8 results
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2. Simulation of Switching Overvoltages and Validation With Field Tests.
- Author
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Cervantes, M., Kocar, I., Montenegro, A., Goldsworthy, D., Tobin, T., Mahseredjian, J., Ramos, R., Marti, J., Noda, T., Ametani, A., and Martin, C.
- Subjects
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ELECTRICAL engineering , *ELECTRIC lines , *ELECTRIC potential , *ELECTRIC switchgear , *SIMULATION methods & models , *WAVE analysis - Abstract
On transmission lines where switching surges are not mitigated with closing resistors and/or surge arresters, high-speed reclosing on a line with trapped charge will produce high overvoltages that have been measured above 3 p.u. Careful simulations of these switching events using available electromagnetic transient (EMT) programs consistently produce significantly higher voltages than the measurements. This indicates a phenomenon present on the line that acts to reduce the switching surge magnitudes but is not typically modeled. This paper aims to identify the required simulation practices in reproducing the field measured overvoltages in EMT simulations and investigates the sensitivity of results to modeling approaches and electrical parameters. Field measurements from a switching surge test of a 230-kV line without surge mitigation have been used for model comparisons. Variations in frequency-dependent line modeling, ground resistivity, skin effect, shunt conductance, parallel lines, and source-side detail have been tested in an unsuccessful attempt to decrease the difference between the field measurements and the higher simulation overvoltages. It is demonstrated that even though the pattern of the transient voltage waveforms can be reproduced very well using frequency-dependent line models, the magnitude of the maximum overvoltage is significantly overestimated unless the effect of corona is considered. Two types of corona models are tested, and both demonstrate that corona is the primary factor that allows the simulations to correctly reproduce high peak overvoltage measurements. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
3. Countermeasures of Zero-Missing Phenomenon in (E)HV Cable Systems.
- Author
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Khalilnezhad, Hossein, Popov, Marjan, van der Sluis, Lou, Bos, Jorrit A., de Jong, Jan P. W., and Ametani, Akihiro
- Subjects
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ELECTRONIC countermeasures , *ELECTRIC cables , *SHUNT electric reactors , *HIGH voltages , *ELECTRIC currents , *SWITCHING circuits , *ELECTRIC lines , *ELECTRIC circuit breakers , *EQUIPMENT & supplies - Abstract
Zero-missing is a phenomenon in shunt-compensated cable systems, in which the current through the line breaker does not cross the zero point for several cycles. This paper deals with a thorough investigation on countermeasures of the zero-missing phenomenon in transmission systems and determines the requirements, benefits, and risks of applying each method. The effectiveness of countermeasures is studied on a simulated cable project with different cable lengths in an actual grid model of the Dutch 380 kV transmission system. Results are analyzed based on three criteria related to the IEC standards and the Dutch grid code. In addition, the switching sequence of circuit breakers is specified to maximize the effectiveness of the countermeasures. A statistical switching analysis is performed for the insulation coordination study since the application of some countermeasures increases the probability of high transient switching overvoltages. Moreover, the closing variation threshold of circuit breakers is calculated as a function of the circuit impedance and the shunt compensation degree. [ABSTRACT FROM PUBLISHER]
- Published
- 2018
- Full Text
- View/download PDF
4. Transformer Switching With Vacuum Circuit Breaker: Case Study of PV Inverter LC Filters Impact on Transient Overvoltages.
- Author
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Kuczek, T., Florkowski, M., and Piasecki, W.
- Subjects
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OVERVOLTAGE , *VACUUM circuit breakers , *PHOTOVOLTAIC power systems , *ELECTRIC transformers , *ELECTRIC filters , *ELECTRIC transients , *SIMULATION methods & models - Abstract
This paper presents the analysis of possible transient overvoltages that can be generated during vacuum circuit-breaker (VCB) operation at the connection point of a photovoltaic powerplant. A typical switching event that is related to the VCB concerns energization and de-energization of the unloaded transformer. However, at the typical photovoltaic powerplant, the transformer is fed by an inverter equipped with LC (or LCL) filters that are necessary for limitation of harmonics and ripple in voltage and current. From the point of view of switching operations, the inductance and capacitance of the low-voltage (LV)-side connected filter affect the natural frequency of the transformer, which is reflected by different transient system response during VCB operation. In this paper, laboratory measurement of overvoltages generated during distribution transformer switching by means of VCBs is analyzed. The impact of the LC filter connected at the LV side on the overvoltages suppression was studied. Electromagnetic Transients Program–Alternative Transients Program simulations were conducted in order to verify the possibility of transients elimination by means of the additional series-connected RL choke at the transformer medium-voltage side. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
