Synchronizing Check Relay for Automatic Synchronizer? 2

[majesus]

I'm looking at a Cumins Parallel Controller used in multiple Gensets.

One of the features included in the controller are:
• Automatic Synchronizer – Voltage and Phase Matching
• Permissive Synchronizing Check Relay

If you have an automatic synchronizer, why would you need the permissive Synchronizing Check Relay?

My thoughts would be a redundant system for backup protection in case the automatic synchronizer wasn't working correctly. Then you'd have the failsafe Check relay to prevent the generator from coming online during a nonsync event.

Just curious to know.

Thanks,
Maj

 

[dpc]

Right - it's just to serve as a backup to the automatic synchronizer in case it loses its mind and tries to do a Really Bad Thing. Also, there is often an option for manual synchronizing and the synch check relay is used to supervise manual as well as auto synchronizing.

 

[slavag]

Agree with Dave.
1. As back-up of automatic synch.
2. Second for manual synch.
3. What we do, to autosynch we connect A-B phases to synch relay A-C or B-C. As Dave saied is really help in several bad cases, for example synch of generator via step-up trafo with voltage matching.
Regards.
Slava

 

[majesus]

Thanks guys...
Excellent as always

 

[Hoxton]

Traditionally, one put the automatic synchroniser in the control panel (in the control room, or near the generating set - depending how the power station was laid out). Sets were often high voltage (I am in England, so that is over 1000V). Then the switchgear was in a separate room, locked, and with restricted access.

There were several problems to avoid, some being:

1) An interposing relay between the control panel and the switchgear, operated slower than expected (perhaps spomeone changed ir for a low speed operation device, rather than the high speed relay originally fitted), the synchronising occured later than expected.

2) Someone modified the panel and shorted out the synchronising close contacts. (Oh yes it happens!).

3) Someone tried to close the generator breaker locally, rather than via the synchroniser.

4) Remember, as we went from the 50's to the 60's, auto synchronisers were pretty advanced stuff! Manual synchronising, using three lights was the normal method.

5) Unless the relevant BS / IEC / ANSI specifications have changed dramatically, they call for the designer to cater for no worse than a three phase short across the generator terminals. A faulty synchronise can give forces many times higher than this.

So as we went to this new synchronising technology, the practice of fitting a check sychroniser across the breaker came in. This was a static device, with no control, just a "permit" window.

What seems to have happened, is that the auto synchroniser became more reliable, and cheaper, and often evolved into a two channnel device, each channel guarding the other, and the concept of a separate check synchroniser across the breaker was forgotten. Not in one of my power plants!

Just had a meeting last week with a lot of clever people (letters after their name - you know) I pointed to the site incomer breaker on the single line and said - is there a check synchroniser across this breaker? I got the usual "this is never going to go wrong, how could this happen? Is not this a maintenance issue?"

 

[slavag]

Hello Hoxton.
Its right!!!! I totally agree with you.
For 6 big generators we bouth dual channel, full redandancy with additional synchrocheck option autosynch. device, but in all case in the last point we add static synchrocheck relay with additional logic, what check also autosynch, manual synchr command and all control status (no trips, dead bus situation, VT MCBs status, CB and disconnectors position, etc). And we connect it to another set of VTs. today price of synchrocheck relay is . But this generators above 250MW. for small not needed so complex system. one autosunch device single channel and one static sunchr. relay.
Regards.
Slava

 

[rovineye]

Amen!
I use Balser BE1-25 sync-check relays. I am so glad these are around these days, as they are not building smarter operators to run my generators.