Siemens partners with NTPC to boost power generation in south India

Siemens Limited started dispatch of the largest-ever ‘Made in India’ single-phase Generator
Step-Up (GSU) Transformer of rating 315 MVA, 23.5kV / 420kV for installation at
NTPC’s Kudgi Super Thermal Power Station in Bijapur, Karnataka. This transformer is an
essential component of the Power Station, which once operational will boost the highcapacity
power generation for the southern states of Karnataka, Andhra Pradesh, Tamil
Nadu and Kerala. NTPC has ordered 10 units of these GSU transformers on Siemens.

Normally the generated voltage is in the range of 11 kV to 24 kV which is not efficient to
transmit the power through the transmission line. Generator transformer is a special purpose
transformer used for stepping up generator voltage to high voltage (400 kV – 765
kV) for efficient transmission of generated power to load centers located at long distances.

Dr. Harald Griem, Executive Vice President and Head of Energy Management, Siemens
Limited, said, “Siemens Limited has manufactured and successfully tested the first singlephase
315 MVA, 420kV Generator Transformer at its Kalwa factory. The Generator
Transformer also successfully underwent short circuit withstand testing in the first attempt,
at KEMA Laboratories in The Netherlands, which was also a first for the test lab, in terms
of current capacity.”

With this milestone, Siemens has once again demonstrated its indigenous manufacturing
and technology capabilities to meet the growing demands of the Indian power sector.

About Generator step-up transformers

Generator step-up transformers (GSU) are the critical link between the generating power station and the transmission network, often operated day and night at full load. They are built to withstand extreme thermal loading without ageing prematurely. Being a most criti-cal component of power system, reliability of such transformers is highly important. GSUs are provided with oil-air unit coolers resulting in compact overall dimensions of generating station.

They are also designed with low flux densities to withstand over voltages due to sudden load rejection conditions. Special design considerations are required for high current, low voltage in terms of windings & terminations to avoid hot spots in conducting and structural parts in its vicinity.

It functions as a two way transformer where it receives the power from the grid and feeds the plant station loads during plant start-up or on generator trip. In normal case it transfers the generated power from the generator to grid power supply as mentioned above.

It also isolates the generator with grid power in large power plants to safe guard the gen-erator during grid transients.