Zhou You-qing

Design of saturated iron core superconducting fault current limiter based on numerical calculation

The saturated iron core superconducting fault current limiter (SCFCL) utilizes the non-linear of ferromagnetic hysteresis to change its inductance. Its cores are saturated deeply under normal operation but driven out of saturation whenever fault occurs, so it is very difficult to design this SCFCL through theoretical calculation and there will be biggish error if deal the magnetization curve with subsection linearization. In this paper, incorporating the Jiles-Atherton hysteresis model which can describe the actual measured hysteresis very well and constructing the dynamic differential equations of a circuit comprising this SCFCL, we put forward a new design method by numerical calculating the dynamic equations with computer. We also set forth the systematization design step and introduce a model designed using the technique. The design computation curves, which are agree well with the experimental date, are presented too. This paper shows that the design method is effective and can well forecast the limiting-current result of this SCFCL

Simulation of short-current limiting performance of 3-phase reactor superconducting fault current limiter

The 3-phase reactor superconducting fault current limiter (SCFCL) consists of three superconducting windings with the same number of turns, which are wound on a single iron core. In a normal condition, it is a good conductor with no impedance because the flux is zero in the iron core. However, under a single-line-to-ground fault, it becomes a reactor with large inductance suppressing the fault current, Furthermore, for two or three-phase short circuits, the reactance of the SCFCL keep zero but it is good for limiting the fault current by the abruptly increasing resistance of the superconducting winding. In this paper, its equivalent impedance under every operating condition has been concluded and the simulations of short-circuit current limiting performance of designed prototype were carried out. The results are in good agreement with the theoretical analysis.

New electronic current transducers for measurement and protection in power system

This paper mainly introduces the principles and constructions of two new available electronic current transducers; one is based on the Rogowski coil and the other is the low power current transducer (LPCT). Meanwhile authors compare the phase displacement of output voltage, the frequency range, the applicable fields and the sensitivity to temperature field and etc. between these two kinds of electronic current transducers.

The research of a rectifier type high temperature superconducting fault current limiter

Superconducting techniques will be used in electrical power systems widely. Installing a high temperature superconducting fault current limiter (HSCFCL) in electrical power systems is an effective measure to limit the fault short circuit current and to reduce breaking capacity of the circuit breaker. In this paper, the scope of critical current of a superconductor is defined. A rectifier type HSCFCL is selected. The fault current-limiting duration of HSCFCL is determined and its principle is sized up. At the end of this paper, the creative characteristics of this scheme are raised.

The simulating research on a improved magnetic shielding type of HTSCFCL

The magnetic shielding type high temperature superconducting fault current limiter, which mainly consists of a primary copper coil, a high-Tc superconducting cylinder as the secondary winding, an iron core and a sub-cooled nitrogen cryostat with a cryocooler, can reduce both the transient and the steady-state fault current significantly, but, the device will reduce the limiting impedance in the HTSCFCL if the magnetizing flux reached the saturation point in the magnetic path having no air gap. A improved magnetic shielding type high temperature superconducting fault current limiter is developed and analysized in the paper. The limiter mainly consists of a copper coil, a superconducting cylinder, a control copper ring, an air gap and the three-legged magnetic core. The copper coil on a superconducting cylinder for generating an AC magnetic field, the superconducting cylinder for shielding the field, the control copper ring for controlling fault currents and the air gap in the three-legged magnetic core for avoiding magnetic saturation under the higher current. The simulation results show the limiter can make the time for recovery shorter, and effectively avoid the reduction of a limiting impedance in the HTSCFCL if the magnetizing flux reached the saturation point.