Means for monitoring the safety of a remote electrical ground connection

Claim 2

Elongate transmission-line means having a source-connection end and a remote load-connection end and comprising powerconductor means, a ground conductor and a pilot conductor; a d-c conducting connection of said power-conductor means to said ground and pilot conductors at the source-connection end; a d-c conducting connection to said power-conductor means at the loadconnection end; whereby relatively constant resistance values characterize the d-c conducting paths from the respective loadconnection ends of said power-conductor means and of said pilotconductor means, to said d-c conducting connection at the sourceconnection end; means for impressing a d-c potential across the full length of said ground conductor, said last-mentioned means including a d-c source in one of said paths and a circuit connection of said one path and said ground conductor at the load-connection ends thereof; and d-c responsive resistancemonitoring means at the load-connection end and including a reference connection to the source-connection end of said ground conductor via the other of said paths, said resistance-monitoring means being also connected to the load-connection end of said ground conductor and thus tracking the instantaneous effective resistance between the source-connection and load-connection ends thereof.

Claim 3

Transmission-line means according to claim 1, in which the path which includes said d-c source is the pilot-conductor path.

Claim 4

Transmission-line means according to claim 1, in which said resistance-monitoring means includes threshold-operative means for responding to a preselected measured-resistance level, said level being preselected to a maximum tolerable level above the known resistance of the ground conductor in good condition.

Claim 5

Transmission-line means according to claim 1, in which said resistance-monitoring means includes connected elements of a bridge circuit having a first excitation terminal at the remote-connection end of said one path and a second excitation terminal at the source-connection end of said one path, a first pair of conjugate fixed-resistance arms between said terminals, said fixed-resistance arms being located at said remote-connection end and including said other path to establish the connection to said second excitation terminal, a second pair of conjugate arms between said terminals, one arm of said second pair being the full length of said ground conductor, and the other arm of said second pair comprising a resistance of value preselected to bear substantially the same relation to the normal good-condition resistance value of said ground conductor that said fixed-resistance arms bear to each other, and means for monitoring voltage observed between the point of connection of the first pair of arms to each other and the point of connection of the second pair of arms to each other.

Claim 6

Transmission-line means according to claim 1, in which said one path includes means for maintaining a substantially constant predetermined d-c current flow in said one path, and in which said monitoring means is voltage-responsive.

Claim 7

Transmission-line means according to claim 1, in which said power-conductor means comprises multiple conductors connected for the remote transmission of three-phase power, an end of said power-conductor means being Y-connected, the d-c conducting connection to said Y-connected end including a grounding resistance and being connected to the center of the Y.

Claim 8

Transmission-line means according to claim 1, in which said power-conductor means comprises multiple conductors connected for the remote transmission of three-phase power, an end of said power-conductor means being Delta -connected, and the d-c conducting connection thereto including separate high-resistance arms connected at one end to the respective power conductors and interconnected at their other ends to define a neutral point, said d-c conducting connection being to said neutral point.

Claim 9

Transmission-line means hAving a source-connection end and a remote load-connection end and comprising multiple power conductors, a ground conductor and a pilot conductor; an independent circuit comprising a pilot arm in which a d-c source is series-connected to said pilot conductor, one end of said arm being connected to the corresponding end of said ground conductor, and means connecting the other ends of said pilot arm and ground conductor, whereby a d-c current will normally flow in said independent circuit; and means including a d-c conducting connection to the load-connection end of said power conductors and a d-c conducting connection to the source-connection end of said ground conductor for sensing the d-c potential end-to-end across the length of said ground conductor.

Claim 10

Transmission-line means hAving a source-connection end and a remote load-connection end and comprising multiple power conductors, a ground conductor and a pilot conductor; an independent circuit comprising a pilot arm in which a d-c source is series-connected to said pilot conductor, one end of said arm being connected to the corresponding end of said ground conductor, and means connecting the other ends of said pilot arm and ground conductor, whereby a d-c current will normally flow in said independent circuit; and means including a d-c conducting connection to the load-connection end of said power conductors and a d-c conducting connection to the source-connection end of said ground conductor for sensing the d-c potential end-to-end across the length of said ground conductor.

Claim 11

Transmission-line means according to claim 8, in which the pilot-conductor part of said independent circuit includes means for regulating current to a substantially constant flow, whereby said sensed d-c potential is directly responsive to the instantaneous value of resistance between the source-connection and load-connection ends of said ground conductor.

