| In distributions, because of its low-level voltage, its neutral point used to disconnect to the ground in order to improve its reliability. However, in recent years the distributions are becoming larger and larger and the enormous use of cables in city power system, which increases the current through the grounded capacitor. These make the single-phase faulty current get greater, which lead to more and more instantaneously grounding faults unable to eliminate naturally. To solve these problems, the compensating method of neutral point grounding through Perterson coil is commonly used in our country.In Perterson coil system, it can be decreased that the capacitor current through fault point and the over-voltage caused by the grounding fault, which is advantage for the extinguishments of electric arc. But there are some disadvantages in this system; especially it is difficult to select the exact line with fault. In this system, once the method of selecting line with fault is perfected, the method of neutral point grounding through Perterson coil will be the preferred method of neutral grounding in power supply networks without doubt. In the system with the traditional Perterson, the method of selecting the line with fault is not very exact, and the problems of unselecting the line with fault or selecting the line without fault are serious, which arise from the off-line adjusting inductance of Perterson coil. In order to settle this problem, Perterson coil adjusted in-line is developed with the load-adjusting switch. However, its adjusting is very slow and the inductance of Perterson coil varies in discontinuousness mode. This paper presents a continuously speedily adjustable Perterson coil that is based on a power electronic controlled, and designs this novel coil with Saber software. The comparable results are listed in this paper. In the distribution with the improved coil, a novel principle of selecting the line with the fault, which makes use of the dynamic changes in the current through the zero order line. This scheme has certain innovation and high-applied value. It provides a quite perfect method of selecting the line with fault for the system of grounding through Perterson coil. This paper proves this criterion in theory and proves the correctness of this criterion with Saber simulation. This paper mainly discusses the new theory of selecting the line with fault in the system of nuclear grounding through Perterson coil. It makes some valuable researches for the selecting line with fault protecting theory in fast adjustable Perterson coil. |
