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Based on the reflection and refraction of traveling waves and vacuum circuit breaker(VCB) characteristics, transformers interruption by VCB may produce current chopping and re-ignition that will cause severe high-frequency transient overvoltages in collection grid of offshore wind farms(OWFs). In such applications, overvoltages protection should be used. In order to study such overvoltage in OWFs,...
Uncontrolled energization of unloaded transformers is usually associated with a large inrush current, several times larger than the rated transformer current. This transient can cause unfavourable consequences including reduction of transformer lifecycle, protective relay misoperations, and reduced power quality of the system. Controlled switching can efficiently eliminate these transients when energizing...
The amount of switching operations of unloaded transformers increases with the developments of smart grids and integration of renewable energy sources. A random energization of an unload transformer can cause high amplitude and high frequency inrush currents. Controlled switching can eliminate the inrush currents effectively, the key to realize which is measuring residual flux in transformer core...
In this paper, the dynamic characteristics of two types of electromagnetic repulsive force actuators are compared using the simulation of finite element method. The two electromagnetic repulsive force actuators are equipped with a single-sided coil and a double-sided coil respectively. Initially, the construction and theory of each of the electromagnetic repulsive force actuators are discussed. Subsequently,...
Hybrid HVDC circuit breakers have become a key component for HVDC grids, which offer the combination of low losses of mechanical switches and fast switching actions of power electronic switches. The parameters of the circuit breakers have a greater impact on its interruption performance and size. In this paper, the transient characteristics of the hybrid HVDC circuit breakers with forced commutation...
The development of a large-scale HVDC power grid requires a reliable, fast and low-loss hybrid HVD circuit breaker. The high speed disconnect switch is an essential part of hybrid HVDC circuit breaker concept. The objective of this paper is to design an electromagnetic repulsion mechanism for high speed vacuum disconnect switch of a hybrid HVDC circuit breaker and meet the premise that the motion...
Switching transient as one of the main transient phenomena in power systems has been simulated and measured in many studies. Since offshore wind farms have been integrated to power system only in recent years, the consequences of switching phenomena in offshore wind farms have not yet been thoroughly analyzed. In this paper, the high frequency transient over-voltages of vacuum circuit breaker switching...
A random energization unload power transformers may cause large inrush currents and overvoltages, which have high magnitudes and rich harmonic components. These transients have undesirable effects, including potential damage or loss-of-life to the power transformer, protective relay misoperation, and reduced power quality on the system. Controlled switching is one of the most effective methods to...
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