Protective relay apparatus and method for providing single-pole tripping

Claim 2

A phasor-comparison protective-relay system detecting the faulted phase conductor of a three-phase ac transmission line section having a circuit interrupter on each of the first, second, and third phase conductors at each of the local and remote terminals thereof, said phasor-comparison protective-relay system comprising: means at each of the local and remote terminals responsive to first, second, and third electrical parameters thereat for providing first and second local derived signals at the local terminal, and first and second remote derived signals at the remote terminal; means at each of the local and remote terminals for transmitting said first and second local derived signals to the remote terminal and for transmitting said first and second remote derived signals to the local terminal; means at each of the local and remote terminals for expanding said first and second derived signals received from the other into first, second, and third local comparison signals at the local terminal and first, second, and third remote comparison signals at the remote terminal; and comparator means at each of the local and remote terminals for logically relating said first, second, and third local comparison signals at the local terminal and said first, second, and third remote comparison signals at the remote terminal to detect the faulted phase conductor and for tripping the circuit interrupter on the faulted phase conductor at each of the local and remote terminals.

Claim 3

The phasor-comparison protective relay system of claim 1 wherein the first, second, and third electrical parameters represent voltages.

Claim 4

The phasor-comparison protective relay system of claim 1 wherein the first, second, and third electrical parameters represent currents.

Claim 5

The phasor-comparison protective relay system of claim 1 wherein the first, second, and third electrical parameters represent power.

Claim 6

The phasor-comparison protective relay system of claim 1 wherein the first local derived signal represents the phasor difference of the first and second electrical parameters at the local terminal, and the second local derived signal represents the phasor difference of the second and third electrical parameters at the local terminal, and wherein the first remote derived signal represents the phasor difference of the first and second electrical parameters at the remote terminal and the second remote derived signal represents the phasor difference of the second and third electrical parameters at the remote terminal.

Claim 7

The phasor-comparison protective relay system of claim 1 including a third local derived signal, wherein said third local derived signal is the phasor sum of the first and second local derived signals.

Claim 8

The phasor-comparison protective relay system of claim 6 including a third remote derived signal wherein said third remote derived signal is the phasor sum of the first and second remote derived signals.

Claim 9

The phasor-comparison protective relay system of claim 7 including means at each of the local and remote terminals for vectorially relating the first, second, and third local derived signals with, respectively, the first, second, and third remote derived signals and for producing the first, second, and third local comparison signals at the local terminal and for producing the first, second, and third remote comparison signals at the remote terminal.

Claim 10

The phasor-comparison protective relay system of claim 8 wherein the first local and first remote comparison signals are the phasor difference of the first local derived signal and the first remote derived signal, and wherein the second local and second remote comparison signals are the phasor difference of the second local derived signal and the second remote derived signal, and wherein the third local and third remote comparison signals are the phasor difference of the third local derived signal and the third remote derived signal.

Claim 11

The phasor-comparison protective relay system of claim 1 wherein the comparator means at the local terminal includes: first level detector means for producing a first local logic signal having a first state when the first local comparison signal is greater than a predetermined value and having a second state when the first local comparison signal is less than said predetermined value; second level detector means for producing a second local logic signal having a first state when the second local comparison signal is greater than a predetermined value and having a second state when the second local comparison signal is less than said predetermined value; third level detector means for producing a third local logic signal having a first state when the third local comparison signal is greater than a predetermined value and having a second state when the third local comparison signal is less than said predetermined value; and evaluation means for evaluating said first, second, and third local logic signals for producing a first local trip signal if the first phase conductor is faulted to ground, for producing a second local trip signal if the second phase conductor is faulted to ground, for producing a third local trip signal if the third phase conductor is faulted to ground, and for producing a fourth local trip signal if said phasor comparison protective relay system is unable to determine on which phase conductor the fault is located, wherein said first local trip signal opens the circuit interrupter at the local terminal on the first phase conductor, wherein said second local trip signal opens the circuit interrupter at the local terminal on the second phase conductor, wherein said third local trip signal opens the circuit interrupter at the local terminal on the third phase conductor, and wherein said fourth local trip signal opens the circuit interrupters at the local terminal on the first, second, and third phase conductors.

