Analysis of Bhutan Power Systems using PSS®E Software

Abstract

Electricity demand in Bhutan has been increasing steadily ever since utility-scale power supply was
introduced into the country in the 1960s and 1970s and Bhutan’s first large-scale hydropower
project, 336 MW Chhukha Hydropower Plant was commissioned in the 1980s. In the past three
years, the rise in the demand has accelerated due to rapid growth in the industrial development. This
has led to increasing stress on the power system infrastructure. Further, the country’s grid is
subjected to varying operating conditions brought about by seasonal variations in generation,
peaking in summer, flexible operation and reaching its lowest level in winter. Additionally, the grid
is connected to Indian systems via thirteen feeders at different voltage levels further increasing the
risks of disturbances and influence from the larger Indian grid. Therefore, it is of paramount
importance to carry out the system analysis at regular intervals to study and assess the behavior of
the power systems, based on which the timely corrective measures can be implemented to ensure
grid stability and efficiency. In this study, the existing power system model of Bhutan is developed
in PSS®E software and simulation is carried out for summer and winter seasons. For summer, the
data sets of 28th July 2024 at 20:00 hours is used while for winter, the data sets of 14th February
2024 at 15:00 hours is used corresponding to the highest generation and the lowest generation
respectively. The simulation results show the overloading of Mangdechhu to Yurmo line,
overloading of transformers at Gedu substations, and under voltage issues in a few substations in
both the study periods. Therefore, to resolve the overloading issues, upgradation of transformers at
Gedu substation and connection of a new line from Mangdechhu to Yurmo is recommended. Further,
to resolve under-voltage issue, shunt capacitor of 12 MVAR is recommended in Damji substation,
which has been determined based on the QV analysis.