DIRECTIONAL DETECTION OF EARTH FAULTS IN AN ELECTRICAL DISTRIBUTION NETWORK

• US 20160091555A1
• Filed: 09/25/2015
• Published: 03/31/2016
• Est. Priority Date: 09/29/2014
• Status: Active Grant

• Current Assignee: Schneider Electric Industries SAS (Schneider Electric SE)
• Original Assignee: Schneider Electric Industries SAS (Schneider Electric SE)
• Inventors: DROUERE, Bernard, Mecreant, Julien
• Granted Patent: US 10,545,184 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01R 19/2513 Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging
• CPC Class Codes: G01R 25/00 Arrangements for measuring phase angle between a voltage and a current or between voltages or currents
• CPC Class Codes: G01R 31/08 Locating faults in cables, transmission lines, or networks
• CPC Class Codes: G01R 31/086 in power transmission or distribution networks, i.e. with interconnected conductors
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: H02H 3/165 for three-phase systems
• CPC Class Codes: H02H 3/385 using at least one homopolar quantity
• CPC Class Codes: H02H 3/40 responsive to ratio of voltage and current
• CPC Class Codes: Y04S 10/52 Outage or fault management, e.g. fault detection or location

Abstract

Method for the directional determination of an earth fault in an electric power distribution network, characterised in that it comprises the steps of:

• • Determining (E2) a residual current phasor and a residual voltage phasor,
  • Determining (E3) an active current,
  • Comparing (E7) the residual voltage phasor module with a threshold (SVR), and
  • as long as the residual voltage phasor module remains higher than the threshold (SVR) or a fraction of the threshold (SVR), and for a predetermined number of iterations:
  • Determining (E9, E12) the integral of the active current and of its sign,
  • Determining the number of times when the residual current phasor module is greater than a predetermined threshold (SIR), during the predetermined number of iterations,
  • If the residual current phasor module is greater than the predetermined threshold (SIR) at least one time, during the predetermined number of iterations,
  • Determining (E16) the location upstream or downstream of the fault according to the number of times when the sign of the integral of the active current was positive or negative during the predetermined number of iterations.

Claims

1. Method for the directional determination of an earth fault in an electric power distribution network, characterised in that it comprises the steps of:

Determining (E2) a residual current phasor,

Determining (E2) a residual voltage phasor,

Determining (E3) an active current by projection of the residual current phasor on the residual voltage phasor,

Determining (E7) of the residual voltage phasor module,

Comparing (E7) the residual voltage phasor module with a threshold (SVR),

and in that it comprises the following steps, as long as the residual voltage phasor module remains higher than the threshold (SVR) or a fraction of the threshold (SVR), and for a predetermined number of iterations starting from the moment when the residual voltage phasor module is greater than the threshold (SVR);

Determining (E9, E12) the integral of the active current and of the sign of the integral of the active current,

Determining (E5) the residual current phasor module,

Determining the number of times when the residual current phasor module is greater than a predetermined threshold (SIR), during the predetermined number of iterations,

If the residual current phasor module is greater than the predetermined threshold (SIR) at least one time, during the predetermined number of iterations,

Determining (E16) the location upstream or downstream of the defect according to the number of times when the sign of the integral of the active current was positive or negative during the predetermined number of iterations.

2. Method for the directional determination of an earth fault according to claim 1, characterised in that the number and the frequency of the iterations are chosen in such a way that the iterations are carried out over one network period.

3. Method for the directional determination of an earth fault according to claim 1, characterised in that the active current is calculated according to the formula:

4. Method for the directional determination of an earth fault according to claim 1, characterised in that the integral of the active current is calculated by adding together the active current values a number of times equal to the predetermined number of iterations.

5. Method for protecting a current line during the appearance of an earth fault, characterised in that it comprises the actuating of a device for cutting off the line whereon an earth fault has been detected by the method for the directional determination of an earth fault according to claim 1.

9. Computer programme comprising instructions for the execution of the steps of the method according to claim 1 when said programme is executed by a computer.

10. Recording support that can be read by a computer whereon is recorded a computer programme that comprises instructions for executing the steps of the method according to claim 1.

6. Device for the directional determination of an earth fault in an electric power distribution network, characterised in that it comprises:

Means (600) for determining a residual current phasor,

Means (601) for determining a residual voltage phasor,

Means (611) for determining an active current by projection of the residual current phasor on the residual voltage phasor,

Means (621) for determining the residual voltage phasor module,

Means (622, 622a) for comparing the residual voltage phasor module with a threshold (SVR),

and in that it comprises the following means, able to operate as long as the residual voltage phasor module remains higher than the threshold (SVR) or a fraction of the threshold (SVR), and for a predetermined number of iterations starting from the moment when the residual voltage phasor module is greater than the threshold (SVR);

Means (641) for determining the integral of the active current and of the sign of the integral of the active current,

Means (631) for determining the residual current phasor module,

Means (631) for determining the number of times when the residual current phasor module is greater than a predetermined threshold (SIR), during the predetermined number of iterations,

Means (644) for determining the location upstream or downstream of the defect according to the number of times when the sign of the integral of the active current was positive or negative during the predetermined number of iterations, if the residual current phasor module is greater than the predetermined threshold (SIR) at least one time, during the predetermined number of iterations.

7. Passage indicator of earth fault characterised in that it comprises the device for the directional determination of an earth fault according to claim 6.

8. Device for protecting a current line during the appearance of an earth fault, characterised in that it comprises means for actuating a device for cutting off the line whereon an earth fault has been detected by the device for directional determination of an earth fault according to claim 6.