Method for detecting electrical ground faults

• US 20080036466A1
• Filed: 08/09/2007
• Published: 02/14/2008
• Est. Priority Date: 08/11/2006
• Status: Active Grant

• Current Assignee: Monte B. Raber
• Original Assignee: Monte B. Raber
• Inventors: Raber, Monte B.
• Granted Patent: US 7,791,351 B2
• Time in Patent Office: Days
• US Class Current: 324/509
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults

Abstract

A method of testing live AC circuits for neutral-ground, neutral-isolated ground, and isolated ground-ground faults, involves measuring impedances of circuit portions, including hot-neutral, neutral-ground, neutral-ground and isolated ground loops. In general either a test current generating a driving voltage is used, or in the case of hot-neutral, a load current generating a load voltage, and the voltage without current are use to measure voltage drop. These voltages are proportionate to the impedances of the circuits, which are expressed as ratios indicating the presence of faults. The method is reliable, despite much variation in circuit characteristics, including oversized neutral, shared neutral same phase, shared neutral opposed phase, supply line impedance, and high impedance grounds, it is easily able to detect faults across conductors and shared neutral loads.

Claims

1. Method of detecting faults in live circuits by comparing voltage drops across portions of the circuit, and expressing ratios of these voltage drops as indicative of faults.

2. Method of claim 1, wherein said live circuits are alternating current circuits.

3. Method of claim 2, wherein said voltage drops are compared by passing electric currents between receptacle poles and measuring voltage drops caused by said electric currents.

4. Method of claim 1, wherein said portions of the circuit are selected from the group consisting of neutral-ground loop, and hot-neutral loop, neutral-isolated ground loop, isolated ground-ground loop, neutral conductor, ground conductor and isolated ground conductor.

5. Method of claim 4, wherein said portions of said circuit compared are the hot-neutral loop and neutral-ground loop.

6. Method of claim 4, wherein said portions of said circuit compared are the hot-neutral loop and neutral-isolated ground loop.

7. Method of claim 4, wherein said portions of said circuit compared are the hot-neutral loop and the neutral conductor.

8. Method of claim 3, for detecting neutral-ground faults wherein the voltage without current between the hot and neutral poles is measured, the load voltage between the hot and neutral poles is measured while passing an electrical load current, and the voltage between neutral and ground poles caused by said electrical load current is measured and expressing the neutral-ground voltage divided by the difference between the voltage without current and the load voltage as a ratio indicative of neutral-ground faults.

9. Method of claim 3, for detecting neutral-isolated ground faults wherein the voltage without current between the hot and neutral poles is measured, the load voltage between the hot and neutral poles is measured while passing an electrical load current, and the voltage between neutral and isolated ground poles caused by said electrical load current is measured and expressing the neutral-isolated ground voltage divided by the difference between the voltage without current and the load voltage as a ratio indicative of neutral-isolated ground faults.

10. Method of claim 3, for detecting isolated ground-ground faults comprising the step wherein the driving voltage to produce an electrical test current between neutral and isolated ground poles is measured, and the step wherein the driving voltage to produce an electrical test current between isolated ground and ground poles is measured, and expressing the driving voltage between isolated ground and ground poles divided by the driving voltage between neutral and isolated ground poles as a ratio indicative of isolated ground-ground faults.

11. Method of claim 3, for detecting neutral-ground faults wherein the voltage without current between the hot and neutral poles is measured, the load voltage between the hot and neutral poles is measured while passing an electrical load current, and the driving voltage to produce a test current between neutral and ground poles is measured, and expressing the neutral to ground driving voltage divided by the difference between the voltage without current and the load voltage as a ratio indicative of neutral-ground faults.

12. Method of claim 3, for detecting neutral-isolated ground faults wherein the voltage without current between the hot and neutral poles is measured, the load voltage between the hot and neutral poles is measured while passing an electrical load current, and the driving voltage to produce a test current between neutral and isolated ground poles is measured, and expressing the neutral to isolated ground driving voltage divided by the difference between the voltage without current and the load voltage as a ratio indicative of neutral-isolated ground faults.

