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Somthing About Hydroelectric Power Plant (2)

May 22, 2020

Hydropower stations are generally composed of four major parts: water-retaining structures (dams), flood discharge structures (spillways or gates), water diversion structures (diversion channels or tunnels, including surge shafts), and power plant buildings (including tailraces and booster stations) composition.

The main components are: hydraulic structures, hydraulic machinery equipment, power generation equipment, substation equipment, power distribution equipment, power transmission equipment and control and auxiliary equipment.

Composition and function of hydraulic structures

1. Composition of hydraulic structures

Water-retaining structure-dam discharge structure-spillway, discharge hole, overflow dam, spillway gate-inlet gate, tail gate, spillway gate

Water-using buildings——water intake and water diversion buildings (channels or tunnels, pressure steel pipes, water inlets) and workshops

2. The role of hydraulic structures

The role of the dam is to intercept water flow, raise the water level, and form a reservoir, resulting in a difference in water level between the upstream and downstream, so that the power station has the basic conditions for hydropower generation. On dam-type hydropower stations with regulated storage capacity, the dam simultaneously achieves the dual role of concentrating the river gap and regulating the flow in the river, not only serving the hydropower plant, but also having the functions of flood control, irrigation, shipping, and industrial water supply.

The role of spillway and discharge hole: to release flood, prevent flooding and ensure the safety of the dam, so it is also called flood discharge building. Some drainage structures can also be used to empty reservoirs or construction diversions. The discharge structure can be divided into two types of spillway and deep discharge channel according to the discharge method.

The role of the gate: to regulate the flow and control the flood. Gates can be divided into low head gates and high head gates according to their different locations. The water inlet gate and bottom gate for power generation belong to the high head gate, and the gate on the spillway belongs to the low head gate. From its structural division, the most common are flat gates and arc gates. The tailgate is mainly used for equipment maintenance.

The role of water-using buildings: It can be divided into water intake and water diversion buildings. It includes water intakes and water diversion channels. Its function is to lead the water in the dam to the water supply turbine generator set of the plant.

Diversion channels can be divided into: channels, tunnels (with and without pressure), pressure water pipes, aqueducts and inverted siphons. Some diversion-type hydropower stations are also equipped with pressure forebays, surge chambers or surge wells on the diversion structures.

Main workshop: the workshop used to install the hydro-generator set and its auxiliary equipment, and the assembly site for assembling and overhauling the generator set.

Auxiliary plant: a plant where power distribution equipment and its operation management facilities are installed. Auxiliary workshops generally include rooms for operation, control, testing, and management of hydropower stations, as well as rooms for operators to work and live.

Composition and function of hydraulic machinery equipment

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1. Composition of hydraulic machinery equipment Main valve turbine shaft guide bearing draft tube

2. The role of hydraulic machinery main valve: (ball valve, butterfly valve) emergency, cut off the water flow to prevent the unit from flying accident; the unit is cut off the water flow during maintenance; close the butterfly valve for a long time shutdown, reduce the amount of water leakage, save water Resources.

Turbine: According to the installation method, it can be divided into vertical type and horizontal type; according to the characteristics of water flow energy conversion, it can be divided into counterattack type (using the kinetic energy and potential energy of water fluid) and impact type (using only the kinetic energy of water flow). Counterattack type: axial flow type (fixed pulp: H: 3 ~ 50m, rotary pulp: H: 3 ~ 80m), mixed flow type (H = 30 ~ 700m), diagonal flow type (H = 40 ~ 200m), cross flow type (2 ~ 30m).

Impact type: suitable for small units with high head and small flow rate, bucket type turbine (cutting type) (40 ~ 2000m, commonly used head range 40 ~ 800m), oblique type turbine (50 ~ 400m), double-click type turbine (6 ~ 150m). The components and function volute of the hydraulic turbine: forming the hydraulic ring volume. Seat ring: bear the full weight of the unit.

Bottom ring and top cover: fixed movable guide vane and form runner room. Runner: Water energy is converted into rotating mechanical energy.

Active guide vane: control the water flow to achieve the purpose of adjusting the speed and output. Shaft: transfer mechanical energy.

Guide bearing: bear radial water thrust and control swing. Draft tube: recover energy and export water flow.

Components and functions of the generator


Main components of generator

Stator, rotor, thrust bearing, guide bearing, shaft, frame, cooler, brake.


2. The role of the main components of the generator stator: to generate induced electric potential. Rotor: generates a rotating magnetic field.

Thrust bearings: bear axial water thrust and the weight of the rotating parts of the unit. Guide bearing: bear radial water thrust and control swing. Shaft: transfer mechanical energy.

Upper frame: Install thrust bearing, upper guide bearing, slip ring, etc. Lower frame: Install the lower guide bearing and brake.

Cooler: The bearing cooler is used to cool the bearing, and the air cooler is used to cool the generator.

