XIAJIANG - WORLD'S BIGGEST BULB UNIT
MULTI-PURPOSE HYDROELECTRIC DAM
The Xiajiang hydropower plant is located in the middle portion of Ganjiang river in Jiangxi Province of China, 160 km from Nanchang city.
The Xiajiang hydropower project is managed by Jiangxi Province Xiajiang Water Control Project Headquarters, and was conceived to provide Jiangxi Province with 1.1 billion kW/h of clean power per year and to optimize its network structure.
The plant will also allow to prevent flood as well as to improve agricultural irrigation and navigation capacity from 300t-class to 1000t-class.
STATE-OF-THE-ART TECHNOLOGY MEETING CUSTOMER’S EXPECTATIONS
Under the terms of the contract, GE is responsible for the supply of five 40 MW bulb turbine and generator units and auxiliary equipment.
The company has been an ardent pioneer in the development of bulb units introducing many outstanding innovations in size, design and operational efficiency, offering both standardised and customised solutions. With a runner diameter of 7.8 m, it is not only the biggest bulb unit manufactured in China but also the biggest custom bulb unit in the world.
GE design concepts ensure reliability in various operating circumstances taking account of the bulb unit’s sensitivity to instability and vibrations due to the horizontal position of the generator. They have been developed to handle conditions such as roundness and air gap concentricity, and have been successfully applied in bulb units up to 60 MVA.
Xiajiang utilizes the Micadur® insulation system for hydro generators up to 23 kV and is highly resistant to oil, dust and other contaminants. Vacuum Pressure impregnation (VPi) avoids air inclusions, increasing bar stability and eliminating partial discharges.
PROVIDING TAILOR-MADE SOLUTIONS
GE has delivered a high performance turbine designed for a wide head range, so as to optimize output in very different seasonal conditions. Major components were especially designed for easy and quick installation on-site.
To ensure an optimum resilience of the rotor to thermal expansion, centrifugal forces and operational torques, the Xiajiang motor generator’s upper bracket, rotor spider and stator frame are equipped with oblique elements. This is particularly important for bulb turbine units which have a reduced air gap between the rotor and the stator.
Oblique elements allow more efficient, compact and reliable generators, participating to the reduction of construction costs thanks to smaller foundation, and increasing the overall lifetime of the generator.