水力发电机组是实现水的位能转化为电能的能量转换装置,一般由水轮机、发电机、调速器、励磁系统、冷却系统和电站控制设备等组成。
A hydroelectric generator set is an energy conversion device that converts the potential energy of water into electrical energy. It generally consists of a water turbine, generator, governor, excitation system, cooling system, and power station control equipment.
(1)水轮机:常用的水轮机有冲击式和反击式两种。
(1) Water turbine: There are two commonly used types of water turbines: impulse and reactive.
(2)发电机:发电机大部分采用同步发电机,其转速较低,一般均在750r/min以下,有的只有几十转/分;由于转速低,故磁极数较多;结构尺寸和重量都较大;水力发电机组的安装形式有立式和卧式两种。
(2) Generators: Most generators use synchronous generators, with lower speeds, usually below 750r/min, and some only have a few tens of revolutions per minute; Due to low rotational speed, there are many magnetic poles; The structural size and weight are both large; There are two installation forms of hydroelectric power units: vertical and horizontal.
(3)调速和控制装置(包括调速器和油压装置):调速器的作用是调节水轮机转速,以保证输出电能的频率符合供电要求,并实现机组操作(开机、停机、变速、增、减负荷)及安全经济运行。为此,调速器的性能应满足快速操作、反应灵敏、迅速稳定、运行、维修方便等要求,它还需要可靠的手动操作及事故停机装置。
(3) Speed regulation and control device (including speed governor and oil pressure device): The function of the speed governor is to regulate the speed of the water turbine to ensure that the frequency of output electrical energy meets the power supply requirements, and to achieve unit operation (startup, shutdown, speed change, load increase, and decrease) and safe and economic operation. Therefore, the performance of the governor should meet the requirements of fast operation, sensitive response, rapid stability, convenient operation and maintenance, and it also requires reliable manual operation and emergency shutdown devices.
(4)励磁系统:水力发电机一般为电磁式同步发电机,通过对直流励磁系统的控制可实现电能的调压、有功功率和无功功率的调节等控制,以提高输出电能的质量。
(4) Excitation system: Hydraulic generators are generally electromagnetic synchronous generators. By controlling the DC excitation system, voltage regulation of electrical energy, active and reactive power regulation, and other controls can be achieved to improve the quality of output electrical energy.
(5)冷却系统:小型水力发电机的冷却主要采用空气冷却,以通风系统向发电机定、转子以及铁心表面进行冷却。但随着单机容量的增长,定、转子的热负荷不断提高,为了在一定转速下提高发电机单位体积的输出功率,大容量水力发电机采用了定、转子绕组直接水冷的方式;或者定子绕组用水冷,而转子用强风冷却。
(5) Cooling system: Air cooling is mainly used for the cooling of small hydroelectric generators, and the ventilation system is used to cool the stator, rotor, and iron core surfaces of the generator. However, with the increase of single machine capacity, the thermal load of the stator and rotor continues to increase. In order to increase the output power of the generator per unit volume at a certain speed, large capacity hydraulic generators adopt direct water cooling of the stator and rotor windings; Alternatively, the stator winding can be cooled by water, while the rotor can be cooled by strong wind.
(6)电站控制设备:电站控制设备主要以微机为主,实现水力发电机的并网、调压、调频、功率因数的调节、保护和通信等功能。
(6) Power station control equipment: The power station control equipment mainly uses microcomputers to achieve functions such as grid connection, voltage regulation, frequency regulation, power factor regulation, protection, and communication of hydraulic generators.
(7)制动装置:额定容量超过一定值的水力发电机均设有制动装置,其作用是在发电机停机过程中,当转速降低到额定转速的30%~40%时,对转子实施连续制动,以避免推力轴承因低转速下油膜被破坏而烧损轴瓦。制动装置的另一作用是在安装、检修和起动前,用高压油顶起发电机的旋转部件。制动装置采用压缩空气进行制动。
(7) Braking device: Hydraulic generators with a rated capacity exceeding a certain value are equipped with a braking device. Its function is to continuously brake the rotor when the speed drops to 30% to 40% of the rated speed during the shutdown process of the generator, in order to prevent the thrust bearing from burning the bearing pads due to the damage of the oil film at low speeds. Another function of the braking device is to use high-pressure oil to lift the rotating parts of the generator before installation, maintenance, and start-up. The braking device uses compressed air for braking.
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