Synchronization in MarkV and MarkVIe

I want to discuss the how synchronization in done MarkV and MarkVIe. I am not expert in this as I am going to read this first time in DETAIL. Please be patient if I am wrong anywhere.


In MarkV three relays are used for Auto/Manual synchronization. These relays reside on TCTG card. These relays are

1. 25 (Auto Synch Relay)
2. 25P (Synch Permissive Relay)
3. 25X (Synch Check Relay)

Although these relays reside on TCTG card, 25P and 25X are actuated (goes to "1") based on the logic in <Q> cores whereas relay 25 is actuated (goes to "1") by the <X>, <Y> and <Z> cores.

For auto synchronization Breaker Coil is connected across terminal 38 and 41 of PTBA card. Breaker voltages are come at PTBA terminal 35 and they will go to terminal 38 through logic in which all the three relays 25, 25P and 25X are in series for auto synchronization. All these three relays must be "1" for auto synchronization. (I will discuss later what logic will make them "1" and for how long they will remain "1".)<pre>
PTBA 35 25 25P 25X PTBA 38
o-----------| |----------| |---------| |----------o--------------------
(Breaker coil)
PTBA 41</pre>
For Manual Synchronization/ Dead bus breaker closure, Breaker Coil will remain connected across PTBA 38 and 41. We have Manual Synchronization / Dead bus breaker closure wire connected at PTBA terminal 42. The manual breaker closure command will go to the terminal 38 when the Manual Breaker Closure button is pressed and relay 25X is actuated (is "1") at that time.<pre>
PTBA 35 25 25P 25X PTBA 38
o-------------| |-------| |-------------| |---------o--------
| |
(Manual command) PTBA 42 o-------- (Breaker coil)
PTBA 41</pre>
Mark Vie

MarkVIe also has three relays for Auto/Manual synchronization. For MarkVIe these relays reside in TTUR. (MarkV has <P> core with TCTG and 3 TCEA cards (i.e. <X>, <Y>, <Z>). Emergency and Primary trip relays (ETRs and PTRs) were physically present in TCTG card in <P> core. Trip solenoid was connected to TCTG and trip was initiated either ETRs or PTRs were actuated. ETRs received signals from <X>, <Y> and <Z> while PTRs received signals from <R>,<S> and <T>. MarkVIe does not have <P> core. It has four cards for synchronization and tripping. These are TRPG, TREG, TTUR and TPRO. TRPG has all the PTRs and TREG has all the ETRs. Yes, one wire of trip solenoid is connected to TRPG while second wire of trip solenoid is connected to TREG card. I guess TCTG has been replaced with two cards (TRPG and TREG) in Mark Vie. TRPG receives signals from <R>, <S>, <T> controllers via TTUR while TREG receives signals from TPRO(<X>, <Y> and <Z> replaced with TPRO?)

These three relays are
1. 25 (Auto Synch Relay)
2. 25P (Synch Permissive Relay)
3. 25A (Synch Check Relay) {This relay was named as 25X in MarkV}

All these relays reside in TTUR. The breaker coil is also connected to TTUR.

Relay 25P is directly driven from controller application code. It is connected to the <R>, <S> and <T> controllers via IO Packs PTUR.

Relay 25 is driven from PTUR auto synch algorithm, which is managed by <R>, <S>, <T> controllers.

Relay 25A receives signal from TPRO (TPRO is connected to TREG and TREG is connected to TRPG AND TRPG is connected to TTUR).

In MarkV 25X is driven from <R>, <S> and <T> cores and its logic was present in CSP. In MarkVIe they have renamed it to 25A and it is driven from TPRO. It is also called backup synch check relay. Are relays 25P and 25 performing the same function? Were they having the similar function in MarkV as well?

It's outage season and many of us are extremely busy right now.

Automatic synchronization almost always involves two "relays"--an automatic synchronization relay AND a synchronization check function. Both relays have to be picked up at the same time for the generator breaker to close. Synchronization is serious business, and serious damage to equipment and transformers and transmission lines can occur if not done properly. The synchronization check relay is almost always used as a permissives to manual synchronization, also--because the risk of damage is very high. The operator manually synchronizing a generator breaker will not be able to close the generator breaker unless the synchronization check relay is also picked up when the operator is trying to close the generator breaker.

