Abstract: This invention is an inexpensive probe apparatus operating at high precision that can be used for both low-frequency and high-frequency measurements. A line with a first and second conductor is extended from a probe connected to a circuit component. A low-frequency or high-frequency device is alternately connected to the line. A third common conductor runs parallel to the aforementioned line and a resistor and capacitor is connected between the probe end of the aforementioned second conductor and the aforementioned common conductor.

Abstract: A contact hazard meter used to measure electromagnetic field induced currents which would flow through a human body to ground upon physical contact with an item carrying such field induced currents includes a conductive contact, a human equivalent circuit coupled to the conductive contact and an electronic circuit coupled to the human equivalent circuit for measuring and displaying a measurement of current flowing from the item and through the human equivalent circuit when the conductive contact is placed in physical contact with the item carrying the field induced currents. The human equivalent circuit approximates the impedance of the human body at varying frequencies. The contact hazard meter has a plurality of range settings, one setting providing the resultant current as a percentage of a safety guideline maximum permissible exposure value.

Abstract: A method and apparatus for detecting high impedance faults and other arcing phenomena in an electrical distribution system. Electrical signals on the distribution system are monitored and a number of frequency components isolated, such as zero-sequence current and voltage, second harmonic voltage, third harmonic current, eighth harmonic voltage and current, and a measure of magnitude of the components are taken over successive data acquisition periods. The measures of the component magnitudes are formed into a pattern for each data acquisition period, and the difference between patterns for successive periods are compared against a pattern threshold which is set to suit the characteristics of the distribution system. A pattern difference greater than the pattern threshold indicates the possibility of an arcing fault, which can then be confirmed by determining whether the frequency components are modulated at twice the fundamental frequency of the distribution system.

Abstract: Impedance of an energized electrical line which carries electrical current at a predetermined line frequency is nondistruptively measured at frequencies which are above and below the predetermined line frequency. A measurement current is generated at a measurement frequency between, for example, 10 Hz and 30 kHz for a 60 Hz line. The current generator is coupled to the energized electrical line by an isolating circuit which blocks only the predetermined line frequency and frequencies which differ from the predetermined line frequency by substantially less than the predetermined line frequency. For example, a notch filter may be used. A current sensor measures the line current in the energized line at the measurement frequency. A voltage sensor measures the line voltage in the energized electrical line at the measurement frequency. An analyzer determines impedance of the energized line at the measurement frequency. The measurement is repeated over a wide range of frequencies above and below the line frequency.

Abstract: A test system having an improved physical layout and electrical design allows the 1/f noise of metal interconnects to be measured at levels close to that of Johnson or thermal noise. A detailed description of examples of operation of the test system provides evidence of the effectiveness of the test system in minimizing system noise to a level significantly lower than Johnson noise. This permits quantitative measurment of the noise contribution attributable to variations in cross-sectional area of connections for various applications and for qualitative prediction of electromigration lifetimes of metal films, particularly aluminum, having different microstructures. The test system includes an enclosure which includes several nested groups of housings including a sample oven within a device under test box which is, in turn, contained within the system enclosure.

Abstract: A circuit interrupter with a digital trip unit automatically sets the sampling interval appropriate for the 50 Hz or 60 Hz distribution system to which the interrupter is connected. In order to avoid falsely shifting the interval in response to distorted currents, the trip unit only changes the interval if the number of zero crossings of the current within a fixed number of samples is within two zero crossings of the number of zero crossings for an undistorted current of the other frequency for two consecutive time periods in which the fixed number of samples are taken. Furthermore, changes in the interval are only written into an EEPROM for use on power-up a fixed number of times to preclude disabling the EEPROM. In one embodiment, a 2 pole filter is utilized in the zero crossing counting circuit to eliminate false counts from noise originating in a chopper used in the trip unit power supply.

Abstract: A pulse-based cable attenuation measurement system provides a measurement of attenuation characteristics of a cable over a wide frequency spectrum. A main test and troubleshooting unit of a cable test instrument applies stimulus signals via a selected one twisted pair in a LAN cable to a pulse receiver in a remote unit that in turn causes a pulse generator to produce a specified pulse of known amplitude and duration that is applied as a measurement pulse to a separate but adjacent twisted pair within the same bundle or cable. A measurement system analyzes the measurement pulse after it reaches the main unit, and provides attenuation versus frequency information to determine whether the amount of signal loss due to attenuation in the cable is acceptable or not.

