Abstract: An electrical contact avoidance device comprises an inductor plate directly or capacitively coupled to the user and coupled to a detector circuit which derives a DC signal corresponding to a voltage induced in the user's body by a radiated high voltage electrostatic field. A comparator compares the DC signal with a reference signal representing the potential difference between the inductor and reference plates, and activates an alarm if the detected signal exceeds a preselected reference level.

Abstract: In a switch with pre-alarm means having level adjusting apparatus (105a) of the pre-alarming and an indicator (103) for showing that value of current flowing on a load corresponds to the pre-alarm level, the level adjusting apparatus (105a) is adjusted with monitoring the indicator (103). When the indicator (103) is lighted, the value shown by level indicator (105b) of the level adjusting apparatus (105a) corresponds to actual value of the current flowing on the load at that time.

Abstract: An electrical connector with visual display connecting an information bus to a computer in an information processing system including electronics mounted within a connector body and coupled to the information bus, the electronics monitoring information flowing through the information bus and providing output signals in response thereto and visual display circuitry mounted in the connector body and connected to receive the output signals from the electronics and provide a visual display in response thereto indicating the flow of information through the bus.

Abstract: A display transducer adapter for obtaining and displaying power system information from a protective relay. The information includes watt, voltage, current, reactive power, and fault location information. The information may be converted from a digitized format into analog signals and those signals may be provided as outputs, the functions of which are user selectable. The user may also selectively scale the outputs to cover a specified range.

Abstract: An apparatus for detecting speed sensor failure in an overspeed protection device is disclosed. The apparatus comprises a plurality of tachometers having outputs for indicating the speed of rotation of a machine relative to plural setpoints. If the comparison indicates that certain conditions exist, then a sensor failue is indicated. The apparatus may also be employed to detect a failure of, or loss of power to or within, one of the tachometers.

Abstract: An apparatus for detecting a power system disturbance. The apparatus may be a current rate-of-change relay for qualifying system-separation transfer-trip commands.

Abstract: A method and an electrical measuring apparatus for analyzing an actual alternating voltage present on an electrical wire or electrical equipment whereby to determine if the voltage originates from a high or low impedance source for the safety of the operator. A bi-impedance probe is connected to the alternating voltage to be analyzed and the voltage signals are processed. The actual probe consists of a first series of uni-directional elements and a second parallel series of high value resistance elements. The output of the parallel connected series of elements is connected to a third series of low value resistance elements. A measuring circuit is connected to the third series of low value resistance elements and is capable of discriminating between the voltage signals from both of the series of resistive elements and is provided with a calculating circuit to determine if the voltage signals originate from a high or low impedance source. The output of the probe is connected to ground.

Abstract: A power status detecting apparatus which is to be applied to a plurality of audio-visual equipments arranged such that currents flowing to AC lines of the respective equipments are detected so as to identify the power condition status of the respective equipments and in which identified information are supplied to a system control apparatus. Thus, system control for a plurality of equipments can be performed more positively and conveniently.

Abstract: A water quality monitor is provided for use in a purified water supply system of the type having a reverse osmosis unit or the like for producing relatively purified water from an ordinary tap or feed water supply. The monitor includes a control circuit having eletrodes in contact with the purified and tap water supplies. The control circuit is activated by depression of a test button to produce a short duration pulse of one polarity which is connected to the electrodes for use in determining the water conductivities. The control circuit compares the conductivities of the purified and tap water supplies, wherein this comparison represents the operational efficiency of the purification system in removing contaminants from the incoming tap water. The control circuit responds to this comparison to illuminate an appropriate indicator light or the like and thereby indicate the operational state of the purification system.

Abstract: A motor control having mechanical switching and pressure reponsive components for connecting and intercepting a circuit between an A.C. source and an A.C. motor in response to pressure changes in a pressure system. The control includes a microcomputer chip and components that detect a voltage across the motor and a current through the motor and provide signals indicative of the level of the motor voltage and current. The control in response to the signals determines the power factor of the current and in response to the detected signals protects the motor from operating malfunctions when the voltage is too high or low, the current is too high or too low, the time of operation of the motor is too long or too short and in response to the character of the malfunction provides a visual coded lamp indication of the cause of the malfunction.

Abstract: A circuit breaker system uses a microprocessor for calculating at least one function of a measured current flow.

