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| Image of a Syncroscope |
For all of you electrical operators out there does this scenario sound familiar? You are in a half power lineup on the port turbine generator. The Starboard Turbine Generator (TG)is ready to go and you need to bring the TG on the bus restoring the plant to a NFPL and restore the ability the answer bells on both main engines. You know the drill.
What are the things which must occur before you shut a breaker? For starters the voltage and frequencies of the incoming load and the running bus must match and the synchroscope needs to rotating clockwise prior to shutting the breaker within the gray area at the 12 o clock position on the gauge. Do you remember why? In short, varying frequencies on the generator could speed up or slow down causing damage or excessive power transients. Likewise a variance in voltages can result in transients as well. Proper shutting of the breaker using the synchroscopes ensures the two buses are on phase in addition to ensure the incoming bus picks up the load.
In any case, normally plant shifts are uneventful. I recall I was on watch as RO and the EO Under Instruction, (UI) was doing a plant shift for qualification. The shift qualified Electric Operator, UI, and the Engineer Officer of the Watch (EOOW) talked through the plant shift prior to operating the plant. Finally, the EOOW gave the order to perform the shift.
In retrospect, I am not sure of the synchroscope’s position when the UI attempted to shut the breaker. Let’s say the position was nowhere close from the loud boom everyone heard. After I looked at my panel my pump configuration I lost a pump on each side i.e.1 Slow- 1 Slow. I had two pumps running on each side before the shift.
After the restoring the plant E Div ensured no damage had occurred to the breaker. On this day we were lucky, for those of you who might not have been so fortunate what was the craziest thing you have seen during a messed up plant shift and what happened afterwards?
Image courtesy of http://metersandinstruments.yokogawa-usa.com/product/analog-switchboard-instruments/ab40-synchroscope-switchboard-meters