Claim 12

Transmission-line means according to claim 8, in which said pilot arm and therefore said d-c source is connected across opposed corners of a resistance-bridge circuit in which said ground conductor and said sensing means form operative component parts, said bridge circuit further including conjugate fixed-resistance arms one of which includes said power conductors and the d-c conducting connections thereto.

Claim 13

Transmission-line means having a source-connection end and a remote load-connection end and comprising a ground conductor, a pilot conductor and multiple further conductors including power conductors; circuit-breaker means for said power conductors at the source-connection end; a d-c conducting connection of at least one of said further conductors to said ground conductor at the source-connection end; a d-c conducting connection for said one further conductor at the load-connection end; an independent circuit comprising a pilot arm in which a d-c source is series-connected to said pilot conductor, one end of said arm being connected to the corresponding end of said ground conductor, and means connecting the other ends of said pilot arm and ground conductor; means including a d-c conducting connection to the load-connection end of said one further conductor for sensing the d-c potential from end to end of said ground conductor; and circuit-breaker trip means operatively connected to said sensing means and responsive to trip said circuit-breaker means upon the sensing of a predetermined level of said d-c potential.

Claim 14

Transmission-line means having a source-connection end and a remote load-connection end and comprising a ground conductor, a pilot conductor and multiple further conductors including power conductors; circuit-breaker means for said power conductors at the source-connection end; a d-c conducting connection of at least one of said further conductors to said ground conductor at the source-connection end; a d-c conducting connection for said one further conductor at the load-connection end; an independent circuit comprising a pilot arm in which a d-c source is series-connected to said pilot conductor, one end of said arm being connected to the corresponding end of said ground conductor, and means connecting the other ends of said pilot arm and ground conductor; means including a d-c conducting connection to the load-connection end of said one further conductor for sensing the d-c potential from end to end of said ground conductor; and circuit-breaker trip means operatively connected to said sensing means and responsive to trip said circuit-breaker means upon the sensing of a predetermined level of said d-c potential.

Claim 15

Transmission-line means having a source-connection end and a remote load-connection end and comprising multiple power conductors, a ground conductor and a pilot conductor; circuit-breaker means for said power conductors at the source-connection end; a d-c conducting connection of said power conductors to said ground conductor at the source-connection end; an independent circuit comprising a pilot arm in which a d-c source is series-connected to said pilot conductor, one end of said arm being connected to the corresponding end of said ground conductor, and means connecting the other ends of said pilot arm and ground conductor; means in said pilot arm for establishing a predetemined d-c current level in said circuit; means at the remote end of said transmission-line means for sensing the d-c potential on at least one of said power conductors with respect to the remote end of said ground conductor; and circuit-breaker trip means operative upon detection by said last-defined means of a predetermined d-c voltage level.

Claim 16

Transmission-line means having a source-connection end and a remote load-connection end and comprising multiple power conductors, a ground conductor and a pilot conductor; circuit-breaker means for said power conductors at the source-connection end; a d-c conducting connection of said power conductors to said ground conductor at the source-connection end; an independent circuit comprising a pilot arm in which a d-c source is series-connected to said pilot conductor, one end of said arm being connected to the corresponding end of said ground conductor, and means connecting the other ends of said pilot arm and ground conductor; means in said pilot arm for establishing a predetemined d-c current level in said circuit; means at the remote end of said transmission-line means for sensing the d-c potential on at least one of said power conductors with respect to the remote end of said ground conductor; and circuit-breaker trip means operative upon detection by said last-defined means of a predetermined d-c voltage level.

Claim 17

Elongate flexible grounding-line means having an electrically conductive reference-potential end and a remote electrically conductive end to be safely ground-referenced to said reference-potential end and comprising multiple conductors including a ground conductor and plural further conductors; an independent saFety-monitoring circuit comprising a pilot arm in which a voltage source is series-connected to one of said further conductors, one end of said arm being connected to the corresponding end of said ground conductor, and means connecting the other ends of said pilot arm and ground conductor; means connecting the reference-potential ends of another of said further conductors and of said ground conductor; means in the pilot arm of said circuit for establishing a predetermined current level in said circuit; means at the remote end of said grounding-line means for sensing the potential on said another conductor with respect to the remote end of said ground conductor; and safety-threshold means operative upon detection by said last-defined means of a predetermined voltage level.