Abstract: An apparatus and method to identify a harmonic producing load on a utility electrical network is described. The apparatus is connected to the utility electrical network at a location adjacent to a load. The apparatus includes a network voltage node to receive a voltage signal, and a network current node to receive a current signal. The apparatus also includes harmonic filters to process the voltage signal and current signal to isolate selected harmonic voltage signals and selected harmonic current signals. A signal processor derives a set of selected power signals from the selected harmonic voltage signals and the selected harmonic current signals. The signal processor also identifies any positive polarity signals in the set of selected power signals. In response to a positive polarity signal, the signal processor activates a sensory output device to indicate that harmonics are being produced by the load.

Abstract: A measurement technique and instrument using rectangular pulse trains of differing repetition rates and synchronously operated lock-in amplifiers to reject electrical noise and capture changes in resistance and capacitance of an electrical element even during a short electrical pulse applied thereto or in the presence of high levels of electrical noise. Particular applications are for electrical programming of fuses and repair of conductors by material deposition.

Abstract: A scheme for judging an active/dead status of a communication cable, which is capable of making an accurate judgement quickly for each cable laid at a working site. In this scheme, data representing a frequency spectrum of signals on a communication cable measured in a state in which the communication cable is known to be active/dead is stored in advance, and the data representing the frequency spectrum of the signals on a communication cable to be judged is measured by detecting signals on the communication cable to be judged while electromagnetically coupling a probe to the communication cable to be judged. Then, the active/dead status of the communication cable to be judged is judged according to a result of comparing a prescribed threshold with a difference of the data representing the frequency spectrum stored in advance and the data representing the frequency spectrum measured by the probe.

Abstract: To test for proper connections of integrated-circuit connection pins (22) on a circuit board (12) to the conductive paths to which they should be connected, a tester (10) applies signals of different frequencies to paths to be connected to different IC pins provided by the same integrated-circuit package (24). The resultant composite electric-field signal in the vicinity of the integrated-circuit package (24) is coupled to a capacitive probe (42), and the probe signal is subjected to frequency analysis (58-1, 58-2 , . . . 58-J) to determine whether the applied frequency components are present in the signal with sufficient magnitudes. If the magnitude in the sensed signal of an applied frequency component is not great enough, the tester generates an indication that the corresponding IC pin has not been properly connected.

Abstract: A principal object of the invention is to detect sparks or arcs (12) in electric circuits (13) or otherwise to detect a spectrum of a broad band of distinct instaneous radio frequencies in radio frequency noise. The invention rejects extraneous narrow-band signals having frequencies within the broad band, such as by means of filters (21, 27, 29) or a balanced mixer arrangement (32-39 ) . The mixer 37 may be fed from a radio frequency signal duplicator (32, 33, 34) having an input (25) coupled to a source of the spectrum, a first output for one spectrum as duplicated by that duplicator connected to one mixer input (35), and a second output for the other spectrum as duplicated by that duplicator connected to tile other mixer input (36). Alternatively, the radio frequency mixer (37) may receive the output of a wide band noise generator (68) at its other input (36, FIG. 5 ).

Abstract: An apparatus which can non-intrusively verify the integrity of shielding on electrical wiring. The method utilizes the natural resonance of the voltage transfer function of the shielded wire. The frequency of this resonance is an indication of the self inductance of the cable. A change in the resonant frequency indicates a change in the self inductance caused by a failure in the shield circuit.

Abstract: Ground fault trip units for circuit breakers are tested by a passive test circuit which includes a test conductor passing through the current transformer sensing coil(s), and a test switch which selectively connects the test conductor in a loop which simulates a neutral-to-ground fault. In a dormant oscillator ground fault test circuit, the test conductor loop passes through both sensing coils. When the neutral-to-ground detector is combined with a sputtering are fault detector sharing a common sensing coil, testing of all the components is accomplished by adding an additional test circuit which injects pulses derived from the line conductor into the sensing coil secondary, or which alternatively, connects a capacitor charged from a DC supply across the sensing coil secondary. Either of these alternative test circuits generates the successive events needed to produce a sputtering arc trip.

Abstract: An arc detector for detecting potentially hazardous arcing in electrical connections comprises detection and signal processing circuitry for monitoring high-frequency noise characteristic of arcing on the power line and distinguishable from other sources of high-frequency noise.

Abstract: 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.

