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Hydro Power Plant Monitoring solutions
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Hydro Power Plant Monitoring solutions
Continuous condition monitoring system that can deliver consistent mechanical and electrical condition information become a compelling element contributing to decrease operational costs while simultaneously improve the operational performance by reducing scheduled and unscheduled downtime.
The economic performance of turbo generators and hydro generators can be considerably enhanced by on-line monitoring technics. Because vibration is an important index showing the soundness of rotating electrical machines, they can be used for early detection of anomalies and troubles. Beside end-winding and shaft vibration, other parameters can be monitored and integrated for comprehensive condition assessment of the entire generator.
HYDRO MONITORING TECHNIQUES
Vibration monitoring
Shaft radial vibration amplitude and radial position are primary indicators of the overall mechanical condition of hydroelectric machinery. It is possible to detect many machine malfunctions including: rotor imbalance; misalignment; bearing wear; and rubs with such measurements. Some machine types produce vibrations that are not easily detected by measuring shaft relative dynamic motion in relation to the bearing. Depending on the bearing stiffness, vibrations can be transmitted directly onto the bearing housings. This may also occur at displacement amplitudes which cannot be detected by shaft measurement methods. In such cases, a piezoelectric accelerometer or seismic velocimeter is used to measure the absolute bearing vibration severity.
Shaft radial vibration amplitude and radial position are primary indicators of the overall mechanical condition of hydroelectric machinery. It is possible to detect many machine malfunctions including: rotor imbalance; misalignment; bearing wear; and rubs with such measurements. Some machine types produce vibrations that are not easily detected by measuring shaft relative dynamic motion in relation to the bearing. Depending on the bearing stiffness, vibrations can be transmitted directly onto the bearing housings. This may also occur at displacement amplitudes which cannot be detected by shaft measurement methods. In such cases, a piezoelectric accelerometer or seismic velocimeter is used to measure the absolute bearing vibration severity.
Airgap monitoring
Large low-speed hydro-generators have a very small air-gap stator bore diameter ratio making it impossible for elements to be perfectly centred during the assembly process. This results in machines operating with a small but relevant misalignment due to a large rotating mass. This can lead to unwanted effects such as considerably unbalanced magnetic pull forces, vibrations and additional losses. It is therefore important to assess the following items: misalignment; minimum and maximum airgaps; stator and rotor shape; the magnetic flux of each pole; and, crucially, to check the machine’s trend to guarantee safe operation and prevent any serious damage.
Large low-speed hydro-generators have a very small air-gap stator bore diameter ratio making it impossible for elements to be perfectly centred during the assembly process. This results in machines operating with a small but relevant misalignment due to a large rotating mass. This can lead to unwanted effects such as considerably unbalanced magnetic pull forces, vibrations and additional losses. It is therefore important to assess the following items: misalignment; minimum and maximum airgaps; stator and rotor shape; the magnetic flux of each pole; and, crucially, to check the machine’s trend to guarantee safe operation and prevent any serious damage.Magnetic Flux monitoring
This particular measurement technique is used in a lot of motor generator applications but plays a very important role in the hydro industry. This sensor is designed to monitor the magnetic field for each rotor pole. Any variations of this can be an indication of a number of faults: Rotor faults: Shorted turns, which can generate hot spots, higher field current and unbalance. Unbalance can create excessive vibrations and overheating of both the stator and rotor. When the magnetic flux is correlated to air gap, it can be used to determine if the rotor unbalance is mechanical (e.g. deformed rotor rim) or electrical (e.g. shorted tums). It can also be correlated to winding temperatures and the rectifier excitation system field voltage and current. Isolated shorted-tums may not necessarily result in an immediate forced outage, but generator performance does deteriorate.
This particular measurement technique is used in a lot of motor generator applications but plays a very important role in the hydro industry. This sensor is designed to monitor the magnetic field for each rotor pole. Any variations of this can be an indication of a number of faults: Rotor faults: Shorted turns, which can generate hot spots, higher field current and unbalance. Unbalance can create excessive vibrations and overheating of both the stator and rotor. When the magnetic flux is correlated to air gap, it can be used to determine if the rotor unbalance is mechanical (e.g. deformed rotor rim) or electrical (e.g. shorted tums). It can also be correlated to winding temperatures and the rectifier excitation system field voltage and current. Isolated shorted-tums may not necessarily result in an immediate forced outage, but generator performance does deteriorate.
