Research On Overhead Ground Wire Disposition Of High Voltage Transmission Lines

The high-voltage transmission lines erected in China have high voltage level,long laid lines,large transmission capacity,and are vulnerable to lightning strikes with poor operating environment.Moreover,with the increase of voltage level and the height of power tower,the probability of lightning strike on tower and transmission lines also increases..If the transmission lines are hit by lightning will lead to the lines trip or even the power equipments are destroyed,it will affect the safe and stable operation of the power system and bring huge power losses.In order to ensure the safe and stable operation of the transmission lines and avoid the lightning stroke of the lines,two overhead ground wires are laid for the high-voltage transmission lines of 220 k V and above in China,one of which is a common ground wire with the function of lightning protection,the other is an optical fiber composite overhead ground wire(OPGW),which has the functions of lightning protection and power communication.The disposition method of overhead ground wire used in engineering is as follows:ordinary ground wire segmented insulation with one-point grounding,OPGW grounding by each tower.Relevant Literature research and engineering operation experience shows that when OPGW is grounded by each tower,the induced current loop of "OPGW to Tower to Earth to Tower to OPGW" will be formed between every near two towers of the whole line.which will generate huge power loss on the ground wire,waste a lot of power,bring huge.economic loss to the power company,and lead to the heating of hardware.Based on the situation,in order to reduce the power loss on the ground wire,this paper puts forward the ground wire disposition: segmented insulation with two-point grounding and middle transposition(SIGT).The main work and research results of this paper are as follows:1.The implementation methods and introduce power characteristics of the four overhead ground wire disposition in the project and related literatures are analyzed.In view of the overhead ground wire arrangement leading to the problem of large power loss on the ground wire,the ground wire disposition of SIGT is proposed.In ATP-EMTP,the simulation line models of SIGT disposition and four comparison schemes are established respectively.The effectiveness of SIGT disposition on reducing ground wire power loss is simulated and analyzed when the circuit is in normal operation.In case of single-phase ground fault of the lines,the influence of ground wire disposition on the second arc current is simulated and analyzed.2.On the basis of simulation,further theoretical calculation and analysis of SIGT disposition are carried out.Firstly,In view of the problem of calculation method of induced voltage neglecting conductor sag in related literatures,a new method for calculating ground wire induced voltage with sag is proposed,and the effectiveness of this method is verified and analyzed.Then,the induction voltage on the ground wire of the transmission line with SIGT disposition is calculated,the disposition structure and current loop of the ground wire are analyzed,the induced current and power loss on the ground wire are calculated.The effectiveness of the SIGT disposition is theoretically calculated and analyzed.3.The influence of different structural parameters and operation parameters of transmission lines on the induced current and power loss of ground wire in SIGT disposition is analyzed.Combined with the corresponding specifications of the transmission line design and related literatures,Select 5 parameters of spans,line length,the distance between the conductor and guound wire,voltage level and transmission capacity.Take several sets of values within the distribution range of each parameter and establish simulation models respectively.The ground wire is modeled using SIGT and engineering disposition.Simulation and analysis the influence law of each parameter on the induced current of ground wire when the ground wire adopted SIGT disposition,calculates the ground wire power loss.Compared with the induced current simulation and power loss calculation results of the disposition in engineering,the effectiveness of the SIGT disposition in the transmission line with parameter changes is analyzed.