Research Of Lightning Over-Voltage In UHV Transmission Lines And Secondary Arc After The Single-Phase Trip-out Caused By Insulator-Flash

Lighting stroke is the main reason of the power system trip accident. According to the statistical report, 50%~70% of the accident in the power system are caused by the lightning. The lightning over-voltage, which produced by the lightning stroke the transmission line, intrudes into the substation. This over-voltage can endanger the safe operation of the equipments in the substation. Substation is the key point of the power system. The fault in substation will cause the blackout of a large area. A lot of equipments in substation have no self-recovery insulation, such as the transformer and the shunt reactors. It is difficult to repair these equipments if damaged. The 2km transmission lines before the substation are the incoming lines. The incoming lines are very important to the lightning protection of the substation. Some measures should be taken in the incoming lines to reduce the amplitude and gradient of intruding over-voltage.The synthetical lightning protection measures of incoming lines are researched in this paper. The phase-module transformation is applied to analyze the lightning transient over-voltage of multi-phase distributed parameter conductors. Many factors are taken into consideration when set up the simulation model, such as the wave distortion caused by the multi-module effect, the volt-time characteristic of insulator, the influence of power frequency voltage. The electromagnetic transient simulation are carried to the quantificational analysis of the protective effect of different measures, including the reduction of tower grounding resistance, the installation of line surge arresters, the installation of the coupling grounding lines, etc. The over-voltage and its gradient under these measures are compared according the simulation result. The problems, which should be pay attention to in the application of these measures are presented in this paper, too.The insulator flashed when the over-voltage curve meet the volt-time characteristic curve of insulator, the arc along the insulator surface is produced. If the power frequency current conducts to earth through this arc, the single-phase grounding fault is formed. 90% of transmission line fault are single phase grounding fault. Most single-phase grounding faults are temporary. These temporary faults can be repaired by single-phase auto re-close. The successful re-close depend on the amplitude of secondary arc at the fault point. The secondary arc self- extinguishment is necessary condition of the successful re-close. The amplitude of secondary arc should be calculated to determine the re-close time of protection relay. Some measures should be taken to reduce the secondary arc if its amplitude exceeding the requirement.Serial compensations are widely used with increase of power transmission capacity. The serial compensations change the uniformity of original distributed parameters oftransmission line. The appearance of serial compensation has negative effect to the secondary arc self-extinguishment. There is energy oscillatory discharge between the serial compensation and the inductance of transmission line. This discharge is a low frequency attenuation component. This component increases the amplitude of secondary arc and decreases cross-zero times of arc. The secondary arc in series-capacitor compensated transmission line is simulated based on the parameter of YangChen project. A measure to reduce the secondary arc of serial compensated transmission line is proposed in this paper. This measure has good effect according to the simulation result.