Download
1 / 38
E N D
GENERATOR COOLING SYSTEM Akash Nandan Deputy Manager Operation 600
WHY GENERATOR COOLING ? Thermal Management: Cooling systems are crucial for managing the heat produced by generators. Without effective cooling, excess heat can lead to overheating, reduced efficiency, and potential damage to generator components. Performance and Reliability: Proper cooling ensures that generators operate within their designed temperature ranges, which enhances performance, reliability, and safety. Effective cooling systems also help prevent thermal stress and fatigue on the generator components. Safety: Cooling systems, including hydrogen cooling, contribute to the overall safety of power generation facilities by preventing overheating and potential fire hazards. Operational Efficiency: By maintaining optimal operating temperatures, cooling systems help generators achieve better fuel efficiency and lower operational costs, contributing to the economic and environmental benefits of power generation.
TYPES OF GENERATOR COOLING SYSTEM 1. Air cooling 2. Water cooling 3. Hydrogen cooling
AIR COOLED GENERATOR Open Ventilated Air Cooled: In the open-vent system, atmospheric air is drawn directly through filters passes through the generator and the exhaust is released back into the atmosphere. In this method of cooling, an exhaust system is used which helps to receive the cool air from the atmosphere and released the hot air back into the atmosphere. The cool air helps to cool the entire system. During this process, the air becomes very hot so it is released back into the atmosphere.
AIR COOLED GENERATOR contd… Totally Enclosed Water to Air Cooled-TEWAC: In the TEWAC design, the air is circulated within the generator, passing through frame-mounted air to water heat exchangers. It is an enclosed system, the air is re-circulated inside to cool the internal parts of the generator. The air is enclosed in the system and just keeps re-circulating in the internal parts of the generator. The hot air is cooled by using water heat exchangers. Which helps to maintain the temperature of the machine. In this method, the same air is used again and again for cooling the circuit.
WATER COOLED GENERATOR Generators with more than 400 MVA ratings require a more efficient cooling method. For this Hydrogen-Water CoolingSystem is used. Water Cooled Stator: The Stator windings are directly cooled by water, supplied by a closed-loop auxiliary system, which flows through hallow copper strands located in the stator windings.Stator Cooling Water System is a closed-loop auxiliary system that supplies high purity water to the generator windings to remove heat generated by electrical losses. It also maintains the temperature of the cooling water.
HYDROGEN COOLED GENERATOR • The Rotor is cooled with Hydrogen gas that passes diagonally through the holes machined in rotor copper to the bottom of the coil. Then the hydrogen travels up the field coil diagonally to the rotor surface where it is discharged into the gas gap. The cooling path provided by the fans is mounted at each end of the generator rotor. • The advantage of using Hydrogen as a cooling media is that it provides efficient cooling due to its low density and high thermal conductivity. • A hydrogen cooled generator has greater efficiency and smaller size compared with an air-cooled generator of an equal rating
HYDROGEN COOLING SYSTEM ROTOR COOLING SYSTEM
Definition of Hydrogen Cooling • Hydrogen Cooling is a method used to dissipate heat in electrical generators by utilizing hydrogen gas. Hydrogen is used due to its high thermal conductivity, which makes it an effective medium for transferring heat away from generator components. • In this cooling process, hydrogen is circulated through the generator to absorb heat produced during operation. The heated hydrogen is then directed to a cooling system where it releases the heat and is recirculated.
Brief Overview of Its Application in Generators • High-Performance Generators: Hydrogen cooling is primarily used in large, high-capacity electrical generators, such as those found in power plants. These generators operate at high temperatures and require efficient cooling systems to maintain optimal performance and prevent overheating. • Improved Efficiency: The use of hydrogen cooling helps maintain the generator's temperature within an optimal range, which enhances efficiency and extends the lifespan of the equipment. • Energy Sector Adoption: Hydrogen-cooled generators are commonly found in large-scale power generation facilities, including fossil fuel and nuclear power plants, due to their ability to handle the significant heat loads generated.
Explanation of the Cooling Mechanism • Hydrogen Circulation : Hydrogen gas is circulated through the generator, specifically through a system of channels or ducts that surround the generator components such as the stator windings . As hydrogen flows through these channels, it absorbs heat from the generator components due to its high thermal conductivity. • Heat Absorption : The hydrogen gas, being an efficient heat transfer medium, picks up heat from the generator's internal components, including the rotor and stator.The heat absorbed by the hydrogen raises its temperature, making it less dense. • Heat Transfer : The heated hydrogen gas is then directed to a heat exchanger or cooling system where it releases the absorbed heat . This process involves transferring the heat from the hydrogen to another medium, such as water or air, or directly to the environment. • Recirculation : After releasing its heat, the cooled hydrogen gas is recirculated back through the generator to absorb more heat, maintaining a continuous cooling cycle.
