公开(公告)号：US3569785A

公开(公告)日：1971-03-09

申请号：US3569785D

申请日：1968-07-09

Applicant: IBM

Inventor： DURBECK ROBERT C ,  MANTLEY PATRICK E

IPC: G01R21/133 ,  H02H3/40

CPC classification number: H02H3/40 ,  G01R21/133

Abstract: A method of controlling the operation of a breaker in a transmission line by first monitoring the current and if the current exceeds a prescribed limit, measuring a sampling of the voltage on the line when the current is at zero and dividing this value by the maximum current on the line to obtain a first quantity which is added to a second quantity obtained by measuring a sampling of the voltage when the current is at its maximum value and dividing this voltage by the maximum current. The previous calculations will provide a measure of impedance since the voltage when the current is zero is equal to Vm sin phi while the voltage when the current is at maximum is equal to Vm cosine phi and impedance in a rectangular coordinate representation is: z R jX Vm cosine phi /Im + j(Vmsin phi /Im). This apparent impedance is then compared against relay characteristics which are implemented in a programmed general purpose computer and in the event the apparent impedance lies within the relay characteristic zone, the associated breaker is tripped.