The Turbine Generator Hydrogen Oil Water System of Shanghai Turbine Generator Co., Ltd. is a technology introduced by Siemens AG of Germany. According to the requirements of the technical agreement, the hydrogen-hydrogen water system of the generator of the gas turbine is designed and manufactured by the Chinese; the design technology of the transfer company of Siemens includes all equipment drawings, specifications of purchased parts and training of technicians. The first hydrogen water water unit has been successfully designed, manufactured and tested. Among them, the sealing oil supply device and the stator cooling water supply device, on the simulation test device of the manufacturer, meet the technical requirements of Siemens through various analog type tests for several weeks. Since the hydrogen oil water system of the gas turbine generator is basically similar to the hydrogen oil water system of the ordinary fire generator, the hydrogen oil water system design of the Siemens 300-500 MW generator is also a typical design.
2 System Introduction 2.1 Hydrogen system The hydrogen system is mainly used for the charging and discharging operation of the generator, and monitors the hydrogen-related parameters such as pressure, purity, flow rate and dew point of the hydrogen in the generator. Some equipment that implements functions through a hydrogen pipeline, such as a hydrogen dryer, an insulation superheat monitoring device, and a liquid leakage detection device, are also included in the hydrogen system.
1 Hydrogen supply from the hydrogen supply system generator hydrogen supply to the hydrogen manifold. The hydrogen in the bottle is first reduced to a moderate level by a first stage pressure reducing device on the hydrogen supply bus, and then the hydrogen pressure is reduced to the pressure required by the generator through a second stage pressure reducing device on the hydrogen control unit. According to the IEC34 specification, a safety valve is provided downstream of the hydrogen pressure reducing valve or pressure reducing valve to prevent damage to the valve or equipment due to excessive pressure. The outlet of the safety valve is connected to the emptying pipe. The hydrogen supply system has a secondary pressure reducing device, and the pressure is relatively stable when the hydrogen flow rate is small.
2 Carbon dioxide system and carbon dioxide evaporator to prevent hydrogen explosion When charging and discharging hydrogen, hydrogen can not be in direct contact with air. When charging and discharging hydrogen, the generator must first be replaced with an intermediate inert gas. The typical design of Siemens uses argon as the intermediate inert gas. With argon, it can be quickly inflated directly into the generator without heating. Carbon dioxide may form corrosive carbonic acid gas after contact with moisture; argon gas will not, and may remain in the generator for a long time if necessary.
If carbon dioxide is used, the gas source is in liquid form in the cylinder. Cylinders must be constructed with a straw to ensure that carbon dioxide is completely discharged in liquid form. The liquid carbon dioxide pressed by the bottle flows into the carbon dioxide evaporator (forcer) through a high-pressure hose and a valve to expand into a gas.
The Siemens Carbon Dioxide Evaporator is a heat exchanger with two parallel and alternating operations. Carbon dioxide must enter the evaporator in liquid form, otherwise the upstream pipeline may create ice plugs at high flow rates. The liquid carbon dioxide expands into a gaseous carbon dioxide after passing through the evaporator. There is a safety valve at the high pressure end of the evaporator to prevent excessive system pressure; the outlet has a pressure relief valve to provide the pressure required by the generator.
2.1.3 Hydrogen Control Device The hydrogen control device is an integrated device that combines a second-stage hydrogen pressure reducing valve, a gas displacement valve, a hydrogen flow meter, a pressure transmitter, a gas purity meter, and the like, as shown.
The gas displacement valve is used to switch when charging or discharging carbon dioxide or hydrogen to the generator. A graphical signage is provided on the device to indicate the position of the valve during each inflation phase for ease of operation. The device is provided with a detachable connecting tube, which can disconnect the air connecting tube when charging hydrogen or disconnect the hydrogen connecting tube when filling the air to prevent hydrogen and air from mixing to form an explosive gas.
(4) According to the IEC specification, there are two independent three-range (carbon dioxide-air; hydrogen-carbon dioxide; hydrogen-air) gas purity meter. Two gas purity meters work simultaneously and are in contrast to reliably monitor the hydrogen purity in the generator.
