ABB UNITOL 6000 excitation system

Abnormal voltage regulation: Check if the secondary side wiring of the PT (voltage transformer) is normal and if there is a blown fuse. Use ECT to view the voltage setpoint and feedback values in AUTO mode. Check if the PID parameters are suitable for the current operating point.

Abnormal excitation current (MAN mode): Check the CT (current transformer) signal. Check if the trigger pulse of the thyristor is normal, and use the thyristor conduction monitoring function. Check if the rotor grounding protection is activated.

PSS not effective: Confirm that PSS has been enabled and put into operation. Check if the active power of the generator is above the PSS start-up threshold. Check if the PSS output limiter is activated. Use a white noise generator for frequency response testing to verify PSS parameters.

Limiter misoperation: Check if the limiter settings (such as U/F limit, under excitation limit) match the actual capacity curve of the generator. View the status and action values of the limiter in ECT.

Advanced diagnosis:

Using SMTS-RT 6000 to reproduce faults: For occasional faults that are difficult to reproduce on site, the controller can be connected to a simulator to reproduce the operating conditions and observe whether the fault is reproduced.

Remote support: If the on-site team is unable to resolve the issue, authorize ABB experts through the RAP platform for remote diagnosis. This is one of the most effective ways to shorten downtime.

Spare parts and maintenance: Plan key spare parts (such as power modules, I/O boards, cooling fans) in advance based on the lifecycle stage. For UNL series converters, use their drawer style design to achieve online replacement.