We have 3 identical Generators CAT3512B & STAMFORD alternator onboard our ship.
GEN 3 is having a problem when in parallel to any of the Generators (1 or 2).

Example: GEN 3 parallel to GEN 2
The moment they are in parallel
GEN 3 Current and kVar rises continuously, pf 0.14.
GEN 2 kVar is less than 0, Current also rises continuously , pf is above 1.0
after 30seconds the PMS alarms "kVar imbalance" (greater than 300kVar)
Bus Tie will open and Generators will supply each bus tie independently

Note: 20-30kW difference between generators, value not rising.

Scenario 1: GEN 3 running alone with load (bow Thruster & Stern Thruster)
all parameters normal (current not rising kvar steady)

Scenario 2: GEN 1 & GEN 2 running in parallel without any problem (almost the same pf 0.7)

Actions done:
1.) Tried to replace new AVR of GEN 3 = same problem occurred
2.) Tried to swap Woodward Load Sharing Module from GEN 2 = same problem occurred
3.) Checked connections and resistance of Droop Current CT connected in the Alternator have almost the same value (39 ohms)
4.) Tried to disconnect connection of GEN 3 Droop CT to AVR = same problem occurred

GEN 1 Droop CT is not connected to the AVR (i dont know why)
GEN 2 Droop CT is connected to the AVR
GEN 3 Droop CT is connected to the AVR

GEN 1 & GEN 3 connected in parallel = same problem occurred

 

This suggests a problem with GEN 3's AVR or its sensing circuit.
Perform a detailed test of GEN 3’s AVR, especially its sensing circuit for voltage and current.