Abstract: A current measurement circuit for determining a start time tSTART, an end time tEND, and/or a peak time tMAX for a current pulse passing through a current conductor. The current measurement circuit includes a pickup coil and a threshold crossing detector. The pickup coil generates a voltage VSENSE? proportional to a magnetic field around the conductor, which is proportional to a change in current over time. The threshold crossing detector compares VSENSE? and a threshold voltage and generates an output signal indicative of a transition time and whether a slope of VSENSE? is positive or negative. The current measurement circuit can also include an integrator and a sample and hold circuit. The integrator integrates VSENSE? over time and generates an integrated signal VSENSE. The sample and hold circuit compares VSENSE to tMAX and generates a second output signal which can be used to measure the pulse current.

Abstract: There is provided a material testing machine that a control device of the material testing machine includes a detection circuit which extracts a resistance component caused by the physical quantity and a capacitive component caused by an electrostatic capacitance of the cable from a measurement signal from the detector, a memory element which stores a normal capacitive component extracted by the detection circuit, and a comparator which compares the current capacitive component extracted by the detection circuit with the normal capacitive component, and when a comparison result from the comparator indicates that a value of the current capacitive component varies beyond a predetermined allowable range with respect to the normal capacitive component, it is treated that the cable is disconnected, and a disconnection warning is provided.

Abstract: Disclosed is a method and apparatus for reducing outbound interference in a broadband powerline communication system. Data is modulated on first and second carrier frequencies and is transmitted via respective first and second lines of the powerline system. A characteristic of at least one of the carrier signals (e.g., phase or amplitude) is adjusted in order to improve the electrical balance of the lines of the transmission system. This improvement in electrical balance reduces the radiated interference of the powerline system. Also disclosed is the use of a line balancing element on or more lines of the powerline system for altering the characteristics of at least one of the power lines in order to compensate for a known imbalance of the transmission system.

Abstract: Device structures and fabrication methods for an on-chip resistor. A first Seebeck terminal is arranged to overlap with first and second resistor bodies of the on-chip resistor. A second Seebeck terminal is also arranged to overlap with the first and second resistor bodies. The second Seebeck terminal has a spaced relationship with the first Seebeck terminal along a length of the first and second resistor bodies. The temperature coefficient of resistance of the on-chip resistor is based at least in part on a Seebeck coefficient of first and second Seebeck terminals.

Abstract: An exemplary test arrangement for in-situ partial discharge measurements in distribution transformers has at least one test system with a plurality of test components including: an AC voltage source for producing a variable test voltage with a measuring apparatus for recording current pulses caused by partial discharge and with an evaluation apparatus for the recorded current pulses, a grounded test container in which at least some of the test components are arranged, and a distribution transformer connected to the AC voltage source as a test object. The test object is arranged on insulation means for electrically insulating the test object. Those parts of the test object which are grounded during normal operation being connected at least to the potential of the grounded test container.

Abstract: Apparatus for remote monitoring of partial discharge events in electrical apparatus 1 includes one or more sensors 5 for detecting partial discharge pulses in one or more conductors 2 conveying electrical power to the apparatus. A programmed computer 5 analyzes measured pulses and discriminates between those originating from the apparatus being monitored and elsewhere. Discrimination is achieved by analyzing pulse shape, and by comparing pulses to partial discharge events measured locally to the sensors. The apparatus enables partial discharge events in electrical apparatus to be monitored without having to install sensors at the equipment itself.

Abstract: Method and apparatus for testing a cable call for extending the cable along a route having at least one curved portion, applying tension in an axial direction to the sheath of the extended cable so as to elongate the sheath, perturbing the tensioned cable in an axial direction and determining whether the perturbations to the tensioned cable have caused any structural distortions in the cable.

Abstract: An alarm system for alarming whenever there is a power leakage from an electronic device, includes a voltage decreasing circuit, a switch circuit and an alarm circuit. The voltage decreasing circuit receives a first voltage from a live wire output terminal and outputs a second voltage. The switch circuit outputs a control signal when the power leakage is detected. The switch circuit is electrically connected to a connection port. The connection port is electrically connected to the live wire output terminal and a neutral wire output terminal. The alarm circuit receives the control signal and alarms. If there is power leakage from the electronic device, the first voltage from the live wire input terminal flows into the ground wire input terminal via the electronic device; the switch circuit turns on and the alarm circuit is closed to alarm.

