Fault Component Impedance Relay with Double Circular Characteristic

Although the fault component impedance relay has many perfect performances, it is still restricted by high fault resistance. In order to improve its resistive tolerance and overcome unreliable operation, a new type relay with double circular characteristic is put forward, as well as its operating boundary and general operating equation are researched in this paper. The relay is comprised of two groups operation equations, one of them is calculated by sampling integral arithmetic to achieve its ultra-high speed while the other by Fourier arithmetic to enhance the relay capability against high resistance. Dynamic simulation test has been made with a typical two sources system operating at 750 kV to verify the relay performance. Theoretical analyses and test results show that the fault component impedance relay with double circular characteristic is simple, reliable and secure with ultra-high speed and great capability against fault resistance.