4 The dew point temperature in the hydrogen dryer generator must be higher than the dew point temperature of the cold hydrogen, otherwise it will bring great harm to the components in the generator. The hydrogen dryer of Siemens is a single-tower adsorption dryer. The desiccant is regenerated with heated air and the regeneration process is manually operated. In the domestic design, the adsorption type hydrogen dryer with double tower closed circulation regeneration is used, which is fully automatic and does not consume hydrogen at all. There are two dew point meters on the dryer, one is installed at the inlet of the dryer to monitor the dew point inside the generator, and the other is located at the outlet of the dryer to monitor the drying effect of the dryer.
5 Leakage detection device The main outlet of the gas turbine is located at the top of the generator. Therefore, only two leakage detection switches (one for each of the steam and the excitation end) are provided in the system. The two switches are combined into one device. The leakage switch is an electronic tuning fork switch that does not cause mechanical failure.
6 Other monitoring instruments According to user requirements, the system is also equipped with insulation overheat monitoring device and online hydrogen leakage monitoring device.
2.2 Sealing oil system The two ends of the generator rotor are sealed by a shaft seal to seal the hydrogen in the generator. The shaft seal uses pressurized oil to prevent the generator from flowing out of the hydrogen while preventing the outside air from entering the generator. As long as the pressure of the seal oil at the generator seal ring is greater than the pressure of the hydrogen, the hydrogen will not flow out. Sealing oil comes from a separate sealed oil supply. The oil source of the seal oil is the same oil system as the oil source of the bearing oil. The sealing oil system consists of a sealing oil supply device, a range hood, and an empty side tank (sealed oil storage tank). 2.2. 1 Sealing oil supply unit Siemens' sealing oil supply unit uses a single-flow sealing oil system with a vacuum treatment system. Two AC sealed oil pumps and one DC oil pump are installed in the device. The oil-hydrogen differential pressure valve, oil cooler, and filter are redundantly set. The structural arrangement of the device is easy to operate and maintain, as shown.
Sealing oil circuit: During normal operation, the oil pump 1 draws oil from the sealing oil tank, passes through the cooler and the filter and enters the sealing ring. The oil entering the sealing ring flows to the hydrogen side and the air side through the gap between the sealing ring and the rotating shaft. The oil flowing to the air side returns directly to the sealing tank together with the bearing oil. The oil flowing to the hydrogen side is first returned to the defoaming tank under the generator end cover and back to the hydrogen side return tank. When the main seal oil pump 1 is out of operation due to a mechanical or electrical failure, the main seal oil pump 2 is automatically started. When the above two main oil pumps are out of operation, the DC backup oil pump automatically starts without disturbance.
Sealing oil pressure regulation: The first stage pressure regulation, the outlet of the sealing oil pump has a self-operated pressure control valve similar to the overflow valve. Based on the pressure setting of the valve and the feedback of the signal pressure (pump outlet pressure signal), the control valve controls the amount of pump bypass oil to maintain the set pressure at the pump outlet. For the second stage pressure regulation, the pressure required for the generator seal oil inlet is controlled by the differential pressure regulating valve. In order to ensure the reliability of the system, two differential pressure regulating valves are set, which are set at different pressure setting values. When working normally, one job, one standby. According to the setting of the differential pressure valve, the differential pressure valve controls the flow to the sealing tile to maintain the pressure of the sealing oil. When the hydrogen pressure and the seal oil pressure signal are unbalanced, the resulting differential pressure pushes the valve core open or closed. When the hydrogen pressure rises or the seal oil pressure decreases, the valve core is pushed downward, the valve is opened to increase the flow rate, and the seal oil pressure is increased. Conversely, pushing the valve core up, closing the valve, reducing the flow, and reducing the seal oil pressure.
Hydrogen side oil return system: Seal the oil hydrogen side back oil, first return to the defoaming tank. In the defoaming tank, the flow rate of the oil is slowed down, the hydrogen contained in the oil is precipitated, and the foam of the oil is eliminated. After the hydrogen side oil of the steam and the excitation end meets outside the generator, it flows to the hydrogen side return tank. There is a float valve inside the box to control the oil level in the tank and prevent hydrogen from leaking out. The oil in the hydrogen side return tank and the oil return to the empty side, and flow into the vacuum tank through the float valve. If there is too much oil flowing to the vacuum tank, the excess oil will overflow into the empty side return tank. A small amount of hydrogen will not cause harm in the empty side return tank, because the empty side return tank is connected to the range hood system to ensure continuous exhaust of the empty side return oil.
