The generator unit 02 at Babarabotuwa Oya Phase 11 MHPP experienced two breakdowns due to electrical flashovers causing damage to the stator winding and slots. After the first breakdown in November 2015, two coils were replaced, but it broke down again in January 2016 after running for 178 hours. Testing found the coils had poor insulation resistance and all 90 coils needed replacing. New coils were manufactured and supplied along with other accessories from Houghton International and installed, with insulation resistance test results in the gigohm range afterwards.

1. Upcountry Power supply International (Pvt) Ltd
Babarabotuwa Oya Phase 11 MHPP
Generator Unit 02 Breakdown and repairing Report
Generator Detail,
Capacity : 1.6MW
Voltage : 6.3kV
Type : SFW16696/1400
Serial No : 130003
Standard No: GB1789A
Date of first breakdown: 1st of November 2015
Description of breakdown:
Electrical flashover has been seen from inside the generator unit 02 while it was
starting. Then after inspection it has been observed that stator winding and slots have
burnt due to erupted fire.
Figure 1: Winding and slots damage due to erupted fire
Thomson Electricals visited site on 3rd November 2015 and MBSL insurance Loss
adjuster who Mr.Sugath Weerarathne visited site on 13th of November.
Then management has decided to repair generator unit 02 from Thomson Electricals.

2. Repairing Methodology
Thomson electricals had decided to replace two damaged winding coil and they used
two spare coils which have supplied with the generator to replace. See appendix 1 for
Thomson report.
Figure 2: stator winding coil repairing
Insulation resistance (IR) test results of stator winding
IR values were as follows after repairing,
U-E=10.6 MΩ V-U=24.22 MΩ
V-E=9.303 MΩ W-U=24.90 MΩ
W-E=10.65 MΩ
V-W=23.93 MΩ

3. Date of second breakdown: 21st of January 2016
Description of breakdown:
Again on 21st of January 2016, a fire had erupted due to flash over in the stator winding
of generator unit 02 while it was shut down. Generator unit 02 has run 178 hours up
to second breakdown after it was repaired.
Figure 3: Winding and slots damage due to erupted fire
Then stator winding coil sample of generator unit 02 was tested by Mr.Ajith
Rathnayeke from Fentons. He concluded that coils have poor insulation resistance and
all coils (90 coils) should replace. (See Appendix 2 for Mr.Ajith Rathnayeke’s report.
Then management has decided to replace all coil and Houghton International in UK
was selected to manufacture coils and supply other necessary accessories. Sample coil
and other accessories sample were sent to Houghton.
While the coil is manufacturing, the generator unit 02 was submitted to The Electrical
Company in Wattla to do the repair.
Winding coil and other accessories were received from Houghton in July 2016.
Repairing Methodology
Please see Appendix 3 for detail method statement of Mr.Alwis who is managing
partner of The Electric Company.
Insulation resistance (IR) test results of stator winding
IR values were as follows after repairing,
U-E=2.28 GΩ V-U=4.1 GΩ
V-E=2.46 GΩ W-U=3.5 GΩ
W-E=2.62 GΩ
V-W=4.55 GΩ