Abstract: Monitoring an electric power distribution circuit having a rated load capacity includes continually sensing an intensity of electric power supplied through that circuit. In response to that sensing a first signal indicating when electric power is supplied through that circuit at a predetermined maximum current usage below rated load capacity is provided. A second signal indicating a safe loading condition is provided when the sensed intensity is substantially below that maximum current usage. A third signal is provided when the mentioned intensity is at a value between the safe loading condition and the maximum current usage.

Abstract: A warning device (10) is provided for use by electrical technicians or the like to indicate the presence of an electrical shock hazard. The warning device is adapted to be worn on the wrists or the like and includes a filtered detection circuit (32,34) for sensing a target signal such as an ac noise signal emitted from an electrical source. When the target signal magnitude exceeds a selected threshold (40), such as when the wearer moves into close proximity with the signal source, the warning device (10) activates an alarm (42,44) to indicate the presence of a shock hazard.

Abstract: A microprocessor-based control/status monitoring arrangement allows for replacement of mechanical memory, cam-operated control board switches, such as used in controlling and monitoring the operation of a conventional electrical power generating station. The control/status monitoring arrangement includes and operator input device, such as a keyboard or "touch screen" cathode ray tube (CRT), to permit operator entries, as well as a video display to provide visual information relating to the operating system, e.g., power generating station, being monitored and controlled. The control/status monitoring arrangement not only offers the advantages of the prior art cam-operated mechanical switches in a solid state system with programming flexibility, but also provides additional equipment status indications and controls, e.g., Lockout, Tripped, Auto Started, etc., and special interlocks to ensure operating safety.

Abstract: An apparatus for measuring a measurable characteristic of an object includes a sensor element which emits an analog sensor output signal, the sensor output signal corresponding to the measurable characteristic of the object, an analog/digital converter for converting analog signals from the sensor element into digital output signals, a processor receiving the digital output signals and supplying a control signal to the controllable auxiliary variable generator. The controllable auxiliary variable generator is controlled by the control signal emitted by the processor, and the auxiliary variable signal is interrupted for a selected time span after each measuring interval.

Abstract: In a preferred embodiment, a reversible DC power supply having an audible alarm, especially for use with electrochemical metallizing equipment. The audible alarm is electrically connected directly to the controls of the power supply so that when the power supply is placed in its "reverse" mode, the audible alarm will continuously sound, thus alerting the operator that the power supply is in that mode. In other embodiments, reversible electric tools, such as drills, may be provided with an audible alarm to indicate when they are in their reverse states.

Abstract: A circuit arrangement is described for automatically monitoring several analog electric signals and for maintaining predetermined ranges of tolerances by successive comparison with reference values. Error alarm signals are produced and stored, dependent upon the comparison and timed (synchronized) simultaneously with the connection of the respective signals to be monitored to a comparator (20). Access is provided to a reference value storage (30) from which reference signals assigned to each single signal and ranges of tolerances defining reference values are timed and led to the comparator (20). The respective outlet (output) signal of the comparator (20) for producing similar error alarm signals to be stored is logically linked with an evaluating signals (ZB 0) indicating which of the two reference values lies at any time on the comparator (20).

Abstract: A monitor for an electric motor, the monitor capable of connection to a supply of electrical energy for the motor, has a microcomputer for measuring the power factor of a voltage applied to the motor and a current flowing to the motor, for storing a desired value of power factor, for comparing a measured value of power factor with the desired value of power factor, and for disconnecting the motor from the supply of electrical energy if the measured value of the power factor differs from the desired value of power factor by an amount that exceeds a predetermined amount. Further, the monitor has means for operating the motor while driving a desired load; means for commanding the microcomputer to measure a power factor of the voltage applied to the motor and the current flowing to the motor while the motor is driving the desired load; and, means for storing the measured value of the power factor, measured while the motor is driving the desired load, as the desired power factor.

Abstract: Electrical circuits for detecting intermittent and continuous electrical parameters such as continuity for open or closed circuits, AC power interruption or decrease in frequency, DC power interruption, missing electrical pulses; and voltage, resistance, and current levels that are greater than or less than present high and low limits. This invention also detects temperature and light (illumination) that is greater or less than present limits. The invention has a memory and both a (variable time delayed) automatic, and a manual memory reset. It provides both visual and a defeatable audio indicators or alarms. The advantage of said invention is that it detects intermittent conditions as brief as fractions of microseconds that may occur as frequently as milliseconds apart or as infrequently as days apart; it also detects steady state conditions.