Abstract: A microprocessor based switch such as a circuit breaker generates digital rms representations of analog load currents from n samples of the analog currents per cycle synchronized to the line frequency, where n is an odd integer equal to a selected highest order harmonic to be detected plus 2. A routine determines whether the power system is 50 or 60 Hz, and automatically sets the sampling interval to provide exactly n samples per cycle for the connected source. Terminals for rapidly resetting an analog memory for calibration and field testing of a long delay trip are hidden behind a removable rating plug.

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.

Abstract: Apparatus and method are disclosed for performing testing and fault isolation of high density passive boards (e.g. unpopulated circuit boards) and substrates. Using a small number of moving probes, simultaneous network resistance and network capacitance measurements may be performed. Thus, test time is minimized by eliminating the need for electrical switching and/or excessive probe movement during the test of a normal circuit board network. Simultaneous network capacitance and network leakage measurement are also achieved using phase-sensitive detection. Dual-frequency measurement techniques allow the measurement of both the capacitance value and resistance value of a leakage path between a network being measured and an unknown network. Any leakage resistance between a network under test and ground or power planes within the circuit board may also be determined from the measurements.

Abstract: A diagnostic measuring system (20) for gas insulated electrical substations having UHF couplers (11) fitted to bus chambers (12) monitors for partial discharge events within the chamber (12) to identify the nature and location of an emergent breakdown condition. The system (20) identifies each partial discharge event but characterizes it by amplitude and its time of occurrence with respect to the start of the 50 Hz power frequency wave. The characterized events are communicated over an optical fiber link (13) configured as a token passing ring to an analyzer (25) where a comparison is made with stored historic data characterizing known events. The analyzer (25) provides a self checking routine for the system (20). A microprocessor (36) forming part of a unit (21) associated with a plurality of couplers (11) provides data compression of events identified from these couplers.

Abstract: A high frequency surge tester includes a high frequency detection circuit which is used to detect microfracture defects in the insulation of wire on wound coils. The high frequency detection circuit includes a high-pass filter which isolates an errant voltage response so that it can be integrated and compared to threshold limits to determine the magnitude of defects. The surge tester also detects shorts between coils and shorts between turns of the same coil.

Abstract: A circuit analyzing system includes a current transformer for extracting current from a phase or neutral conductor of a three phase line, a filter connected to the output of the current transformer and functioning to substantially trap current at the fundamental frequency while substantially passing currents at various harmonic frequencies thereof, and signal processing circuitry connected to the output of the filter to perform various functions with the harmonic frequency current input thereto. Among these functions, as shown in various preferred embodiments, are measurement of the harmonic signal in RMS and conveyance of the output to a display instrument for a user or utility's convenience in monitoring harmonic frequency circuits, which have become more common with the advent of electronic equipment having internal power supplies such as personal computers, work stations, printers, and the like.

Abstract: This invention is an apparatus for detecting and pinpointing the sources of sparking electromagnetic RF radiation emanating from high and extra high voltage power lines in the presence of high level corona (RF) radiations which are often present on such lines. It uses a unique metal and plastic rod antenna which will not emit corona when brought up close to a high voltage conductor, and which acts as an attenuator and sensitivity indicator when pushed in steps into a special metal attenuator collar and into its metallic housing. Within the housing, the antenna rod is connected to receiving circuitry which provides sound output of the source noise-signal detected. The housing with its adapter may be removably attached to the tool holder of a standard power line hot stick to permit safe use of the apparatus as a proximity detector in pinpointing sources on power lines. The apparatus receives at a nominal UHF frequency of 430 MHz to permit detection of sparking without detecting corona.

Abstract: A principal object of the invention is to detect sparks or arcs (12) in electric circuits (13) or otherwise to detect a signal having a spectrum of a broad band of distinct instantaneous radio frequencies in radio frequency noise. The invention rejects extraneous narrow-band signals having frequencies within the broad band, such as by means of filters (21, 27, 29) or a balanced mixer arrangement (32-39). The mixer 37 may be fed from a radio frequency signal unbalanced to balanced converter (32) having an input (25) coupled to a source of the signal having the spectrum and having balanced outputs connected to the mixer inputs (35, 36). Alternatively, the radio frequency mixer (37) may receive the output of a wide band noise generator (68) at its other input (36, FIG. 5).

Abstract: An apparatus for the analysis of power quality and the effects of harmonic distortions on machinery or equipment. The apparatus is compact, portable, and non-invasive in that the apparatus can be operatively connected to an electrical carrier without power interruption. A display device is built in allowing graphical display of averaged or continuously updated measurements and analysis. A central processing unit analyzes measurements using Fourier analysis.