Claim 18

Elongate flexible grounding-line means having an electrically conductive reference-potential end and a remote electrically conductive end to be safely ground-referenced to said reference-potential end and comprising multiple conductors including a ground conductor and plural further conductors; an independent saFety-monitoring circuit comprising a pilot arm in which a voltage source is series-connected to one of said further conductors, one end of said arm being connected to the corresponding end of said ground conductor, and means connecting the other ends of said pilot arm and ground conductor; means connecting the reference-potential ends of another of said further conductors and of said ground conductor; means in the pilot arm of said circuit for establishing a predetermined current level in said circuit; means at the remote end of said grounding-line means for sensing the potential on said another conductor with respect to the remote end of said ground conductor; and safety-threshold means operative upon detection by said last-defined means of a predetermined voltage level.

Claim 19

Elongate flexible grounding-line means having an electrically conductive reference-potential end and a remote electrically conductive end to be safely ground-referenced to said reference-potential end and comprising multiple conductors including a ground conductor and plural further conductors; an independent safety-monitoring circuit comprising a pilot arm in which a voltage source is series-connected to one of said further conductors, one end of said arm being connected to the corresponding end of said ground conductor, and means connecting the other ends of said pilot arm and ground conductor; means connecting the reference-potential ends of another of said further conductors and of said ground conductor; means including a connection to the remote end of said another further conductor and a connection to the remote end of said ground conductor for sensing the resistance between ends of said ground conductor; and safety-threshold means operative upon detection by said last-defined means of a predetermined resistance level.

Claim 20

Elongate flexible grounding-line means having an electrically conductive reference-potential end and a remote electrically conductive end to be safely ground-referenced to said reference-potential end and comprising multiple conductors including a ground conductor and plural further conductors; an independent safety-monitoring circuit comprising a pilot arm in which a voltage source is series-connected to one of said further conductors, one end of said arm being connected to the corresponding end of said ground conductor, and means connecting the other ends of said pilot arm and ground conductor; means connecting the reference-potential ends of another of said further conductors and of said ground conductor; means including a connection to the remote end of said another further conductor and a connection to the remote end of said ground conductor for sensing the resistance between ends of said ground conductor; and safety-threshold means operative upon detection by said last-defined means of a predetermined resistance level.

Claim 21

Elongate flexible grounding-line means having an electrically conductive reference-potential end and a remote electrically conductive end to be safely ground-referenced to said reference-potential end and comprising multiple conductors including a ground conductor and a pilot conductor having a conductive connection to each other at one end, and resistance-bridge elements connected to the other ends of said ground and pilot conductors; said bridge elements comprising connected conjugate fixed-resistance members between opposed bridge-excitation points, a voltage source connecting one of said points to to said other end of said pilot conductor, a monitoring resistance selected for value substantially corresponding to the desired safety-limit value of said ground conductor and in substantially the same proportional relationship therewith as the values of said fixed-resistance members bear to each other, said monitoring resistance connecting the said other end of said ground conductor to said one point, thereby defining second conjugate members connected between said points, and voltage-responsive means interconnecting said conjugate arms at the respective member-to-member connections thereof.

Claim 22

Elongate flexible grounding-line means having an electrically conductive reference-potential end and a remote electrically conductive end to be safely ground-referenced to said reference-potential end and comprising multiple conductors including a ground conductor and a pilot conductor having a conductive connection to each other at one end, and resistance-bridge elements connected to the other ends of said ground and pilot conductors; said bridge elements comprising connected conjugate fixed-resistance members between opposed bridge-excitation points, a voltage source connecting one of said points to to said other end of said pilot conductor, a monitoring resistance selected for value substantially corresponding to the desired safety-limit value of said ground conductor and in substantially the same proportional relationship therewith as the values of said fixed-resistance members bear to each other, said monitoring resistance connecting the said other end of said ground conductor to said one point, thereby defining second conjugate members connected between said points, and voltage-responsive means interconnecting said conjugate arms at the respective member-to-member connections thereof.

