Ultra-high-speed relay

Claim 2

A protective relay for determining the direction to a fault, from a measuring point on an electrical power transmission line energized by an ac power source, said protective relay comprising: first means for providing a current-derived signal as a function of time, said current-derived signal being representative of the fault-generated current deviation from the steady-state pre-fault current; second means for providing a voltage-derived signal as a function of time, said voltage-derived signal being representative of the fault-generated voltage deviation from the steady-state pre-fault voltage; filter means for removing transients due to traveling wave activity from each of said current-derived and voltage-derived signals, thereby producing a filtered current-derived signal and a filtered voltage-derived signal; third means for transforming at least one of said filtered current-derived signal and said filtered voltage-derived signal such that the transformation results in the order of differentiation of said filtered current-derived signal being one order higher than the order of said filtered voltage-derived signal, with said filtered voltage-derived signal and said filtered current-derived signal of different order being referred to as first and second signals respectively; fourth means for generating a time-varying trajectory in an X-Y plane using said first and second signals as X and Y coordinates respectively; fifth means for generating a time-varying threshold boundary in at least two predetermined quadrants of said X-Y plane; and sixth means for determining when said time-varying trajectory exceeds said time-varying threshold boundary for a predetermined time thereby indicating that the fault is in a first direction from the measuring point.

Claim 3

The protective relay of claim 1 wherein the third means includes means for differentiating the filtered current-derived signal.

Claim 4

The protective relay of claim 1 wherein the third means includes means for integrating the filtered voltage-derived signal.

Claim 5

The protective relay of claim 1 wherein the Y-axis coordinate is the product of the second signal and the reactance of the electrical power transmission line at a predetermined distance from the measuring point.

Claim 6

The protective relay of claim 4 wherein the two predetermined quadrants include the second and fourth quadrants.

Claim 7

The protective relay of claim 5 wherein the time-varying threshold boundary has unit slope and a Y-axis intercept in the second and fourth quadrants representing the time-varying pre-fault voltage at the fault.

Claim 8

The protective relay of claim 6 wherein the time-varying pre-fault voltage at the measuring point represents the time-varying pre-fault voltage at the fault.

Claim 9

The protective relay of claim 6 wherein the first direction is the forward direction.

Claim 10

The protective relay of claim 1 wherein the fifth means generates the time-varying threshold boundaries in four quadrants of the X-Y plane and wherein the sixth means determines when the time-varying trajectory exceeds the time-varying threshold boundaries for a predetermined time thereby indicating that the fault is in a first or a second direction from the measuring point.

Claim 11

The protective relay of claim 1 wherein the sixth means includes a coincidence timer for determining if the time-varying trajectory exceeds the time-varying threshold boundary for the predetermined time.

Claim 12

A protective relay for determining if a fault on an electrical power transmission line energized by an ac power source is within a predetermined distance from a measuring point, said protective relay comprising: first means for providing a current-derived signal as a function of time, said current-derived signal being representative of the fault-generated current deviation from the steady-state pre-fault current; second means for providing a voltage-derived signal as a function of time, said voltage-derived signal being representative of the fault-generated voltage deviation from the steady-state pre-fault voltage; filter means for removing transients due to traveling wave activity from each of said current-derived and voltage-derived signals, thereby producing a filtered current-derived signal and a filtered voltage-derived signal; third means for transforming at least one of said filtered current-derived signal and said filtered voltage-derived signal such that the transformation results in the order of differentiation of said filtered current-derived signal being one order higher than the order of said filtered voltage-derived signal, with said filtered voltage-derived signal and said filtered current-derived signal of different order being referred to as first and second signals respectively; fourth means for generating a time-varying trajectory in an X-Y plane using said first and second signals as X and Y coordinates respectively; fifth means for generating a time-varying threshold boundary in at least two predetermined quadrants of said X-Y plane; and sixth means for determining when said time-varying trajectory exceeds said time-varying threshold boundary for a predetermined time thereby indicating that the fault is within the predetermined distance from the measuring point.