I believe I wrote in my previous response to this question in a previous thread that the Mark V did the synchronization check function in <Q> and the auto synchronization function in <P>, and that the Mark VIe does the automatic synchronization function in <Q> and the synchronization check function in <P>. I believe that's what you described in both threads (the PPRO I/O Packs on the TPRO serve as the Protective Processors (<P>) for the Mark VIe (as the TCEA cards did for the Mark V)).

If the Mark VIe automatic synchronization function is working properly, what does it matter which function is done in which processor group? I believe the reason GE switched the functions between processor groups is because the more important of the two functions is the synchronization check function and the PPROs run at 100 Hz, while the <Q> processors run at 40 msec (25 Hz). So the more important function is run at the faster execution rate for more protection.

Yes, the Mark V TCTG was replaced with two cards (the TRPG and the TREG) in the Mark VIe. That was done to provide more isolation between the Primary Trip relays (of <Q>) and the Emergency Trip relays (of <P>, or the PPROs).

The synchronization relays were previously on the TCTG card, and I believe there was more space on the TRPG card than the TREG for them.

I hope this helps!

>The synchronization relays were previously on the TCTG card,
>and I believe there was more space on the <b>TTUR</b> card than the
>TREG <b>or TRPG </b>for them.

Also, since every Mark VIe doesn't use a TRPG or TREG but most every Mark VIe's includes a TTUR, the synchronizing relays were mounted on the TTUR (even if the application isn't for a generator drive unit).

Sometimes I have more time for research and explanation, but it's unusually busy right now--and I have been known to make a mistake or few in the past, and I seem to have muddled the GE printed circuit card alphabet soup. This morning was an unexpected break due to mechanical issues, so I have a little more time than last night after a VERY long week of VERY long days.

You have mostly described the differences very well--you just seem to be unsure of why the auto synch and synch check functions were changed from one group of processors to the other. Again, my personal opinion is because the synch check function is critical to both manual- and auto synchronization, and the execution rate in the PPROs is faster than the execution rate in the UCSx cards. And, yes, sometimes GE changes the mnemonics (signal names; I/O designations) without any rhyme or reason (mostly to comport with some country's or regions conventions). There's a relay that closes when the auto synch function wants to close the generator breaker; one that closes when the phasing is within a certain windows (the synch check function); and one the allows automatic synchronization (after several permissives have been met)--for a total of three relays in both the Mark V and the Mark VIe.

Hope this helps! Sorry I haven't had more time recently. And, thanks for keeping up up-to-date and informed on the issues you are finding with the upgradation; it is helpful to others considering the process.

I know that you must be very busy. We are very lucky to have a person like you. It is better to read your one post here rather then reading number of manuals. Its so kind of you that you somehow manage to take some time out from your busy schedule and answer the questions. I thank you SIR for that.

I want to discuss each and every rung of synchronization. I will not ask you to post any rung or describe it. I will post them myself with description. I will just request you to look at those posts and give your valuable comments whenever possible.

Is this questioning about deadbus breaker closure???

In my personal opinion, the rungs in the Mark VIe should be identical to those in the Mark V. Realize that there are some external permissives for deadbus breaker closure--that are usually hardwired into the generator breaker close circuit. They should be shown on the schematic for the generator breaker close circuit, along with the Manual and Automatic synch contacts from the Mark VIe and the manual generator breaker CLOSE switch.

Relay 25 is the actual relay contact the Mark* closes to close the generator breaker during an automatic synchronization. Relay 25A or 25X has to also be closed, in addition to relay 25P.

Relay 25P is the relay that says that all the permissives <i><b>in the Mark*</b></i> for automatic synchronization have been met (such as achieving "Complete Sequence" (meaning the auxiliary pumps are not running, the unit is at rated speed and on speed control, etc.--the signal name is L3).