Claim 23

Transmission-line means having a source-connection end and a remote load-connection end and comprising multiple power conductors, a ground conductor and a pilot conductor, said ground conductor and pilot conductor being connected to each other at one of said ends; circuit-breaker means for said power conductors at the source-connection end; resistance-bridge elements connected to said ground and pilot conductors at said other end, said bridge elements comprising connected conjugate fixed-resistance members between opposed bridge-excitation points, a voltage source connecting one of said points to said other end of said pilot conductor, a monitoring resistance selected for value substantially corresponding to the desired safety-limited value of said ground conductor and in substantially the same proportional relationship therewith as the values of said fixed-resistance members bear to each other, said monitoring resistance connecting said other end of said ground conductor to said one poInt, thereby defining second conjugate members connected between said points, and voltage-responsive means interconnecting said conjugate arms at the respective member-to-member connections thereof; and circuit-breaker trip means operative upon detection by said last-defined means of a predetermined voltage level.

Claim 24

Transmission-line means having a source-connection end and a remote load-connection end and comprising multiple power conductors, a ground conductor and a pilot conductor, said ground conductor and pilot conductor being connected to each other at one of said ends; circuit-breaker means for said power conductors at the source-connection end; resistance-bridge elements connected to said ground and pilot conductors at said other end, said bridge elements comprising connected conjugate fixed-resistance members between opposed bridge-excitation points, a voltage source connecting one of said points to said other end of said pilot conductor, a monitoring resistance selected for value substantially corresponding to the desired safety-limited value of said ground conductor and in substantially the same proportional relationship therewith as the values of said fixed-resistance members bear to each other, said monitoring resistance connecting said other end of said ground conductor to said one poInt, thereby defining second conjugate members connected between said points, and voltage-responsive means interconnecting said conjugate arms at the respective member-to-member connections thereof; and circuit-breaker trip means operative upon detection by said last-defined means of a predetermined voltage level.

Claim 25

Transmission-line means according to claim 14, in which said fixed-resistance members are selected for substantially equal value, and in which said trip means is operative upon detection of a voltage level of polarity opposite to that which is detected when the ground-conductor resistance is observed to be less than that of said monitoring resistance.

Claim 26

Transmission-line means having a source-connection end and a remote load-connection end and comprising a ground conductor and multiple further conductors, including power conductors; a d-c conducting connection of at least one of said multiple conductors to said ground conductor at one of said ends, said at least one conductor including a d-c connection at said other end; circuit-breaker means for said power conductors at the source-connection end; resistance-bridge elements connected to said ground conductor and to the d-c connection of said at least one conductor at said other end, said bridge elements comprising connected conjugate fixed-resistance members between opposed bridge-excitation points, a d-c voltage source connecting one of said points to the d-c connection at said other end of said at least one conductor, a monitoring resistance selected for value substantially corresponding to the desired safety-limit value of said ground conductor and in substantially the same proportional relationship therewith as the values of said fixed-resistance members bear to each other, said monitoring resistance connecting said other end of said ground conductor to said one point, thereby defining second conjugate members connected between said conjugate arms at the respective member-to-member connections thereof; and circuit-breaker trip means operative upon detection by said last-defined means of a predetermined voltage level.

Claim 27

Transmission-line means having a source-connection end and a remote load-connection end and comprising a ground conductor and multiple further conductors, including power conductors; a d-c conducting connection of at least one of said multiple conductors to said ground conductor at one of said ends, said at least one conductor including a d-c connection at said other end; circuit-breaker means for said power conductors at the source-connection end; resistance-bridge elements connected to said ground conductor and to the d-c connection of said at least one conductor at said other end, said bridge elements comprising connected conjugate fixed-resistance members between opposed bridge-excitation points, a d-c voltage source connecting one of said points to the d-c connection at said other end of said at least one conductor, a monitoring resistance selected for value substantially corresponding to the desired safety-limit value of said ground conductor and in substantially the same proportional relationship therewith as the values of said fixed-resistance members bear to each other, said monitoring resistance connecting said other end of said ground conductor to said one point, thereby defining second conjugate members connected between said conjugate arms at the respective member-to-member connections thereof; and circuit-breaker trip means operative upon detection by said last-defined means of a predetermined voltage level.