Sealing tile floating oil: In order to ensure that the sealing tile moves freely at high hydrogen pressure, the sealing tile floating oil system is installed in the system. When the generator is in normal operation, the floating oil system must be put into operation.
The floating oil is controlled by the differential pressure before the generator seal oil inlet. The floating oil of the steam and the excitation end is controlled by a differential pressure valve and a flow meter. When the control valve exits for any reason, the bypass valve can be manually adjusted and the flow meter can be observed to control the floating oil.
The 2-row hood is continuously vented due to hydrogen leaking into the bearing chamber or accumulating in the vacuum tank to prevent hydrogen from entering the turbine room or lubricating oil system. The exhaust gas is discharged directly from the exhaust pipe through the relevant pipeline to the outside of the turbine room.
2 sets of hoods, spare for each other. The range hood system from Siemens is a spare part that is assembled on site by the user. The domestic design is an assembled structure with two micro pressure transmitters. In normal operation, one machine works, the other is spare, and can be switched automatically.
The negative pressure inside the bearing chamber can effectively prevent the lubricating oil mist from spreading into the turbine room through the oil block. At the same time, when the sealing oil system fails, the range hood also discharges hydrogen leaking into the bearing chamber out of the factory. The mixture of bearing oil and seal oil flowing into the seal oil tank may contain a small portion of hydrogen, which is also discharged by the range hood. A vacuum pump is used to discharge air and hydrogen from the seal oil. This system is also connected to the range hood.
3 Air side return tank Siemens' empty side return tank is called sealed oil storage tank. The volume of this tank is larger than that of Westinghouse. Therefore, the sealing oil system can work independently from the lubricating oil system within a certain period of time. Generator commissioning phase. The air-side return tank outlet has a *U*-shaped tube to prevent hydrogen from the generator seal oil from entering the turbine lubricating oil system. The empty side return tank is connected to the range hood to discharge the separated hydrogen from the oil out of the system.
2.3 Stator coil cooling water system The stator water system is used to cool the stator coils. The rotor, core, phase-to-phase and outlet bushings of the generator are cooled with hydrogen, and only the stator bars are cooled with water. The conduit for water passing through the wire rod is made of non-magnetic stainless steel material, and the system does not cause copper ion corrosion. Therefore, there is no ion exchanger in the system, and the system adopts a continuous small amount of water-repellent-overflow structure. The stator water system is a closed circulation system, which includes a stator coil cooling water supply device (), a water tank, and a monitoring instrument on the generator water outlet pipe.
Stator water supply system loop: The stator cooling water passes through a high-precision filter and then leads to the inlet manifold at the bottom of the generator and flows into the stator coil. Hot water flows from the top of the generator from the manifold at the other end of the generator back to the water supply. This design ensures that there are no gases in the water pipes and bars. According to the user's request, the generator's inlet and outlet ports are equipped with backwashing valves, which can backwash the stator coils when the generator is stopped.
Water pump: There are 2 identical pumps in the system, which are reserved for each other.
Filter: The cooling water must be pure and free of impurities to avoid causing fouling or blockage of the coil. To this end, the system is equipped with a high-precision filter. The bypass filter is not allowed during operation. A differential pressure transmitter is provided at both ends of the filter to give an alarm when the filter is fouled.
Cooler: The stator water system is a closed system. The Siemens standard is designed as two coolers, each bearing 50% of the load. Currently, the localization design is two 100% coolers. The cooler is a plate cooler, and the part in contact with water is a stainless steel tube. At the hot water end of the cooler, there are two small tubes in parallel as the exhaust pipe, and a small part of the water with bubbles flows through the exhaust pipe to the water tank and is deposited on the top of the water tank.
