A large solar plant in Europe has experienced more than twenty transformers failures in less than... more A large solar plant in Europe has experienced more than twenty transformers failures in less than six months. A multidisciplinary fault analysis was required with the following activities: transformers inspection, on-site measurements, network simulations, transformers manufacturing audit as well as dielectric and water content tests on insulation material taken from failed transformers. The paper describes the multidisciplinary approach utilized for the transformers fault analysis in order to identify the root causes, including those addressable to operations, system integration and transformer manufacturing.
IEEE Transactions on Appiled Superconductivity, 2003
Power system studies on potential applications of superconducting cables and fault-current limite... more Power system studies on potential applications of superconducting cables and fault-current limiters and their impact on utility networks were performed by digital models developed in ATP (Alternative Transients Program). Simulation results from lightning overvoltage and fault analyses on 132 kV cable and 3-phase faults on 20 kV current limiter are reported.
Over the past years, a relatively high number of Solar Plant step-up Transformers (SP Transformer... more Over the past years, a relatively high number of Solar Plant step-up Transformers (SP Transformers) have failed at various locations around the world. This fact has produced a tangible economic damage and significant profit losses especially in terms of undelivered energy. Regular routine transformer dielectric tests and even specific dielectric tests, are not always sufficient to detect defects before they result in problems. Particularly, issues addressable to system design and equipment selection can provoke system faults very difficult to be detected. A large solar plant has experienced more than twenty SP transformers failures in less than six months. A multidisciplinary fault analysis based on the following services was carried out: transformers inspection, on-site measurements, network simulations, transformers manufacturing audit, dielectric and water content tests on insulation material samples.
Transformers inspection The activity, done at manufacturer’s premises, has allowed to assess the presence of the same fault signs pattern on all the transformers.
On-site measurements Wide bandwidth current and voltage transducers has permitted to make on-site measurement of high accuracy even at very high frequencies, directly on the MV system. Using split-core Rogowski coils and capacitive voltage dividers, it was possible to characterize the interaction between network, vacuum circuit breakers and SP transformers. In particular, high frequency overvoltages produced by the vacuum circuit breakers operations were recognized.
Network simulations Network studies have the scope to find out possible weak points of the MV power system from the dielectric point of view. Electromagnetic Transient simulations have permitted to assess a good performance regarding the overvoltages and their damping behaviour over time.
Manufacturing audit The SP transformer manufacturer audit has covered the review of the manufacturing process (drying, assembly, etc.), the factory environment cleanliness and the storage and handling of insulation material.
Dielectric and water content investigations Dielectric and water content tests, in different working conditions, were performed on samples taken from "laminated barriers" of two failed SP transformers. The tests has permitted to have a detailed picture of the SP transformer insulation .
This multidisciplinary approach is a powerful tool for transformers fault analysis. It allows the identification of the real causes, including those addressable to operations, system integration, transformer manufacturing, which no longer comply with the withstand requirements that should be considered when making decisions in all the processes from design to purchase. Finally, this approach will benefit all parties involved in the transformer manufacturing process, the power plant system integration and the plant operation, granting them the means to verify the real causes of the fault and accordingly optimize their processes.
A large solar plant in Europe has experienced more than twenty transformers failures in less than... more A large solar plant in Europe has experienced more than twenty transformers failures in less than six months. A multidisciplinary fault analysis was required with the following activities: transformers inspection, on-site measurements, network simulations, transformers manufacturing audit as well as dielectric and water content tests on insulation material taken from failed transformers. The paper describes the multidisciplinary approach utilized for the transformers fault analysis in order to identify the root causes, including those addressable to operations, system integration and transformer manufacturing.
IEEE Transactions on Appiled Superconductivity, 2003
Power system studies on potential applications of superconducting cables and fault-current limite... more Power system studies on potential applications of superconducting cables and fault-current limiters and their impact on utility networks were performed by digital models developed in ATP (Alternative Transients Program). Simulation results from lightning overvoltage and fault analyses on 132 kV cable and 3-phase faults on 20 kV current limiter are reported.
Over the past years, a relatively high number of Solar Plant step-up Transformers (SP Transformer... more Over the past years, a relatively high number of Solar Plant step-up Transformers (SP Transformers) have failed at various locations around the world. This fact has produced a tangible economic damage and significant profit losses especially in terms of undelivered energy. Regular routine transformer dielectric tests and even specific dielectric tests, are not always sufficient to detect defects before they result in problems. Particularly, issues addressable to system design and equipment selection can provoke system faults very difficult to be detected. A large solar plant has experienced more than twenty SP transformers failures in less than six months. A multidisciplinary fault analysis based on the following services was carried out: transformers inspection, on-site measurements, network simulations, transformers manufacturing audit, dielectric and water content tests on insulation material samples.
Transformers inspection The activity, done at manufacturer’s premises, has allowed to assess the presence of the same fault signs pattern on all the transformers.
