Abstract: An approved method and apparatus for detecting partial discharge events within a transformer comprises asserting a MEMS acoustical probe through the wall of the transformer to optically measure partial discharge events. In an enhanced embodiment, temperature compensation is also possible, and detection may be confirmed via an independent electromagnetic or other sensor.

Abstract: A detection module and remote load voltage sensor determine a location of a parallel arc for a power circuit between a power source and a load in real time. The detection module provides a value of voltage from the power source. A current sensor measures a value of current flowing in the power circuit to or from the power source. The remote load voltage sensor measures a value of voltage at the load. A microprocessor determines the parallel arc location from the value of voltage from the power source, the value of current, the value of voltage at the load, and a wire resistance or conductance per unit length of the power circuit. In one case, connector resistance is accounted for. In another case, the load voltage is encoded at a predetermined frequency using a switched precision resistor near the load, thereby providing a power line carrier type communication.

Abstract: A protection circuit, configured to detect and suppress electrical pre-arcing and arcing conditions in a resistive heater wire circuit, comprises a transient voltage suppressor, signal level sensing load coupled to the output of the voltage suppressor, detection and control circuitry, and a high-speed switch or electrical gate. The control circuitry is configured to control the operation of the switch, coupled between said control circuitry and the heater wire, wherein the switch is opened in response to an electrical pre-arcing or arcing condition or a short circuit condition.

Abstract: A frequency harmonic identifier for detecting series arcs on a power line includes a frequency analyzer for providing the harmonic content of a sensed current signal and a decision logic for comparing a tested signal to at least one reference signal band. The reference signal band or bands may represent a variety of common loads and if the tested signal does not match any of the sets of reference signal bands, then the logic determines the tested signal to be a series arc signal. The frequency harmonic identifier may be provided within a circuit interrupter and may issue a trip signal if the tested signal is determined to be a series arc signal. Also disclosed is a method for detecting series arcs, and a storage medium having instructions for causing a computer to implement the method.

Abstract: A system and method for detecting partial discharges or arcing in wiring or cables is disclosed. The system employs a high-voltage AC power source to generate a high-voltage low-current AC waveform, which is propagated through a selected wire, which in turn, produces the return signal. The return signal is processed using a signal processor and the analyzed for indications of the occurrence of a partial discharge. The method detects damage to a selected wire by utilizing high voltage, low current AC waveforms to induce partial discharges in a controlled manner and detecting a return signal resulting from the discharge.

Abstract: Apparatus and methods for detecting high level arc faults in aircraft power systems are disclosed. One embodiment of the invention with reduced susceptibility to nuisance trips includes three low pass filters each having an output connected to a threshold detector. In addition, a three input comparator is connected to an output of each of the threshold detectors and a fault verification circuit is connected to an output of the three input comparator. An embodiment of the method of the invention for detecting arc faults in three phase aircraft power systems involves detecting at least one of the three phases having a current exceeding a predetermined threshold, detecting differences between the three phases and generating a signal indicative of difference being detected between the three phases for a time period exceeding a predetermined duration.

Abstract: An automated test method for performing a hi-pot test procedure for an electrical device through the use of a test program installed in a factory information system (FIS) and a test instrument connected to the FIS. The test program sends a control command to the test instrument that in turn executes the hi-pot test for the electrical device. Test results are obtained by the test program from the test instrument and sent to the FIS. The test results are stored in the FIS for future reference.

Abstract: The present invention discloses an arc fault detector including a shunt resistor deployed in a circuit being protected, an arc discriminator sensing voltages across the shunt resistor and outputting an arc detection signal when it detects current variations caused by parallel and series arc faults, a signal transformer buffering the arc detection signal and outputting a pulse, a switch transient detector detecting a voltage differential across load switches and outputting a pulsed switch transient detection signal when the voltage differential across load switches exceeds a reference value, a line interrupter such as a static relay, a switch controller including logic gates generating a trip signal based on predetermined criteria, and a manual switch for resetting the line interrupter. A second embodiment of the present invention senses voltage induced in a coil wrapped around a toroidal core to detect current variations in conductors which pass through the center of the toroidal core.

Abstract: There is here disclosed a method and apparatus for detecting the occurrence of arcing of a conductor by monitoring the current on an AC power line. The signal detected is split and directed along four separate paths to generate four signals having separate characteristics which represent the current in the line. A first path is for a signal representative of the current flowing in the line. A second path is for a signal having a pulse for each occurrence of a positive step change in current that is significant and has a di/dt value above a predetermined value. A third path is for a signal having a pulse for each occurrence of a negative step change in current that is significant and has a di/dt value above a predetermined value. A fourth path is for a signal having a voltage level representative of the broadband noise signal on the line. Using at least one of five different methods in combination with one of three input signals, a reference signal designated as “SINE” is generated.