Why Hydrogen ? • High Thermal Conductivity ( 7-10 Times better than Air ) Hydrogen has one of the highest thermal conductivities of any gas. This means it can absorb and transfer heat more effectively than other gases, making it ideal for cooling high-performance generators . Improved heat transfer efficiency leads to better temperature control and enhanced overall performance of the generator. • Lower Density ( 1:14 to Air ) Reduced Generator Weight: Hydrogen is much less dense than air or water, which means that hydrogen-cooled generators can be lighter and more compact. This is beneficial for both the design and installation of large-scale generators.
Why Hydrogen ? • Improved Safety: Reduced Fire Risk: Hydrogen has a high ignition point compared to many other gases. When managed properly, it presents a lower risk of fire or explosion compared to flammable coolants like certain oils. Inert Nature: Hydrogen does not chemically react with most materials used in generators, reducing the risk of corrosive damage. • High Efficiency at High Temperatures: Optimal Performance: Hydrogen cooling is particularly effective in high-temperature environments, such as those found in large power generators. It maintains efficiency and performance even as operational temperatures increase. Thermal Management: Effective thermal management ensures that generator components operate within safe temperature limits, preventing overheating and potential damage.
HYDROGEN PURITY • Hydrogen purity is crucial in hydrogen-cooled generators for several important reasons, primarily related to efficiency, safety, and the longevity of the generator. • For maintaining Hydrogen Purity several measures are taken which primarily include the use of Hydrogen Driers. • Apart from this regular purging is done to ensure the purity of hydrogen gas is optimum.
WHY hydrogen purity is essential…?? Optimal Cooling Performance • Superior Heat Transfer: Hydrogen is used in generators because of its excellent heat-transfer properties. It has the highest thermal conductivity of any gas, making it ideal for efficiently removing heat from the generator's components (e.g., the rotor and stator). • Impurity Effects: When hydrogen contains impurities (e.g., air, moisture), its thermal conductivity decreases, reducing the cooling efficiency. This can lead to overheating, which in turn reduces the generator’s operational efficiency and increases the risk of damage.
WHY hydrogen purity is essential…?? Reduced WindageLosses • Low Density: Hydrogen has a much lower density than air, which results in lower windage losses (frictional losses from moving gas). This is important because lower windage means less drag on the rotating parts of the generator, leading to improved efficiency. • Impurities Increase Windage: If the hydrogen is impure and mixed with heavier gases like air, the density increases, leading to higher windage losses and reduced mechanical efficiency.
WHY hydrogen purity is essential…?? Minimized Risk of Explosive Mixtures • Safety Concern with Oxygen: One of the major safety concerns in hydrogen-cooled generators is the potential for an explosive mixture of hydrogen and oxygen. Hydrogen is highly flammable, and if air (which contains oxygen) enters the system, it can create a dangerous situation. • High Purity Hydrogen is Safer: Maintaining high hydrogen purity (typically above 95% or higher) helps to minimize the risk of forming a flammable or explosive mixture with oxygen. In case of a leak or system malfunction, higher purity means the hydrogen won’t easily mix with oxygen in concentrations that could ignite.
WHY hydrogen purity is essential…?? • Moisture as an Impurity: Moisture, introduced by air or poor hydrogen quality, can cause condensation inside the generator. This leads to corrosion of internal components, especially metal parts, which can degrade the generator's efficiency and lifespan. • Impact on Electrical Insulation: Water also has a negative effect on the electrical insulation of generator components. High hydrogen purity ensures low moisture content, maintaining the insulation's integrity and preventing potential short circuits or electrical failures.
DEW POINT • The dew point is the temperature at which air becomes saturated with water vapor, causing the vapor to condense into liquid water. • In other words, it's the temperature at which air can no longer hold all of its moisture in the form of gas, and the water vapor starts to condense into dew Key points about the dew point: • High dew point means the air contains a lot of moisture. When the air cools to that temperature, water will start to condense. • Low dew point means the air is dry and has less moisture content. • For example, if the dew point is 15°C and the air temperature drops to 15°C, condensation (dew) will form because the air has reached 100% relative humidity.
Dew Point Matters … Prevention of Moisture Formation • Hydrogen's Role in Cooling: In hydrogen-cooled generators, hydrogen gas is used due to its excellent heat-transfer properties and low density, which reduces windage losses. However, if the dew point is too high (indicating excessive moisture), water vapor can condense inside the generator. • Electrical Insulation: When moisture condenses, it can interfere with the electrical insulation properties of the generator components. Water is conductive, and any moisture in the system can cause electrical short circuits, potentially damaging the generator.
Dew Point Matters … Prevention of Corrosion • Hydrogen Purity and Corrosion: High moisture levels lower the purity of hydrogen, making the system more prone to corrosion. Condensed water can accelerate the corrosion of metallic parts within the generator, especially the rotor and stator, affecting the generator's lifespan. Improved Efficiency • Thermal Efficiency: Moisture in the hydrogen can reduce its cooling efficiency. Hydrogen’s thermal conductivity is reduced when moisture is present, leading to less efficient cooling. This can cause the generator to overheat, reducing its operational efficiency and potentially leading to outages or even equipment failure.
