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Lingjintan HPP, located in Taoyuan County of Hunan Province, is 40km and 80km upstream of Taoyuan County Seat and Changde City, respectively, and 47.5km downstream of Wuqiangxi HPP. The project has a 52.05m-high concrete gravity dam and an installed capacity of 270MW. It is classified as a Rank 2 Large (2) project and is mainly for power generation and concurrently for navigation. It was awarded first prize for excellent investigation of Hunan Province and gold prize of China’s Patent Technology Fair.
The catchment area above the dam site is 85,800km2, the mean annual discharge at the dam site 2,400m3/s, and the mean annual runoff 6.56 million m3. The project has a NPL of 51.00m, a limiting level during flood season of 50.00m, and total reservoir storage of 6.34 million m3. The project is installed with 9 sets of 30MW tubular bulb turbo-generator units, and has a total installed capacity of 270MW and a mean annual energy output of 1215 GWh.
The project mainly consists of concrete gravity dams on banks, sluice, powerhouse and ship lock. The sluice is on the right side of the river course, the powerhouse on the left side of the river course, the ship lock on the right bank, and concrete gravity dams on both banks. The dams have a crest elevation of 65.50m, total crest length of 915.11m, and maximum height of 52.05m (at powerhouse dam section).
Main Technical Features and Key Technical Issues:
Firstly, with a unit capacity of 30MW, the turbo-generator units of Lingjintan HPP were the largest low-head large-discharge tubular units in the world at that time, and there were no practical experience for reference in design, manufacturing and installation.
Secondly, 160t2 incense coil type hoist was first employed to operate large plain service gate, and high concrete bent normally adopted was cancelled.
Thirdly, the powerhouse is of water retaining type and has a high flood protection level. Since the powerhouse is quite long along the river, two longitudinal joints were provided for the powerhouse during construction. Due to the installation of units, the lifting height of the upstream and downstream blocks was higher than the middle one. In addition, the upstream and downstream blocks were required to retain water in flood season, so flood protection during construction was a major challenge. A solution of butted joint and grouting for the lower part of longitudinal joints prior to flood season was adopted. The guide wall section of powerhouse dam section downstream of dam monolith No. 20 was also the longitudinal cofferdam for powerhouse foundation pit, thus it was placed in 4 independent cross blocks to ensure the construction progress and to handle the flood protection during construction and steady stress during the operation period.
Fourthly, a single-lift ship lock was employed as the navigation structure with a design head of 13.2m. Short-gallery centralized water delivery system was adopted.
Fifthly, the construction of permanent ship lock and temporary ship lock was considered together. The permanent ship lock was utilized for temporary navigation to tackle the problem of navigation during construction.