Hydropower Plant Stator Restoration

This solved assignment focuses on the restoration of damaged stator bars in a hydropower plant (Chhukha). The document outlines the project's initiation, planning, execution, including teamwork, safety measures, technical expertise in winding replacement and testing. It concludes with the successful completion ahead of schedule, highlighting cost-saving and operational benefits.

Career Episode 1: Restoration of stator winding of Generator-1
a. Introduction
CE1.1: The following career episode deals with the demonstration of the role played by me in
restoration of Chhukha Hydropower Plant’s (CHP’s) stator winding of the generator-1. The role
of restoration of Chhukha Hydropower Plant’s (CHP’s) stator winding of the generator-1 was
played by me when I was working at CHP as an Assistant Electrical Engineer at Generator
Maintenance Unit under the Maintenance Division of Chhukha Hydropower Plant. I had been
working there from 29th January 2010 to 21st August 2013. The Chhukha Hydropower Plant was
located in Chhukha district of Bhutan which is geographically 80 miles away from the capital
city of Thimphu, Bhutan. The company named DGPC or Druk Green Power Corporation
Limited is the owner of Chhukha Hydropower Plant along with 3 other hydropower plants.
b. Background
CE2.2: Chhukha Hydropower Plant was built and had been in working efficiently since the year
1983.The plant provides approximately 84 MW (eighty four megawatt) of power with the help of
the four 11 KV (eleven Kilo-voltage) of power generators. The use of the four power generators
has helped the Chhukha Hydropower Plant for achieving a total capacity of 336 MW (three
hundred and thirty six megawatt). The power generated in the Chhukha Hydropower Plant would
be transferred in India through the 4 power lines of 220 KV (two hundred and twenty kilo volts)
and 66 KV (sixty six kilo volts) that would help in meeting the needs of domestic consumption.
CE2.3: The Chhukha Hydropower Plant is deployed for aligning with the improved functional
analysis. The power plant had been experiencing massive winding failure at the generator-1 that
has been caused due to the extreme grid disturbances occurred in September 2011. The issue of

massive winding failure happened during the peak months when the Chhukha Hydropower Plant
had been operating at full throttle. The hazard of losing the machine of Chhukha Hydropower
Plant was unpredictable at that time. The loss of the machine’s functionality would result in
forming the hindrances in power generation and for even one hour of power transmission loss
would result in forming an overall loss in income of 4 million. The executive engineer has been
instructed by the management of Maintenance Division for restoring the machine in the shortest
possible time so that loss due to absence of power generation would be minimized.
CE2.4: The Executive Engineer for the Maintenance Division of Chhukha Hydropower Plant
had instructed me to restore the stator. I was assigned the task to restoration of the stator of the
generator-1 of Chhukha Hydropower Plant within the period of 3 weeks of duration. I had been
assured by the Executive Engineer to be assisted completely from other non-technical and
technical staffs present in Chhukha Hydropower Plant. I had to play the role of project manager
by managing and leading the restoration team for restoring the stator. Some of the
responsibilities that I had to comply with are,
 Development of complete plan for the restoration of the stator
 Inspecting the site and forming an estimation determination of the resources that would
be required for the project
 Installing and Commissioning the power generator along with the new replaced stator
bars
 Forming the co-ordination among the Engineers of Original Equipment Manufacturer
with the project team
 Reporting and documenting the progress of work with the help of completion report

