200825 - Site Visit by Carl Brothers visited the site to attend to several project deficiencies including, further
investigation of the VFD Short Circuit Fault 2340 Code.
I first checked the parameter settings on the T6 drive a
suggested by Simon page in an earlier email. He was correct in noting a few parameters were
unique, and incorrect in T6.
I changed the parameter 99.04 from Scalar to DTC.
I changed the parameter 21-19 to Normal
I retested a test start and the error 2340 was still engaged.
After several repeated 2340 Errors, I changed
Parameter 2502 from 8.0 to 2 and
Parameter 2503 from 0.35 to 4.35
The unit again tripped on a 2340 error
Megger Tests
I conducted megger tests on T5 and T6 to determine if there was an obvious fault on T6. Things
tested fine using both a multimeter and a 500 V megger, as summarized in Table 1.
Kipnuk T5 / T6 Generator Megger Tests – From control building
T5 – 35 m Drive to Gen T6 – 125 m Drive to Gen
Multimeter 500 V Megger Multimeter 500 V Megger
L1-L2 0.2 Ω 0.1 Ω 0.2 Ω 0.1 Ω
L2-L3 0.2 Ω 0.1 Ω 0.2 Ω 0.1 Ω
L3-L1 0.2 Ω 0.1 Ω 0.2 Ω 0.1 Ω
L1-Gnd OL 20 MΩ OL 15 MΩ
L2 -Gnd OL 20 MΩ OL 15 MΩ
L3-Gnd OL 20 MΩ OL 15 MΩ
Table 1
The turbine has not operated since the spring and the megger readings, noted above, suggest
there is nothing failed on the generator. I climbed the tower to inspect the cable and connections
and can find nothing out of the ordinary. No unusual smells.
I conducted a series of tests on the VFDs to see how they responded
Tests completed
Switching VFDs – T4, T5 and T6 VFDs are in the same 20’ container and we were able to find a
long enough jumper cable to connect T5 and T6 with reverse controller / generator configuration.
Test #1 - Test T5
T5 - Place in Service mode; Release brake; Jog motor; Rotor accelerates to 400 rpm
Test #2 - Test T6
T6 - Place in Service mode; Release brake; Jog motor; “Error 2340 – Short circuit in motor /
cable”.
Test #3 - Test T6 drive on T5 generator
Connecting T6 Drive to T5 generator – Released brakes on both turbines
Place T5 & T6 in Service mode; Release brake; Jog motor on T6. T5 rotor accelerates to 400
RPM
Test #4 - Test T5 drive on T6 generator
Connecting T5 Drive to T6 generator – Released
Place T5 & T6 in Service mode; Release brakes on both turbines; Jog T6 motor on T5 drive.
“Error 2340 – Short circuit in motor / cable”.
This would seem to suggest that T6 generator has failed. But the resistance and megger tests
suggest otherwise. And the operational history of the generator indicates no problem with the
device. It may be possible that the increased conductor distance between the drive and T6
generator is triggering a trip from a marginally set parameter.
Test #5 – Non-zero rpm test
I climbed the tower with the service wand and released the brake and manually rotated the shaft
so the rotor was not moving when energized. The generator speed was 50-100 rpm when I
pushed the ‘Jog’ and the unit tripped on error 2340.
Where to from here?
I am confident the generator is not burned. It has had no service since it operated as expected,
there is no smell and the megger tests suggest it is fine. But something is tripping both T5 and T6
drives with the present parameter configuration we have and we need some advice from ABB on
how to further investigate and resolve this problem.
What is the drive measuring when it detects a short circuit on the motor cable? It must be
measuring the impedance to ground. How can we monitor what the drive is seeing to compare it
to what the megger is seeing?
200715 - Insulations Tests on the replacement generator #2 has determined that the insulation appears fine.
Here are results of insulation tests on T6 original generator (#1) and T6 replacement generator (#2): https://drive.google.com/file/d/1jIg1CJow8ciudOv4GnXUTgAsZiMlGNfP/view?usp=sharing
200720 - Installed dv/dt filter on T6 but still getting Regen Drive "Short Circuit Fault Code 2340" so it is possible that even though T6 is passing the insulation tests but something has changed that the Regen Drive is picking up as a short circuit.