Abstract: An arc fault protection device protects a branch circuit portion of an electrical distribution system. The branch circuit is connected to a load. A first sensor detects fluctuations in load current, while a second sensor detects fluctuations in line voltage. The polarities of the fluctuations are compared, and the comparison indicates whether an arc signature, potentially indicative of an arc fault, is located in the branch circuit portion or located in a remainder of the electrical distribution system.

Abstract: A system and method for high voltage testing of twisted insulated conductors includes a high voltage power supply to be disposed within a rotating mechanism of a twinner. An electrode is coupled to the power supply and is to be disposed adjacent to a take-up reel within the rotating mechanism of the twinner. The electrode is for generating sparks between the electrode and the twisted insulated conductors when a fault in the insulation of the twisted conductors, when being wound on the take-up reel, passes by the electrode. A transmitter is to be disposed within the rotating mechanism for transmitting a signal carrying information representative of fault detection characteristics of the twisted insulated conductors. The information is derived from the sparks generated between the electrode and the twisted insulated conductors. A receiver is to be disposed outside of the rotating mechanism for receiving the signal from the transmitter.

Abstract: An arc fault detector, as a stand alone device or in combination with a circuit interrupting device such as a ground fault interrupter (GFCI), protects from potentially dangerous arc fault conditions. The device utilizes a line side or load side series connected inductance having an air or magnetic core to generate the derivative di/dt signal of the arc current in the conductor. The derivative signal is fed to an arc fault detector where it is analyzed for the presence of arcing. The device can have two series connected inductors inductively coupled to each other such that the signal from one inductor is inductively coupled into the other inductor for coupling to the arc fault detector.

Abstract: A contactless IC card having an antenna, a transmit/receive circuit for recovering data (clock) and electric power from a carrier signal received by the antenna, a logic circuit operated with the electric power supplied thereto from the transmit/receive circuit, and a memory. The transmit/receive circuit has a rectifier circuit for outputting data (clock) and rectifier circuits for electric power in such a manner that the carrier signal is inputted to each of the rectifier circuit for outputting data (clock) and the rectifier circuit for electric power. With this configuration, high frequency matching can be optimized separately for the rectifier circuit for outputting data (clock) and the rectifier circuit for electric power. It is also possible to separately optimize adjustments to a voltage of recovered data (clock) and a recovered supply voltage.

Abstract: A system is provided for remotely detecting and locating damaged conductors. The system includes at least one slave controller disposed proximate at least one load and electrically connected to the loads via at least one conductor. The slave controller includes at least one solid-state switch capable of controllably altering the input current to the loads, and at least one measuring element for measuring at least one parameter associated with the loads and the solid-state switches. In this regard, the solid-state switches controllably alter the input current to the loads according to the parameters. The system also includes at least one arc fault detector electrically connected to the conductors between the slave controller and the loads, where the fault detector is capable of detecting an electric arc event.

Abstract: Disclosed herein is a hybrid type sensor for detecting high frequency partial discharge which can detect high frequency partial discharge at a high signal-to-noise ratio without being influenced by power noise and surrounding noise, and guarantee the safety of a test when breakdown occurs. The sensor forms two or three signal paths with different impedances wherein a low frequency power signal is bypassed to ground through a first path, and a high frequency partial discharge current is allowed to flow through a second path and is detected as a resistance component through a resistor. Further, a surge voltage input to the sensor due to breakdown is input to the ground through a third path.

Abstract: A partial discharge detection test link and system is disclosed to detect partial discharge of a power cable accessory. The power cable accessory includes a first accessory component and a second accessory component connected to each other. The partial discharge detection test link is a permanent or temporary substitute for a conventional service link, connects directly across the power cable accessory and includes a conductor member and a partial discharge sensor. The conductor member has an electrically conductive element and an insulation surrounding and extending along the electrically conductive element. The electrically conductive element is electrically connected directly between the first and second accessory components. The partial discharge sensor is disposed about the conductor member and has the electrically conductive element as a primary winding and a secondary winding with the insulation positioned between the primary and secondary windings.

