MEOL Oral Prep Questions

Hi Ya Folks,

I am prepping for my MEOL Oral and am at the Electrical Chapter and would like some advice from you more Experienced Engineers out there. I have the notes/done the Oral Prep Course and googling like crazy, but just need clarification on a few things.

My First Question is on the Reverse Power Trip.

(I know that this can only happen when Generators are synchronized and running in Parallel and that the Reverse Power Trip is a Safety Device)

From what I can gather it will trip the breaker at the Main Busbar on the generator that is shutting down unexpectedly due to High Coolant Temp/Low Oil Pressure or Fuel Starvation or other reasons. This is safety trip due to the Generators abilty to start acting like a motor and drawing current from the Switchboard which can cause damage to the prime mover and Generator itself which would possibly overload and knock off the second generator running in parallel and blacking out the entire ship) Please correct me if I am wrong??

How does one test Reverse Power Trip onboard your vessel? What would you do if the trip failed to work? Is this test in your safety checklists?

Could I just close the battery switch to activate the fuel shutoff solenoid??

Thanks

Globe

Thanks there C4ENG, How about when you are running them both online and Synced and operate the Switch(Governor Control) and unload the the Kw(Load) on the Genset and as it unloads the other generator will start to take the load and as the unloading generator starts going into reverse power it will eventually trip out on Reverse Power Trip(That is if it is working)

What you say does make sense but like you said it would be nice to hear more folks experiences on this. Also if the Trip Failed, I would manually open up the circuit breaker taking it off the Bus Bar and then get the electricians in to resolve the issue.

I would like to extend this topic further.

I am all clear on Synchronising two Gensets using Syncroscope and all but what safety is there to prevent a person manually closing the breaker of incoming Genset 180degree's out of phase????(Of course there is one as paralleling out of phase would could serious damage to Generators and Prime Movers as they tried to compensate and Torque to get in Phase.

I will keep extending this topic as I go and hope that other can learn from this as I learn as well.

Thanks

Globe

I do not want to Confuse things here but what you say C4ENG sounds like the following which I got directly from the notes in this chapter.

"Under-voltage Trip

Closure by mistake of an alternator breaker when the machine is dead is prevented by an under-voltage trip. This protective measure is fitted when alternators are arranged for parallel operation. Instantaneous operation of the trip is necessary to prevent closure of the breaker. However, an under-voltage trip also gives protection against loss of voltage while the machine is connected to the switchboard. Tripping in this case must be delayed for discrimination purposes, so that if the volt drop is caused by a fault then time is allowed for the appropriate fuse or breaker to operate and the voltage to receiver without loss of the power supply."

Okay I passed, These were just the things I needed clarification on.

Anyways See you around

Globe76