5. A Study of Synchronous Breaker Switching With Preinsertion Resistor for Capacitors Banks.
- Author
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Sun, Rui, McVey, Mark, Stage, James R., and Yang, Duotong
- Subjects
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SWITCHING circuits , *ELECTRIC circuit breakers , *CAPACITOR banks , *ELECTRIC resistors , *SWITCHING transients , *EQUIPMENT & supplies - Abstract
Shunt power capacitors are essential to system operation and reliability as a critical reactive power source to increase system capacity, support voltage magnitude, improve power quality, and reduce reactive current flow. To mitigate capbank switching transients, the synchronous switching with preinsertion resistor technology is developed and used at an extra-high voltage transmission system. In this paper, the coupling relationship between several key factors that contribute to switching transients is studied. Optimization solutions are developed to improve the switching process. Field operations with an updated setting are compared with original setting records to prove the correctness of the study. [ABSTRACT FROM PUBLISHER]
- Published
- 2018
- Full Text
- View/download PDF
6. General Analysis of Vacuum Circuit Breaker Switching Overvoltages in Offshore Wind Farms.
- Author
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Ghafourian, S. M., Terzija, V., Arana, I., Sorensen, T., Holboll, J., and Popov, M.
- Subjects
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OFFSHORE wind power plants , *OVERVOLTAGE , *SUBMARINE cables , *SWITCHING transients , *TIME-domain analysis , *VACUUM circuit breakers - Abstract
Understanding mechanisms of switching transient overvoltages in modern electrical power systems is a necessity to ensure a proper design of power plants and switchgear and the required level of reliable and secure system operation. High fidelity plant modelling and accurate transient analysis is a prerequisite for understanding the mechanisms of how overvoltages are created and whether or not the voltage withstand capabilities of system components will be exceeded. This research is focused on switching overvoltages typical for an offshore wind farm power collection grid configuration that comprises vacuum circuit breakers (VCBs), cables and transformers. An in-depth understanding of the prestrike effects in VCBs is a prerequisite for studying switching transient overvoltages. In this paper, the impact of VCB parameters (e.g., stray capacitance and withstand voltage ability)and cable length on the transformer terminal voltage during closing operation was studied. A wind farm power collection system was modelled in ATP-EMTP environment. To validate the results obtained through computer simulation, field measurements from an actual system were used. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
7. Relevant Parameters in a Statistical Analysis—Application to Transmission-Line Energization.
- Author
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Mestas, Patricia and Tavares, Maria Cristina
- Subjects
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ELECTRIC lines , *ELECTRIC circuit breakers , *TRANSIENT analysis , *SURGE arresters , *STATISTICS - Abstract
This paper summarizes the important factors that affect statistical switching transients studies during transmission-line energization. These factors include the number of repetitions to ensure the statistical characteristic of the study, the variation range of the mean closing time of the circuit-breaker contacts, the model used for the representation of the transmission line, and the influence of transposition. In addition, a statistical analysis of mitigation methods to reduce overvoltages during transmission-line energization maneuver is presented, specifically the use of surge arresters, of controlled switching, and of a preinsertion resistor. The shunt compensation degree is considered as an independent parameter. Digital simulations were performed with PSCAD. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
8. Improved Overcurrent Protection of Capacitor Banks Using Mathematical Morphology.
- Author
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Buggaveeti, Sravan K. and Brahma, Sukumar M.
- Subjects
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OVERHEAD electric lines , *CAPACITOR banks , *MATHEMATICAL models , *ELECTRIC relays , *MORPHOLOGY , *ELECTRIC power system protection , *MICROPROCESSORS , *ELECTROMECHANICAL devices - Abstract
Numerical overcurrent relays used to protect capacitor banks can better discriminate between faults and switching inrush compared to their electromechanical counterparts. However, there is still scope and use for faster and reliable operation. This paper describes the implementation of a filter based on mathematical morphology that creates distinct signatures for capacitor inrush and faults. These signatures are then used to propose a rule-based classification method that can be easily implemented in microprocessor-based relays. Extensive simulations are carried out to test the classification method using waveforms generated from PSCAD/EMTDC simulation of a standardized test system. The classification method is shown to be very reliable, general, and significantly faster than methods currently used or previously proposed. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
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