【文章內(nèi)容簡介】 type intermittent fault of SCt =l0ms duration time, Pt =l0ms pause time, Ctype intermittent fault of SCt =l0ms duration time, Pt =l00ms pause time, Dtype intermittent fault of SCt =50ms duration time, Pt =50ms pause time. All faults have been modelled at the beginning of the line 1,adjacent to the bus following magnitudes have been registered: work voltage zero ponent, 0U ,as well as the zero ponent current of the damaged line, 01I ,and that of the undamaged line, 02I . Ⅲ . RESULTS OF EXPERMENTS ADMTI39。ANCE CRITERION Among the criterion values for protections as specified in section 1,for the 39。difficult39。 fault cases such as intermittent earth ones, thc most effective is either the admittance, 0Y ,or one of its ponents: conductance, 0G ,or susceptance, 0B . To implement the admittancetype eaah fault protections,the amplitude parators (CAI,CA2 in Fig 2) are the simplest case,the input signals created according to the following rules are being pared: iIkS 011? (1) 022 UkS ? (2) 033 UkS ? (3) The 1k , 2k and 3k ,coefficients determine the proportionality of the input signal processing in the measuring paths. . Admittancetype earth fault protection equivalent scheme The earth fault protection responding to the zero admittance module pares the 1S and 2S parison takes place within the amplitude parator CA1. The protection in the i th line acts when 2S ≤ 1S (4) It means that the operation area of protection located in the ith line is determined by the ends of admittance vectors of values meeting the condition: 21000 kkUiY ii ?? (5) In ,the startup response of such a protection is is a plainadmittance curve including equally all quarters of the plex admittance plane. Supplementary clause of the protection operation is a proper level of voltage zero ponent. In such a solution,the startup unit is the amplitude parator CA2 in which the 3S signal level is pared to that of the 4S startup signal level, according the the clause: 4033 SUkS ?? (6) where the 4S is the preset startup value due to which the earth fault can be differentiated from the normal work operation. Fig3 Startup response of the admittancetype earthfaul protenion In ,the current zero ponents in the damaged line, 01I ,and in the undamaged line, 02I , voltage zero ponent 0U as well as zeroadmittances in the damaged line, 01Y , and undamaged line, 02Y , during continuous fault (Atype) in line 1 are presented. Continuous eanh fault (Atype) in line 1 The zero admittance measured in the damaged line is somefold higher than that in the undamaged of damaged line according to criterion (4) should not pose the problems. Similar case is for an intermittent fault of relatively high interruption frequency (Btype), the corresponding runs of nalysed magnitudes are shown in . After decay of the transient state resulting from the fault ocurrence,the zero voltage remains at the level adjacent to the voltage during the continuous fault,and the admittance measured in the damaged line is all the time evidently higher than the admittance measured in the undamaged line. earth fault (Btype) in line1 earth fault (Ctype) in line1 ..Intermittent earth fault (Dtype) in line1 A discrimination of the shortcircuited line in case when the pause between successive faults is relatively long (long time Pt C and D types) can he more difficult. The runs related to such faults are shown in figures 6 and 7. During entire duration of fault,the voltage zero ponent(to which the startup signal 3S is proportional) remains at the high level。it means that the fault detection should not be difficult due to the relatively low attenuation of the voltage transients after instantaneous disappearing of the , the problems could arise with damaged line to the features of the transient process in the work resulting from the cyclic arc ignition