The scope of work shall comprise, but not be limited to, engineering, design, manufacture, supply, installation, testing and commissioning of the generator components of units II and IV including stator frame, stator core, stator winding, rotor field winding, generator air coolers along with temperature transmitters for monitoring inlet and outlet air, DC lead assembly including DC cables, generator condition monitoring system, slip-ring assembly with carbon dust collector system, and ancillaries (vapour sealing system, brake/jack system, hydrostatic lubrication system, air guides, air baffle ring and stator space heater) as well as slip-ring assembly with carbon dust collector system, online condition monitoring system of generator and generator ancillaries of units I and III.
The four 84 MW units, comprising Pelton turbines, were manufactured and supplied by India’s Bharat Heavy Electricals (BHEL). The first two units were commissioned in 1986, while the other two units were commissioned in 1988. The units are continuously loaded at 92 MW (10 per cent overload) during peak seasons when the inflow is high typically from mid-May to October and then partly loaded during off-peak seasons. Therefore, the units are subjected to varying load cycles. A series of phased renovation and modernization works are being carried out at the plant. During Phase I, governor system and excitation were replaced. In Phase II, top and bottom brackets of generator were replaced in units I and II in 2011 and 2013, respectively. In Phase III, stator winding, stator core, stator frame and field windings were replaced at units III and I in 2017 and 2018, respectively. However, no major upgrades have been carried out on units II and IV. Moreover, there are technical issues and problems with the existing components of the generator and systems.
The lowering of new stator including installation, testing and commissioning of generator auxiliaries must be scheduled as per the annual maintenance schedule, which is usually from November to April. During the other months of the year, materials can be supplied and new stator can be built at the service bay, inside the powerhouse. Only one stator can be built at a time due to space constraints at site. A tentative schedule expects award of work by 1 August 2022 with onsite work expected to take part between June 2023 and May 2025. The Request for Expressions of Interest (RfEOI) comprising instructions to bidders, qualification criteria, forms and abridged technical specifications is available for downloading from the website: www.dgpc.bt.
Expressions of Interest must be delivered to the address below on 26 May by 3:00 PM (Bhutan Standard Time). Bidders shall also be permitted to submit their EOI proposals through email, which shall be in PDF format with password protection. EOI proposals should be marked as “EOI for Replacement of Unit II & Unit IV Generators and Ancillaries of all Four Units of Chhukha Hydropower Plant. For further information, contact: Head, Contracts Management and Procurement Divisions (CMPD), Contracts and Procurement Department (CPD), Druk Green Power Corporation Ltd. (DGPC), Post Box 131, Thimphu, Bhutan; Tel.: +975 2 330979; E-mail: t.wangchuk792@drukgreen.bt