Abstract: A monitoring system includes at least one partial discharge (PD) sensor. The PD sensor is configured to monitor a component of an aircraft wiring system and to acquire a monitoring signal. A method embodiment for monitoring an aircraft wiring system includes acquiring a number of monitoring signals for a number of components of the aircraft wiring system using a number of partial discharge PD sensors. The method further includes conveying the monitoring signals from at least one of the PD sensors to a data acquisition system.

Abstract: A system for locating parallel arcing faults in a set of wires is described. The system includes three devices that can be used in combination or alone. A first device applies a current to a wire while grounding the remaining wires of the set of wires so as to cause the parallel arc, the first device being adapted to locate the parallel arcing fault using one or more leading edges of one or more electromagnetic waveforms being conducted on the wire under test. A second device comprises a controller and two or more receivers, each receiver being electrically coupled to the controller for receiving one or more leading edges of one or more electromagnetic waveforms being radiated by the parallel arcing fault. A third device senses one or more leading edges of one or more electromagnetic waveforms as well as the ultrasonic emissions emitted from the parallel arcing fault.

Abstract: An electrical high tension test device having first and second contacts connectable to a high tension circuit, a first electrode connected to one contact; a second electrode connected to the second contact, the first and second electrodes being spaced apart from one another by an air gap defining a predetermined resistance preset to a resistance corresponding to the high tension voltage in the high tension circuit to be tested, and, a signal device responsive to high tension discharge across said air gap to generate a signal such that when a predetermined high tension voltage is applied to the first and second contacts, a spark will jump the gap between them and in this way activating the signal device, and when a high tension voltage is applied which is less than the predetermined voltage no spark will jump the gap, and no signal will be generated.

Abstract: A method of inspecting insulators such as spark plug insulators for defects, whereby a plurality of insulators are inspected concurrently by being disposed with a plurality of first electrodes engaged in respective apertures in the insulators, and with apertures formed in a second electrode being disposed to peripherally enclose respective insulators. With the insulators and electrodes set in a closed chamber under high air pressure, and high voltage applied between the first and second electrodes, any defect is detected based on a level of leakage current which then flows.

Abstract: A device for measuring the AC voltage drop across a series of connections under load with no direct electrical contact to the conductors. The presence of a substantial resistance at series contacts is indicative of a series arcing fault. The device comprises a capacitive probe for clamping to the outer insulation layer of the wire to sense a first voltage at a first node. The device further comprises a floating high-impedance meter having a ground reference coupled to the source of common-mode voltage at a second node, the floating high-impedance meter being adapted to measure a voltage difference between the two nodes and being further adapted to indicate the presence of the series fault when the measured voltage exceeds a predetermined level.

Abstract: This invention teaches an arc detection and arc reduction circuit for use with power supplies for delivering power to a plasma processing system that utilizes a resonant circuit that stores energy and when the voltage drops between the cathode and anode of the processing chamber the stored energy generates a current in a current transformer in response to the voltage change to switch a magnetically coupled inductor in parallel with the cathode and anode causing a reversal of the voltage that reduces arcs in the plasma chamber. In an alternate embodiment the magnetically coupled inductor is replaced by a pulse transformer and the pulse transformer is placed in parallel with the cathode and anode causing a reversal of the voltage that reduces arcs in the plasma chamber.

Abstract: An arc fault interrupter tester creates a simulated arc fault current through a full wave bridge rectifier, a load resistor and a switch connected in series. These components are rated at currents and wattage well below the current of the simulated arc fault. Thermal management in the form of a temperature sensor and control pulse timing and duration prevent damage to the low-rated components.

Abstract: A device for detecting and locating arcs in a set of wires is discussed. The device comprises a probe for discharging controlled current to an exposed portion of a wire in the set of wires. The probe includes a handleable enclosure and an elongated structure which projects from the enclosure for conducting a gas and for enclosing a needle that has a tip. A suitable gas includes gases that have low electron attachment, such as helium. The device further comprises a control unit for communicating control signals as well as the gas to the probe. The control unit includes a controller, a valve being controllable by the controller and being capable of regulating the flow of the gas, and a high-voltage generator being controllable by the controller to generate a high-voltage signal, which can be communicated to the probe by the control unit.

