voltage match functions are operating as desired.

A few things to note,

I find a bunch of these wired to the 2301 output on systems with 2301A governors, the speed bias doesn't work right in not wired correctly.

Make sure of all the jumpers, there are a number of options and ranges on these synchronizers set using jumpers, amazing how many units I work on that have been in service for quite some time with improper setup. I guess the intial installer gets it online and calls it good enough.

I would really try and do a field "as-built" if you can of the logic used to select sensing and bias outputs, on a large number of systems I work on with single synchronizers and multiple gens the drawings and documentation is not correct, if it exists at all.

Hope that helps, Mike L.

 

[iamjohnmack]

Mike- Great stuff. Ill verify with the jumper to make sure it reacts correctly. Before I get to far out in front of this I was thinking about something when I was setting up the VR6 regulators on all of these sets that confused me. The set up instructions for the regulator reads " if remote voltage adjust pot is used, turn voltage adjust setting fully clockwise" I turned this pot ( with the engine off) in a clockwise direction but it does not stop. I counted the number of turns and promptly turned it back to about where I started. The question is what is fully clockwise on this. I am apprehensive to attempt to turn it "fully clockwise" while running for fear of driving the voltage up too far. Another issue is the manual voltage control on these sets are Cat 7c-2700 cards on the doors of the gear. There is a component on the rear of the card that over time is showing signs of taking some heat. I have gone through the wiring and found that the as builts show that two wires coming from the series boost 4 and 5 Land on terminals 41 and 42 of the MVC 7c-2700. The Caterpillar Instructions for the VR6 show the wires are to go on 44 and 45. Does anyone know what the terminals 41 through 46 on the 7c-2700 card are? When we recieved new MVC cards there were no instructions. THANKS!!!!!!

 

[IBRCAN]

I checked the VR6 manual and yes, it does say to turn the voltage adjust pot on the regulator fully CW--not sure why it says that--yes the voltage would go way high. The way I do it is set the remote pot in the approximate middle of its travel, then adjust voltage on the regulator to the desired value.

 

[catserveng]

The on board VR6 voltage adjust pot has a ratchet stop, if you're someplace quiet (like that ever happens around a genset) when you get to maximum you can hear a faint click. Usually I just turn it 10 turns because I lost the ability to hear a sound that small years ago. I you have a sensitive touch you can also feel it.

Look at Illustration 6 in the attached, it is for a VR3 and 7C2700 with series boost, should work fine for a VR6 as well.

Note, when you did the voltage regualtor conversions, did you add an isolation relay? Is required when going from a VR3 to VR6 using Manual Voltage Adjust. May be why your card is getting hot.

Mike L.

 

[catserveng]

Here is an instruction for adding the isolation relay,

If you need to get a hold of me directly again, try my website.

Good Luck.

Mike L.
www.pactectric.com