Abstract: Disclosed is a Device Under Test (DUT) fault detection and location circuit. A first circuit port is connected to the DUT for fault detection and location. A signal source for generating a series of signals across the operating frequency range of the DUT is connected to a second circuit port. A divider divides each signal generated by the source so as to provide first and second fractions of the signal, the second fraction passing to the device under test. A fault detection section provides a DUT fault detection voltage for each respective frequency. The circuit also has a branch including an impedance section and a fault location section. The branch receives the first fraction, and the fault location section provides a DUT fault location voltage for each respective frequency.

Abstract: An instrument employs a high-pass filter and an associated amplifier to reduce the number of Analog-to-Digital-Converter bits required to determine the amplitude of harmonics contained in digitally sampled AC (alternating current) power system voltage or current waveforms. The instrument is coupled to a power system having a line conductor and a neutral conductor for obtaining time-domain representations of the current flowing in the line conductor and the voltage difference between the line conductor and the neutral conductor. The time-domain representations are converted to frequency-domain representations by a single-chip microprocessor.

Abstract: Electrically conductive patterns such as antenna patterns on window glass are inspected for a wire break or a short circuit. The impedances between an electrically conductive pattern and an electrically conductive layer on an inspective table are measured at predetermined frequencies, or the levels of signals reflected from the electrically conductive pattern are measured at predetermined frequencies. A decision unit determines whether the electrically conductive pattern is acceptable or not based on the frequency characteristics of the electrically conductive pattern and the reference frequency characteristics of a reference electrically conductive pattern.

Abstract: A method and apparatus for locating an incipient fault at a point along the length of an insulated power line includes the application of an excitation voltage at an open end of the power line, and the signal pulse transmitted along the power line to the open end is passed through a high pass filter to remove the portion of the signal which is at a frequency below the excitation voltage and its harmonics. The filtered signal is amplified and passed through a band pass filter to remove a high frequency portion of the signal containing a large proportion of noise relative to the frequency of the partial discharge frequency from the incipient fault. This filtered signal is passed to a digital storage device adapted to be triggered by a signal of a predetermined amplitude, and the triggered digital storage device receives the amplified signal directly from the amplifier and stores digital data concerning amplitude and time for the peaks of the amplified signal for a predetermined period of time.

Abstract: A high frequency surge tester includes a high frequency detection circuit which is used to detect microfracture defects in the insulation of wire on wound coils. The high frequency detection circuit includes a high-pass filter which isolates an errant voltage response so that it can be integrated and compared to threshold limits to determine the magnitude of defects. The surge tester also detects shorts between coils and shorts between turns of the same coil.

Abstract: A power apparatus has a network formed by a plurality of interconnected components being, e.g., one or more high voltage conductors in a casing of a metal filled with an insulating gas. Detectors are provided which detect electromagnetic waves, which are generated if there is a fault. The electromagnetic waves are analyzed to detect the location of the fault. The analysis may make use of attenuation coefficients corresponding to each component of the network to extrapolate between detectors on either side of the fault and/or to compare with predetermined wave strengths. A map of the network may be stored in a suitable memory to assist in the calculation of the fault location, and the memory may also store the attenuation coefficients themselves. The location of the fault may then be displayed by a suitable display, to give the time variation of the fault.

Abstract: An arc detector for 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 occurs every half-cycle of the power frequency, arcing is determined to be present, and an alarm is given.

Abstract: A method and an apparatus for locating from above the ground or water the position of or cable fault in a cable buried underground or underwater. An alternating magnetic field generated by high-powered electromagnet or a rotating magnet induces an indicator signal current in the wires of a cable to be examined. At one or both ends of the cable, the indicator signal is monitored by means of a receiver connected to the cable wires. The received and amplified indicator signal is transmitted by a radio phone back to the point of transmission, whereat the indicator signal is listened to for detecting the location of a cable and its possibly faulty section. According to the invention, a sufficient direct voltage is supplied between the wires of the cable. This creates a current whose loop closes through a faulty location and the indicator signal is separated from the current produced by the direct voltage.

Abstract: A system and method for detecting partial discharge of gas-insulated switchgear wherein a high-frequency component and the fundamental wave component of the voltage applied to the conductor of the gas-insulated switchgear are detected, the zero-cross point of the fundamental wave component is set as the starting point for the voltage, and the presence of partial discharge and the reason for the occurrence of partial discharge are ascertained based on the phase difference between the phase of the detected high-frequency component and the phase of the starting point of the voltage.

