Improvement and uprating of hydro generator Of high dam hydro power plant in Egypt

摘要

Egyptian Electricity Holding Company (EEHC) produces more than 22600 MW. The hydro power plants produces 2840 MW represents about 12.5% of the total annual generating energy in Egypt. The High Dam Hydro Power Plant (HDHPP) is the biggest hydro power plant in Egypt, it consists of the 12 generation units each capacity 175 MW with a total installed capacity 2100 MW producing about 11 million kWhr/year. It has been commissioned between 1967 and 1970. The turbine are Francis type, each rated 175 MW at 100 rpm and 57.5 meters head. The discharge to generate the max. power at the design head is 343 m~3/s power generated by the turbine and controlled by 24 blade moving ring surrounding the turbine. The generators are Umbrella type, each rated 206 MVA and nominally output voltage is 15.75 kV. Many cracks appeared in the runner blades surface after one year from the first starting of the units, due to the weak of thickness at cone area and lower band caused mechanical stress of the blades. Great efforts have been exerted to clear the cracks by welding; once by the original manufacturer and second by others but the cracks transferred to the cone area also. The decision had been taken to change the runner completely. In the new runner, the design head had been increased to 62 meters instead of 57.5 M. Accordingly the capacity of the turbine is uprating to 200 MW and its efficiency increased by 5% as well as adding the new life time of the plant by 35 years. In 2003 the Instrumentation and Control (I & C) upgreaded by DCS/DAS. The achievements of such project were: 1. Increase the availability of the station to manage the load economically. 2. Better control flexibility. 3. Integration of the generators protection system and control logic. 4. Improve the liability due to redundant processor. 5. Post rip analysis. 6. Decrease forced outage of the units. In the period of 1994-1999 several investigations were conducted on the generators and the outcome of these investigations were: 1. The stator winding were found very aged, insulation strength have decreased and the rewedeing found loose in 1986. 2. The vibration of the core had increased compared with measurements in 1970, the core was found seriously buckled and the joints damaged. The deterioration of the core is extensive and might accelerate rapidly in future. 3. The rotor of some generators had sign of rim displacement, some of rotor coil conductor had cracks. 4. One pole in unit 4 turn insulation was displaced which show that the deterioration had started. The conclusion was the stator core and stator winding should be replaced. In Oct. 2003 a contract had been signed to execute such project for each 2 units (sharing one tunnel) annually within 6 years started in 2004 and end in June 2010.