Turbo alternator tripped by reverse power

[SA07]

Hi
We have 2 turbo alternator exporting to utility grid. One turbo alternator tripped by reverse power and generator breaker opened. From fault recorder, we do not see a big fault or disturbance on the network. Feedback from Utility: they were switching flow of power to another substation.
Any idea what might be the cause of reverse power trip in this situation?

 

[crshears]

Possible setting corruption, or, more likely, maladjustment in micro-processor based protection for the unit that tripped? System "bumps" are not all that uncommon, and generator protection settings may need subtle but important tweaks to reduce sensitivity and susceptibility to operating for present but essentially harmless grid perturbations.

I recall how at a new substation where transformers were placed on potential by motorized high-side disconnect switch, the 'new-fangled" electronic protections had quite a few more detection capabilities than the older electro-mechanical prots, and the settings chosen for the new transformer prots led to random but overly frequent clearing of the energizing zone by transfer trip. In-depth analysis of the waveforms as gathered from on-site and neighbouring Digital Fault Recorders and old-school direct-to-digital-tape oscillographs was required to determine what was actually occurring; it became clear that certain harmonic content was overly weighted in the prot settings. Once these were reprogrammed, spurious circuit trips upon transformer energization were reduced to occurring < 1% of the time [the conscious determination was made to live with this moving forward so as to not overly desensitize the prot scheme when taken as a whole].

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]