Abstract: A portable instrument for locating and measuring harmonic distortion in a conductor. The instrument permits voltage and current harmonics to be easily read while the load is changing. Thus, the instrument may provide a great deal of insight as to the source of problem causing harmonics.

Abstract: A method and apparatus for locating an abnormality in a gas-insulated electric device, operative to locate the spot of an insulation abnormality, which emerges inside a metallic container, from outside of said metallic container. A plurality of detectors (S.sub.0 -S.sub.n) disposed at certain positions in the metallic container produce detected signals, from which spectrum strengths (YH) in a high frequency band of 500 MHz or above are evaluated, and a position which renders a maximum spectrum strength is calculated from the relation between the spectrum strengths and the installation positions of the detectors and is determined to be the spot (x) of partial discharge.

Abstract: A plurality of current detectors are provided in a plurality of prescribed spots of a transmission line for locating a fault caused, e.g. by lightning. A plurality of discriminators are provided in correspondence to the plurality of current detectors. Each discriminator receives detected signals from an arbitrary pair of the plurality of current detectors for detecting a relative difference between arrival times of the detected signals while extracting low-frequency components from the detected signals respectively and for detecting a phase difference between the extracted low-frequency components. A locator receives relative time difference data and phase difference data from the plurality of discriminators, to locate a faulty point in the transmission line on the basis of the received data.

Abstract: A digital isolation monitor comprises a digital processing signal processor P1 designed to synthesize a sine wave in real time by a table, and to send the digital values of this sine wave to a digital-to-analog converter of an input channel to generate a low-frequency AC reference signal with a very low, stable phase distortion factor. An acquisition channel is fitted with a switching unit operating in conjunction with a dual measurement circuit to send an injected voltage signal and a leakage current signal to a low-pass analog filter in series with a sample-and-hold circuit and an analog-to-digital converter. The processor P1 then performs synchronous demodulation and transmits the data to a microcontroller P2.

Abstract: A system for detecting an arcing fault in a telephone central office DC power distribution conductor repeatedly measures the current flow in the distribution line, as with an inductive coupling, and derives a Fourier transform analysis spectrum from such measurements. The power values at intervals across the frequency spectrum are compared with recorded threshold template values encompassing the spectrum typical of an arcing event and an alarm condition is established when such threshold levels are exceeded.

Abstract: A contact abnormality detection system for use in a gas-insulated switchgear or other power transmission or distribution apparatus. A gas-insulated switchgear includes a hermetic housing, an insulating gas sealed in the housing, and conductors in the housing having contacts for providing a path for a large current and being electrically insulated from the housing. An abnormality in the contacts causes the contacts to generate vibrations when a large current flows through them. A vibration detector detects vibrations generated by the switchgear including the vibrations generated by the contacts. The frequency spectrum of the vibrations detected by the vibration detector is analyzed to detect if the vibrations contain frequency components in the range of 200 to 500 Hz which meet predetermined criteria.

Abstract: A data compression method and apparatus particularly suitable for use in electrical power line fault data recorders. The system performs both gain compression and frequency compression. For gain compression, a predetermined number of samples are analyzed to determine a gain setting common to each sample in the set of samples. A reduced data string consisting of a gain code and data words having fewer bits than the input words are transmitted as a compressed data string. For frequency compression, a sample set representing the input signal is decimated until there remain only a sufficient number of data samples to satisfy the Nyquist criterion for the highest frequency component of interest. The frequency compressed output data string comprises a frequency code representing the highest frequency of interest followed by the set of decimated data samples.

Abstract: A high frequency and two low frequency electromagnetic signals are generated (1), the low ones being coherent with the second being a sub-harmonic of the first. The high frequency is modulated (4) by the second low frequency and applied (7,9) as a composite signal to an underground conductor, while the first low frequency is applied (9,10) additively. A receiver traversed over the line has aerials (12,21) or ground probes (24,25) for picking up these signals in separate channels. The high frequency is demodulated (18) to provide a reference signal for a synchronous detector (20) to which the first low frequency is fed. That suffers a phase reversal if there is a fault, and the output of the synchronous detector is arranged to indicate that.

