Preferential Trip On Ship With Diagram

Preferential tripping
           It is the tripping of non essential loads when an overload occurs on a generator. When the generator becomes overloaded, the preferential trip relay gets operated with an alarm to trip the selected non essential loads.

Why preferential trip is necessary in onboard vessels?
          If preferential trip is not installed , when a generator gets overloaded, overload trip gets activated resulting in total power failure as well as shut down of the ship. So it is better to maintain the generator operating by disconnecting some of the connecting load, which can be effectively done by installing preferential trip in onboard vessels

Must Read:> Reverse Power Flow, Motoring Effect And Reverse Power Relay

How Preferential Trip Is Arranged on Circuit? Where it is Installed?
            Each generator has its own preferential trip and overload trip. These trips are installed between generator and busbar. Overload trip is set at 150% current with 20 second time delay and preferential trip is set at 110% current with instantaneous operation.

           If the generator gets overloaded, then preferential trip gets activated and operate time delay, which will disconnect non essential services in specific order at specific interval according to priority. 

Order Of Tripping

        Order of tripping varies in each vessel, most of the ships have the following order
5 sec-  Air-condition and ventilation
10 sec- Refrigerated cargo plant
15 sec- Deck equipment 

       If the over current still exist after the tripping of non essential services, then overload trip gets activated aftr 20 secs and trips whole ship circuit.

How Preferential Tripping Is Tested?

       Preferential tripping is tested by current injection.


>> Your Comments are always appreciated...
>> Discussion is an exchange of knowledge It Make the Mariner Perfect.... Please Discuss below...

  1. Please include the alarm circuit also in the diagram

  2. The preference trip light on my generator can not go off and the generator refused to take load while the preference trip light is on. If I start the other generator, it also can not go off . Why

  3. How test will conducted by current injection

Previous Post Next Post