Claim 13

A protective relay for determining if a fault on an electrical power transmission line energized by an ac power source is within a predetermined distance from a measuring point, said protective relay comprising: first means for providing a current-derived signal as a function of time, said current-derived signal being representative of the fault-generated current deviation from the steady-state pre-fault current; second means for providing a voltage-derived signal as a function of time, said voltage-derived signal being representative of the fault-generated voltage deviation from the steady-state pre-fault voltage; filter means for removing transients due to traveling wave activity from each of said current-derived and voltage-derived signals, thereby producing a filtered current-derived signal and a filtered voltage-derived signal; third means for transforming at least one of said filtered current-derived signal and said filtered voltage-derived signal such that the transformation results in the order of differentiation of said filtered current-derived signal being one order higher than the order of said filtered voltage-derived signal, with said filtered voltage-derived signal and said filtered current-derived signal of different order being referred to as first and second signals respectively; fourth means for generating a time-varying trajectory in an X-Y plane using said first and second signals as X and Y coordinates respectively; fifth means for generating a time-varying threshold boundary in at least two predetermined quadrants of said X-Y plane; and sixth means for determining when said time-varying trajectory exceeds said time-varying threshold boundary for a predetermined time thereby indicating that the fault is within the predetermined distance from the measuring point.

Claim 14

A protective relay for determining the direction to a fault, from a measuring point on an electrical power transmission line energized by an ac power source, and for determining if the fault is within a predetermined distance from the measuring point, said protective relay comprising: first means for providing a current-derived signal as a function of time, said current-derived signal being representative of the fault-generated current deviation from the steady-state pre-fault current; second means for providing a voltage-derived signal as a function of time, said voltage-derived signal being representative of the fault-generated voltage deviation from the steady-state pre-fault voltage; filter means for removing transients due to traveling wave activity from each of said current-derived and voltage-derived signals, thereby producing a filtered current-derived signal and a filtered voltage-derived signal; differentiating means for producing a differentiated signal in response to said filtered current-derived signal; third means for generating a time-varying trajectory in an X-Y plane wherein the product of said differentiated signal and the reactance of the electrical power transmission line at the predetermined distance from the measuring point is the Y coordinate, and wherein the filtered voltage-derived signal is the X coordinate; fourth means for generating a first time-varying threshold boundary in the second and fourth quadrants of said X-Y plane wherein said first time-varying threshold boundary has unit slope and a Y-axis intercept in the second and fourth quadrants representing the time-varying pre-fault voltage at the fault, and for generating a second time-varying threshold boundary in the first and third quadrants of said X-Y plane wherein said second time-varying threshold boundary has negative unit slope and a Y-axis intercept in the first and third quadrants representing the negative of the time-varying pre-fault voltage at the fault; and fifth means for determining when said time-varying trajectory exceeds said time-varying threshold boundary for a predetermined time in the second or fourth quadrants of said X-Y plane thereby indicating that the fault is in a forward direction and within the predetermined distance from the measuring point, and for determining when said time-varying trajectory exceeds said time-varying threshold boundary for a predetermined time in the first or third quadrants of said X-Y plane thereby indicating that the fault is in a reverse direction and within the predetermined distance from the measuring point.

Claim 15

A protective relay for determining the direction to a fault, from a measuring point on an electrical power transmission line energized by an ac power source, and for determining if the fault is within a predetermined distance from the measuring point, said protective relay comprising: first means for providing a current-derived signal as a function of time, said current-derived signal being representative of the fault-generated current deviation from the steady-state pre-fault current; second means for providing a voltage-derived signal as a function of time, said voltage-derived signal being representative of the fault-generated voltage deviation from the steady-state pre-fault voltage; filter means for removing transients due to traveling wave activity from each of said current-derived and voltage-derived signals, thereby producing a filtered current-derived signal and a filtered voltage-derived signal; differentiating means for producing a differentiated signal in response to said filtered current-derived signal; third means for generating a time-varying trajectory in an X-Y plane wherein the product of said differentiated signal and the reactance of the electrical power transmission line at the predetermined distance from the measuring point is the Y coordinate, and wherein the filtered voltage-derived signal is the X coordinate; fourth means for generating a first time-varying threshold boundary in the second and fourth quadrants of said X-Y plane wherein said first time-varying threshold boundary has unit slope and a Y-axis intercept in the second and fourth quadrants representing the time-varying pre-fault voltage at the fault, and for generating a second time-varying threshold boundary in the first and third quadrants of said X-Y plane wherein said second time-varying threshold boundary has negative unit slope and a Y-axis intercept in the first and third quadrants representing the negative of the time-varying pre-fault voltage at the fault; and fifth means for determining when said time-varying trajectory exceeds said time-varying threshold boundary for a predetermined time in the second or fourth quadrants of said X-Y plane thereby indicating that the fault is in a forward direction and within the predetermined distance from the measuring point, and for determining when said time-varying trajectory exceeds said time-varying threshold boundary for a predetermined time in the first or third quadrants of said X-Y plane thereby indicating that the fault is in a reverse direction and within the predetermined distance from the measuring point.