So, when an operator initiates an Automatic Synchronization, the Mark* checks all of its parameters and if they are good then L25P is set to a logic "1" which closes contact 25P in the series string you entered.
At that point the sychronization check function (the 25X or 25A function) also begins checking to see when the two voltage signals (generator terminal (INCOMING) voltage and running (BUS) voltage) are nearly in phase with each other (there is an allowable "window" of phase angle, with some degrees before actual 0 degree phase difference and some degrees after 0 degree phase difference). Every time during synchronization that the actual phase difference is within the allowable window 25A or 25X contacts will close and remain closed until the phase difference is no longer within the allowable window (range).

At the same time the Automatic Synchronization function is checking to make sure the two voltages are "matched", and is also making the adjustments to "match" the generator frequency to the grid frequency; actually the Automatic Synchronization function wants to make the actual frequency just slightly greater than the grid frequency--so that when it closes the generator breaker there will be positive watts (or MW) flowing out of the generator and it won't trip on reverse power. When all of the conditions of Automatic Synchronization are met, and usually a few degrees before the two signals are completely in phase with each other, the Mark* will close the 25 relay contact.

When all three sets of contacts are closed, and any other physical permissives in the generator breaker close circuit are met, the coil to actuate the generator breaker close mechanism is then actuated--closing the generator breaker.

It needs to be noted that the generator frequency does NOT have to be greater than the grid frequency. It just has to be within an allowable difference (of frequency) and the Mark* will close the 25 contact to close the breaker. This sometimes happens when the unit frequency is "relatively" low when the operator selects Automatic Synchronization and it is enabled. The synchronization functions of the Mark* are VERY fast in determining if they are met, and sometimes they are met when the generator frequency is a little lower than the grid frequency. This is okay for most generators--but it can cause some consternation and grief for the operators if they are watching the synch scope and see it rotating in the wrong direction when the generator breaker closes. As long as the unit doesn't trip on reverse power, it's usually okay. And, if it does trip on reverse power--then something is wrong with parameters of Full Speed-No Load that it will allow Automatic Synchronization to begin when the unit speed is too low, or the function in the Mark* that issues an immediate RAISE SPEED/LOAD when the breaker is closed and the unit is in Droop Speed Control mode is not set up correctly. (The Mark* will try to make sure the power flow out of the unit is positive immediately after breaker closure, and load the unit to what's called "Spinning Reserve" to ensure the power output stays positive.)

That's the functions of the three relays (even if the names have been changed). When the unit is being Manually Synchronized, the 25A or 25X function is still in the generator breaker close circuit--but the 25P and 25 contacts are not. The operator can hold the generator breaker close switch handle in the CLOSE position at any time when the synch scope is spinning clockwise and is above approximately the 10:30 o'clock position and when the Mark* closes the 25A or 25X contact the generator breaker will close, and the operator can release the generator breaker close switch handle. (Too often operators, unaccustomed to manually synchronizing the generator, will too quickly operate the generator breaker close switch handle--usually too early or too late during the synch scope revolution, and miss the 25A or 25X contact closure. The Mark* then gets blamed for not allowing manual synchronization--when it was the operator who was not performing the process properly! It's best to just train operators to hold the generator breaker close switch handle in the CLOSE position beginning at about the 10:30 o'clock position on the synch scope and keep holding it in the CLOSE position until the breaker closes or until the synch scope needle gets to about the 2:00 o'clock position. If it gets to the 2:00 o'clock position and the breaker hasn't closed, something is wrong--usually with some other permissive in the generator breaker close circuit, but occasionally with the Mark* synch check function--but not often!)

Hope this helps!

You have explained it all. You are so good at explaining things.

On our site we have three options for synchronization
1. Auto synchronization from HMI (Uses all three relays)

2. Manual Synchronization from HMI (Uses all three relays. There is bypass logic for some relays in CSP)

3. Manual Synchronization from the desk (Only uses 25X)

Similarly we have two methods for dead bus closure
1. Dead bus closure from HMI (Uses all three relays)
2. Dead bus closure form the desk (only uses relay 25x)

Thanks for explaining the functions of all the relays in detail. It was really helpful.