Arcing in an AC power system is detected by monitoring the power waveform for wideband high-frequency noise, and examining the detected noise for patterns of variation in its amplitude synchronized to the power waveform. A narrowband, swept-frequency detector and synchronous averaging may be employed to improve discrimination of arc noise from background interference. An arcing fault interrupter for controlling a single circuit, and a whole house monitor, for detecting arcing anywhere in a house, are described.

Method and apparatus for detecting arcing in ac power systems by monitoring high frequency noise

In an electric circuit supplying AC line current rent to a load (30, 31) from an AC source (26) of given frequency providing repetitive cycles, arc detection is provided by sensing cycle to cycle changes in the AC line current. The AC line current is sampled with a harmonic notch filter (72) at a plurality of n phases Θ 1 through Θ n during each of a plurality of m cycles of the AC source (26), to provide a plurality of currents I n ,m, where n is the phase and m is the cycle. The differences (I n ,m)-(I n ,m-x), where x is a designated number of cycles, provide a plurality of current difference signals. The absolute values of these current difference signals ID are accumulated in a synchronous summer (94) over the m cycles. An arc indicative signal is generated in response to given conditions and given combinations of conditions (116) of the cumulative absolute current difference signals ID. Cycle to cycle changes in AC line voltage are also sensed with a harmonic notch filter (146), and the arc indicative signal is disarmed in response to a given voltage condition. In further embodiments, subcycle changes are sensed.

Arc detection using current variation

An arc detector or detecting potentially hazardous arcing in electrical connections comprises detection and signal processing circuitry for monitoring high-frequency noise on the power line characteristic of arcing and distinguishable from other sources of high-frequency noise. If high-frequency noise is present and a gap is detected at intervals synchronous to the power frequency, arcing is determined to be present, and an alarm is given.

Method and apparatus for detecting arcing in alternating current power systems by monitoring high-frequency noise

A system to detect arcing faults in an electrical distribution system with a line conductor connected to a utility power transformer. The system monitors the rate of change of electrical current in the line conductor and produces a signal which represents the rate of change. The system produces a pulse each time the rate-of-change signal exceeds a selected threshold, filters the rate-of-change signal and/or the pulses to substantially eliminate a signal or pulse which represents changes in the electrical current outside a selected frequency range, monitors the remaining pulses to detect when the number of pulses that occur within a selected time interval exceeds a predetermined threshold, and generates an arc-fault-detection signal in response to the occurrence of a number of pulses which exceed the threshold within the selected time interval.

Arcing fault detection system

A trip indicator for a circuit breaker in an electrical distribution system. The trip indicator provides a visual indication of the activation of a trip signal caused by arcing fault detector (AFD) or ground fault interrupter (GFI) circuitry. The trip indicator comprises one or more light sources, one or more plungers having a colored tip or one or more bimetal disk having a colored top. In response to activation of a trip signal by the AFD or GFI circuitry, the light source(s) illuminate, the plunger(s) move from a retracted position to an extended position and the bimetal disk(s) move from a generally flat position to a convex position. A conduit is provided within the housing of the protective device for conveying light or the reflection of light between the light source(s), plunger(s) or bimetal disk(s) and an opening of the housing. Where the circuit breaker includes both GFI and AFD circuitry, each generating a respective trip signal in response to the detection of a ground fault or arcing fault, the trip indicator is designed to indicate which of the respective fault conditions activated the trip signal.

Trip indicators for circuit protection devices

A method and apparatus for determining the presence of partial discharge ivity (corona) which makes use of corona current signals in the 20 MHz to 50 MHz frequency range and provides for identification of the corona source in a capacitor matrix. A current probe coupled to the high potential side of the capacitor detects corona discharge current signals that are fed to a bandpass filter which passes signals in the frequency range of 20 MHz to 50 MHz. The signals from the bandpass filter are amplified and integrated to provide a d.c. level proportional to the corona activity. The d.c. level signal is encoded by a voltage controlled oscillator and then converted to light. A fiber optic link transmits the converted signal to a remote console where the encoded light is reconverted to a d.c. level signal which can be displayed as an analog signal as well as activating an audio or visual alarm. A plurality of local current sensors and related circuitry corresponding to the number of capacitors in the capacitor matrix are provided to provide for comparisons of the corona signal levels from each capacitor to provide identification of the source capacitor containing the highest corona activity.

VLF Capacitor corona detection

A method and apparatus of determining defects in semiconductors, by scann with small spot of light. As the semiconductor is scanned, a voltage is generated which may be used to indicate gross defects as well as the reduction in carrier lifetime due to the defects.

Method and apparatus for semiconductor profiling using an optical probe

A method and means of monitoring the quality of a fluid dielectric capacitor by measuring the Kerr signal of a dielectric fluid which has the desired dielectric and breakdown properties and continually measuring the Kerr signal of the same fluid dielectric while in use to determine if there is any degradation of the fluid in use. The means for measuring the Kerr signal is by projecting a high intensity light beam such as from a laser source through the dielectric fluid of a capacitor between two of the plates and detecting the amount of light passed through the dielectric which is an indication of the condition of the dielectric liquid.

Neil M. Davis

Papers

VLF Capacitor corona detection

Method and apparatus for semiconductor profiling using an optical probe

Method and means of monitoring the quality of a fluid dielectric