Segregated phase comparison system
AssigneeWestinghouse Electric Corp.
InventorKalyan K. Mustaphi
Life of this patent
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Abstract
This disclosure relates to phase comparison relaying systems for a three phase power transmission line in which the current is measured at each end of each phase conductor. The phasor difference of the currents in a selected two of the phase conductors is determined at each end of the selected conductors and is phase compared to determine the location of phase-to-phase faults whether or not a ground fault is involved while the phasor sum of the current in all three of the phase conductors is determined at each end of the phase conductors and is phase compared to determine the location of phase-to-ground faults.
Claims6
A phase comparing relay for protecting a line section of a three phase power transmitting network, said relay comprising, a plurality of current sensing means, a first and a second and a third of said sensing means being individually associated with the phase conductors of said line section at a first location therealong and providing output current quantities proportional to the phase and magnitude of the current in the said phase conductor with which it is associated, first current quantity summing means connected to said first and said second sensing means and providing a first output signal which is a measure of the phasor difference of said current quantities of said first and second sensing means, second current quantity summing means connected to said first and second and third sensing means and providing a second output signal which is a measure of the phasor sum of said current quantities of said first and second and third sensing means, a first and a second signal comparing means, a first signal receiving means adapted to receive a first and a second transmitter signal, circuit means interconnecting said first and second comparing means with said first and second summing means respectively and with said first receiving means for energization of said first comparing means with said first output signal and said first transmitted signal and for energization of said second comparing means with said second output signals and said second transmitted signal, a first actuating circuit connected to said first and second comparing means, each of said first and second comparing means being effective to actuate said first actuating circuit at predetermined relationships of the said signals supplied thereto.
The method of comparing the relative phase of the current at the opposite end portions of a three conductor three phase power transmission line section, said method comprising the steps of obtaining first and second phasor quantities proportional to the phasor difference of the current of two of the conductors existing at substantially concurrently first and second end portions of the line section, of comparing the phase of said first and said second phasor quantities to determine whether a conductor-to-conductor fault is internal to or external to the line section, of obtaining third and fourth phasor quantities proportional to the phasor sum of the current in the three conductors existing substantially concurrently at said first and said second end portions of the line section, of comparing the phase of said third and said fourth phasor quantities to determine whether a conductor-to-ground fault is internal to or external to the line section, and of preventing the disconnecting of the line section from its power source unless at least one of said comparisons determines that the fault is internal to said line section.
Dependencies are inferred from the claim text.