Electrical Systems of a Grid Connected 2 MW Mini Hydro
Power Project at Siripagama

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ABSTRACT
This paper presents the electrical system design of a 2MW Mini Hydropower Power Plant (MHPP) project
at Siripagama. Catchments area of 19.1 km2 and annual average rainfall of 3935 mm yield to 3.5 m3/s
designed flow. Net head was found as 68 m. Plant was sized to 2 MW and accordingly structural
components and electro-mechanical system were designed. Two numbers of electro-mechanical units in
which each unit consists of Francis turbine of 1054 kW, synchronous generator of 1250 kVA, 400 V and
two number of 33 kV 1800 kVA step up transformers.


INTRODUCTION
One of main sources of power generation in Sri Lanka is hydroelectric. According to the statistical data
published by Ceylon Electricity Board (CEB) for the year 2006, 49.4% of total generation is met by
hydropower. In 1996, Sri Lanka Government encouraged private sector participation in power generation.
As a result at the end of year 2006, 60 numbers of mini hydropower plants were connected to the national
grid adding total of 109 MW with an annual generation of 346 GWh (4% of gross production) [1].


ELECTRICAL SYSTEMS
Generating voltage of the plant was selected as 415 V in order to avoid auxiliary transformer and related
controls. This voltage was step up to 33 kV to interconnect with national grid. Therefore, electrical system
of the power plant consisted of Low Voltage (415 V) switch boards and the Medium Voltage (33 kV)
Switchyard [8].


SYSTEM STUDIES
a. Power flow studies
Power flow studies were carried out to check the normal operating status of the distribution network after
connecting an embedded generator. Voltage at every point in the distribution network should be within the
acceptable limits for all expected loading conditions and with and without the embedded generator.
Thereby the interconnection line of the embedded generator to the distribution network was determined.
Computer package called SYNERGEE-version 2.1 developed by Stoners Electric, USA was used in this
simulation [11].