Abstract: A non-intrusive monitor of energy consumption of residential appliances is described in which sensors, coupled to the power circuits entering a residence, supply analog voltage and current signals which are converted to digital format and processed to detect changes in certain residential load parameters, i.e., admittance. Cluster analysis techniques are employed to group change measurements into certain categories, and logic is applied to identify individual appliances and the energy consumed by each.

Abstract: An analog ASIC (Application Specific Integrated Circuit) circuit has a power control section, a conductivity filter testing section, a light emitting diode (LED) driving section, and a bias section. The LED driving section is responsive to the conductivity filter testing section for indicating when the filter should be replaced. The power control section, conductivity filter testing section, LED driving section, and bias section are all operated in a controlled timed relation by a digital ASIC logic system to minimize power use.

Abstract: The present invention relates to a proximity detector between a metallic mass and an element subjected to an electric voltage, with an electric circuit feeding a safety device such as the coil controlling a circuit-breaker, the feed switch of a motor controlling the displacement of the mass, an auditory or visual alarm, or an emergency ground. The circuit includes an element which is normally non-conductive but made conductive when there is a potential appearing on the metallic mass to be protected, or on the antenna in which the electric circuit is fed by a DC autonomous power source. The conductibility of the element whose conductibility is modified by the variation of the electrostatic potential is controlled by the potential at an intermediate point between the metalic mass or the antenna and a pole of the DC source, with interposition between the intermediate point and the pole of a resistive or capacitive element.

Abstract: A device to be used in a motor vehicle or motorboat for performing a wide variety of warning and monitoring functions. It includes apparatus to electrically connect to a positive battery cable (1,2), to a negative battery cable (3,4), and to the vehicle chassis (5,6); apparatus for warning sound and light (7,8); an electronic circuitry (9); and a cigarette-lighter size plastic enclosure (10). The electronic circuitry includes a Voltage Sensing Circuit to sense the battery voltage and battery cable connection conditions at engine starting and to turn on warning sound and light on low battery and bad battery connection detection, a Current Sensing Circuit to sense the battery discharge current and to turn on intermittent or continuous said warning sound on detection of a left-on headlight a battery charging system malfunction or failure, brake light failure, and too-low engine idle speed. The device can be attached to a battery cable and requires no skill and no tools for installation according to FIG. 1.

Abstract: A toroidal sensor module having a metallic outer skin and mounting means for installation upon and removal from an energized power conductor providing synchronized measurements of electrical parameters. In one embodiment the module is adapted to measure the values of voltage, current and phase angle of the conductor upon which it is mounted, and to communicate data representing such values to a ground station in the vicinity of the sensor module. The voltage and current are sensed simultaneously to provide time-synchronized readings with respect to voltage zero crossings from which the phase relationship is determined. The metallic skin of the module may be either capacitively or electrically coupled to the conductor for purposes of making conductor voltage measurements.

Abstract: An apparatus and method are disclosed for transferring information into an integrated circuit over the power supply pins of the integrated circuit. The apparatus and method are used to load a test program into memory of the computer system and the system is caused to execute the test program to verify proper operation of the computer system. The apparatus and method are implemented by converting the information to be loaded into a serial bit stream, using the serial bit stream to modulate the power supply voltage of the computer system. Inside the computer system, the low power supply levels are sensed by a low power supply detection unit an fed to a serial-to-parallel converter where it is converted back into the original information.

Abstract: An electrical power monitoring and control system including individual sensor modules for mounting directly upon energized electrical power conductors and systems employing such modules, with principal emphasis upon the provision of both data transmitting and receiving means in each sensor module and at an associated ground station. The modules sense the instantaneous values of all parameters necessary to perform complete metering functions and, in one embodiment, are synchronized by a signal transmitted from the ground station and received by all modules so that the values are measured simultaneously on all conductors at a substation. The signals are transmitted by the modules in a time-synchronized manner and are in a condition for use directly by the ground station microprocessor. In another embodiment, data transmissions by a plurality of modules is synchronized to avoid data collisions by self-contained means within each module, requiring no synchronizing signal from the ground station.

