Polyphase electric system protective apparatus

Claim 2

Circuit means for outputting a voltage responsive to reverse phase, open phase, and voltage unbalance conditions in a conventional three-phase alternating-current electric system having first, second, and third line conductors each carrying a phase voltage, said phase voltages having a predetermined positive phase sequence of first, second, and third, and normally spaced apart 120 electrical degrees, comprising: a first impedance connected between said first line conductor and a first output point; a second impedance connected between said second line conductor and said first output point; a third impedance connected between said second line conductor and a second output point; and a fourth impedance connected between said third line conductor and said second output point; wherein said impedances generally satisfy the relation: in which: Zc is the value of said first impedance; R1 is the value of said second impedance; R2 is the value of said third impedance; and R3 is the value of said fourth impedance.

Claim 3

Apparatus for use with three-phase, three-wire and three-phase, four-wire alternating-current electric systems having first, second, and third line conductors each carrying a phase voltage, said voltages having a predetermined positive phase sequence of first, second, and third, comprising: a negative-sequence voltage filter network connected in line-to-line relationship with said conductors to output a voltage responsive to the negative-sequence components of the line voltages and having: a first leg, including first and second impedances in series, connected between the first and second line conductors and defining a first output point between said first and second impedances; and a second leg, including third and fourth impedances in series, connected at one end to said first leg at a point between the second impedance and the second line conductor and connected at the other end to the third line conductor and defining a second output point between said third and fourth impedances; and voltage-responsive means connected to the output of said network to respond to said output voltages representative of reversed phase and open phase conditions in said system; wherein the relative values of said impedance generally satisfy the relation: in which: Zc is the value of said first impedance; R1 is the value of said second impedance; R2 is the value of said third impedance; and R3 is the value of said fourth impedance.

Claim 4

Apparatus for use with three-phase, three-wire and three-phase, four-wire alternating-current electric systems having first, second, and third line conductors each carrying a phase voltage, said voltages having a predetermined positive phase sequence of first, second, and third, comprising: a negative-sequence voltage filter network connected in line-to-line relationship with said conductors to output a voltage responsive to the negative-sequence components of the line voltages and having: a first leg, including first and second impedances in series, connected between the first and second line conductors and defining a first output point between said first and second impedances; and a second leg, including third and fourth impedances in series, connected at one end to said first leg at a point between the second impedance and the second line conductor and connected at the other end to the third line conductor and defining a second output point between said third and fourth impedances; and voltage-responsive means connected to the output of said network to respond to said output voltages representative of reversed phase and open phase conditions in said system; wherein the relative values of said impedance generally satisfy the relation: in which: Zc is the value of said first impedance; R1 is the value of said second impedance; R2 is the value of said third impedance; and R3 is the value of said fourth impedance.

Claim 5

Apparatus as recited in claim 2, wherein said second, third, and fourth impedances comprise approximately equal resistances and said first impedance comprises a capacitive reactance.

Claim 6

Apparatus as recited in claim 2, wherein said third and fourth impedances are of equal value and the value of said second impedance is related to the value of said first impedance by the relation: R1 -( Zc/j Square Root 3)

Claim 7

Apparatus as recited in claim 2, wherein said second impedance comprises a plurality of impedance elements.

Claim 8

Apparatus as recited in claim 2, wherein said second impedance comprises a variable resistor.

Claim 9

Apparatus as recited in claim 2 including a full-wave bridge rectifier between the output of said negative-sequence voltage filter network and said voltage-responsive means to rectify the alternating-current voltage output of said filter network and provide a direct-current voltage proportional thereto to said voltage-responsive means.

Claim 10

Apparatus as recited in claim 2 including a Zener diode connected in parallel with said voltage-responsive means to limit the voltage differential between the output points of said network.

Claim 11

Apparatus as recited in claim 2 including a Zener diode in series with said voltage-responsive means tO establish a voltage threshold below which no current is applied to said voltage-responsive means.

Claim 12

Apparatus as recited in claim 2, wherein said voltage-responsive means comprises relay means actuated by the output of said negative-sequence voltage filter network.

Claim 13

Apparatus as recited in claim 10, wherein said relay means is suitable for operating a circuit interruptor to simultaneously open said line conductors.

Claim 14

Apparatus as recited in claim 2, wherein said voltage-responsive means comprises a warning signal.

Claim 15

Apparatus for use with three-phase, three-wire and three-phase, four-wire alternating-current electric systems having first, second, and third line conductors each carrying a phase voltage, said voltages having a predetermined positive phase sequence of first, second, and third, comprising: a negative-sequence voltage filter network connected in line-to-line relationship with said conductors to output a voltage responsive to the negative-sequence components of the line voltages and having: a first leg, including first and second impedances in series, connected between the first and second line conductors and defining a first output point between said first and second impedances; and a second leg, including third and fourth impedances in series, connected at one end to said first leg at a point between the second impedance and the second line conductor and connected at the other end to the third line conductor and defining a second output point between said third and fourth impedances; wherein the relative values of said impedances generally satisfy the relation: in which: Zc is the value of said first impedance; R1 is the value of said second impedance; R2 is the value of said third impedance; and R3 is the value of said fourth impedance; and amplifier-driven voltage-responsive means connected to the output of said network to respond to said output voltages representative of reverse phase, open phase, and voltage unbalance conditions in said systems.

