Liao Tong Huang Runlan (Zhaoqing Hejiang Electric Power Development Co., Ltd., Fengkai County, Guangdong 526500) 1 Overview of Power Station Duping Power Plant is located in Duping Town, Fengkai County, Guangdong Province, Hejiang River Basin, a tributary of Xijiang River. It is a limited development of Hejiang Power in Zhaoqing City. The company's upstream first-stage power station for the cascade development of the Guangdong section of the Hejiang River Basin. The power plant has two 15MW large-bulb tubular flow units, all of which are manufactured by Tianjin Power Generation Equipment Factory. The first unit was put into operation in November 1992, and the second unit was put into operation in April 1993. The largest type of cross-flow synchronous generator set. 2 Generator and Fan Cooling Introduction The generator model of Duping Power Plant is SFWG15 -68/5400, rated capacity S/P=16304kVA/15000kW, stator rated voltage is 6300V, stator rated current is 1494A, rotor rated voltage is 210V, The rated current of the rotor is 1000A. The generator stator winding, stator core and rotor windings are all Class F insulated. The maximum temperature is allowed to be 140. The control temperature is 120. The generator is cooled by closed air forced circulation axial ventilation. Driven by a centrifugal fan, the hot air is cooled by heat exchange through the metal shell of the unit bulb surface and the runner water. The forced circulation of the cooling air is achieved by the addition of six centrifugal fans. Six centrifugal fans are arranged between the arms of the rotor on the upstream side of the rotor. The original centrifugal fan has a diameter of 450 mm, the motor power is 18.5 kW, and the rated current is 35.5 A. During normal operation, the total operating current of the six fans is determined. 72A. 3 Generator Cooling Fan Circuit Reconstruction The generator cooling fan was originally designed to automatically operate when the unit was turned on. When the oil switch was turned off for a few minutes, the cooling fan automatically stopped running. Since the cooling effect of the fan on the generator is very important, it is stipulated that all six centrifugal fans of the generator should be put into operation in 30 operations. When one of the fans fails, the unit is allowed to run under load. When two or more fans fail, they must be shut down immediately. Therefore, the control loop of the generator cooling fan is also required to be particularly strict. Due to the large current of the generator, the heat generated during operation is also very large. The original centrifugal fan cannot meet the full-load operation of the unit, especially the need for full-load operation of the unit in summer. In order to improve the cooling effect of the generator, in December 1996, the aircraft's winter overhaul was used to increase the fan's blades from 450mm to 500mm, and the coupling between the motor and the fan was replaced. Considering that the load of the motor is not increased much, and the operating current after the fan blade is increased by a single test, the rated current is still not reached. In order to save the cost, the motor is not replaced, and the total operating current of the six fans is increased after the replacement of the blades. To 94A. Considering that the fan is directly started, the starting current is 7 times of the rated current, the motor power of each fan is 18.5kW, the rated current is 35.5A, and 6 fans are started at the same time. The starting current reaches 1500A. The impact is great. In the actual operation before the control loop is reformed, the manual start-by-stage start mode is adopted for a long time, and the manual cut is performed after the stop. In this way, the labor intensity of the operating personnel is increased, and it is easy to cause misoperation. In order to simplify the operating procedures of the operators, increase the reliability, improve the automation level, reduce the labor intensity, shorten the boot time, and restore the automatic control of the cooling fan, we have specially changed the control loop of the fan. The original design unit start relay 1Q and the oil switch auxiliary contact relay 4Z1 start 6 fans in parallel, 4Z1 power loss (ie, the oil switch is off), 4Z1 normally closed contact, through the fan magnetic starter 6Q start 6S relay, 6S Delay the normally closed contact, 12Z, 13Z relay power loss, disconnect the motor power, fan (down to page 47) is 13%. The low rural electrification rate provides space for the development of micro hydropower projects. The electricity forecast report prepared by the National Electricity Authority of Nepal (NEA) shows that by 2020, 30% of households in the country will be connected to the grid. The rural electrification construction in Nepal will be extended by the national grid in the low-lying areas of the south, which will account for 40% of the country's population in 2005. In the mountainous areas with inconvenient transportation, it will be built through the construction of isolated power grids. Realize electrification. Nepal has about 80,000 MW of hydropower available. In terms of resource utilization and national electrification, political and expert views are divided into two camps. One side supports the vigorous development of large-scale hydropower stations to export electricity to India, accompanied by electrification of the national grid. The other party argued that the fundamental focus of the hydropower policy should be stopped (on page 30) (after the unit is connected to the grid, the 4Z1 and 1Q normally open contacts are disconnected). Now use the unit start relay to restart the No. 2, No. 4 and No. 6 fans. After the start of the power switch, the oil switch is closed, and the oil switch auxiliary contact relay relay starts the No. 1, No. 3, No. 5 fans, so that it can be successfully The starting current is halved. The machine is cut off after a delay (see and). The development of micro-hydropower. The technical cost of micro-hydropower is relatively low, and it can rely on domestic production technology, which is very suitable for supplying electricity to isolated mountain villages. 63 of the 75 regions in Nepal have potential for hydropower development. Since the 1970s, with the support of international NGOs, Nepal has successfully established an industrial sector to manufacture and install all components except micro-hydro power units with a capacity of less than 300 kW. The government supported the development of micro hydropower through different technical and financial plans. In Nepal, the development potential of economically viable micro-hydropower is expected to be approximately 42MI per kW US 1,200~US1,600 (converted at the US dollar exchange rate of 1993). After the generator cooling fan circuit is rebuilt, the specific working process of the fan control circuit is as follows: after the unit is turned on, the start relay 1Q is normally open and connected, and the 12Z is ​​started and maintained. The fans of No. 2, No. 4 and No. 6 are started by 12Z; The speed intermediate relay 4Z1 is normally open and close, and the 1st, 3rd, and 5th fans are started by 13Z; after the unit is stopped, the generator brake intermediate relay 5Z1 is combined, 6S is started by 6Q, and 12Z, 13Z loop is disconnected after delay, 6 sets The fan is automatically stopped, and the 16Z and 6S are added in parallel, so that after the fan is stopped, the 6S remains charged, and the normally closed contact that is disconnected by the 6S delay is disconnected, and the fan starting circuit is cut off. 4 Summary This transformation has five characteristics: 1) reduce the starting current of the generator cooling fan, reduce the impact on the plant power, through the actual measurement, the starting current after the modification is about 750A, about half of the change. 2) Change the original unit disengagement stop fan to the unit stop brake and cast the talent stop fan, so as to cool the generator more effectively. 3) Reduce the labor intensity of the operating personnel, reduce misuse, and improve the level of automation. 4) Shorten the boot time. 5) Through the transformation, the problem of insufficient output of the unit due to excessive temperature rise is solved, the loss of water resources (especially the flood season) is reduced, and the economic benefits of the power plant are increased. 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