Research on the dynamic characteristics of the electromagnetic repulsion mechanism of a self-driving fault current limiter

A fault self-driven current limiter is proposed in the paper, which uses a special fault current direct-driven electromagnetic repulsion mechanism to realize the first half-wave of the fault current over the zero point into the current-limiting reactance. The paper analyzes the working principle of the self-driven electromagnetic repulsion mechanism, establishes the equivalent model of the mechanism, and simulates the dynamic characteristics of the electromagnetic repulsion mechanism through the calculation of the double-layer iterative algorithm in time and space. The LC oscillation loop test platform is built, and the stroke–time curve of the prototype is measured. In the test, the prototype is driven by a 3 kA current, and the first half-wave stroke (FHWS) is 3.55 mm past the zero point, which is consistent with the simulation and test results. The effects of structural parameters such as the radius, thickness, and number of turns of the self-driven electromagnetic repulsion mechanism on the dynamic characteristics of the electromagnetic repulsion mechanism are investigated, and it is found that the first half-wave stroke can be significantly improved by increasing the number of turns and outer diameter of the coil. The optimum height of the dynamic repulsion coil is approximately 3 mm

Vacuum Switching Technology for Future of Power Systems

Even though switching in vacuum is a technology with almost 100 years of history, its recent developments are still changing the future of power transmission and distribution systems. First, current switching in vacuum is an eco-friendly technology compared to switching in SF6 gas, which is the strongest greenhouse gas according to the Kyoto Protocol. Vacuum, an eco-friendly natural medium, is promising for reducing the usage of SF6 gas in current switching in transmission voltage. Second, switching in vacuum achieves faster current interruption than existing alternating current (AC) switching technologies. A vacuum circuit breaker (VCB) that uses an electromagnetic repulsion actuator is able to achieve a theoretical limit of AC interruption, which can interrupt a short-circuit current in the first half-cycle of a fault current, compared to the more common three cycles for existing current switching technologies. This can thus greatly enhance the transient stability of power networks in the presence of short-circuit faults, especially for ultra- and extra-high-voltage power transmission lines. Third, based on fast vacuum switching technology, various brilliant applications emerge, which are benefiting the power systems. They include the applications in the fields of direct current (DC) circuit breakers (CBs), fault current limiting, power quality improvement, generator CBs, and so forth. Fast vacuum switching technology is promising for controlled switching technology in power systems because it has low variation in terms of opening and closing times. With this controlled switching, vacuum switching technology may change the “gene” of power systems, by which power switching transients will become smoother

Problems and counter measures of arc suppression coilin 10 kV distribution system

The arc suppression coil determines whether it can effectively extinguish the arc when it is grounded in the neutral non-effective grounding system. An artificial grounding test is an importantway to verify its performance. In this study, 13 substations with the 10 kV system in the Ningxia areawere selected and considered. Based on the artificial single-phase grounding test, the residual current, the compensation current and the off-resonance degree were measured in the arc suppression coil, and the performance of the arc suppression coil in the 10 kV system was verified. The experimental results show that the error of arc suppression coil automatic measurement is large, the off-resonance degree is large, the resistive component in the compensation current is excessive, the harmonic component exists in the compensating current and capacitive current. To solve these problems, this paper puts forward the corresponding countermeasures for reference

Study on voltage distribution characteristic of a 363 kV fast multi-break vacuum circuit breaker

Vacuum circuit breaker (VCB) has a longer life and shorter opening time than SF(6) circuit breaker, but current single-break VCB cannot be applied in high-voltage power system directly. Here, a fast 363 kV multi-break VCB design is presented and its voltage distribution characteristic and stray capacitors are analysed. A three-dimensional finite-element model of modularised hexa-break VCB composed of 12 vacuum interrupter modules installed on three series connected platforms is developed to calculate the voltage distribution and distributed capacitances. The result shows that the voltage distribution is uneven, and the first break shares the 67.974% of the whole applied voltage. On account of distributed capacitances parameters, an equivalent capacitance model with PSCAD is built to discuss the voltage distribution characteristic at different grading capacitance values, and the optimal grading capacitance value is determined to 10 nF