Research And Emulation Of Adaptive Reclosure In Transmission Lines

The faults of transmission lines are most temporary ones in power system. So, the auto-reclosure technique has been widely applied in real power systems now. It is an effective method to improve the stability and synchronism of power systems. However, the present auto-reclosure technique normally employs a prescribed reclosure time, that is, the breaker is re-closed after a fixed period following a tripping operation without estimating fault nature. Main problem with the conventional reclosure scheme is a risk of a second shock to the system in the case of a permanent fault, when may lead to system oscillation.In order to avoid the power system disaster caused by reclosing on the permanent fault of transmission line , adaptive autoreclosure based on microproeessor-based protection arises at the historic moment,but is still in the stage of theory study.This paper has proposed one new way of thought of differentiating the fault type. After observing the physical course of the single-phase grounding of transmission line,analyzing the different characters of phases affected by the arc between the temporary faults from permanent ones during the fault period from the moment that single- phased grounding occurs to the moment that line breakers work , and emulating by PSB in MATLAB ,we can distinguish temporary fault from permanent one through the phase form. As far as time cost and accuracy are concerned,this criterion based on wave form discernment is superior to the traditional one based on the transmission 1ine voltage amplitude sampled after breakers work and has been verified its exactness by dynamic emulation.Finally, the disadvantages of existent schemes and proposals to improve the criteria are pointed out.