05-03-2010 05:25 AM
First of all George, if you are working in Riyadh, then this problem was actually created by your own team. As i visited the site & on the very first visit i found droop CTs were fixed on phase V rather phase U and this information was passed by your own technicians from Jeddah. These are the wordings which your technicians have informed me. Originally the case was that AVRs were burning due to unknown reason, as Droop CT rating wasn't clear among the specsheets of R448. Later i explored the R448 catalogue & found out the rating was 1A on secondary end. The wrong information was spread among your collegues that shifting all CTs on phase V of 1600:5A will solve their problem which actually wasn't the case. This is my personal experience which i have solved & send notification to your Co. aswell.
1) Droop CT shall be of 1600:1 or 2000:1 not 1600:5 or 2000:5 (bigger CT of 5Acan be used if the secondary end has less amperage)
2) NO STEP SHOULD BE TAKEN IF YOU ARE NOT SURE WHAT WILL BE THE OUTCOME OF IT.
04-12-2010 10:45 PM
WQuader do you have the same load sharing module on both units or compatable LSM and have they been setup for the same voltage output at full load? Most Woodwards LSM are 6 volts at full load. You should be able to parallel units at no-load. You may have some units that are quarky and won't like it but most should do with out issues for a short term. Can you put any kind of load on them at the start, station service or something, just 50 to 100 kw's should do.
04-12-2010 10:32 PM - edited 04-12-2010 10:38 PM
Carl (cjcesare), the system that George has he is basically the utility. Yes you are right you can't run a small or single generator in Isoch to a utility grid or Infinite Bus as we call it. For putting a generator onto an infinite bus you need a special controller to parallel with the grid. You need a var/pf controller to maintain a constant power factor or set Vars.
In George's case he is the utility and he will have to run unit's in Isoch to maintain the system frequency.
04-02-2010 07:18 AM
LOAD SHARING MODULE
I too have a question ( & problem ) on the LSM on my new C15 Gen (1000KVA) . I have hooked it up to an older model CAT generator same capacity.
When I start both engines, they will NOT synchronise without load. The synchronization works ONLY after load is applied. I do not like this becasue the load is taken up b ythe MASTER ( the new gen.) then transfered to the second
Is this how it is supoed to work ??
03-31-2010 11:02 AM
My experience is the isoschronous mode with a governor is needed when the engine generator operates independently from the utility, i.e. using a transfer switch so that the engine genertor are never paralleled with the utility source or other engine generators. When there are multiple engines that operate in parallel with each other and the utility source, drop mode is used because the speed, hence frequency of the large machines speed will match the utility source or the first generator connect to a common bus. I always thought that one of the machines in a multiple engine generator say 6-3516's, would need to be in the isoschronous mode and the rest in the drop mode as George stated. I have used Woodward DSLC, and LSM's in the past but normally a technician has made the adjustment., probably ignoring what was specified. Clarification would help?
02-14-2010 01:36 AM
A few more comments.
When a unit comes on in droop the unit should be at 0 load and you have to increase speed for the unit to pickup load.
When running units in Isoch the speed control can still affect the bias on the LSM and will change the load compared to the other Isoch units. If you adjust all Isoch units your system frequency will be affected. Be cautious adjusting Isoch units. If one or two units have their bias adjusted too far out and they are the only units left on-line during or after a disturbance your frequency is going to swing to their setpoint with the bias, thus high or low.
02-14-2010 01:18 AM
A few comments to the above statements:
You can connect different rating of droop units to the same system.
The load sharing units (or Isoch) are the master units controlling the frequency. The droop units are along for the ride or slaves so to speak to the Isoch units.
CT current needs to be 80 to 100% of range (4 - 5 amps) at full load (typical secondary is 5 amps). Spec sheet says 3 to 7 amps for FLA.
Unit breaker auxilliary contact must block (open circuit) input to LSM when off-line, open is droop, closed is Isoch.
Also a switch is usually added in series with the breaker auxilliary contact to select droop or Isoch (only affects operation when the breaker is closed).
Load sharing lines must be connected between all possible Isoch units, polarity sensitive.
Droop is the change in speed from no-load to full load and is a unit characteristic and usually not setable. New electronic controls allow to be set.
Droop units do not put a signal on the load sharing lines.
To change load on droop unit adjust unit speed, speed stays constant but load changes.
Droop units stay at set load as long as the frequency is maintained.
When the system frequency changes the droop units load will change. Frequency goes down, unit picks up load and vise versa if frequency increases.
Isoch units maintains the system frequency, to a set value. In North America usually 60 Hz, in your case probably 50 Hz.
Isoch units will increase or decrease load according to system demands. Demand goes up, unit load goes up.
If an Isoch unit(s) can't maintain the system frequency or shifts off 60 Hz (during fault, load loss), the droop units will pickup or drop load accordingly.
If you loose your Isoch unit(s), your system frequency is going in the tank. You want mulitple units in Isoch to prevent this.
Most people run their droop units with 80 to 90% load. This is where they are most fuel efficient.
Load sharing lines need to be adjusted for 3 volt output at full load (most are 6 volt as stated, but spec says 3 volt for this LSM). Usually done with a load bank, isolated from system during commissioning.
If the load sharing lines are opened or shorted your system is going in the tank again. Isoch units will fight each other, one to min load (possibly reverse power)and one to max load or overload.
An operator has to watch system load to ensure enough units are running to carry the load or add more load to existing droop units.
You want much more in Droop than in Isoch. I would say no more than 10 % in Isoch, 6 units for 60 total.
We have a policy to have enough spinning reserve for the loss of the largest unit on the system. But with your system so large you may want more.
01-30-2010 12:40 AM
10-13-2009 10:37 PM
Firstly let me explain the 2 modes of operation of the load share modules to you... Firstly the droop mode... This will introduce a droop in the generator speed as the load increases and will not do any load share function.. This mode is used when you are parallel to the grid or you have external load control.
The Isochronous mode will activate the load control between units through the load share lines.. If the C18's are the only source of power what you need to do is to run all the units in isochronous mode with the load share lines connected. This will activate the load sharing function of the woodward load share units... If the load share modules are run on droop mode there will be no load sharing function activated in the LSM... Adjustment to share the correct load can be made by adjusting the load gain in the LSM to get correct load sharing...
Hope this will help...
09-25-2009 09:40 PM
There is no "master" generator with a LSM setup. A LSM in droop will lower the speed command as the individual generator load increases, and will not react with the load sharing lines at all. A LSM in isochronous will adjust the speed command to drive the generator load percentage to the bus average without changing the system speed. In order for load sharing to work properly, all LSMs with generators connected to the bus need to be in the same mode. For isochronous operation, the droop connection should be tied into the paralleling circuit breaker auxillary contacts for that generator so that the LSM is in droop with the generator isolated, and isochronous with the generator on the bus (regardless of whether another generator is connected or not) -- at no time should the LSM be in isochronous with the generator paralleling breaker open, or it will cause the speed of the generators on the bus to decrease.
As for the CT sizing, I'm not sure if you'll be able to adjust the LSM load gain to get 6 volts across the test points with only 2 amps on the CT secondary, but you should be able to get the system to operate properly (although possibly with less accuracy) by setting the load gain to get a lower voltage across the test points that is the same on all generators at full load.