Abstract: An apparatus includes at least one Rogowski coil and a processor. The at least one Rogowski coil is positioned within an electrical power distribution network to detect a first traveling wave current caused by a fault on an electrical power transmission line of the network, generate a first signal indicative of detection of the first traveling wave, detect a second traveling wave current caused by the fault on the transmission line, and generate a second signal indicative of detection of the second traveling wave. The processor is adapted to receive the first signal and the second signal and to determine, based on the first signal and the second signal, where on the transmission line the fault occurred.

Abstract: Provided is a drive device for an alternating current motor which performs vector control on sensorless driving of the alternating current motor in an extremely low speed region without applying a harmonic voltage intentionally while maintaining an ideal PWM waveform. A current and a current change rate of the alternating current motor are detected, and a magnetic flux position inside of the alternating current motor is estimated and calculated in consideration of an output voltage of an inverter which causes this current change. The current change rate is generated on the basis of a pulse waveform of the inverter, and hence the magnetic flux position inside of the alternating current motor can be estimated and calculated without applying a harmonic wave intentionally.

Abstract: In a particular embodiment, a method includes receiving a powered device (PD) detection signal at a PD from a powered network and applying the PD detection signal to an external resistor to provide a detection signature to the powered network. Further, the method includes receiving a PD classification mark signal at the PD, applying the received PD classification mark signal to the external resistor, and selectively activating a classification mark current path in parallel with the external resistor to produce a classification mark signature.

Abstract: An apparatus and method for protecting against electrocution hazards that arise when an appliance is electrically connected to a miswired single-phase AC electrical source which includes an energized ground lead are described. The apparatus includes one or more sensors that detect electrical energy in the ground lead combined with a miswiring condition in the hot and common leads. A tester embodiment is also illustrated. The method includes the steps of detecting if the putative ground of the electrical source is energized and whether the hot and common leads are reversed.

Abstract: A method and system for incorporating electronic signature analysis in a low voltage power supply to centrally monitor current consumption is disclosed. The electrical loads powered by the low voltage power supply can be tested individually via an automatic test routine by measuring and scaling of current through a differential amplifier. The current consumption of each electrical load can be measured by analyzing a “delta” in the current draw of each electrical load's ON and OFF condition. This value can be compared against a stored table of high and low limits for each electrical load. If a load's current is outside the limits, it will be logged for repairs. A current sensing device can be inserted in series with the output(s) of the low voltage power supply, while in test mode, to allow the automatic test routine to run, and then be shorted out for normal operation.

Abstract: Test system and method for analog-to-digital converter (ADC) based on a loopback architecture are provided to test an M-bit ADC. In the invention, an N-bit digital-to-analog converter (DAC) converts a digital input to a basic test signal, a segmentation circuit scales the basic test signal and superposes it with segmentation DC levels for providing corresponding segmented test signals, such that the ADC converts the segmented test signals to reflect result of testing. With the invention, practical loopback architecture of low-cost can be adopted for testing.

Abstract: An apparatus includes at least one Rogowski coil and a processor. The at least one Rogowski coil is positioned within an electrical power distribution network to detect a first traveling wave current caused by a fault on an electrical power transmission line of the network, generate a first signal indicative of detection of the first traveling wave, detect a second traveling wave current caused by the fault on the transmission line, and generate a second signal indicative of detection of the second traveling wave. The processor is adapted to receive the first signal and the second signal and to determine, based on the first signal and the second signal, where on the transmission line the fault occurred.

Abstract: A fault interrupter and load break switch includes a trip assembly configured to automatically open a transformer circuit electrically coupled to stationary contacts of the switch upon the occurrence of a fault condition. The fault condition causes a Curie metal element electrically coupled to at least one of the stationary contacts to release a magnetic latch. The release causes a trip rotor of the trip assembly to rotate a rotor assembly. This rotation causes ends of a movable contact of the rotor assembly to electrically disengage the stationary contacts, thereby opening the circuit. The switch also includes a handle for manually opening and closing the electrical circuit in fault and non-fault conditions. Actuation of the handle coupled to the rotor assembly via a spring-loaded rotor causes the movable contact ends to selectively engage or disengage the stationary contacts.

Abstract: Methods for detecting wet arc faults are based on the direct current (DC) signature analysis and pattern matching pertaining to wet arc characteristics. While magnifying some wet arc fault signatures, it may be found that the wet arc current signal itself resembles a normal current signal in both time and frequency domains. The change in magnitude or high frequency behavior found may not be enough to distinguish a wet arc fault signature from a normal signature. Embodiments of the present invention may look at the magnitude change in the DC content per cycle of the wet arc current signal, which may be more positive in one cycle while, in the next cycle, it may be negative in a relative manner. A particular number of these changes may be determinative of a wet arc fault.