Brake: brake the generator when it is stopped to prevent long-term low-speed rotation to damage the thrust bearing.

Components and functions of substation equipment

1. Composition of substation equipment

Oil-immersed transformer: base, bell jar, oil pillow, iron core, winding and heat dissipation device. Dry-type transformers: iron cores, windings, cabinets and heat sinks.

2. The role of transformer equipment

Transformer: Increase AC voltage or decrease AC voltage.

1. Power distribution equipment mainly includes: circuit breaker (switch), isolating switch (blade knife), transformer, lightning arrester, bus bar, wire, etc.

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2. The role of power distribution equipment

Circuit breaker (switch): closing, carrying, and breaking the normal current and overload current of the running circuit.

Isolating switch (blade knife): It carries normal circuit current and overload current when closing, and meets the insulation distance and has a clear disconnection mark when opening.

The composition and function of power distribution equipment

Voltage transformer (PT): The high voltage is reduced to the standard voltage for protection, measurement, instrumentation and other devices. The general standard voltage is 100V.

Current transformer (CT): reduce large current to standard current for protection, measurement, instrumentation and other devices. The general standard current is 5A or 1A.

Lightning arrester: limit overvoltage to protect electrical equipment.

Bus: collect, distribute and transmit electrical energy.

Wire: Transmit electrical energy.

Composition and function of power transmission equipment

1. Composition of power transmission equipment

Lines, towers (electric poles), lightning conductors, etc.

2. Function line of power transmission equipment: transmit electrical energy. Iron tower (electric pole): fixed conductor and lightning conductor. Lightning conductor: protect overhead transmission lines

The composition and function of control equipment

1. The control equipment mainly includes:

Excitation device, speed control device, relay protection, synchronization device, automatic device, computer monitoring system, DC system, etc.

2. The role of control equipment

Excitation device: provide direct current to the generator rotor to establish a magnetic field, control the generator terminal voltage or adjust the reactive power of the unit.

Speed ​​control device: control the speed of the unit or adjust the active power of the unit.

Relay protection: monitor the normal operation of the power system. When the protected component fails, it will automatically and quickly issue a trip command to remove the faulty equipment from the system to ensure that the normal equipment continues to operate and limit the accident to a minimum. Range, improve the reliability of system operation, and ensure maximum safe and continuous power supply to users.

Synchronization device: Synchronization between different power sources. Type: self-synchronization, quasi-synchronization (automatic quasi-synchronization, manual quasi-synchronization, quasi-synchronization with lights off).

Automatic device: an automatic device that performs certain functions. Type: reclosing device, low cycle starting device, high cycle cutting device.

Computer monitoring system: Through the collection and processing of various equipment information of the power station, the functions of automatic monitoring, control, regulation and protection are realized to ensure the safe and stable operation of the equipment, and the optimized operation according to the requirements of the power system, the reasonable and full use of water energy to ensure electrical energy Quality, reduce operation and maintenance costs, improve operating conditions, and achieve unattended or fewer people on duty.

The hardware components are: workstation, server, network equipment, GPS clock, UPS power supply, local LCU, data acquisition equipment and communication equipment.

DC system: Provide reliable energy for the operation of switchgear and secondary equipment. DC system composition: battery, charging device, power distribution device.

Composition and function of auxiliary equipment

1. Composition of auxiliary equipment of hydropower plant:

Water system: technical water supply, leakage drainage, maintenance drainage. Oil system: insulating oil, lubricating oil.

Gas system: high-pressure gas, medium-pressure gas and low-pressure gas.

2. The role of auxiliary equipment in hydropower plants

Main objects: generator air cooler, generator thrust bearing bush and guide bearing cooler, turbine guide bearing cooler, main shaft seal, water-cooled transformer, water-cooled air compressor, deep well pump lubricating water, fire fighting water, etc.

Technical water supply sources: upstream reservoir (pressure steel pipe or volute, water intake in front of the dam), downstream reservoir, groundwater source, etc.

Technical water supply methods: gravity water supply, water pump water supply, mixed water supply, jet water supply.

Drainage system: prevent water accumulation and moisture inside the plant, and ensure the maintenance of the overcurrent parts of the unit and the underwater part of the plant.

Including: drainage of production water, maintenance drainage, leakage drainage, and drainage in the factory area.

Oil system:

Lubricating oil: Turbine oil, air compressor oil, mechanical oil and grease.

The role of lubricating oil: lubrication, heat dissipation, energy transmission.

Insulation oil: transformer oil, cable oil, switch oil.

The role of insulating oil: insulation, heat dissipation, arc suppression.

Gas system:

High-pressure gas system: supplying gas to the pressure tank of the oil supply pressure device.

Medium-pressure gas system: water guide bearing overhaul sealing shroud, butterfly valve water stop shroud.

Low-pressure gas system: unit shutdown brake, phase-modulated water pressure, pneumatic tools, purge gas.