13. Method of claim 3, for detecting neutral-ground faults wherein an electrical load current is passed between hot and neutral poles, and the voltage between the neutral pole and independent reference ground caused by said electrical load current is measured and the driving voltage necessary to produce an electrical test current between neutral and ground poles is measured, and expressing the neutral to ground driving voltage divided by neutral to independent reference ground voltage caused by said load current as a ratio indicative of neutral-ground faults.

14. Method of claim 3, for detecting neutral-isolated ground faults wherein an electrical load current is passed between hot and neutral poles, and the voltage between the neutral pole and independent reference ground caused by said electrical load current is measured and the driving voltage necessary to produce an electrical test current between neutral and isolated ground poles is measured, and expressing the neutral to isolated ground driving voltage divided by neutral to independent reference ground voltage caused by said load current as a ratio indicative of neutral-isolated ground faults.

15. Method of claim 3, for detecting neutral-ground faults wherein an electrical load current is passed between hot and neutral poles, and the voltage between the neutral pole and independent reference ground caused by said electrical load current is measured, and the voltage between the ground pole and independent reference ground measured and expressing the ground to independent ground voltage divided by neutral to independent reference ground voltage caused by said load current as a ratio indicative of neutral-ground faults.

16. Method of claim 3, for detecting neutral-isolated ground faults wherein an electrical load current is passed between hot and neutral poles, and the voltage between the neutral pole and independent reference ground caused by said electrical load current is measured, and the voltage between the isolated ground pole and independent reference ground is measured and expressing the isolated ground to independent reference ground voltage divided by neutral to independent reference ground voltage caused by said load current as a ratio indicative of neutral-isolated ground faults.

17. Method of claim 3, for detecting neutral-ground faults wherein the voltage without current between hot and neutral poles is measured, the load voltage between hot and neutral poles is measured while passing an electrical load current, and the voltage between ground and neutral poles is measured while passing a test current between hot and ground poles, and expressing the voltage between ground and neutral poles while said test current is passed divided by the difference between voltage without current and load voltage, as a ratio indicative of neutral-ground faults.

18. Method of claim 3, for detecting neutral-isolated ground faults wherein the voltage without current between hot and neutral poles is measured, the load voltage between hot and neutral poles is measured while passing an electrical load current, and the voltage between isolated ground and neutral poles is measured while passing a test current between hot and isolated ground poles, and expressing the voltage between isolated ground and neutral poles while said test current is passed divided by the difference between voltage without current and load voltage, as a ratio indicative of neutral-isolated ground faults.

19. Method of claim 3, for detecting isolated ground-ground faults, wherein the voltage between neutral and isolated ground poles and the voltage between isolated ground and ground poles are measured while passing a test current from hot to isolated ground poles and expressing the isolated ground to ground voltage divided by the neutral to isolated ground voltage as a ratio indicative of isolated ground-ground faults.

20. Method of claim 3, for detecting isolated ground-ground faults wherein the voltage without current between hot and neutral poles is measured, the load voltage between hot and neutral poles is measured while passing an electrical load current, and the voltage between hot and ground is measured while passing a test current between hot and ground poles, and expressing the difference between the voltage without current and the voltage between hot and ground poles while said test current is passed divided by the difference between voltage without current and load voltage, as a ratio indicative of isolated ground-ground faults.

21. Method of claim 3, for detecting isolated ground-ground faults wherein the voltage without current between hot and neutral poles is measured, the load voltage between hot and neutral poles is measured while passing an electrical load current, and the voltage between hot and isolated ground poles is measured while passing a test current between hot and isolated ground poles, and expressing the difference between the voltage without current and the voltage between hot and isolated ground poles while said test current is passed divided by the difference between voltage without current and load voltage, as a ratio indicative of isolated ground-ground faults.