On-site measurements Wide bandwidth current and voltage transducers has permitted to make on-site measurement of high accuracy even at very high frequencies, directly on the MV system. Using split-core Rogowski coils and capacitive voltage dividers, it was possible to characterize the interaction between network, vacuum circuit breakers and SP transformers. In particular, high frequency overvoltages produced by the vacuum circuit breakers operations were recognized.
Network simulations Network studies have the scope to find out possible weak points of the MV power system from the dielectric point of view. Electromagnetic Transient simulations have permitted to assess a good performance regarding the overvoltages and their damping behaviour over time.
Manufacturing audit The SP transformer manufacturer audit has covered the review of the manufacturing process (drying, assembly, etc.), the factory environment cleanliness and the storage and handling of insulation material.
Dielectric and water content investigations Dielectric and water content tests, in different working conditions, were performed on samples taken from "laminated barriers" of two failed SP transformers. The tests has permitted to have a detailed picture of the SP transformer insulation .
This multidisciplinary approach is a powerful tool for transformers fault analysis. It allows the identification of the real causes, including those addressable to operations, system integration, transformer manufacturing, which no longer comply with the withstand requirements that should be considered when making decisions in all the processes from design to purchase. Finally, this approach will benefit all parties involved in the transformer manufacturing process, the power plant system integration and the plant operation, granting them the means to verify the real causes of the fault and accordingly optimize their processes.
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Papers by Giuseppe Cappai
A large solar plant has experienced more than twenty SP transformers failures in less than six months. A multidisciplinary fault analysis based on the following services was carried out: transformers inspection, on-site measurements, network simulations, transformers manufacturing audit, dielectric and water content tests on insulation material samples.
Transformers inspection
The activity, done at manufacturer’s premises, has allowed to assess the presence of the same fault signs pattern on all the transformers.
On-site measurements
Wide bandwidth current and voltage transducers has permitted to make on-site measurement of high accuracy even at very high frequencies, directly on the MV system.
Using split-core Rogowski coils and capacitive voltage dividers, it was possible to characterize the interaction between network, vacuum circuit breakers and SP transformers.
In particular, high frequency overvoltages produced by the vacuum circuit breakers operations were recognized.
Network simulations
Network studies have the scope to find out possible weak points of the MV power system from the dielectric point of view. Electromagnetic Transient simulations have permitted to assess a good performance regarding the overvoltages and their damping behaviour over time.
Manufacturing audit
The SP transformer manufacturer audit has covered the review of the manufacturing process (drying, assembly, etc.), the factory environment cleanliness and the storage and handling of insulation material.
Dielectric and water content investigations
Dielectric and water content tests, in different working conditions, were performed on samples taken from "laminated barriers" of two failed SP transformers.
The tests has permitted to have a detailed picture of the SP transformer insulation .
This multidisciplinary approach is a powerful tool for transformers fault analysis. It allows the identification of the real causes, including those addressable to operations, system integration, transformer manufacturing, which no longer comply with the withstand requirements that should be considered when making decisions in all the processes from design to purchase.
Finally, this approach will benefit all parties involved in the transformer manufacturing process, the power plant system integration and the plant operation, granting them the means to verify the real causes of the fault and accordingly optimize their processes.
A large solar plant has experienced more than twenty SP transformers failures in less than six months. A multidisciplinary fault analysis based on the following services was carried out: transformers inspection, on-site measurements, network simulations, transformers manufacturing audit, dielectric and water content tests on insulation material samples.
Transformers inspection
The activity, done at manufacturer’s premises, has allowed to assess the presence of the same fault signs pattern on all the transformers.
On-site measurements
Wide bandwidth current and voltage transducers has permitted to make on-site measurement of high accuracy even at very high frequencies, directly on the MV system.
Using split-core Rogowski coils and capacitive voltage dividers, it was possible to characterize the interaction between network, vacuum circuit breakers and SP transformers.
In particular, high frequency overvoltages produced by the vacuum circuit breakers operations were recognized.
Network simulations
Network studies have the scope to find out possible weak points of the MV power system from the dielectric point of view. Electromagnetic Transient simulations have permitted to assess a good performance regarding the overvoltages and their damping behaviour over time.
Manufacturing audit
The SP transformer manufacturer audit has covered the review of the manufacturing process (drying, assembly, etc.), the factory environment cleanliness and the storage and handling of insulation material.
Dielectric and water content investigations
Dielectric and water content tests, in different working conditions, were performed on samples taken from "laminated barriers" of two failed SP transformers.
The tests has permitted to have a detailed picture of the SP transformer insulation .
This multidisciplinary approach is a powerful tool for transformers fault analysis. It allows the identification of the real causes, including those addressable to operations, system integration, transformer manufacturing, which no longer comply with the withstand requirements that should be considered when making decisions in all the processes from design to purchase.
Finally, this approach will benefit all parties involved in the transformer manufacturing process, the power plant system integration and the plant operation, granting them the means to verify the real causes of the fault and accordingly optimize their processes.