Claim 16

Apparatus for use with three-phase, three-wire and three-phase, four-wire alternating-current electric systems having first, second, and third line conductors each carrying a phase voltage, said voltages having a predetermined positive phase sequence of first, second, and third, comprising: a negative-sequence voltage filter network connected in line-to-line relationship with said conductors to output a voltage responsive to the negative-sequence components of the line voltages and having: a first leg, including first and second impedances in series, connected between the first and second line conductors and defining a first output point between said first and second impedances; and a second leg, including third and fourth impedances in series, connected at one end to said first leg at a point between the second impedance and the second line conductor and connected at the other end to the third line conductor and defining a second output point between said third and fourth impedances; wherein the relative values of said impedances generally satisfy the relation: in which: Zc is the value of said first impedance; R1 is the value of said second impedance; R2 is the value of said third impedance; and R3 is the value of said fourth impedance; and amplifier-driven voltage-responsive means connected to the output of said network to respond to said output voltages representative of reverse phase, open phase, and voltage unbalance conditions in said systems.

Claim 17

Apparatus as recited in claim 13, wherein amplifier bias power is provided from said line conductors to said amplifier through two transformers connected in open delta primary and secondary and a full-wave bridge rectifier.

Claim 18

Apparatus as recited in claim 13, wherein said amplifier-driven voltage responsive means includes a plurality of amplification stages.

Claim 19

Apparatus as recited in claim 13, wherein said amplifier-driven voltage responsive means comprise relay means to operate a circuit interruptor to simultaneously open said line conductors.

Claim 20

Circuit means for outputting a voltage responsive to positive-sequence components of voltage in a conventional three-phase alternating-current electric system having first, second, and third line conductors each carrying a phase voltage, said phase voltages having a predetermined positive phase sequence of first, second, and third, and normally spaced apart 120 electrical degrees comprising: a first impedance connected between said first line conductor and a first output point; a second impedance connected between said second line conductor and said first output point; a third impedance connected between said second line conductor and a second output point; and a fourth impedance connected between said third line conductor and said second output point; wherein said impedances generally satisfy the relation: in which: Zc is the value of said first impedance; R1 is the value of said second impedance; R2 is the value of said third impedance; and R3 is the value of said fourth impedance.

Claim 21

Circuit means for outputting a voltage responsive to positive-sequence components of voltage in a conventional three-phase alternating-current electric system having first, second, and third line conductors each carrying a phase voltage, said phase voltages having a predetermined positive phase sequence of first, second, and third, and normally spaced apart 120 electrical degrees comprising: a first impedance connected between said first line conductor and a first output point; a second impedance connected between said second line conductor and said first output point; a third impedance connected between said second line conductor and a second output point; and a fourth impedance connected between said third line conductor and said second output point; wherein said impedances generally satisfy the relation: in which: Zc is the value of said first impedance; R1 is the value of said second impedance; R2 is the value of said third impedance; and R3 is the value of said fourth impedance.

Claim 22

Circuit means for outputting a voltage responsive to positive-sequence components of voltage in a conventional three-phase alternating-current electric system having first, second, and third line condUctors each carrying a phase voltage, said phase voltages having a predetermined positive phase sequence of first, second, and third, and normally spaced apart 120 electrical degrees, comprising: a first impedance connected between said first line conductor and a first output point; a second impedance connected between said third line conductor and said first output point; a third impedance connected between said third line conductor and a second output point; and a fourth impedance connected between said second line conductor and said second output point; wherein said impedances generally satisfy the relation: in which: Zc is the value of said first impedance; R1 is the value of said second impedance; R2 is the value of said third impedance; and R3 is the value of said fourth impedance.

Claim 23

Circuit means for outputting a voltage responsive to positive-sequence components of voltage in a conventional three-phase alternating-current electric system having first, second, and third line condUctors each carrying a phase voltage, said phase voltages having a predetermined positive phase sequence of first, second, and third, and normally spaced apart 120 electrical degrees, comprising: a first impedance connected between said first line conductor and a first output point; a second impedance connected between said third line conductor and said first output point; a third impedance connected between said third line conductor and a second output point; and a fourth impedance connected between said second line conductor and said second output point; wherein said impedances generally satisfy the relation: in which: Zc is the value of said first impedance; R1 is the value of said second impedance; R2 is the value of said third impedance; and R3 is the value of said fourth impedance.

Claim 24

Circuit means for outputting a voltage responsive to reverse phase, open phase, and voltage unbalance conditions in a conventional three-phase alternating-current electric system having first, second, and third line conductors each carrying a phase voltage, said phase voltages having a predetermined positive phase sequence of first, second, and third, and normally spaced apart 120 electrical degrees, comprising: a first impedance connected between said first line conductor and a first output point; a second impedance connected between said third line conductor and said first output point; a third impedance connected between said third line conductor and a second output point; and a fourth impedance connected between said second line conductor and said second output point; wherein said impedances generally satisfy the relation: in which: Zc is the value of said first impedance; R1 is the value of said second impedance; R2 is the value of said third impedance; and R3 is the value of said fourth impedance.

Claim 25

Circuit means for outputting a voltage responsive to reverse phase, open phase, and voltage unbalance conditions in a conventional three-phase alternating-current electric system having first, second, and third line conductors each carrying a phase voltage, said phase voltages having a predetermined positive phase sequence of first, second, and third, and normally spaced apart 120 electrical degrees, comprising: a first impedance connected between said first line conductor and a first output point; a second impedance connected between said third line conductor and said first output point; a third impedance connected between said third line conductor and a second output point; and a fourth impedance connected between said second line conductor and said second output point; wherein said impedances generally satisfy the relation: in which: Zc is the value of said first impedance; R1 is the value of said second impedance; R2 is the value of said third impedance; and R3 is the value of said fourth impedance.