Abstract: In a particular embodiment, a method includes receiving a powered device (PD) detection signal at a PD from a powered network and applying the PD detection signal to an external resistor to provide a detection signature to the powered network. Further, the method includes receiving a PD classification mark signal at the PD, applying the received PD classification mark signal to the external resistor, and selectively activating a classification mark current path in parallel with the external resistor to produce a classification mark signature.

Abstract: The present invention can speedily and accurately estimate an SOC of a secondary battery immediately after a charge/discharge operation resumes. A determination unit determines whether a dormant period is longer than a predetermined time in response to an initiation of power supply from a secondary battery to a motor generator. The dormant period is equivalent to the duration from a previous stop of power supply to a present initiation of power supply. If the dormant period is longer than the predetermined time, a state-of-charge estimating unit sets an initial SOC based on a peak battery voltage drop ?Vs and a peak discharge current Is, wherein the peak battery voltage drop ?Vs represents a difference between a battery voltage Vo measured before initiating power supply and a lowest battery voltage Vs measured after initiating power supply and the peak discharge current Is represents a maximum current value measured after initiating power supply.

Abstract: An electrical continuity test system with a tester and a remote probe. The tester includes circuitry for creating a pulsed current, an output for connection to a local end of a first test conductive element, to inject the pulses into the first test conductive element, an input for connection to a local end of a second test conductive element, and a visual and/or aural indication when the injected pulses are present on the second test conductive element. The remote probe includes an input for connection to a remote end of a first unidentified conductive element, an output for connection to a remote end of a second unidentified conductive element, a first visual and/or aural indication when the first unidentified conductive element is the first test conductive element, and a different visual and/or aural indication when the first unidentified conductive element is the second test conductive element.

Abstract: To provide a method for the self-testing of a reference voltage in electronic components, by means of which method there is defined a circuit arrangement for a self-test of the reference voltage that can be implemented in the form of an on-chip test, i.e. for which no external reference-voltage source is required, provision is made for the reference voltage (Uref) to be the variable of a function f(Uref) that has an extreme at the point where the selected nominal value (Uref.

Abstract: A small, lightweight, portable, and inexpensive self-processing integrated damage assessment sensor (SPIDAS) that may be temporarily or permanently attached to a structure for structural health monitoring is provided. The SPIDAS device employs an electromechanical impedance measuring method to directly measure the high-frequency local impedance spectrum of the structure, process the electromechanical impedance data, and issue structural health reports that the device may transmit over a wireless connection.

Abstract: The transmitter of the circuit breaker locator draws large amplitude, short duration, phase locked unipolar pulses of current from the power source at a frequency lower than that of the AC line frequency. The audible and visual indicators of the transmitter are triggered at the rate of the current pulses drawn from the AC line. The receiver of the circuit breaker locator has a pick-up coil that responds to magnetic field surrounding the circuit breaker, an amplifier for boosting the signal from the pick-up coil, and a single shot pulse stretcher triggered by the amplifier. The pulse stretcher drives both audible and visual signals, and at the same time charges a memory capacitor in a staircase generator fashion. The magnitude of the memory capacitor voltage in turn controls the gain of the amplifier. A switch controls the voltage applied to the amplifier, which increases by a predetermined amount when released.

Abstract: A cable tester includes a pretest module that senses activity on a cable and selectively enables testing depending upon the sensed activity. A test module is enabled by the pretest module, transmits test pulses on the cable, measures a refelction amplitude, calculates a cable length, and determines a cable status based on the measures amplitude and the calculated cable length. A polarity detector communicates with the cable tester and detects a polarity of at least one pair of the cable. The test module senses activity on a first pair of the cable, enables testing if activity is not detected for a first period, and enables testing of the first pair if, during the first period, activity is detected on the first pair and is subsequently not detected on the first pair for a second period after the activity is detected.

Abstract: A circuit protection device connected between two lines of an AC power source self checks for an introduced simulated ground fault every half cycle during a period when a trip SCR cannot conduct. If the self check fails, the device is tripped on the next half cycle of different phase. Possible responses to the self check failure include lighting an indicator lamp and locking out the device reset mechanism.

