Detection of arcs in power cables using plasma noise or negtive resistance of the arcs

• US 5,418,463 A
• Filed: 11/24/1993
• Issued: 05/23/1995
• Est. Priority Date: 11/24/1993
• Status: Expired due to Term

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Fleming, Debra A., Peterson, George E.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): DO, DIEP N
• Application Number:
  US08/157,857
• Time in Patent Office: 545 Days
• Field of Search: 324/520, 324/536, 324/543, 324/544, 324/551, 324/102, 324/158 MG, 324/772, 361/14, 361/49, 361/50, 361/111, 361/113, 361/115, 340/635, 340/649, 340/650
• US Class Current: 324/520
• CPC Class Codes: G01R 31/12 Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing G01R31/08, G01R31/327 and G01R31/72 take precedence; measuring in plasmas G01R19/0061; measuring dielectric constants G01R27/2617; ESD, EMC or EMP testing of circuits G01R31/002
• CPC Class Codes: G01R 31/50 Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections testing of sparking plugs H01T13/58
• CPC Class Codes: H02H 1/0015 Using arc detectors

Abstract

A process for detecting arc discharges in power cables connecting power supply board and at least one equipment rack, the power supply board including circuit breakers operable at a preset current level, said arc discharge occurring at a fraction of said current level. After the arc discharge is detected, a signal representing the presence of the arc discharge is supplied to a power supply control, and a control signal is provided by the power supply control to cause said at least one circuit breaker to open interrupting supply of power to an affected power cable.

Claims

1. A method of detecting arc discharges in power cables connecting power supply board and at least one equipment rack, said power supply board including circuit breakers operating at a preset current level, and said arc discharge occurring at a fraction of said current level, which method comprises

detecting an arc discharge in at least one power cable,

supplying a signal representing the presence of the arc discharge to a power supply control, and

providing a control signal from said power supply control sufficient to cause said at least one circuit breaker to open interrupting supply of power from the power supply board to an affected power cable, in which

said arc discharge radiates a plasma noise with radio frequency noise,

said detecting is conducted by means of a microwave antenna and a microwave receiver which upon detecting said plasma noise provide said arc discharge-representing signal to the power supply control, said microwave antenna being positioned above said at least one power cable and being responsive to radiation in a 1 MHz to 3 GHz frequency range.

2. The method of claim 1 in which a separate microwave antenna is provided for each of a plurality of power cables.

3. The method of claim 1 in which said microwave antenna is responsive to radiation in a 1 to 2 GHz frequency range.

4. A method of detecting arc discharges in power cables connecting power supply board and at least one equipment rack, said power supply board including circuit breakers operating at a preset current level, and said arc discharge occurring at a fraction of said current level, which method comprises

detecting an arc discharge in at least one power cable,

supplying a signal representing the presence of the arc discharge to a power supply control, and

providing a control signal from said power supply control sufficient to cause said at least one circuit breaker to open interrupting supply of power from the power supply board to an affected power cable, in which

said arc discharge detection is provided by placing a tuned circuit across said power cable, said tuned circuit including a capacitor (C), a resistance (R) and an inductance connected in series and having a positive resistance, said arc discharge has a negative resistance which counteracts the positive resistance resulting in oscillations or noise of the tuned circuit supplying said signal to the power supply control.

5. The method of claim 4 in which said arc discharge detection is provided for each of a plurality of power cables.