Endwinding monitoring
Current operating practices impose severe thermal and mechanical stresses on the rotors and stators of large pump storage hydro-generators and turbo-generators. One such practice involves multiple daily run-ups and run-downs of machines which can lead to premature ageing and cycle-related stator winding deterioration. Pump storage, hydro-generator and nuclear turbo-generator designs feature extremely long end-winding mechanisms and complex bracing systems which are subjected to strong mechanical and electrical stress. Life extension and increased availability can only be achieved through the continuous monitoring of end-winding structures and stator bars for expected deterioration. Generator end-windings experience mechanical vibration during operation. The frequency of this vibration is twice the electrical synchronous frequency of the generator. High vibration can lead to loosening of entire end-winding support system, wear of insulation material, rupture of coil, and fatigue cracking of conductors, all of which require extensive out-of-service repairs. On-line monitoring system can considerably enhance the economical operation of turbo and hydro generators. Data collection and analysis, with longterm perspective help to anticipate generator end-winding vibration problems, predict future maintenance needs, extend intervals between inspections, and minimise maintenance downtime.
Current operating practices impose severe thermal and mechanical stresses on the rotors and stators of large pump storage hydro-generators and turbo-generators. One such practice involves multiple daily run-ups and run-downs of machines which can lead to premature ageing and cycle-related stator winding deterioration. Pump storage, hydro-generator and nuclear turbo-generator designs feature extremely long end-winding mechanisms and complex bracing systems which are subjected to strong mechanical and electrical stress. Life extension and increased availability can only be achieved through the continuous monitoring of end-winding structures and stator bars for expected deterioration. Generator end-windings experience mechanical vibration during operation. The frequency of this vibration is twice the electrical synchronous frequency of the generator. High vibration can lead to loosening of entire end-winding support system, wear of insulation material, rupture of coil, and fatigue cracking of conductors, all of which require extensive out-of-service repairs. On-line monitoring system can considerably enhance the economical operation of turbo and hydro generators. Data collection and analysis, with longterm perspective help to anticipate generator end-winding vibration problems, predict future maintenance needs, extend intervals between inspections, and minimise maintenance downtime.
Partial discharge monitoring
Online partial discharge measurements are the only available technology on the market to qualify stator winding insulation while the machine is in service. The big advantage is that all thermal, electrical, ambient, and mechanical forces are present. The online partial discharge measurement requires one partial discharge sensor (often referred to as coupling capacitors) at each phase exit. Once partial discharge sensors are installed, online measurements can be taken either periodically with a portable partial discharge analyzer or continuously with a permanently installed monitoring system. As well as the partial discharge signals, this also acquires, operation parameters such as winding temperatures and load conditions for correlation with the measured partial discharge results.
Online partial discharge measurements are the only available technology on the market to qualify stator winding insulation while the machine is in service. The big advantage is that all thermal, electrical, ambient, and mechanical forces are present. The online partial discharge measurement requires one partial discharge sensor (often referred to as coupling capacitors) at each phase exit. Once partial discharge sensors are installed, online measurements can be taken either periodically with a portable partial discharge analyzer or continuously with a permanently installed monitoring system. As well as the partial discharge signals, this also acquires, operation parameters such as winding temperatures and load conditions for correlation with the measured partial discharge results.Runner Clearance Monitoring
The runner blade clearance sensor measures distance variations between the turbine blade tip in relation to the throat ring surface. The surface of the turbine blade tip consists of NiCr conductive material absorbing high frequency eddy currents generated by the measuring probe in order to provide an electrical signal proportional to the water gap. The probe itself is flush mounted on the throat ring at the turbine centreline and measures static and dynamic distances in harsh hydraulic environments such as propeller or Kaplan turbines in large hydroelectric generators.
The runner blade clearance sensor measures distance variations between the turbine blade tip in relation to the throat ring surface. The surface of the turbine blade tip consists of NiCr conductive material absorbing high frequency eddy currents generated by the measuring probe in order to provide an electrical signal proportional to the water gap. The probe itself is flush mounted on the throat ring at the turbine centreline and measures static and dynamic distances in harsh hydraulic environments such as propeller or Kaplan turbines in large hydroelectric generators.
PROTECTION & DIAGNOSTICS
Turbines are “critical” equipment at the heart of a power plant. They have different priorities than the auxiliary equipment of the facility. Therefore, critical equipment must be monitored by appropriate systems that meet their special requirements. Vibration monitoring systems produced only for “diagnostic” needs are suitable for condition monitoring of auxiliary machines. They are insufficient to meet the “protective” needs of critical equipment such as turbines. The systems we propose fully meet all the “protective” and “diagnostic” needs of critical machines in hydroelectric power plants.
Turbines are “critical” equipment at the heart of a power plant. They have different priorities than the auxiliary equipment of the facility. Therefore, critical equipment must be monitored by appropriate systems that meet their special requirements. Vibration monitoring systems produced only for “diagnostic” needs are suitable for condition monitoring of auxiliary machines. They are insufficient to meet the “protective” needs of critical equipment such as turbines. The systems we propose fully meet all the “protective” and “diagnostic” needs of critical machines in hydroelectric power plants.
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