The following diagram would show the contemporary organogram depicting my position in the
green block below,
Figure 1: Figure 1. Organizational structure of Chhukha Hydropower Plant
c. Personnel Engineering Activity
CE2.5: I had to inspect the broken part of the winding stator of generator-1 for Chhukha
Hydropower Plant. The work also included the calculation of the estimation about the new stator
bars for the Chhukha Hydropower Plant. The associated windings material requirements were to
be estimated for the initiation of the stator restoration works. The double wave winding type of
Chief
Engineer(CE
)
Maintenance
Division
Control &
Protection
Unit(C&PU)
Generator
Mainteannce
Unit(GMU)
Turbine
Maintenance
Unit(TMU)
Switchyard
Maintenance
Unit(SMU)
Operation
Division
Civil
Dision Human
Resource and
Administratio
n Dvision
Finance
Division
Technical Support
Unit(TSU)

the stator winding was used for the stator of the Chhukha Hydropower Plant. I had located the
issues and came to an inference that the number 78 and 79 winding cap had been faulty for the
issue of the stator. The fault was located closer to the generator-1’s neutral terminal. I examined
the specific winding caps that are helpful for the forming the decision of number of the stator
bars to be removed. The 13 top bars and the 8 bottom bars were included in the removal
decision. After that bill of approximate cost of the materials were prepared and it was submitted
to the management for getting the approval.
CE2.6: I had gathered the human resources and manpower that would be required for
dismantling the section identified for being defected at the stator windings. The time for the
completion of the project was limited and the defect needed to be rectified on an urgent notice.
Hence, I formed a 24 hour of shift system and while the process of dismantling was going on, I
provided employees with appropriate Personnel Protective Equipment that would be suitable for
protecting them while performing their roles and responsibilities in dismantling the stator. The
removal of the stator bar would require the proper disposal of the stator bar. I have also
organized specific meeting for educating each team about the work plan and it would also help in
emphasizing the significance of completing the work with urgent priority. It would help in
reducing the loss generation for Chhukha Hydropower Plant due to down time of machine.
CE2.7: I was responsible for accelerating the restoration of the generator-1 for Chhukha
Hydropower Plant. I deployed the idea of using spare stator bars that were available at the
warehouse of Chhukha Hydropower Plant. It would save our time that we were required for
using while we wait for delivering of the new stator bars. The winding bars required careful
installation to escape from the probability of being damaged and marked with scratches. We
achieved it by installing them at specific core slots of the machine. I even did conduct insulation

process and test of AC high voltage on the spare bars. The test helped in determining the
healthiness of the stator bars and the value of test results lied between the standards set
internationally by IEEE /IEC/CIGRE. I again had to check the core slot which were installed
with stator bars for high voltage and IR issues so that the windings could not be damaged while
the installation process. I had instructed the winders to imply brazing at the winding joints at
both top and bottom of windings of the stator core. The brazing machines and ferrule were used
for brazing with the help of Original Equipment Manufacturer. I even checked the brazed joints
for probability of cracks and non-destructive tests and it yielded that the quality of the braised
joints were more than 50% (acceptable standards).
CE2.9: I had examined and verified the items of my pre-developed checklist before the system
was commissioned as it would aim for the successful and safe start of the machine. I had to
encounter an issue of insulation resistant measurement values. The 11kv stator had IR values that
were below the acceptable standards and the machine had to be kept on dry run for a time of 7
hours and for 30 minutes the IR measurement. The implication of the effective processing would
imply the management for loading the machine to full load successfully.
CE2.10: I had recorded the activities of the process of restoration and even carried on the
electrical testing. The performance of the workmanship would be ensured with the help of
regular monitoring process.
c. Summary
CE2.11: I have completed the project of restoration of the stator bars for the development of the
improved operations. The project was developed for ensuring that the improved functional
development would be implied. The completion date of the project was before the final deadline

given by the management. The management had applauded me for the quick work and the smart
actions for the project. The management boards were impressed as the restoration had helped in
reducing the loss of power generation and additionally for completing the project in two less
days than expected. I had decided to use the spare stator and it had helped the project by
providing an acceleration due to which the overall project was completed in two less days than
expected. The waiting and then testing of the new stator bars would have resulted in delaying the
restoration process and more loss of the power due to the issues. Moreover, the new stator bars
acquitted after some days were kept in the storage plant for ensuring the presence of spare parts
for future use.