Abstract: A device for generating an alarm signal in the event of an environmental abnormality has multiple sensors, with a multiplier associated with each sensor, an adder, and a comparator. The sensors are disposed in respective sensing volumes, which may be different. The sensors detect a level of smoke, heat, gas or other environmental abnormality within each sensing volume, and convert the level into an electrical analog signal. The associated multiplier multiplies a coefficient proportional to the sensing volume for the associated sensor with the analog signals from the sensor. The adder adds the outputs of the multipliers. The comparator generates an alarm signal at an output thereof when the output of the adder exceeds a predetermined value.

Abstract: Self contained radio transmitting state estimator modules are mounted on power conductors on both sides of power transformers in electrical substations and on power conductors at various places along electrical transmission lines. They are electrically isolated from ground and all other conductors. These modules are capable of measuring current, voltage, frequency and power factor (or the fourier components thereof) the temperature of the conductor, and the temperature of the ambient air. The modules transmit these parameters to local receivers. The receivers are connected by an appropriate data transmission link, to a power control center which allows determination of the state of the power system. The module measures the Fourier components of voltage and current over a number of cycles and transmits the components to the local receiver.

Abstract: A portable monitoring system for detecting a radiated electrostatic field and producing an audible warning when the detected field exceeds a selected value is characterized by a switching device which can be used to reset the threshold warning level and which is not affected by the hand proximity effect. An alarm is sounded when a signal corresponding to the detected field exceeds a value which is stored. The stored value can be reset by a manually operated switching circuit including a delay device operable to delay the storage of a reference level corresponding to the intensity of the field currently detected.

Abstract: An electrical power monitoring and control system including individual sensor modules for mounting directly upon energized electrical power conductors and systems employing such modules, with principal emphasis upon the provision of both data transmitting and receiving means in each sensor module and at an associated ground station. The modules sense the instantaneous values of all parameters necessary to perform complete metering functions and, in one embodiment, are synchronized by a signal transmitted from the ground station and received by all modules so that the values are measured simultaneously on all conductors at a substation. The signals are transmitted by the modules in a time-synchronized manner and are in a condition for use directly by the ground station microprocessor. In another embodiment, data transmissions by a plurality of modules is synchronized to avoid data collisions by self-contained means within each module, requiring no synchronizing signal from the ground station.

Abstract: The invention is primarily directed to sensor modules for mounting directly upon energized electrical power lines to monitor parameters associated with operation thereof, wherein the modules have a more compact lateral configuration than prior art modules designed for the same purpose. The modules include a first, cylindrical housing portion containing the sensing means and other electronic data processing and transmitting elements, and a second housing portion, affixed to the exterior of the first portion and extending not more than about 150.degree. around the periphery thereof, and enclosing mechanical elements of the module mounting means.

Abstract: Self contained radio transmitting state estimator modules are mounted on power conductors on both sides of power transformers in electrical substations and on power conductors at various places along electrical transmission lines. They are electrically isolated from ground and all other conductors. These modules are capable of measuring current, voltage, frequency and power factor (or the Fouier components thereof), the temperature of the conductor and the temperature of the ambient air. The modules transmit these parameters to local receivers. The receivers are connected by an appropriate data transmission link to a power control center which allows determination of the state of the power system. Appropriate control signals are transmitted back to the electrical switchgear of the system to bring it to the appropriate optimum state. Direct local control may also be effected, for example, the prevention of overloading a transformer.

Abstract: In a solid state electricity meter, a display consisting of a number of juxtaposed display elements provides, in a vector form, an indication of the direction and range of power flow in the line being measured. Circuitry for driving the vector display comprises a first memory storing a plurality of power measurement references and a second memory storing corresponding vector symbols. A microprocessor compares each power measurement with the reference stored in the first memory to determine the range of power measurement and, in response, reads the corresponding vector symbol from the second memory to drive the display.

Abstract: An optical indication circuit in which a light-emitting diode is included in the feed current path of an IC which is energized via a dissipation resistor and a rectifier diode directly from the alternating voltage supply.

Abstract: A ground continuity monitor for a tool stop controller includes a pair of resistive conductors connected in series between the power line hot and neutral leads. At the junction therebetween they are connected to the ground lead and to a controllable shunt. The resistive conductors maintain a sufficient voltage at the junction to hold the shunt in a conducting state until the junction is connected to ground through a low impedance, preferably less than substantially 100 ohms. An indicator, such as a lamp, indicates the state of conduction of the shunt, thereby providing the tool operator with an indication of the actual electrical continuity of the ground path from the tool ground lead back to ground at the power line source. In the event of a ground fault, no high voltage is imposed by the monitor on the tool case.

