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The 2G superconducting tapes are widely applied in the field of electric power because of low-impedance current-carrying characteristics in the superconducting state and the overcurrent-limiting in the normal state, and Superconducting Fault Current-Limiting Transformer (SFCLT) is one of the most important applications of superconducting tapes in power equipment. In this paper, a simulation model of superconducting tape is established to analyze the overcurrent limiting ability of superconducting tape, and then AC impact experiments are carried out with different types of superconducting tapes to study the quench and recovery characteristics. The experimental results demonstrates the correctness of the simulation model. The results in this paper can be utilized to select the suitable superconducting tapes for SFCLT.

With the increasing power grid capacity and voltage level, the fault current of the system is getting higher, which will have a great impact on the economy of the region and the safety of the power system. In order to solve this problem, the researchers have developed a variety of superconducting fault current limiting devices based on the characteristics of the second-generation (2G) high-temperature superconducting (HTS) tapes with high resistivity after quenching. Among them, the superconducting fault current limiting transformer (SFCLT) has the dual functions of a transformer and a fault current limiter. In this paper, an HTS conductor for superconducting current limiting transformer is proposed. Based on the short circuit fault current of the secondary winding of 120 kVA HTS transformer, the specific structural parameters of the conductor are given. On the basis of the parameters, combined with the numerical analysis of conductor’s circuit and thermal equations, the critical current and current limiting characteristics of the conductor are obtained by modeling and simulation. The simulation results show that the conductor can limit the fault current well, and it is a scheme for the superconducting current limiting transformer winding.

Distributed generation access to distribution network will change its power flow and node voltage distribution, which may affect the safe and stable operation of distribution network. In this paper, the minimum active power loss is taken as the objective to model the distribution network with distributed generations, and the extremum optimization algorithm is introduced to improve it. Finally, an example is given to verify the superiority of the improved algorithm over other typical optimization algorithms.

In practice, the output impedance and lead impedance of the parallel inverter are often inconsistent, and the inconsistency of the equivalent impedance also causes uneven power between the inverters. In this thesis, the parallel inverter system circulating current is analyzed, and the output impedance inconsistency problem is improved by adaptive virtual impedance. The virtual impedance is different from the actual output impedance, which can optimize the power sharing problem without introducing additional power loss.

Ferroresonance overvoltage is one of the most important factors to impact electric equipment inner insulation. In system with non-effectively earthed neutral, the equipment damage caused by ferroresonance overvoltage possesses great proportion. This paper derives the criterion of power frequency ferroresonance in system with non-effectively earthed neutral in detailed, in order to conveniently judge whether there is power frequency ferroresonance when system transferring working mode. This criterion derives the relation between equivalent circuit resistance and critical resistance using analytical method and can be used for determining the zero sequence resistance value in cascade with PT secondary side for eliminating ferroresonance. The method is verified by an example under two conditions. Finally, the effect of neutral connecting arc suppression coil on ferroresonance is analyzed.

This paper introduces the detection and analysis for an abnormal corona defect of a 500kV B-class earthing switch using combined detection technique of ultraviolet imaging and non-contact ultrasonic. Combined with ultraviolet detection spectrum, ultrasonic partial discharge spectrum and equipment inspection results of corona defect location, the principle of arc extinguishing system and failure reason is analyzed. The fault is due to poor contact between drain line of arc extinguishing chamber and main contact conductor, which causes Continuous induction discharge around the contact area with earthing switch in open position. Due to early detection and timely treatment of this defect, possible loss is avoided.