Claim 12

The phasor-comparison protective relay system of claim 10 wherein the first local trip signal is produced when the first and third local logic signals are in the first state and the second local logic signal is in the second state.

Claim 13

The phasor-comparison protective relay system of claim 10 wherein the second local trip signal is produced when the first and second local logic signals are in the first state and the third local logic signal is in the second state.

Claim 14

The phasor-comparison protective relay system of claim 10 wherein the third local trip signal is produced when the second and third local logic signals are in the first state and the first local logic signal is in the second state.

Claim 15

The phasor-comparison protective relay system of claim 10 wherein the fourth local trip signal is produced when the first, second, and third local logic signals are in the first state.

Claim 16

The phasor-comparison protective relay system of claim 1 wherein the comparator means at the remote terminal includes: first level detector means for producing a first remote logic signal having a first state when the first remote comparison signal is greater than a predetermined value and having a second state when the first remote comparison signal is less than said predetermined value; second level detector means for producing a second remote logic signal having a first state when the second remote comparison signal is greater than a predetermined value and having a second state when the second remote comparison signal is less than said predetermined value; third level detector means for producing a third remote logic signal having a first state when the third remote comparison signal is greater than a predetermined value and having a second state when the third remote comparison signal is less than said predetermined value; and evaluation means for evaluating the first, second, and third remote logic signals for producing a first remote trip signal if the first phase conductor is faulted to ground, for producing a second remote trip signal if the second phase conductor is faulted to ground, for producing a third remote trip signal if the third phase conductor is faulted to ground, and for producing a fourth remote trip signal if said phasor comparison protective relay system is unable to determine on which phase conductor the fault is located, wherein said first remote trip signal opens the circuit interrupter at the remote terminal on the first phase conductor, wherein said second remote trip signal opens the circuit interrupter at the remote terminal on the second phase conductor, wherein said third remote trip signal opens the circuit interrupter at the remote terminal on the third phase conductor, and wherein said fourth remote trip signal opens the circuit interrupters at the remote terminal on the first, second, and third phase conductors.

Claim 17

The phasor-comparison protective relay system of claim 15 wherein the first remote trip signal is produced when the first and third remote logic signals are in the first state and the second remote logic signal is in the second state.

Claim 18

The phasor-comparison protective relay system of claim 15 wherein the second remote trip signal is produced when the first and second remote logic signals are in the first state and the third remote logic signal is in the second state.

Claim 19

The phasor-comparison protective relay system of claim 15 wherein the third remote trip signal is produced when the second and third remote logic signals are in the first state and the first remote logic signal is in the second state.

Claim 20

The phasor-comparison protective relay system of claim 15 wherein the fourth remote trip signal is produced when the first, second, and third remote logic signals are in the first state.

Claim 21

A phasor-comparison protective relay tripping a faulted conductor of a three-phase ac transmission line section having a circuit interrupter on each of a first, second, and third phase conductors at local and remote terminals thereof, wherein local circuit interrupters are controlled by said phasor-comparison protective relay at the local terminal and remote circuit interrupters are controlled by a remote protective relay located at the remote terminal, and wherein said phasor-comparison protective relay and the remote protective relay are in communication via a communications channel, and wherein the remote protective relay includes a remote receiver and a remote transmitter, and wherein the remote transmitter transmits a plurality of remote status signals to said phasor-comparison protective relay representative of the electrical status of the first, second, and third phase conductors at the remote terminal, said phasor-comparison protective relay comprising: means at the local terminal responsive to first, second, and third electrical parameters thereat for providing first and second local derived signals; local transmitter means for transmitting said first and second local derived signals to the remote receiver via the communications channel, wherein the remote protective relay is responsive to said first and second local derived signals for controlling the circuit interrupters at the remote end; local receiver means responsive to the plurality of remote status signals transmitted by the remote transmitter via the communications channel, for producing a plurality of received signals in response thereto; means reponsive to the plurality of received signals for producing first and second remote derived signals; means for expanding said first and second local derived signals and said first and second remote derived signals into first, second, and third comparison signals; comparator means for logically relating said first, second, and third comparison signals to detect the faulted phase conductor and for tripping the local circuit interrupter on the faulted phase conductor.

