Eliminate The Development Of The Arc Harmonic Elimination Line Selection Device

The most distribution network and power supply of large industrial-mining enterprises of our country are Non-ground or Peterson-coil-ground system. The Peterson-coil can eliminate the power-frequency electric arc, but the application of Peterson-coil, in one hand make the fault line's selection more difficult; in second hand, with the enlarge of the town and countryside's power network and the addition of the cable, the electric arc is difficult to extinguish by it. The study of line selection of single phase earth fault, make many progress. But the line selection device base of these fault line selection principle, didn't have the reliability and veracity of apply in the power system.So a new type device is introduced, which can take the place of Peterson-coil to eliminate arcing fault, and distinguish the single phase fault and ferroresonance fault, then eliminate it. The line selection of this device is high.At the first, the paper analyze the single phase fault and ferroresonance fault, these process are emulated by Matlab. By the alternate electric arc theory, the electric arc will extinguish at the time of the current crossing zero, whether the electric arc can extinguish, is decided by the relationship of medium renew intension U_jf and renew voltage U_fh. When the fault phase's renew voltage raise to a high value, if the U_jf >U_fh, the electric arc will ignite again, this case went on, a steady arcing fault is formed. If we can make the renew voltage don't raise at the set point value, and keep it some time, while the medium renew intension and dissociate rate raise with time. This can make U_jf fh, then the electric arc will not ignite again, the aim of eliminating the electric arc is reached. With what we said above, we advance some plans that adopt limiting the fault phase voltage raise rate to replace the Peterson-coil: using metal oxide nonlinearity resistance to restrain the renew rate of fault phase voltage to eliminate the electric arc; or earth the fault phase directly, then the arcing fault which is more harm to power system, is changed to metal earth fault.The paper analyze the shadowy earth fault which is caused by PT saturation,and find out the difference between the this and single phase earth fault, the method of eliminating ferroresonance of this device is given.Later the paper analyses the line selection ago and find out the advantage and disadvantage of them, put forward to change the parameter of power system, adding the fault information to select the fault line.The foremost character of this device is replacing the Peterson-coil to eliminate the electric arc, divide the single phase fault case into metal earth fault, intermittent arcing fault, permanence arcing fault, changing the line selection problem to the line selection in the case of metal earth fault and permanence arcing fault of ungrounded power systems, this make line selection veracity increase more.At last, base on the theory said above, the paper advances the design o f this device, which is based on PC 104. The device action mechanism is introduced, the information what is needed to collect and sampling rate, request of hardware is explained. Then we choose the hardware thought comparing some project and make software design, including the criterion of the fault judgment and algorithm of line selection, eliminate electric arc and ferroresonance program.