Abstract: An electrical short-circuit detection device includes a first signal processing module for receiving a signal representative of an electrical current and supplying a first signal representative of the value of the electrical current and a second signal representative of the differential of the electrical current, and a second processing module for receiving the signals and comprising a short-circuit detection module for supplying a detection signal according to a curve overshoot. The second processing module monitors a limit curve overshoot and a ratio between variations of the signals. A short-circuit detection signal is supplied when the ratio exceeds a preset threshold. A circuit breaker incorporates such a device. The process comprises monitoring limit curve overshoot and the ratio between variations of the signals.

Abstract: In one embodiment, an integrated differential isolation loss detector is disclosed that generates a first temperature that is a function of a high side current and a second temperature that is a function of a low side current. A temperature sensor senses the difference between the first and second temperatures and provides an output signal that is indicative of the magnitude and the polarity of the sensed difference. A controller receives the output signal and if the difference is greater than a predetermined magnitude the high side current, the low side current, or both can be disconnected from the load.

Abstract: A method and system for determining the resistance of a winding insulation. The method includes applying a pulsed voltage having a maximum value and a minimum value to the winding insulation. The maximum and minimum values of the pulsed voltage are both negative values in certain exemplary implementations. The values of the maximum and minimum current flowing through the winding insulation are determined, and the winding insulation resistance is calculated based on the difference between the maximum and minimum current. A ground fault may be detected based on the calculated winding insulation resistance. The winding insulation monitoring system includes a sense resistor connected to the winding insulation and a pulsed voltage source is coupled to the sense resistor to apply the pulsed voltage to the winding insulation via the sense resistor.

Abstract: In an overload current protection device for cutting off power from a power supply to a load (3) such as a motor by means of a contactor (switch) (2) at overloading, an MI element having a magnetic impedance (MI) effect as current detectors (4a, 4b, and 4c) is installed at a position capable of detecting a current flowing through the secondary winding of power supply transformers (5a, 5b, and 5c) that generate a control power supply to thereby reduce costs without using a constant voltage power supply and expand a current detection range by eliminating magnetic saturation due to a core, a problem with a conventional current transformer, thereby providing at low costs a high-precision overload current protection device having a wide current detection range.

Abstract: A circuit protection device connected between two lines of an AC power source self checks for an introduced simulated ground fault every half cycle during a period when a trip SCR cannot conduct. If the self check fails, the device is tripped on the next half cycle of different phase. Possible responses to the self check failure include lighting an indicator lamp and locking out the device reset mechanism.

Abstract: To monitor an electrode lead composed of two lines in a bipolar HVDCT system, a balanced-to-ground pulse formed from an unbalanced-to-ground pulse in push/pull mode is fed into the lines and an actual echo curve is recorded from the echo signals and compared to a dynamic target echo curve, a fault signal being generated when a tolerance band placed around the echo difference curve is exceeded. In this way, a monitoring method is achieved which is nearly independent of the sharply fluctuating ground conductance, which has a higher range with simultaneously lower dispersion of the echo, which radiates less electromagnetic energy and which requires no additional decoupling elements.

Abstract: A method, an arrangement, and a current measurement device with which a signal that characterizes a fault current in an electrical conductor having at least three conductor ends can be produced in a particularly simple fashion. In particular, a current measurement device is provided for measuring a current in a conductor. The current measurement device includes at least one measurement value input and at least one measurement value output, and has an arithmetic unit that adds a current measurement value corresponding to the current to a measurement value present at the at least one measurement value input. A resulting summation current measurement value is output at the at least one measurement value output.

Abstract: An apparatus for diagnosing automobile audio systems having a system integrity analyzer which includes speaker testing. The speaker testing includes a member for supplying an input to each of the positive and negative leads while supplying ground to the other of the positive and negative lead. This, in turn, facilitates diagnosis of the operation of the audio system of the vehicle. In addition, the apparatus comprises a system for analyzing vibrations comprising a frequency transmitter and an oscillator. The frequency transmitter is capable of transmitting a signal generated by the oscillator on a frequency that is receivable by a vehicle audio system. The oscillator includes altering the signal generated by the oscillator between the lower audible range and the upper audible range.