Claim 22

A phasor-comparison protective relay tripping a faulted conductor of a three-phase ac transmission line section having a circuit interrupter on each of a first, second, and third phase conductors at local and remote terminals thereof, wherein local circuit interrupters are controlled by said phasor-comparison protective relay at the local terminal and remote circuit interrupters are controlled by a remote protective relay located at the remote terminal, and wherein said phasor-comparison protective relay and the remote protective relay are in communication via a communications channel, and wherein the remote protective relay includes a remote receiver and a remote transmitter, and wherein the remote transmitter transmits a plurality of remote status signals to said phasor-comparison protective relay representative of the electrical status of the first, second, and third phase conductors at the remote terminal, said phasor-comparison protective relay comprising: means at the local terminal responsive to first, second, and third electrical parameters thereat for providing first and second local derived signals; local transmitter means for transmitting said first and second local derived signals to the remote receiver via the communications channel, wherein the remote protective relay is responsive to said first and second local derived signals for controlling the circuit interrupters at the remote end; local receiver means responsive to the plurality of remote status signals transmitted by the remote transmitter via the communications channel, for producing a plurality of received signals in response thereto; means reponsive to the plurality of received signals for producing first and second remote derived signals; means for expanding said first and second local derived signals and said first and second remote derived signals into first, second, and third comparison signals; comparator means for logically relating said first, second, and third comparison signals to detect the faulted phase conductor and for tripping the local circuit interrupter on the faulted phase conductor.

Claim 23

The phasor-comparison protective relay of claim 20 wherein the first, second, and third electrical parameters represent the voltages on, respectively, the first, second, and third phase conductors at the local terminal.

Claim 24

The phasor-comparison protective relay of claim 20 wherein the first, second, and third electrical parameters represent the currents on, respectively, the first, second, and third phase conductors at the local terminal.

Claim 25

The phasor-comparison protective relay of claim 20 wherein the first, second, and third electrical parameters represent the power on, respectively, the first, second, and third phase conductors at the local terminal.

Claim 26

The phasor-comparison protective relay of claim 20 wherein the first local derived signal represents the phasor difference of the first and second electrical parameters, and wherein the second local derived signal represents the phasor difference of the second and third electrical parameters.

Claim 27

The phasor-comparison protective relay of claim 20 including a third local derived signal, wherein said third local derived signal is the phasor sum of the first and second local derived signals.

Claim 28

The phasor-comparison protective relay of claim 25 wherein the first comparison signal is the phasor difference of the first local derived signal and the first remote derived signal, and wherein the second comparison signal is the phasor difference of the second local derived signal and the second remote derived signal, and wherein the third comparison signal is the phasor difference of the third local derived and the third remote derived signal.

Claim 29

The phasor comparison protective relay of claim 20 wherein the comparator means includes: first level detector means for producing a first logic signal having a first state when the first comparison signal is greater than a predetermined value and having a second state when the first comparison signal is less than said predetermined value; second level detector means for producing a second logic signal having a first state when the second comparison signal is greater than a predetermined value and having a second state when the second comparison signal is less than said predetermined value; third level detector means for producing a third logic signal having a first state when the third comparison signal is greater than a predetermined value and having a second state when the third logic signal is less than said predetermined value; and evaluation means for evaluating said first, second, and third logic signals for producing a first trip signal if the first phase conductor is faulted to ground, for producing a second trip signal if the second phase conductor is faulted to ground, for producing a third trip signal if the third phase conductor is faulted to ground, and for producing a fourth trip signal if said phasor comparison protective relay is unable to determine on which phase conductor the fault is located, wherein said first trip signal opens the circuit interrupter on the first phase conductor, wherein said second trip signal opens the circuit interrupter on the second phase conductor, wherein said third trip signal opens the circuit interrupter on the third phase conductor, and wherein said fourth trip signal opens the circuit interrupters on the first, second, and third phase conductors.