Claim 28

Transmission-line means according to claim 16, in which a system ground to earth is provided at said one end of said ground conductor and in which said other end includes a local-grounding frame member, and means including normally closed contacts at said other end and connecting the corresponding end of said ground conductor to said frame member, the ground connection of said bridge elements at said other end being made to said frame member, whereby upon opening said contacts said voltage-responsive means and said monitoring resistance may serve to measure then-existing earth resistance to the system ground via such path or paths as may exist between said frame member and the local electrical relation thereto to earth.

Claim 29

Transmission-line means having a source-connection end and a remote load-connection end and comprising a ground conductor and multiple further conductors, including power conductors; a first d-c conducting connection of at least one of said multiple conductors to said ground conductor at one of said ends, said at least one conductor including a d-c connection at said other end; a second d-c conducting connection of another of said multiple conductors to said ground conductor at said one end; circuit-breaker means for said power conductors at the source-connection end; Wheatstone-bridge elements at the other of said ends and utilizing, as one corner of the bridge, the said interconnection of multiple conductors and ground conductor at said one end, so that the ground conductor itself may be one of the arms of a completed bridge; said bridge elements at said other end comprising two serially connected resistance arms of ohmic value much higher than that for which the ground conductor is to be monitored, thereby defining a second bridge corner at the interconnection of said high-resistance arms, a low-resistance arm of ohmic value comparable to that for whicH the ground conductor is to be monitored, said low resistance arm being connected to the otherwise-free end of one of said high-resistance arms, thereby defining a third bridge corner at interconnection of high and low-resistance arms, and thereby also defining first and second otherwise-available free ends of a high-resistance arm and of the low resistance arm respectively; means including said at least one conductor and connecting one of said otherwise-available free ends to said first-defined bridge corner, and means connecting the other of said otherwise-available free ends to said other end of said ground conductor, thereby defining the fourth bridge corner, and thereby establishing the series-loop connection of all four bridge corners via said arms; a voltage-excitation source diagonally connecting a first two opposite bridge corners, and voltage-responsive means diagonally connecting the remaining two opposite bridge corners, said source and voltage-responsive means being located at said other end, and said another conductor being the means of completing the requisite one of said diagonal connections to said first-defined corner; and means responsive to attainment of a predetermined response of said voltage-responsive means for tripping said circuit-breaker means.

Claim 30

Transmission-line means having a source-connection end and a remote load-connection end and comprising a ground conductor and multiple further conductors, including power conductors; a first d-c conducting connection of at least one of said multiple conductors to said ground conductor at one of said ends, said at least one conductor including a d-c connection at said other end; a second d-c conducting connection of another of said multiple conductors to said ground conductor at said one end; circuit-breaker means for said power conductors at the source-connection end; Wheatstone-bridge elements at the other of said ends and utilizing, as one corner of the bridge, the said interconnection of multiple conductors and ground conductor at said one end, so that the ground conductor itself may be one of the arms of a completed bridge; said bridge elements at said other end comprising two serially connected resistance arms of ohmic value much higher than that for which the ground conductor is to be monitored, thereby defining a second bridge corner at the interconnection of said high-resistance arms, a low-resistance arm of ohmic value comparable to that for whicH the ground conductor is to be monitored, said low resistance arm being connected to the otherwise-free end of one of said high-resistance arms, thereby defining a third bridge corner at interconnection of high and low-resistance arms, and thereby also defining first and second otherwise-available free ends of a high-resistance arm and of the low resistance arm respectively; means including said at least one conductor and connecting one of said otherwise-available free ends to said first-defined bridge corner, and means connecting the other of said otherwise-available free ends to said other end of said ground conductor, thereby defining the fourth bridge corner, and thereby establishing the series-loop connection of all four bridge corners via said arms; a voltage-excitation source diagonally connecting a first two opposite bridge corners, and voltage-responsive means diagonally connecting the remaining two opposite bridge corners, said source and voltage-responsive means being located at said other end, and said another conductor being the means of completing the requisite one of said diagonal connections to said first-defined corner; and means responsive to attainment of a predetermined response of said voltage-responsive means for tripping said circuit-breaker means.

Claim 31

Transmission-line means according to claim 20, in which the high-resistance arms are of substantially matched ohmic value, and in which the ohmic value of the low-resistance arm is to a predetermined safety-monitoring level of ground-conductor resistance, said voltage-responsive means being polarity sensitive and operative to actuate said last-defined means upon detection of a polarity reversal of voltage.