| Due to the high voltage level and large transmission power of the ultra-high AC voltage transmission and transformation line,the value of the induced current is large and the secondary arc is not easy to be extinguished when a single phase grounding fault occurs,which reduces the reliability and rapidity of the power supply.The Ultra Class B induction current rapid release device on ultra-high voltage GIL is a grounding switch installed at the head and end of the GIL pipe gallery for releasing the induced current.Whether it can successfully break the induced current directly affects whether the line can successfully reclose.Therefore,in this paper,arc simulation,dielectric recovery characteristics,breaking characteristics and its influencing factors are researched in the breaking process of Ultra Class B induction current rapid release device.The research results provide a theoretical basis for the design of high speed grounding switches.Firstly,taking Sutong GIL utility tunnel project as background,the induced current and voltage values under different conditions are calculated when a single-phase grounding fault occurs on the line and the working principle of induction current rapid release device is analyzed in this paper.Secondly,the arc model of the breaking process is established,the free arc-burning process in the gas chamber is simulated,and the electric field distribution is calculated.Then,the gas breakdown criterion is derived and corrected,the post arc recovery strength of the medium is calculated,the recovery characteristic is analyzed,and whether the switch can break the induced current is judged.Finally,the dielectric recovery characteristics under different opening speeds,chamber pressures and breaking angles are calculated to optimize the mechanical properties,select the appropriate chamber pressure and control the opening phase angle.The results shows that when a single-phase grounding fault occurs,the maximum values of electrostatic induced voltage and current are 94.8kV and 37 A,which do not exceed the upper limit of the Class B earthing switch,indicating that the Class B earthing switch can be used to open and close the electrostatic induced current.While the maximum values of electromagnetic induction voltage and current are 40 kV and 800 A,which exceed the upper limit standard value of the Class B earthing switch,indicating that the Class B earthing switch cannot complete the opening and closing of the electromagnetic induction current,and the Ultra Class B induction current rapid release device is required.During the opening process of the switch,the gas hole of the moving contact has a pumping effect on the arc,which is beneficial to the arc extinction and the temperature does not exceed 10000 K when arc burning,During the post-arc recovery process,the critical breakdown voltage is always greater than TRV and the minimum breakdown margin is 11.40%,indicating that the possibility of dielectric breakdown is low.When the speed of the device is reduced to 10%,the gas chamber pressure is 0.38 MPa,or the breaking phase angle is less than 0.55?,the dielectric recovery strength is greater than the TRV,and the minimum breakdown margin is 1.22%,1.04%,and 5.70%,indicating that the probability of dielectric breakdown is low and the probability of successfully breaking the 800 A electromagnetic induction current is extremely high.In combination with contact life and cost,the original mechanical characteristics is proposed to be reduced to 10%,and the chamber pressure is proposed to be 0.38 MPa or controlling breaking phase angle to be less than 0.55?. |
PDF Full Text Request