Abstract: An apparatus and corresponding method for detecting, locating, or defining a short in a thin-film module. The apparatus includes a mechanical fixture supporting the module. A current source provides a current pulse to the module which produces a magnetic field and heating nearby the short which turns on and off as the pulsed current in the short turns on and off. Polarized light is directed onto the module, with an intermediate element disposed between the module and the source of the polarized light. The intermediate element may be a stress birefringent coating (e.g., a polyimide insulating layer) disposed on the module and onto which the polarized light is directed. The sample is rotated 0 to 45 degrees to maximize the birefringent effect. Alternatively, the intermediate element may be a magneto-optical Faraday rotator.

Abstract: A device for sensing electric discharges in a test object with at least two electric connection conductors comprises transducer equipment and evaluation equipment. The transducer equipment comprises at least one transducer for direction-sensitive sensing of current pulses through the connection conductors by sensing a magnetic field, generated by the current pulses, and the polarity thereof. The transducer delivers a transducer signal to the evaluation equipment in dependence on said current pulses and their direction. The evaluation equipment generates, in dependence on received transducer signals, an indicated signal indicating an electric discharge in the test object.

Abstract: An uninterruptible power supply unit for coupling between an adapter with an adapter connector and an electronic device in accordance with one embodiment of the present invention includes a self-contained housing, a backup power supply, and an output switch system. The self-contained housing has an input port for coupling with the adapter connector from the adapter and an output connector extending from the housing for coupling with the electronic device. The backup power supply is located in the housing and provides the backup power. The output switch system is also located in the housing. The output switch system is coupled between the output connector and the input port and the backup power supply and couples the backup power from the backup power supply to the electronic device when incoming power from the adapter fails.

Abstract: A semiconductor device having thin film capacitors and containing resistance measuring elementsis disclosed. The thin film capacitor comprises a bottom electrode, a high permittivity dielectric, and a top electrode stacked on an interlayer insulation film and at least one of a plurality of contact formed in electrical contact with the substrate at the desired position of an interlayer insulation film formed on a semiconductor substrate. The bottom electrode comprises at least two layers.

Abstract: Apparatus and methods for detecting the direction of a fault in relation to a switch connected between a source and a load are shown to include a voltage sampler for generating samples of the voltage during first and second power cycles. A current sampler generates samples of the current during first and second cycles. A first comparator compares the current samples from the first cycle to the current samples from the second cycle and determines the sign of the difference between the samples. A second comparator compares the sign of the voltage from the first cycle to the sign of the current difference determined by the first comparator and provides an indication of fault direction in relation to such comparison. The apparatus also includes a fault inception determiner, for providing a fault inception indication in relation to the voltage samples from the first and second cycles.

Abstract: A method of and an apparatus for determining an electric wiring state, having the steps of: feeding at least one pulse voltage signal into one of two lines short-circuited at their two source portions; detecting the pulse voltage signal at two end portions corresponding to the two source portions; and discriminating wiring state between the two source portions and the corresponding two end portions upon a comparison of polarities between the fed pulse voltage signal and the detected signal.

Abstract: A novel method and apparatus are used for monitoring cables for wear and damage. The system is particularly applicable to a cable system with multiple branch terminations. The cables have detection conductors, for example the metal cable jackets or other detection conductors extending the length of the conductors. These are connected electrically at the splice points in the system. At the end of each branch and at the end of the main cable, the detection conductors are each connected to a novel termination circuit. In the normal monitoring mode, the termination circuit appears as an open circuit. A DC voltage is normally applied to the detection conductors. Any current is a result of current leakage at a resistive fault along the detection conductors. The termination circuits are activated by altering the DC voltage, e.g. by reversing the polarity and increasing the magnitude of the voltage. This causes the termination circuit to perform a series of functional tests.

Abstract: A circuit detects insulation defects in a coil assembly including a plurality of series connected coils. A first voltage pulse is applied to a first coil of the coil assembly, a second voltage pulse is applied to a second coil of the coil assembly, the first and second coils being substantially diametrically opposite to one another, and the first and second voltage pulses being substantially equal to one another and oppositely poled relative to the coil assembly. A first voltage waveform across the first coil is monitored, and a second voltage waveform across the second coil is monitored. A first signal is derived from the first voltage waveform, a second signal is derived from the second voltage waveform, and a differential percentage value based on the first signal and the second signal is computed. An insulation defect is then determined based upon the differential percentage value.

Abstract: A power plant system architecture includes a plurality of battery polarity switching circuits for providing uninterruptible power/voltage to a plurality of loads, each of which is powered by low frequency AC, and which is also powered by a DC voltage. DC voltage is substituted for the AC voltage applied to the load should the voltage polarity processing circuitry in the power plant fail.