Claim 30

The phasor-comparison protective relay of claim 27 wherein the first trip signal is produced when the first and third logic signals are in the first state and the second logic signal is in the second state.

Claim 31

The phasor-comparison protective relay of claim 27 wherein the second trip signal is produced when the first and second logic signals are in the first state and the third logic signal is in the second state.

Claim 32

The phasor-comparison protective relay of claim 27 wherein the third trip signal is produced when the second and third logic signals are in the first state and the first logic signal is in the second state.

Claim 33

The phasor-comparison protective relay of claim 27 wherein the fourth trip signal is produced when the first, second, and third logic signals are in the first state.

Claim 36

The method of claim 32 wherein the step of providing the first and second local derived signals includes substracting the electrical parameter on the second phase conductor at the local terminal from the electrical parameter on the first phase conductor at the local terminal to produce the first local derived signal, and subtracting the electrical parameter on the third phase conductor at the local terminal from the electrical parameter on the second phase conductor at the local terminal to produce the second local derived signal.

Claim 37

The method of claim 32 wherein the step of providing the first and second remote derived signals includes subtracting the electrical parameter on the second phase conductor at the remote terminal from the electrical parameter on the first phase conductor at the remote terminal to produce the first remote derived signal, and subtracting the electrical parameter on the third phase conductor at the remote terminal from the electrical parameter on the second phase conductor at the remote terminal to produce the second remote derived signal.

Claim 38

The method of claim 32 wherein the step of expanding the first and second local derived signals includes adding the first and second local derived signals to produce a third local derived signal at each of the local and remote terminals.

Claim 39

The method of claim 35 wherein the step of expanding the first and second remote derived signals includes adding the first and second remote derived signals to produce a third remote derived signal at each of the local and remote terminals.

Claim 40

The method of claim 36 wherein the step of logically relating the first, second, and third comparison signals at each of the local and remote terminals includes vectorially substracting the first remote derived signal from the first local derived signal to produce the first comparison signal at each of the local and remote terminals, vectorially subtracting the second remote derived signal from the second local derived signal to produce the second comparison signal at each of the local and remote terminals, and vectorially subtracting the third remote derived signal from the third local derived signal to produce the third comparison signal at each of the local and remote terminals.

Claim 41

The method of claim 37 wherein the step of logically relating the first, second, and third comparison signals at each of the local and remote terminals includes: producing a first logic signal at each of the local and remote terminals having a first state when the first comparison signal at each of the local and remote terminals is greater than a predetermined value and having a second state when the first comparison signal is less than said predetermined value; producing a second logic signal at each of the local and remote terminals having a first state when the second comparison signal at each of the local and remote terminals is greater than a predetermined value, and having a second state when the first comparison signal is less than said predetermined value; producing a third logic signal at each of the local and remote terminals having a first state when the third comparison signal at each of the local and remote terminals is greater than a predetermined value, and having a second state when the third comparison signal is less than said predetermined value; and evaluating said first, second, and third logic signals at each of the local and remote terminals to produce a first trip signal at each of the local and remote terminals when said first and third logic signals are in the first state and said second logic signal is in the second state, to produce a second trip signal at each of the local and remote terminals when said first and second logic signals are in the first state and said third logic signal is in the second state, to produce a third trip signal at each of the local and remote terminals when said second and third logic signals are in the first state and said first logic signal is in the second state, and to produce a fourth trip signal when said first, second, and third logic signals are in the first state, wherein said first trip signal opens the circuit interrupter at each of the local and remote terminals on the first phase conductor, and wherein said second trip signal opens the circuit interrupter at each of the local and remote terminals on the second phase conductor, and wherein said third trip signal opens the circuit interrupter at each of the local and remote terminals on the third phase conductor, and wherein said fourth trip signal opens the circuit interrupters at each of the local and remote terminals on the first, second, and third phase conductors.