The Analysis Of The Different Grounding Modes Of Overhead Ground Wire For500kV Transmission Line

Overhead ground wire has an important role in transmission line lightning protection and short-circuit current shunting. In this paper, through the studing of the lightning protection range、protection angle and economy of overhead ground wire, The principle of laying overhead ground wire for different voltage level transmission line was cleared and definited.During normal operation, the grounding mode impacts the current flowing in the overhead ground wire. In the directly grounding mode, current was traversed annularly through the ground wire and ground. The current loop brings loss and fever, and the hardware heating creats the potential for security problems. In the sectional insulation and single point grounding mode, the current loop can not be formed. The ground line was be isolated from tow by the insulator with gap. The distance of the gap is difficult to set. If the distance was setted short, the current in the normal frequency can not be cut off easily, and the gap may be breakdown chronically during heavy load current, this is harm to hardware and OPGW. If the distance was setted long, the gap can not be breakdown during a short circuit fault, the shunt effect is not good. It has an adverse impact on the Relay protection setting and the power system communication.As the development of overhead ground wire, OPGW possesses the characteristics of lightning protection and communication. The interior is optical fiber, and the exterior is metal wire. The OPGW has adopted an idiosyncratic connect approach to the tower, and the grounding mode is also divided int directly grounding mode and sectional insulation single point grounding mode.To solve this problem, the odd section grounding\even section transposition method was proposed in this paper. Using the characteristic that the voltage phase of the double overhead ground wires is nearly opposite, the voltage is neutralized and the current is reduced through the transposition of double ground wires. Odd towers are grounding, so the change of fault shunt coefficient and the effect on step voltage is little.The study on different grounding modes of overhead ground wire has important significance. The Analysis of the Lightning protection effect、Lightning protection range、Protective angle and Economy Provides a clear basis for the design of overhead ground wire. The study on the Characteristics of different grounding modes according to the induced voltage and current, is propitious to the hidden danger investigation and pre-control measure making.