Mark VI Automatic Synchronization Control in VTUR

Dear all,

Hope you can take my doubts out. First of all sorry for my english.
It's a fact that according to GEH-6421, VTUR requires generator "have been lagging for the last 10 consecutive cycles, and projected (anticipated) to be leading when the breaker actually reaches closure".
1. What this means? K25 will close leading after counting 20 cycles (200ms for 50Hz) plus Breaker Closing Time lagging. OR It doesn't matter since VTUR is counting Breaker Closing Time in between the 20 cycles lag period.
2. Why I am asking it?
The installation sync schematic includes and extra sync relay and this relay provides conditions in a [-12º, 12º] angle. I need to understand clearly VTUR calculations in order to calculate the minimum equivalent angle time to achieve conditions in both sync relays.
For instance, if i have angle window [-12,12º] equivalent to 480ms it may be impossible to sincronize since VTUR works in [-10,10º] which is equivalent to 400ms, and VTUR requires minimum of 20 cycles lag (200ms).

According to GE manual phase error can get maximum of 30 is adjusted to 10 degrees as you mentionned..
It may be possible to get enlarged that sync window...
We have no drawings that allows us make decisions on the "extra sync relay". Mark V and VI usually did synch without any help from external or EXTRA synch relays
Installation extra relay behaves exactly as VPRO but for [-12;12] and the benefit it logs exactly synch periods. I know MVI doesn't need this relay and that's why it's only required for 2nd breaker selection (sorry about not being totally clear about). I just want to figure out VTUR calculations to conclude which the minimum period which VTUR/VPRO/Extra relay are aligned in case of 2n breaker sync.

Re read my latests posts here...You should provide SLD and SYNCHRO PROTOCOL /PROCEDURE that you intending to do ...

Selection of second breaker is another thing ....We know nothing about plant synchro there Dead bus selection/synchro solution implemented...

My thinking is that you are not sure about what you are inetnding to do so you come here and try to get help...
But without replying to posts and adding needed /asked will not possible for me at least to support on this case...

So hasta la vista ! Best for all with that case...

It's not necessary to make the external synchronization check relay have exactly the same synchronizing parameters as those used for 52G. As long as there is overlap between 25A and the external relay's windows of closure, then it's all good.

And each breaker has different characteristics and so do the circuits they are used to connect to the turbine-generator.

The purpose of having two relays in series is to ensure that if one relay were to try to allow closing when excessively out of phase the other would prevent that from occurring. Think of 25A as the "narrow window" of breaker closure, and the "synch check" relay as the wide window. (When the breaker is manually synchronized, the synch check relay is there to ensure someone doesn't try to close the breaker out of phase.... So, the operator's close signal has to fall within the synch check relay's close window.)

As the the other gobble-dee-gook about 20 cycles this and nn cycles that, what that's trying to say is that there needs to be some "slip" between the two voltages. In other words, the generator voltage frequency can't be exactly the same as the running voltage frequency or the Mark* can't detect phase angle very well. It's trying to say that the generator voltage frequency has to be higher or lower than the running voltage frequency for nn number of cycles or it won't issue a close command. A LOT of operators, when trying to synchronize manually, will try to stop ("freeze") the synch scope needle at or very near the 12 o'clock position and they keep adjusting the turbine-generator speed such that the synch scope needle never leaves a very narrow band on either side of 12 o'clock. Then, when they try to close the breaker, it won't close (the Mark*'s synch check function) won't let it close), and they think the Mark* isn't working correctly--when it's really their "thinking" which isn't correct. MANY times when people are watching the synch display and the unit is synchronizing automatically the synch scope needle is moving very fast (or at least faster than they "think" it should be moving) and closes the breaker and startles the observers (some of whom "think" the Mark* isn't working correctly--are we starting to see a pattern here? the Mark* gets incorrectly blamed for a lot of ills which are not ills! because someone (or -two or -three) "think" that what they are observing shouldn't be happening, when, in fact, they haven't really given any thought to the situation whatsoever).

The second relay you are trying to configure just needs to be configured to protect the generator and whatever equipment is connected to the breaker being synchronized. The settings don't need to perfectly match those used for the generator breaker, though quite often they do. There just needs to "overlap" between the Mark*'s closure signal and the synch check relay's closure "window"--the Mark usually has the narrow window of closure and the synch check window has the wider window of closure. But the two must overlap near 12 o'clock in order for the breaker close coil to be energized.

Hope this helps!
The only diagnostic alarm I do have is a code 53 Breaker #2 Slower/Faster Than Limits Allow. As Breaker #2 adaption limit = Breaker #2 closing time (90ms) i think it may be expected every time something it deviates. I believe this is another point i have to explore in the future since breaker compensation is limited here.
I would agree with your analysis. I'm unaware of any ability to automatically select between multiple breaker close times in the Mark VI.