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Triggered vacuum switch (TVS) is one of the important switch apparatuses in the fields of high-pulsed power system. Its working lifetime is due to trigger failure of the trigger pin, so the parameters of trigger source become the key of lifetime dilatation. A sample of field-breakdown TVS coated with nothing is fabricated, which has much longer lifetime than the TVS coated with trigger materials, but more trouble in the trigger process. A trigger system and a LC test circuit are designed to find the operational characteristics of the TVS sample. The trigger system generates a negative pulse with peak value of 30 kV/500 A, the system delay and its scatter is controlled in 70-100 μs, and the triggered rate of success reaches 96%. Test results show that the sample has a wide working voltage range of 0.3-40 kV. The delay of its switching-on is stable in hundreds of nanoseconds, which will be reduced with the increase of main gap voltage. The arcing is steady in the conducting process, keeping arc voltage at 20 V approximately. The arc current drops to zero as current zero is approached, leading to a voltage remained in the capacitance. [ABSTRACT FROM AUTHOR]

High current switch is a key component of a pulsed power source. Triggered vacuum switch (TVS) possesses many advantages including wide range of operating voltage, compact structure, low cost and so on, so it is considered as one of the most compelling switch in pulsed power system. This paper describes two types (A and B) of TVS samples with different main electrodes and triggering electrodes. Based on theoretical analysis and experimental results, the triggering characteristics of TVS samples have been researched. The triggering polarity, triggering energy and operating voltage influence the triggering delay and the jitter of delay. To recover the failure of TVS samples caused by decreased triggering energy, series air gap was tried. In the lifetime test, the resistance between the triggering electrodes dropped gradually, leading to the failure of TVS. Both types of TVS have discharges number of 100 shots with 70 kA peak current. The ablation on the main electrodes of type B TVS was slighter than that of type A. [ABSTRACT FROM AUTHOR]

The objective of this project was to assess the specific transformer grounding and connection methods that are used at the subject utility for distributed generators (DGs) and provide a risk assessment in terms of potential impact, ways to minimize the impact, and site specific screening criteria for additional protection that may be required for DG interconnection. The utility has standardized on a grounded wye-grounded wye transformer connection for customers connected to their distribution system. When a backup generator exists in the customer's facility that could be paralleled with the utility system, a contactor is installed on the neutral to ground connection on the generator. This contactor is opened at any time that the generator is paralleled. The utility is considering remotely dispatching these distributed generation assets in times of peak load in the future. This will require the generators to run paralleled for extended periods of time. Grounding practices for auxiliary generators were evaluated, and simulations of both steady-state and fault conditions were conducted. The most critical factors were found to be assuring that the generator ground switch was closed during islanding and that the overvoltage protection operates correctly to isolate the generator during fault conditions. Recommendations for overvoltage protection and testing were developed based upon the results. [ABSTRACT FROM AUTHOR]

The operation of modern high-power bipolar switches has been analyzed to estimate the influence of the magnitude and distribution of an excess charge, which has to be extracted upon turn-off, on the integral dynamic losses. It is shown that these losses can be significantly reduced by properly matching the structural parameters and selecting the gate regime. [ABSTRACT FROM AUTHOR]

Abstract: Superconducting fault current limiters (SFCLs) have been developed in many countries, and they are expected to be used in the recent electric power systems, because of their great efficiency for operating these power system stably. It is necessary for resistive FCLs to generate resistance immediately and to have a fast recovery characteristic after the fault clearance, because of re-closing operation. Short-circuit tests are performed to obtained current limiting operational and recovery characteristics of the FCL by a fault controller using a power switching device. The power switching device consists of anti-parallel connected thyristors. The fault occurs at the desired angle by controlling the firing angle of thyristors. Resistive SFCLs have different current limiting characteristics with respect to the fault angle in the first swing during the fault. This study deals with the short-circuit characteristic of FCL coils using two different YBCO coated conductors (CCs), 344 and 344s, by controlling the fault angle and experimental studies on the recovery characteristic by a small current flowing through the SFCL after the fault clearance. Tests are performed at various voltages applied to the SFCL in a saturated liquid nitrogen cooling system. [Copyright &y& Elsevier]

The utilization of dynamic voltage restorers to protect sensitive loads against short-term voltage disturbances has been proven to be a competitive solution in medium- and high-power applications. For low-power applications further cost reductions are required to make the technology even more competitive, although just a few numbers of studies have already been conducted in this area. This paper discusses the design and operation of a three- phase dynamic voltage compensator, including control strategies for the converters. The proposed topology and control strategies are evaluated through simulation studies based on measured data, selected by the IEEE Power Quality Task Force for the characterization of power quality events and device performance evaluation, along with disturbances recorded in a steel plant, in Minas Gerais State, Brazil. An experimental implementation of the compensator is developed to allow a better evaluation of specific and critical operating modes, such as the forced commutation of the bypass thyristors and inverter operation. [ABSTRACT FROM AUTHOR]

We previously proposed a six-phase pole change induction motor (six-phase PCIM) for electric vehicles (EVs), and have presented its operating principle and steady state characteristics. The six-phase PCIM expands the constant power operation range using the pole change technique without mechanical contactors; therefore it possesses superb characteristics for miniaturizing EV driving systems. This paper proposes a new analysis method for the six-phase PCIM in order to derive basic equations which can be used to analyze transient phenomena caused by pole change and to create control methods. First, a “six-phase tensor-transformed rotational d-q axis” is defined and its physical meaning made clear. By using this axis, voltage and torque equations which can uniformly deal with the steady state and transient states will be derived. Next, we compare measured and simulated results of voltage, current, and torque characteristics in steady state and in transient states at the pole change operation and both-pole dual operation. Through these comparisons, the validity of our theory and its effectiveness to performance analysis and application to the control method for the six-phase PCIM is discussed in detail. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(2): 59–71, 1997 [ABSTRACT FROM AUTHOR]