Abstract: The invention relates to a method for detecting accidental arcs (arc tracking) on a cable (1), especially on a cable of an aircraft electrical system. According to said method, an alternating current signal (I(t)) that has been detected is sampled time-discretely and a trigonometric function (I(k)) imitating the alternating current characteristic is determined by interpolation of a number of sampling values (y(k)). The current alternating frequency (?) is then derived from this trigonometric function. The result of a comparison of the current alternating current frequency (?) and a set or reference frequency (??) is used to determine the presence of an accidental arc (ISA,IGA) and a warning signal (Sarc) is optionally generated. A device which functions according to this method is advantageously integrated into a circuit-breaker (7) for the aircraft electrical system, so that the latter is equipped to detect and deactivate accidental arcs that occur on the electrical system cable (1).

Abstract: A method and apparatus for detecting electrical arcs in an electrical system having a periodic power supply is disclosed. A method according to the invention compares instantaneous values of a monitored waveform both with (a) their past values at corresponding phases of the AC supply waveform, and (b) their future values at corresponding phases of the AC supply waveform. The monitored waveform is delayed or stored to allow such comparisons in near real time, to produce an output which is only slightly delayed behind the monitored waveform. An apparatus according to the present invention discloses a sampling circuit that samples electrical signals indicative of transient load conditions to produce a sampling circuit output. A storage device receives the sampling circuit's output and stores a time history of that output over an interval.

Abstract: An arc fault circuit interrupter (AFCI) detects arc faults by identifying the various signature patterns of arc fault noise while rejecting arc mimicking noise from normal load phenomena.

Abstract: The present invention discloses an arc fault detector including a shunt resistor deployed in a circuit being protected, an arc discriminator sensing voltages across the shunt resistor and outputting an arc detection signal when it detects current variations caused by parallel and series arc faults, a signal transformer buffering the arc detection signal and outputting a pulse, a switch transient detector detecting a voltage differential across load switches and outputting a pulsed switch transient detection signal when the voltage differential across load switches exceeds a reference value, a line interrupter such as a static relay, a switch controller including logic gates generating a trip signal based on predetermined criteria, and a manual switch for resetting the line interrupter. A second embodiment of the present invention senses voltage induced in a coil wrapped around a toroidal core to detect current variations in conductors which pass through the center of the toroidal core.

Abstract: Methods and systems for reliable arc detecting in systems having power signals that experience decay or increase in amplitude. One embodiment of a system for detecting electrical arcs by monitoring an alternating current power supply comprises a sampling circuit which samples electrical signals. It further comprises a delay circuit which receives the sampling circuit output and stores a time history of the output over an interval including a past, present and future versions of the history. Causal/non-causal logic compares the present version with the past and future versions to determine which will be used as an arc monitoring version to compare the present version to for arc monitoring. A dynamic processing module compensates for any amplitude differences between the present version and the arc monitoring version. An arc monitoring circuit analyzes the present version and adjusted arc monitoring version to determine if an arc signal is present.

Abstract: A direct current electrical circuit having a smart wire harness that has integrated electronics which measure both voltage and current through wires of the harness to detect and protect the electrical current from parallel and serial arc faults occurring within a protection zone. The protection zone is disposed directly between two smart connectors of the wire harness which are in communication with one another via a series of signal wires of the harness to detect serial or parallel arc faults within the protection zone. To measure serial arc faults, a voltage drop of the positive wire is measured at each smart connector and a difference taken which equals the serial arc voltage. If this voltage differential increases to a preset value, a switching device which provides power to the smart wire harness is opened.

Abstract: Method for detecting partial discharges and diagnostic system for electrical apparatus.

Abstract: This invention teaches an arc detection and arc reduction circuit for use with power supplies for delivering power to a plasma processing system that utilizes a resonant circuit that stores energy and when the voltage drops between the cathode and anode of the processing chamber the stored energy generates a current in a current transformer in response to the voltage change to switch a magnetically coupled inductor in parallel with the cathode and anode causing a reversal of the voltage that reduces arcs in the plasma chamber. In an alternate embodiment the magnetically coupled inductor is replaced by a pulse transformer and the pulse transformer is placed in parallel with the cathode and anode causing a reversal of the voltage that reduces arcs in the plasma chamber.

Abstract: An apparatus and method for simulating arcing events for use in testing arc fault circuit interrupters. The apparatus and method utilizes a plurality of motion sensitive switches, for example, mercury switches or ball-tilt switches, secured within the housing. When the apparatus is moved the switches interrupt a current flow mimicking arcing events.

