ELECTRICAL FAULT LOCATION METHOD

• US 20170176510A1
• Filed: 11/22/2016
• Published: 06/22/2017
• Est. Priority Date: 12/21/2015
• Status: Active Grant

• Current Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Original Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Inventors: FLETCHER, Steven, NORMAN, Patrick, GALLOWAY, Stuart J.
• Granted Patent: US 9,863,998 B2
• Time in Patent Office: Days
• CPC Class Codes: G01R 31/08 Locating faults in cables, transmission lines, or networks
• CPC Class Codes: G01R 31/088 Aspects of digital computing
• CPC Class Codes: H02H 3/042 combined with means for locating the fault locating faults in cables G01R31/08
• CPC Class Codes: H02H 3/087 for dc applications

Abstract

A method of determining the location of a fault within a first inductive part of an electrical circuit, including a voltage source, first inductive part and second inductive part. A shortened circuit created by the fault includes the voltage source, a portion of the first inductive part and the second, connected in series. The fault occurs across first and second points in the first inductive part. The length of first inductive part between a positive terminal and first point is substantially equal to the length of first inductive part between a negative terminal and second point. The voltage source supplies a known voltage V_s when the fault occurs and the second inductive part has a known inductance L₂ when the fault occurs. The method takes advantage of the initial transient response of the circuit to determine the inductance of the portion of the first inductive part in the shortened circuit.

Claims

1. A method of determining the location of a fault within a first inductive part of an electrical circuit, where the electrical circuit comprises a voltage source, the first inductive part and a second inductive part and a shortened circuit of the electrical circuit created by the fault comprises the voltage source, a portion of the first inductive part and the second inductive part, all connected in series, and where further the fault occurs across first and second points in the first inductive part, the length of first inductive part between a positive terminal of the voltage source and the first point being substantially equal to the length of first inductive part between a negative terminal of the voltage source and the second point, and where further the voltage source supplies a known voltage V_s at the time the fault occurs and the second inductive part has a known inductance L₂ at the time the fault occurs,

the method comprising:

i) determining a voltage V₂ across the second inductive part immediately after the fault occurs;

ii) equating the ratio of V₂ to V_s with the ratio of L₂ to L₂+an unknown inductance L_1s of the portion of the first inductive part in the shortened circuit;

iii) determining the length l_1s of the portion of the first inductive part by either;

a) expressing L_1s in the equation of ii) as a proportion n_s of a known inductance L₁ of the first inductive part, solving for n_s and, given that the first inductive part is known to have a linear inductance to length relationship, equating n_s with the ratio of l_1s to a known length of the first inductive part and solving for l_1s;

 

or;

b) solving for L_1s in the equation of ii) and either;

i) given that the first inductive part is known to have a linear inductance to length relationship, equating the ratio of L_1s to a known inductance L₁ of the first inductive part with the ratio of l_1s to a known length of the first inductive part and solving for l_1s;

or

i) using L_1s in combination with a known inductance to length relationship of the first inductive part to determine l_1s;

iv) inferring the location of the fault as occurring at the position along the electrical circuit at which ½

l_1s is exhausted when starting from either of the positive and negative terminals.

2. A method of determining the location of a fault in according to claim 1 where the first and second inductive parts encompass all inductive parts of the shortened circuit.

3. A method of determining the location of a fault in according to claim 1 where the first and second points are respectively on positive and negative sides of the electrical circuit with respect to an interconnecting network.

4. A method of determining the location of a fault according to claim 1 where the proportion n_s of L₁ is calculated in accordance with the equation:

5. A method of determining the location of a fault according to claim 1 where the electrical circuit further comprises a circuit breaker and the method includes activating the circuit breaker to break the circuit immediately after the fault has occurred.

6. A method of determining the location of a fault according to claim 1 where the first and second points are respectively on separate conductors of the electrical circuit.

7. A method of determining the location of a fault according to claim 6 where the separate conductors are provided in a single insulated structure.

8. A method of determining the location of a fault according to claim 1 where the second inductive part comprises an inductive filter or current limiting inductor.

9. A method of determining the location of a fault according to claim 1 where the second inductive part comprises multiple inductive components.

10. A method of determining the location of a fault according to claim 1 where the electrical circuit is a direct current circuit.

11. An electrical fault locator for an electrical circuit comprising a processor programmed to perform the method of claim 1.

12. An electrical fault locator according to claim 11 further comprising a voltmeter arranged in use to measure and send a V₂ value to the processor.

13. A computer program that, when read by a computer, causes performance of the method of claim 1.