CGCM AVR with block Generator-Step up transformer scheme

Hello,
we are buying a used 5MW gas turbine generator and retrofiting its generator control system with a Rockwell CGCM (Basler).
The alternator is an 11kV machine and we intend to use it directly connected to a 11/33kV YNd11 generator step up transformer,
in order to connect the block generator-transformer to an industrial grid.
The generator does not have 11kV GCB nor 11kV VTs.
circuit breaker, line and bus VTs are available at 33kV switchgear.
Hence the CGCM shall synchronize and perform AVR control with 33kV VTs.
1) will this work ?
2) are there some limitations with this scheme ?

thank you20210727_153757.jpg20210727_153757.jpg
 
Alex...
I'd like to help, but as shown, your scheme is not clear. Do you actually intend to reconnect the existing protection PTs, CTs, and neutral from the Generator side to Y-side of the new Transformer?
Regards, Phil Corso
 
Alex...
I'd like to help, but as shown, your scheme is not clear. Do you actually intend to reconnect the existing protection PTs, CTs, and neutral from the Generator side to Y-side of the new Transformer?
Regards, Phil Corso

Hi Phil,

some CTs from generator neutral side (not shown on this diag) will be connected to the 33kV switchgear protection relay (Sepam G88), for block generator-transformer differential protection (87T+G).
Other CTs from generator neutral will be connected to CGCM for some alternator protections and AVR functions.
PTs are only available at 33kV switchgear (Y side of transformer).
Hope it clarifies the setup
 
Alex...
My comments were to determine if you intended to change the protection system so that Generator and Transformer were protected individually? Or did you intend to combine the two, as is usually done when the Xfmr, in this case serves as a GSU or Generator Step Up Unit.
The reason I ask is because the SEPAM G88, in particular, may not be suitable !
Stay well, Phil Corso
 
Alex...
One additional (non-electrical) precaution:
Make sure the GSU Xfmr is properly distanced, oil-spill containment curbed, and shielded so that fire or oil-leak doesn't affect equipment around it! (Saw this catastrophe happen too many times when Xfmr location was overlooked in planning phase) !
Phil
 
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