Abstract: Provided is an apparatus and method used to perform automatic high potential (hi-pot), megohmeter and continuity, circuit test which includes a power source connected to a central processing unit (cpu) having a floppy drive, a hard drive, an analog to digital (A/D) printed circuit board (pcb), and a predetermined number of digital I/O pcb's, a hi-pot device, and a power supply. A data entry device is connected to the cpu for providing input thereto. A display device is provided for displaying data. A hi-pot device is connected to the A/D pcb and to a digital I/O pcb for providing an input voltage of a predetermined magnitude. A multiplexer is connected to the power supply and to a digital I/O pcb and the hi-pot device for communicating the input voltage to a predetermined number of external circuits to provide testing of the external circuits.

Abstract: An arc fault interrupter tester creates a simulated arc fault current through a full wave bridge rectifier, a load resistor and a switch connected in series. These components are rated at currents and wattage well below the current of the simulated arc fault. Thermal management in the form of a temperature sensor and control pulse timing and duration prevent damage to the low-rated components.

Abstract: An apparatus and method for simulating arcing events for use in testing arc fault circuit interrupters. The apparatus and method utilizes a plurality of motion sensitive switches, for example, mercury switches or ball-tilt switches, secured within the housing. When the apparatus is moved the switches interrupt a current flow mimicking arcing events.

Abstract: An electrical high tension test device having first and second contacts connectable to a high tension circuit, a first electrode connected to one contact; a second electrode connected to the second contact, the first and second electrodes being spaced apart from one another by an air gap defining a predetermined resistance preset to a resistance corresponding to the high tension voltage in the high tension circuit to be tested, and, a signal device responsive to high tension discharge across said air gap to generate a signal such that when a predetermined high tension voltage is applied to the first and second contacts, a spark will jump the gap between them and in this way activating the signal device, and when a high tension voltage is applied which is less than the predetermined voltage no spark will jump the gap, and no signal will be generated.

Abstract: A system for locating parallel arcing faults in a set of wires is described. The system includes three devices that can be used in combination or alone. A first device applies a current to a wire while grounding the remaining wires of the set of wires so as to cause the parallel arc, the first device being adapted to locate the parallel arcing fault using one or more leading edges of one or more electromagnetic waveforms being conducted on the wire under test. A second device comprises a controller and two or more receivers, each receiver being electrically coupled to the controller for receiving one or more leading edges of one or more electromagnetic waveforms being radiated by the parallel arcing fault. A third device senses one or more leading edges of one or more electromagnetic waveforms as well as the ultrasonic emissions emitted from the parallel arcing fault.

Abstract: An apparatus for detecting partial discharge in on-line high voltage electrical equipment containing a dielectric, such as high voltage transformers. The apparatus includes an ultrasonic transducer and an annular capacitive plate for detecting, respectively, the ultrasonic pulse and the radio frequency pulse generated by the occurrence of partial discharge in the equipment.

Abstract: A direct current electrical circuit having a smart wire harness that has integrated electronics which measure both voltage and current through wires of the harness to detect and protect the electrical current from parallel and serial arc faults occurring within a protection zone. The protection zone is disposed directly between two smart connectors of the wire harness which are in communication with one another via a series of signal wires of the harness to detect serial or parallel arc faults within the protection zone. To measure serial arc faults, a voltage drop of the positive wire is measured at each smart connector and a difference taken which equals the serial arc voltage. If this voltage differential increases to a preset value, a switching device which provides power to the smart wire harness is opened.

Abstract: Provided is an apparatus and method used to perform automatic high potential (hi-pot), megohmeter and continuity, circuit test which includes a power source connected to a central processing unit (cpu) having a floppy drive, a hard drive, an analog to digital (A/D) printed circuit board (pcb), and a predetermined number of digital I/O pcb's, a hi-pot device, and a power supply. A data entry device is connected to the cpu for providing input thereto. A display device is provided for displaying data. A hi-pot device is connected to the A/D pcb and to a digital I/O pcb for providing an input voltage of a predetermined magnitude. A multiplexer is connected to the power supply and to a digital I/O pcb and the hi-pot device for communicating the input voltage to a predetermined number of external circuits to provide testing of the external circuits.

Abstract: Disclosed herein is a hybrid type sensor for detecting high frequency partial discharge. The hybrid type sensor of the present invention can detect high frequency partial discharge at a high signal-to-noise ratio without being influenced by power noise and surrounding noise, and guarantee the safety of a test when breakdown occurs. The sensor of the present invention forms two or three signal paths with different impedances. A low frequency power signal is bypassed to ground through a first path, and a high frequency partial discharge current is allowed to flow through a second path and is detected as a resistance component through a resistor. Further, a surge voltage input to the sensor due to breakdown is input to the ground through a third path. Therefore, the present invention can precisely and safely detect the amount of high frequency partial discharge.