Abstract: The orientation of a polarized capacitor is determined by applying a voltage signal to one of the leads of the capacitor and a reference signal to the other lead. The magnitude of the electric field thus generated by the capacitor is measured. Then the voltage signal and the reference signal are reversed. The magnitude of the new electric field thus generated by the capacitor is measured. The ratio of the magnitudes of the first measured electric field to the second measured electric field is computed. If the ratio is greater than one, then the capacitor is determined to be properly oriented. If the ratio is less than one, then the capacitor is determined to be improperly oriented.

Abstract: A plurality of sensors, such as a door handle lift switch, a headlight switch, and an ignition switch, are normally provided in an automotive electrical system. A master microcontroller normally is coupled to each of these sensors for receiving a signal therefrom and responsive thereto generating a corresponding controller signal. Power drivers, each operatively coupled to the master controller, normally are provided for energizing and powering loads coupled thereto, with each load being either an indicator or actuator that is operated responsive to its corresponding sensor. The self-diagnostic method includes the steps of mechanically actuating a selected one of the sensors, and then electrically actuating a first confirming indicator, such as an audible chime, indicative of the master controller receiving and successfully processing the corresponding sensing signal.

Abstract: An apparatus for monitoring and testing a twisted pair, particularly useful for an Ethernet network. First and second DC currents alternated with one another are applied to both ends of the line, asynchronously. By monitoring the potential on the line, a determination is made as to the condition of the line. For example, shorted, crossed, improperly terminated or open conditions can be detected. A visual indication of the condition of the line is provided and additionally, the visual indication provides an indication of the traffic level in the network.

Abstract: The relay includes means for obtaining current and voltage samples on the power transmission line for a particular possible fault type. The current sample is multiplied by the replica impedance of the power transmission line, while the voltage sample is multiplied by a polarizing voltage to provide a first complex expression having a real portion and an imaginary portion. The product of the current sample and the replica impedance is multiplied by the polarizing voltage to produce a second complex expression having a real portion and an imaginary portion. The real portion of the first complex expression is then divided by the real portion of the second complex expression to produce a scale value m which is compared against known reference scale values for each zone, so as to determine underimpedance conditions in any one of the zones.

Abstract: The operation of energized substation circuit breakers in electrical power distribution systems is directly monitored. For each circuit breaker in a multi-phase breaker arrangement, the flow of electrical current is sensed. A signal is then formed for each phase representative of the sensed current flow. The signals so formed for the multi-phases are combined into a composite waveform for monitoring and diagnostic purposes. In the composite waveform, the signal for each phase of the circuit breaker is identifiable by its time relationship to others and by a distinctive voltage level.

Abstract: An apparatus can locate a short between a first and second network with a pair of probes, a measurement device and a current source. The measurement device can measure the potential between the probes. The current source can be connected to the first and second network for injecting between them a current in excess of 1/8 Amp. A larger system can use a matrix connected between a plurality of probes and the measurement device. The matrix can selectively connect a selected one of the probes to the measurement device. This larger system includes a manual keyboard for manually producing a command signal indicating selected pairs of the probes. A processor is coupled to the matrix and the manual keyboard for operting the matrix in response to the command signal to record the potential differences between selected pairs of the probes. A display can spatially display the selected pairs of probes and can also display the polarity of the potential between each of them, as measured by the measurement means.

Abstract: A test module incorporating a unique diagnostic circuit for monitoring the magnitude of electrical parameters existing between an electrical driver such as the electronic control module (ECM) of an automotive vehicle and an electrical load in the vehicle's electrical system. The circuit employs a visual indicator connected to a point adjacent the driver to provide a visual signal when the voltage at the point of connection lies within a predetermined range with respect to electrical ground. An additional visual indicator, separate from the first, is connected to a point adjacent to the electrical load, and provides a visual signal when the voltage at its point of connection lies within a predetermined range with respect to electrical ground. A third visual indicator is connected between the driver and load, and provides a visual signal in response to current flowing between the driver and load.

Abstract: A method of and apparatus for determining which if any phase of duplex supply lines wherein each phase w is assigned two conductors w1 and w2. The method and apparatus use an asymmetry value, for example a function of the relationship (output of 9) of the difference Iw1-Iw2 (output of 5) to the sum Iw1+Iw2 (output of 6) of the currents in the conductors w1 and w2. If the asymmetry level exceeds in absolute value a threshold level K(see 12 and 13), the conductor passing the current having the lowest amplitude is indicated as being sound.