Abstract: A system and method is disclosed for detecting an abnormality in a network for distributing or transmitting electric power at a predetermined fundamental frequency. The system produces a signal representing the fundamental frequency and another signal representing a harmonic current occurring in the network. The phase relation between the fundamental voltage and harmonic current representing signal are compared. The system produces a signal indicating the occurrence of a high impedence fault in response to a predetermined change in the compared phase relationship.

Abstract: Disclosed is a system for detecting and processing an abnormality in electromagnetic shielding for use in an intelligent building which is constructed using an electromagnetic shielding material for the skeleton and openings such as windows and doorways so that the whole of the building is formed into an electromagnetic shielding structure in order to carry out radio communication inside the building. The system has radio wave detecting means for detecting an external radio wave inside the building, level judging means for judging the level of an external radio wave detected by the radio wave detecting means, and processing means for detecting and processing an abnormality on the basis of an output from the level judging means, whereby an abnormality in the electromagnetic shielding performance is detected on the basis of the intensity level of a detected radio wave intruding into the building from the outside.

Abstract: A circuit tester provides an indication of open circuit faults of individual conductors in cables. An oscillator circuit in the tesster includes a capacitance as an internal part of the circuit. Test probes connect conductor pairs to the oscillator circuit, thus changing the effective capacitance of the circuit. This changes the frequency output of the oscillator in accordance with the length of the conductors. Test indications may include a low pass filter and an audio circuit, or a circuit to convert frequency to a voltage or digitalized output. The tester may be used with automated test equipment.

Abstract: Disclosed is a radio wave leakage diagnosing system for use in an intelligent building which is constructed using an electromagnetic shielding material for the skeleton and openings such as windows and doorways so that the whole of the building is formed into an electromagnetic shielding structure. The system has a radio wave detector disposed outside the building for detecting a predetermined radio wave transmitted from each floor of the building, so that a floor, togethere with a specific position, where there is a leakage of radio wave is detected on the basis of the intensity of the detected radio wave. With this arrangement, a predetermined radio wave is transmitted from each floor of the building and the transmitted radio wave is detected by the radio wave detector.

Abstract: The control apparatus has an antenna (10) for the reception of electromagnetic radiation emitted from the alternating current transmission line. The antenna (10) is connected to an amplifying device (20) the signal output (22) of which is connected to an oscilloscope (30) in such a manner that the output signals of the amplifying device (20) effect both vertical and horizontal deflection of the image spot on the image screen of the oscilloscope (30). The amplifying device (20) is constructed for the amplification of a broad frequency range extending from below the line frequency to at least 20 kHz, wherein the amplification in the frequency range below about 10 kHz is reduced. The whole frequency spectrum of the output signals of the amplifier device (20) is fed to the oscilloscope (30).

Abstract: Apparatus for the detection of ground leakage in a normally ungrounded DC system includes a DC power supply and conductors from the supply for supplying power to a load connected to the DC system. There is an indicator connected between the DC system and a ground point such that a ground leakage in the system closes a circuit to activate the indicator. With such activation, a pulser periodically interrupts the circuit to effectively generate an interrupted ground fault signal. Such signal is detected by a sensor located relative to the DC system such that an interrupted ground signal detected by the sensor locates the ground fault. Noise introduced into the pulse signal by the periodic interruption of the circuit during the ground fault occurrence is suppressed by the sensor means.

Abstract: A method of locating an electrostatic discharge event in a predetermined ucture by sensing electromagnetically that an electrostatic discharge event has occurred and producing a trigger signal from the electromagnetic sensing to control a recording device for the starting of time, utilizing a plurality of acoustic detectors about the structure for sensing the acoustic of the electrostatic discharge event, determining the time elapsed between the starting of time by the electromagnetic sensing and the signals sensed by the acoustic detectors and utilizing the information gained from the times sensed and the predetermined locations of the sensors to determine the location of the electrostatic discharge event in the predetermined structure.

Abstract: A method and apparatus for locating an incipient fault at a point along the length of an insulated power line includes the application of an excitation voltage at an open end of the power line, and the signal pulse transmitted along the power line to the open end is passed through a high pass filter to remove the portion of the signal which is at a frequency below the excitation voltage and its harmonics. The filtered signal is amplified and passed through a band pass filter to remove a high frequency portion of the signal containing a large proportion of noise relative to the frequency of the partial discharge frequency from the incipient fault. This filtered signal is passed to a digital storage device adapted to be triggered by a signal of a predetermined amplitude, and the triggered digital storage device receives the amplified signal directly from the amplifier and stores digital data concerning amplitude and time for the peaks of the amplified signal for a predetermined period of time.