Abstract: An arc gage (30) includes a non-electrically conductive housing (42) and a first electrically conductive pin (44) that is disposed therein. The first pin (44) has a first end (44A) disposed within the housing (42) and a second end (44B) disposed outside the housing (42). A second electrically conductive pin (46) that has a third end (46A) within the housing (42) and spaced apart from the first end (44A) forms a gap (52) therebetween. A fourth end (46B) of the second electrically conductive pin (46) is disposed outside the housing (42). The arc gage (30) may be a stand alone device or used as part of a spark checking device that includes a device housing a voltage generator and a wand (26) that is electrically coupled to the power terminal of a voltage generator (34) disposed within the device housing (28).

Abstract: The invention relates to a device (100, 200) for use in the detection of the power that passes through an electronic device, comprising means (110) for division of the power that enters the device into a first and a second branch. Each branch receives a predetermined proportion of the total input power with a predetermined phase difference between the signals that go into the branches, and the device comprises a first power detector (140) for the first branch and a means (130) for summation of the power in the two branches. The invention is characterized in that the device (100, 200) further comprises a second power detector (150) for the second branch, and in that the means (130) for summation can be controlled with regard to which branch and thereby to which power detector (140, 150) the sum of the power is diverted, and in that the device comprises, in one of its branches, means (120) for said control of the summator.

Abstract: An electronically controlled circuit breaker for detecting arc and a method for detecting arc conditions are disclosed. The circuit breaker and method uses digital Fourier transformation on sampled line current signals and bins the even, odd, and fundamental transforms. Even arc signals and non-harmonic arc signals are calculated from the values in the bins and used within an expert arc algorithm which uses an accumulator to sum an increment based on whether the even arc signals and non harmonic arc signals exceed a fixed threshold. A trip signal is issued when the increment exceeds a predetermined value.

Abstract: Electric arc monitoring is effected by exploiting the discovery that electric arcs are fractal phenomena in that all essential information that signifies an “arc” is contained in each fractal subset. The fractal subsets are logarithmically distributed over the arc spectrum. Monitoring of arcs is most advantageously effected on a fractal subset of low logarithmic order where the amplitude is higher pursuant to the 1/f characteristic of electric arcs, where cross-induction among neighboring circuits is lower, and where travel between the arc and the arc signature pickup is longer that at the high frequency customary for electric arc detection. Fractal subset information reduces the danger of false alarms. Arc signature portions may be processed in out of phase paths or treated as modulated carriers for monitoring.

Abstract: Arc fault detector device (such as arc fault circuit interrupter) testing apparatus and methods including generating a true arc fault current by energizing a contact relay at a predetermined frequency, applying and regulating the true arc fault current to a detection device under test by selecting a load from a resistor bank that is coupled to the tested device, determining whether the device under test was able to detect the arc fault current. The invention is useful for determining whether an arc fault circuit interrupter is capable of tripping in response to an arc fault current.

Abstract: A testing device for detecting and locating an arcing fault in an electrical system includes a detector circuit for detecting one or more characteristics of the arcing fault proximate the arcing fault and outputting a responsive signal. An annunciator speaker or display annunciates the responsive signal when the detector circuit is proximate the arcing fault, in order to locate the arcing fault in the electrical system.

Abstract: An apparatus (10) for detecting the occurrence of partial discharge in electrical equipment, such as high voltage transformers. The apparatus comprises a detecting means including an ultrasonic transducer (11) mounted at one end of an electrically insulating elongate rod (13). The ultrasonic transducer (11) is adapted to detect ultrasonic pulses or waves generated by the occurrence of a partial discharge in the electrical equipment. A radio frequency (RF) transducer (17) is also utilized to detect radio frequency (RF) pulses or waves also generated by the partial discharge. The rod (13) can be mounted in the wall of the electrical equipment and so provide a mechanism for adjusting the position of the detecting means within the electrical equipment. The apparatus is also removable from the electrical equipment and re-locatable to other equipment.

Abstract: An abnormal current discriminating method including an arc current detecting method and the apparatus for performing the same in which the arc current method includes the steps of: extracting a predetermined transition pattern specified by the combination of fluctuation patterns of peak values of three continuous half waves from the peak value for each half wave detected from an alternating current flowing to the AC load circuit which is sampled in a predetermined cycle and converted into a digital value, counting the number of appearances of the predetermined transition pattern, and comparing the count value with a predetermined threshold.