Analysis on Lightning Strike Cause of Directly Buried Optical Cable in Wind Farm and Its Prevention Methods

Directly buried metal optical cable is a form of erecting optical fiber ring network communication system in wind farms. Although the directly buried optical cable is much less than the overhead optical cable affected by lightning, sometimes lightning damaging optical cable and flashover discharge accidents of optical cable port occurred. In this paper, the amplitude spectrum of lightning wave, the breakdown depth and breakdown distance of lightning wave to soil, the metal components of optical cable port and the impedance characteristics of grounding wire are systematically analyzed, and the prevention methods of directly buried optical cable in wind farm to avoid lightning damage are proposed.

Study on Characteristics of Underground Horizontal Electric Field Caused by Lightning Return Stroke Based on FDTD Method

Based on the MTLL lightning return stroke model,a two-dimensional cylindrical finite-difference time-domain( FDTD) model for underground horizontal electric field was established,and the effects of distance from lightning channel,depth,soil electrical conductivity and its distribution,and return stroke current on the characteristics of underground horizontal electric field were analyzed. The results showed that as long as the electrical conductivity of soil existed,the peak of underground horizontal electric field decreased with the increase in the horizontal distance from lightning channel. When the electrical conductivity of the upper soil was much smaller than that of the lower soil,the peak of corresponding horizontal electric field was larger than the electric field peak as the electrical conductivity of the upper soil was larger than that of the lower soil. When the electrical conductivity of the upper soil was less than that of the lower soil,the growth and decay of the horizontal electric field were faster than the growth and decay as the electrical conductivity of the upper soil was larger than that of the lower soil.

Protective Measures to Oil Depot Against Lightning Stroke and Electrostatic Spark

Introduction Lightning can cause great destruction. According to the record in the northern China, more than 150 lightning strokes occur on a power system annually. High voltage (millions of volts) and large current (hundreds of -kA) associated with lightning, will damage property and even kill people and livestocks. It will be very dangerous if a lightning stroke strikes oil depot of power plant or substation. In addition, the high voltage induced by the electrostatic charge generated due to oil flowing will probably cause damage unless the electrification has been limited and drained off.

Analysis of Dispersed Lightning Stroke around a Mobile Communication Base Station

A case of villagers suffering lightning stroke around the tower of a mobile communication base station was investigated to analyze its reasons,and the countermeasures against lightning stroke were proposed. The results show that the lightning stroke event is related to dispersed lightning stroke. To avoid the damage caused by lightning stroke,it is needed to equip a house in the dispersed lightning stroke zone with lightning protection system and spread lightning protection knowledge among the villagers.

Thermal damage analysis of aircraft composite laminate suffered from lightning swept stroke and arc propagation

Lightning strike is a complicated process involving multi-field coupling.In order to investigate the thermal damage mechanism of carbon fiber reinforced composites subject to lightning swept stroke,a complete numerical method is presented.Numerical model of lightning discharge is established based on Magneto Hydro Dynamics(MHD)and calculated by FLUENT secondary development technology.Considering aerodynamic flow effect,channel formation and evolution process during lightning discharge is analyzed for lightning current waveform A.Thermal-electric Coupling model is presented according to Radial Basis Function(RBF)interpolation theory,which is implemented by compiling program to make lightning current and heat energy inject into composite laminate.Consequently,damage mechanism of composite laminate under lightning swept stroke is studied based on the coupled numerical model and element deletion method.Ablation damage morphology of composite laminate is analyzed to understand plasma expansion and reattachment in arc root.The results show that aerodynamic flow makes the lightning channel move fast and composite laminate is deteriorated due to thermal damage.

Novel transient-energy-based directional pilot protection method for HVDC line

This paper proposes a novel directional pilot protection method based on the transient energy for bipolar HVDC line.Supposing the positive direction of current is from DC bus to the DC line,in the case of an internal line fault,the transient energies detected on both sides of the line are all negative within a short time,which denotes the positive direction fault;while for an external fault,the transient energy on one end is positive,which means a negative direction fault,but the transient energy on the opposite end is negative,which indicates that the fault direction is positive.According to these characteristics,an integration criterion identifying fault direction is constructed.In addition,through setting a fixed energy threshold,the faulted line and lightning disturbance can also be discriminated.Simulation results from UHVDC transmission system show the validity of the proposed protection method.