To realize the high-voltage vacuum circuit breaker, we investigated the voltage-distribution ratio after current interruption at the double-break vacuum circuit breaker. We used the spiral CuCr (20%) ...electrodes and the axial magnetic-field CuCr (50%) electrodes as the experimental electrodes. At the double-break vacuum circuit breaker, where two vacuum interruptions that had the same and different characteristics of the electrode structure and contact materials were connected in series, there was a bias in the voltage-distribution ratio of each vacuum interrupter after current interruption. This seems to be because there was difference in the postarc current that passed through each vacuum interrupter after current interruption.
Non-metallic structural materials that act as an electrical insulation are needed for cryogenic power applications. One of the extensively utilized materials is glass fiber reinforced resins (GFRR) ...and may also be known as GFRP and FRP. They are created from glass fiber cloth that are impregnated with an epoxy resin under pressure and heat. Although the materials based on GFRR have been employed extensively, reports about their dielectric properties at cryogenic temperatures and larger thicknesses are generally lacking in the literature. Therefore to guide electrical apparatus designers for cryogenic applications, GFRR samples with different thicknesses are tested in a liquid nitrogen bath. Scaling relation between the dielectric breakdown strength and the GFFR thickness is established. Their loss tangents are also reported at various frequencies.
It is widely recognized that arcing faults in switchboards contain large amounts of power and can create significant damage, including melting switchboards, destroying substations, disabling ships, ...and causing human fatalities. While arcing faults occur with a fairly high frequency, electricity is so ubiquitous in our lives that most engineers will not personally be associated with a major arcing fault. The Navy has invested 25 years investigating the causes, behavior, and prevention of arcing failures in low- and medium-voltage switchboards. Laboratory testing used to help understand the behavior of arcs in switchboards is presented. Those data are then used to analyze actual switchboard arcing events and, thus, to determine the root causes of the events. Additional testing used to confirm the cause of each event is discussed.
A comparative investigation of the resistance and ability to trigger high voltage（HV） discharge for a single filament（SF） and multiple filaments（MFs） has been carried out.The experimental results ...show that the trend of the breakdown threshold of the SF exactly follows that of its resistance,but this is not the case for the MF.The MF＇s resistance is much smaller than the SF＇s.However,the MF shows a slightly higher HV breakdown threshold than the SF.The underlying physics is that the measured resistance of the MF is collectively contributed by every filament in the MF while the HV breakdown threshold is determined by only one single discharging path.
This paper presents descriptive equations on the voltage breakdown in ultra-quick circuit breakers (UQCB). In this paper, main breakdown characteristics of UQCB's are presented. Gaseous breakdown in ...the sub-nanosecond regime is of interest for fast pulsed power switching, short pulse electromagnetics, and for plasma limiters to protect devices from high power microwave radiation. In order to study pulsed gas breakdown initiation dynamics, a sub-nanosecond voltage pulse is simulated by Electro-Magnetic Transient Program (EMTP).
Mica-based insulation systems are an essential part of high voltage (HV) electric motors and generators. Accordingly, the performance and reliability of the machine are directly impacted by the ...dependability of the insulation. This paper aims to assess the impact of different design factors on various dielectric indices. These indices include breakdown voltage, dissipation factor, and partial discharge measurements, collected from empirical tests to assess insulation system resilience and endurance. All these evaluation measurements are carried out for fresh samples and thermally aged samples. Thermal aging is performed with different temperatures and durations. After that all samples are tested for voltage endurance in accordance with IEC 60034-18-32 and IEEE 1553, to evaluate their lifetimes. Analyzing the test outcomes, a number of practical methods and techniques are identified that help engineers improve their design and ensure higher longevity of HV electrical machines.
The quest for component size reduction raises concerns regarding device temperatures, particularly in power semi-conductor devices. In the pursuit of improved heat dissipation, several strategies can ...be used to optimize the heat transfer. This paper investigates the use of an oil immersed converter to enhance temperature performance in power converters. Prototypes were developed and tested in both air and Cargill FR3 oil. The case temperature of the IGBTs was monitored under various test scenarios involving power flow and switching frequency variations. The results consistently demonstrated lower IGBT temperatures in the oil-immersed converter across all test scenarios. In steady state, the temperature difference reached a significant 52% reduction compared to the ambient-air converter at the same operating point. These findings highlight the effectiveness of oil immersion in improving thermal performance in power converters. Hi-Pot tests demonstrate that when submerged in oil, high voltage levels can be applied to the board without experiencing voltage breakdown accompanied by sparks.
with the increasing application of power electronic components in driving rotating machines, the electrical stress factors were significantly changed. This paper deals with the investigation of ...lifetime characteristics for insulation of type II rotating machines performed by breakdown measurement of pulse voltage at the different waveforms and rise time. The results were compared with those gathered at power frequency, using different time scaling parameters (number of pulses, effective time). It is found that the effective time of stress voltage provides a clearer perception to study the lifetime behaviour than the number of pulses, especially for comparing the effect of the different applied voltage waveforms on acceleration aging. The results indicate that the rise time of the pulse voltage is considered the main influence on the life of insulations, it leads to insulation failure in a lower time. Additionally, the effect of combined stress (electrical, thermal, mechanical) was studied by using a specially developed sample, which included the curved parts of windings. It was found that the most critical part of such "coil-windings" are those curved parts because they are stressed not only by higher mechanical but also by larger electrical field strength.
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