Stator water tank: The stator water tank is arranged at a position higher than the generator, and its function is to buffer the volume change caused by the temperature change of the cooling water, discharge excess water in the system, and remove the water in the water. The water in the main waterway is brought into the water tank through a small flow of water in the water tank. Drainage and venting are simultaneously carried out through a water-filled U-tube. The U-tube automatically fills the hydration system, so it is not necessary to monitor the U-tube. Considering that a small amount of hydrogen may enter the water system, the water tank pressure will increase and the water level will decrease. However, due to the siphon action of the drain pipe, the gas in the water tank can be discharged, so that the water tank maintains a certain pressure. The system is equipped with a nitrogen pipe to replace the air in the tank.
Monitoring instrument: There are three flow transmitters on the generator water outlet pipe to monitor the stator water flow and form a “three take two†water cut protection signal. In addition, a temperature sensor is also provided to monitor the outlet water temperature of the coil.
3 Hydrogen oil water system control Compared with the large number of 300, 600 MW generators currently put into operation, Siemens' hydrogen engine oil water control system makes full use of the computer system of the power plant to control and monitor, and the performance is better. At present, most generators use the pressure/pressure difference switch signal on the sealed oil pump. The operator of the main control room only knows the opening or closing of the oil pump from the display. The switching between the oil pumps is directly controlled by the switch, and the computer data acquisition system ( The historical content recorded on the DAS) is only the time when the switch is turned on or off, and does not fully reflect the working state of the oil pump.
In addition, the general oil pump is about 1.3 MPa during normal operation, and the oil pump output pressure is reduced due to oil pump wear, seal failure, increased seal oil quantity, drift of the safety valve set value of the oil pump outlet, and insufficient oil supply. When the alarm signal has not been activated, the personnel in the main control room cannot know the hidden danger of the accident and its development process in time. If the transmitter is used instead of the switch, in addition to setting the alarm signal on the computer, history, real-time display, multi-channel control, unit protection and other functions can be set, and the process of fault change can be seen at a glance.
Similarly, the alarm of the differential pressure switch on the filter is also a development process in which the filter is gradually blocked. If the operator knows this process in time, you can understand the water/oil quality conditions and prepare and respond in advance. Such a function can only be achieved by the differential pressure switch at both ends of the filter. If an analog signal (pressure difference transmitter) is set, other analog signals such as liquid level and flow rate are treated in the same way.
With the widespread use of computer technology in power plants, other controls for hydrogen-oil water systems are also done by computers. For example, the density gas purity meter originally introduced from Westinghouse Company is based on the gas density signal measured by the purity fan (pressure difference transmitter, 4~20mA) and the internal pressure signal (pressure transmitter, 4~20mA) is sent to a set of computing components. After linear operation, the gas purity parameters in the generator are obtained. Although the operation principle and operation process are very simple, the linear component is used to realize this function. The structure of the component is very complicated and depends on imported parts. If the density analog signal and the pressure analog signal are sent to the computer, the computer completes the calculation process, but it is very simple. Another example: the amount of hydrogen replenished by the generator, as long as a flow transmitter is set in the pipeline of the hydrogen system, and the instantaneous flow signal on the transmitter is sent to the computer, the accumulated flow can be conveniently obtained, prompting hydrogen supplementation, supplementing A series of functions such as hydrogen over-limit alarm.
In this design of the gas turbine generator hydrogen oil water system, a large number of transmitters were used, which greatly improved the automation of the auxiliary system of the generator. A small number of pressure switches configured in the system are considered to be safe and protective in case the DCS system fails.
4 Conclusion The main features of the Siemens gas turbine generator hydrogen oil water system is the high degree of assembly, the operation and maintenance are more humanized; the degree of computer control and monitoring is high. The domestic design of the hydrogen-oil water system of the gas turbine generator is 0 inch. According to the user's requirements, the instrument-controlled terminal box is installed on each device to facilitate on-site wiring. In the future, on the hydrogen and oil water control system of 300 and 600 MW generators, it is necessary to keep up with the pace of modern advanced technology, extensively adopt and adopt advanced technology of Siemens, and further optimize the existing hydrogen oil water system technology.
The overall design and development of the machine hydrogen oil water system, 021-64626666X6187. (Editor: Du Jianjun) hWp
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