Safety and Handling of Hydrogen Cooling Systems • Flammability : Hydrogen is highly flammable and can form explosive mixtures with air. It has a wide flammability range, from 4% to 75% by volume in air. • High Ignition Energy: It requires a relatively small amount of energy to ignite, which makes proper handling crucial. • Storage : Hydrogen is stored as a gas in pressurized tanks or in liquid form at very low temperatures. Storage tanks must be robust and well-maintained to prevent leaks.
MEASURES TO BE TAKEN Leak Detection : Install hydrogen detectors and alarms in areas where hydrogen is used or stored. These sensors can detect leaks and trigger alarms to alert personnel. Regular Inspections: Conduct routine inspections and maintenance of hydrogen storage and handling equipment to identify and address potential leaks early. Ventilation Systems : Ensure that areas containing hydrogen are well-ventilated to disperse any accidental leaks and prevent the accumulation of hydrogen in enclosed spaces.
MEASURES TO BE TAKEN CONTD.. • Training and Procedures:Provide comprehensive training for personnel on the safe handling and storage of hydrogen, including emergency response procedures. • Safety Protocols: Develop and implement safety protocols for dealing with hydrogen, including handling procedures, emergency response plans, and evacuation routes. hydrogen safely involves understanding its properties, implementing robust safety measures, and adhering to industry regulations and best practices. Proper leak detection, effective ventilation, and compliance with standards are crucial for minimizing risks and ensuring the safe operation of hydrogen cooling systems.
PRIMARY WATER COOLING SYSTEM STATOR COOLING SYSTEM
Introduction to Stator Water Cooling • Stator Cooling : Stator cooling refers to the process of managing and dissipating the heat generated within the stator of an electrical generator. The stator is a stationary part of the generator that houses the windings through which electrical current flows, generating significant heat due to electrical resistance and magnetic losses. • Cooling Mechanism: Effective cooling systems are essential to maintain the stator's temperature within safe operational limits, thereby ensuring optimal performance and preventing damage.
PURPOSE • Why Cooling is Necessary for the Stator : The stator experiences substantial heat generation due to electrical resistance in the windings and core losses from the magnetic field. • Prevent Overheating: Without proper cooling, excessive heat can lead to overheating, which can degrade insulation, reduce the efficiency of the generator, and potentially cause failures or even catastrophic damage. • Ensure Efficiency: Effective cooling helps maintain the electrical resistance of the stator windings at optimal levels, ensuring that the generator operates efficiently and reliably. • Extend Equipment Life: By controlling the temperature, cooling systems help prolong the lifespan of the stator and other critical components, reducing maintenance needs and operational costs.
COOLING MECHANISM • Circulation: Water is pumped through a network of tubes or cooling jackets that are in close contact with the stator windings. This circulation ensures that water flows uniformly around the stator, maximizing contact with the heat-producing components. • Heat Absorption: As the water flows through the cooling jackets or tubes, it absorbs heat generated by the stator windings due to electrical resistance and magnetic losses. The water’s high specific heat capacity allows it to absorb a significant amount of thermal energy from the stator. • Heat Exchange: The heated water is then directed to a heat exchanger, where the absorbed heat is transferred from the water to another medium, such as air or an external cooling system.This step is essential for removing the absorbed heat from the water so that it can be cooled down and reused in the system. • Recirculation: After releasing the heat in the heat exchanger, the cooled water is pumped back to the stator to continue the cooling process. Recirculating the cooled water ensures a continuous cooling cycle, maintaining the stator at an optimal operating temperature.
Challenges of Water Cooling • Risk of Corrosion: • Description: Water, particularly when it contains impurities or is not properly treated, can lead to corrosion of metal components within the cooling system, such as cooling jackets, tubes, and heat exchangers. • Causes: Corrosion can be accelerated by factors such as acidic or alkaline pH, high chloride content, and the presence of dissolved gases like oxygen. • Impact: Corrosion can lead to leaks, reduced thermal efficiency, and potential failures of the cooling system components.
Challenges of Water Cooling contd.. • Mitigation Measures: • Corrosion Inhibitors: Use of chemical additives to prevent or reduce corrosion. • Material Selection: Use of corrosion-resistant materials for components in contact with water. • Regular Inspections: Routine checks for signs of corrosion and timely maintenance or replacement of affected components.
Challenges of Water Cooling contd.. • Need for Proper Water Treatment: • Description: Maintaining high water quality is essential to prevent scaling, fouling, and other issues that can impair system performance. • Treatment Methods: Includes filtration, chemical dosing, and deionization to control hardness, pH, and contaminant levels. • Monitoring: Regular water analysis is required to ensure that treatment processes are effective and to adjust treatments as necessary.
THANK YOU Any Questions …??
