SYSTEM FOR LOGIC POWER SELECTIVE PROTECTION OF PARALLEL ELECTRIC CIRCUITS Russian patent published in 2008 - IPC H02H7/00 H02H3/16 

FIELD: electric engineering.

SUBSTANCE: system can be used for protection of parallel circuits from short circuit current. System for protection of parallel circuits, having number of steps of protection being equal to K starting from current source, keys with maximal current release mechanisms are mounted at last, K-th step; adjusted setting equals to Is without time delay for switching-off. Selective switches are mounted at steps K-1-th. Those switches have maximal current release mechanisms which have adjusted current settings I_s1 and I_s2 in area of short circuit currents. Within short circuit currents from I_s1 to I_s2, time of operation of maximal current release mechanism is delayed to provide set of fixed delay times (t_sc=const). In case short circuit currents exceed cut-off current I_s2, special delay of time of operation of maximal current release mechanism is absent (t_sc=0). There is also arc maximal power or maximal pressure switching-off release mechanisms in switches of described system, which pressure is provided by extraction of energy of switching-off arc. Setting of maxima; power of switch-off arc Ws or pressure p_s of any mentioned selective switch is chosen within (1,5-3) range of values of maximal energy of arc switching-off W_ams or pressure p_ms, which energy releases in any specified switch when short circuit emerges at output terminals of switches standing below and at combined switching-off of that short-circuited circuit by selective switch standing above and by one of apparatus standing below till (0,9-1,0) value of arc switch energy W_aso or pressure p_so in case when mentioned switch commutates short-circuit current being equal to setting of cut-off current of its release mechanism.

EFFECT: selectiveness; minimal time of switching of short-circuit current off at any steps of protection.

6 dwg