In the severe winter, we received the call from our customers. They said that there were high water temperature alarm shutdown and low oil pressure alarm shutdown in the condition of generator set safe operation. The B phase load power was negative when the unit ran normally.
After checking out the scene, we found that the terminal 40 of HGM6110N was connected with the negative electrode of the charger inside the control cabinet. And the original ground screw was not tightened firmly. Considering the interference problem, we wired a single line from the terminal 40 to the ground stud of the unit. After starting unit, it was normal and the alarms didn't appear again.
About the negative B phase load power, because the P1 and P2 of three-phase current transformer are reverse. At the same time , the A phase and C phase current sampling are reverse. These reasons result in the negative active power. The solution is adjusting the direction of current transformer and the A phase & C phase current sampling.
In fact, if we pay more attention to these small details in the application, there won't be a similar problem.