Abstract: An analog signal processing circuit including both an analog signal multiplexer and a ranging circuit in cascade therewith is adapted for use in an integrated circuit. The multiplexer has a plurality of input current paths and an output current path. It responds to a set of coded selection signals to couple one of the input current paths to the output current path to permit current therebetween and includes another circuit for maintaining the selected input current path at a predetermined potential, preferably ground potential. The ranging circuit has its input current path coupled to the output current path of the multiplexer and includes a plurality of current splitters coupled in a cascaded chain having one end of the chain coupled to its input current path. The ranging circuit responds to another set of coded selection signals to draw current from one and another current paths to the output current path of the multiplexer.

Abstract: An apparatus for controllably delivering power from a device to a workpiece is useful, for example, in performing qualitative material tests on various materials. In the instant apparatus, a sonic generator means controllably supplies sonic power to a workpiece, causing the surface of the workpiece to erode. A sensing means produces an actual power signal having a magnitude responsive to the power consumed by the sonic generator means. A settable means produces a desired power signal, and a control means compares the desired and actual power signals and supplies motor control signals in response to the respective magnitudes of the power signals and to a tracking time interval signal. In response to termination of the tracking time signal, the control means blocks the motor control signals. A motor means controllably moves the sonic generator means relative to the workpiece in response to receiving the motor control signals.

Abstract: A static VAR generator for providing reactive compensation incorporating a malfunction detector. The static VAR generator comprises a reactance which is linearly responsive to a first linearized control signal and produces an output signal proportional to the reactive compensation which provides a feedback signal. A director control uses the feedback signal and an adjustable reference signal to provide the first linearized control signal based on the difference between the reference and feedback signals. A tracker controller provides a second linearized control signal based on the reference and feedback signals. The second control signal is compensated by an equalizer that determines the difference between the first and second control signals. The compensation counters the difference between the first and second control signals caused by the offset and component tolerances in the two controllers and makes the second control signal substantially equal to and track the first control signal.

Abstract: A multilayer tape probe for measuring the movement of charge has at least a pickup electrode comprising one layer of electrically conductive tape and a shield electrode comprising another layer of electrically conductive tape, the pickup and shield electrodes being separated by a dielectric strip. Circuitry is connected to the probe to drive the shield electrode and to monitor the potential difference between ground and pickup electrodes and actuate an alarm if an unwanted charge is present.

Abstract: In a method for controlling output of alarm information in a system for monitoring a plant wherein process variables including analog type process variables at respective sensing points in the plant are sampled and each of the sampled analog type process variables is compared with a normal range limit value for determination as to whether it is within a normal range or within an abnormal range, an alarm limit level is determined in accordance with changes that have occurred in the process variable during the latest sampling interval. Output of alarm information is permitted in connection with the process variables that have a priority level whose value is higher than the value of the alarm limit level.

Abstract: Current provided to a generally constant impedance load is monitored to detect a predetermined load current decrease not resulting from normal load voltage fluctuations, such decrease indicating an abnormal increase in load impedance. A latching alarm is actuated when the predetermined load current decrease is detected. The degree of load current decrease tolerable without activating the alarm is determined by a user-adjustable percentage-of-change sensitivity control. A logic gate blocks alarm functions when the load current decreases to an abnormally low level. The disclosed device can be used to monitor the status of a line voltage energized heat trace cable constituted by a plurality of parallel-connected resistance wire heating elements. Multiple monitoring devices can be used in conjunction with a master alarm which can be reset without resetting the particular monitoring device alarm that triggered the master alarm.

Abstract: A low charge detector, for a measuring instrument incorporating a meter for indicating measurement readings, includes a "low battery detector" circuit which causes a first output to be released from a 1 Hz oscillator, when a battery pack supplying power to the instrument discharges to a predetermined level. The first output is then applied to a pointer on the meter, thus causing the pointer to execute oscillations of a relatively small amplitude.When the battery pack is substantially dead, a "dead battery detector" circuit causes a second output to be released from the oscillator and to combine with the first output. The combined output is then applied to the pointer, thus causing the pointer to execute oscillations of a substantially greater amplitude, thereby indicating that recharging of the battery pack is required.

