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In recent years, with the rapid development of the power electronic technology, various power electronic devices and nonlinear elements, especially of many kinds of rectifier and switcher, are applied widely in power system. Harmonics have produced serious adverse effects in the equipment of power generators and distribution system, and of their control and protection, as well as the users and the...
The current transformer (CT) may saturate during internal fault, external fault, exciting inrush current, over-excitation and other phenomena. If CT reaches to the saturation point and the current difference between the two both sides of the transformer is larger than the restrain current, it will result in the mal-operation of the percentage differential protection. As a result, it is vital to identify...
Arc grounding over-voltage is one of the worst over-voltages in the neutral isolated system. It is an important factor to be considered when selecting neutral ground mode. At present, system simulation is the main method for the study of the arc grounding over-voltage. Arc extinguish and re-ignition is simulated by controlling the switch on or off. However, the switch opening or closing need to be...
Modeling study provides a more effective and flexible way for research of high impedance fault (HIF) detection. An accurate model which can reveal most features of HIF is very important. In this paper, based on extensive investigation into documented test results, a set of most common and agreeable features of HIF has been summarized: the arc features, the non-linearity, the time-varied resistance...
The principles of the equivalent circuit principle and the magnetic property theory are not affected by the inrush current and over-excitation, which enable protection to act rapidly and reliably and implement ideas different from differential protection. However, the leakage inductance and resistance of each winding are required as priori parameters. At present, there is no accurate measurement method...
The key issue of current differential protection is the correct reorganization inrush current and the internal fault current. The algorithm based on equivalent instantaneous inductance can correctly discriminate inrush current from the internal fault current since it makes full use of the measured voltage information. For the Y-Delta connected three-phase transformer, the phase current of the delta...
Autoreclosure schemes have been widely used in power system and an effective way to improve greatly the dependability and stability of power systems. However, most of these schemes adopt a presetting time to reclose breaker after a tripping operation. There are many problems due to the conventional reclosure schemes. In this paper, a self-adaptive auto-reclosure criterion using dual-window transient...
This paper presents the extended study on current differential protection schemes based on symmetrical components. The principles of the protection schemes are analyzed firstly. Their performances are evaluated on a typical 500 kV power transmission line system model using EMTP. Extensive simulation studies are presented under various system and fault conditions, such as variations in system load...
This paper presents a new directional comparison protection scheme specially designed for distribution systems. A number of well-proved directional techniques were chosen for this study. To evaluate their performances, a typical distribution line system was modeled using EMTP, which is able to offer many variations to cover all possible fault conditions such as with different fault types, fault locations,...
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