Abstract: A smoke detector receiving at two input terminals DC power from a remote source not only gives an alarm indication in response to a significant density of smoke, but senses the polarity of DC power at the terminals and generates a secondary signal, distinguishable from the alarm signal, when the polarity of power source is reversed.

Abstract: A method and apparatus for increasing the response sensitivity and the interference resistance in an alarm system such as a fire alarm system which cyclically samples a plurality of alarm units in the system for obtaining a series of measured values from each alarm unit, the measured values being utilized to form a quiescent value which is stored in a quiescent value memory. With each sampling cycle a current comparison value is formed from the alarm measured value, the stored quiescent value, and a comparison value from a previous sampling cycle stored in a comparison value memory. The current comparison value is then written in the comparison value memory as the new comparison value. The current comparison value is compared with a rated limiting value, and if the comparison value is greater than or equal to the rated limiting value, a display unit is activated indicating an alarm.

Abstract: Apparatus for transferring power from the battery of a service vehicle to the battery of a second vehicle, wherein the final connection between the batteries is made from a remote location via a radio transmitter and a receiver which is mounted in the casing of the apparatus to actuate a solenoid in response to a signal from the transmitter. The circuit between the solenoid and the receiver includes a transistor to control current through the solenoid coil and the base of the transistor is connected to the battery of the second vehicle. Cables used to attach the apparatus to the second vehicle battery are wound on a spool having an interrupted ratchet on one end thereof, the ratchet engaging a ratchet lock that pivots in one direction to hold the reel when the reel is turned in one direction to pay out the battery cables and the ratchet lock pivoting in the other direction within a ratchet wheel interruption to permit free rotation of the reel in the opposite direction for retrieval of the cables on the reel.

Abstract: A non-contact noise detection apparatus is provided with a detector not connected to the source of the noise for detecting the high frequency field generated by the source. A high pass filter and amplifier passes the high frequency pulse components only of the output of the detector. A pulse generator is responsive to the output of the high pass filter to provide a pulse signal of predetermined width, and an indicator is responsive to the pulse generator.

Abstract: A respiration monitor for use in an apnea monitor is disclosed in which a threshold value signal is automatically generated proportional to the average value of the monitored impedance of the subject during a base period selected by the operator. A comparator circuit operates to indicate respiration when the ratio between the threshold value signal and the impedance signal reaches a predetermined proportionality factor.

Abstract: A system for, and a method of, detecting the proximity of a source of an alternating magnetic field, such as that emanating from power transmission cables, comprising a sensor coil sensitive to the magnetic field under detection, processing means to derive from the signal induced in the coil a warning signal indicative of the proximity of the magnetic field under detection, and cancelling means operable to cancel the earth's field in the region of the sensor coil. The sensor coil may be one of a pair operable to provide a signal representative of the directional heading of the magnetic field under detection, with respect to the system, which embodiment is particularly useful in helicopters for detecting the proximity of power cables.

Abstract: An interface device for the remote control of pulse activated, mechanically held relays or master switches by control devices which have a continuous output, such as time clocks, security system devices, and thermostats. The presence of a continuous input signal is decoded by the electronic circuitry into a momentary output signal to be applied to the "on" side of a remote control relay. When the input signal is removed, the device decodes this lack of signal and produces a momentary signal to be applied to the "off" coil of the relay. Input terminals are provided with four types of input signals -120 volts AC, 12 volts DC, a contact closure, and a contact opening. Three output terminals are provided, namely, "common," "on," and "off" terminals for connection to the remote control relays. Another set of terminals can be provided to allow the use of an external power supply load with the device, by incorporating a control relay within the device capable of handling 20 amps.

Abstract: A power line fault detector (10) includes a capacitive impedance (12) and another impedance (14) connected in series between the hot and ground conductors of the power line, with a trigger circuit (16) being connected between the neutral conductor of the power line and the junction of the impedances. The impedances have values selected such that the voltage at the junction thereof with respect to the neutral conductor does not exceed a preselected limit unless the power line is faultily connected. The trigger circuit normally has a high impedance but switches to a low impedance when the voltage across it exceeds the preselected limit, then producing a surge of capacitive impedance charging current. A sensing circuit (20, 21, 26) senses the surges of current in the trigger circuit and provides an indication to the operator that the power line is faulted.