Abstract: A mutually induced filter for filtering radio frequency (RF) power from signals supplied to a load is described. The mutually induced filter includes a first portion connected to a first load element of the load for filtering RF power from one of the signals supplied to the first load element. The load is associated with a pedestal of a plasma chamber. The mutually induced filter further includes a second portion connected to a second load element of the load for filtering RF power from another one of the signals supplied to the second load element. The first and second portions are twisted with each other to be mutually coupled with each other to further facilitate a coupling of a resonant frequency associated with the first portion to the second portion.

Abstract: A protection circuit is disclosed. The protection circuit includes a direct current (DC) blocking component electrically connected between a neutral of the transformer and a ground, and an overvoltage protection device electrically connected in parallel with the DC blocking component. The overvoltage protection device is constructed to repeatably and reliably provide overvoltage protection in response to a voltage at the transformer neutral above a threshold. The DC blocking component has an impedance below a predetermined value, thereby effectively grounding the neutral of the transformer. The DC blocking component is persistently maintained in connection to the transformer neutral.

Abstract: The invention provides a radio frequency (RF) amplifier apparatus including an amplifier and a resonance circuit. An input terminal of the amplifier receives an RF signal. The amplifier amplifies a first frequency component of the RF signal and outputs the amplified first frequency component to an output terminal of the amplifier. A first terminal and a second terminal of the resonance circuit are respectively coupled to the input terminal and the output terminal of the amplifier. The resonance circuit provides a low impedance path for a second frequency component of the RF signal between the input terminal and the output terminal of the amplifier, and provides a high impedance path for the first frequency component of the RF signal between the input terminal and the output terminal of the amplifier.

Abstract: A protection circuit is disclosed. The protection circuit includes a direct current (DC) blocking component electrically connected between a neutral of the transformer and a ground, and an overvoltage protection device electrically connected in parallel with the DC blocking component. The overvoltage protection device is constructed to repeatably and reliably provide overvoltage protection in response to a voltage at the transformer neutral above a threshold. The DC blocking component has an impedance below a predetermined value, thereby effectively grounding the neutral of the transformer. The DC blocking component is persistently maintained in connection to the transformer neutral.

Abstract: An appliance having a heater connectable to a power source to create a heater circuit is disclosed. The appliance includes a controller and a heater switch configured to be selectively closed in response to a control signal from the controller to complete the heater circuit and enable current to flow from the power source to the electric heater. The appliance further includes a heater feedback circuit comprising a plurality of resistors and configured to be connected to the power source and further configured to generate an output signal to the controller having a first state indicative of no current leakage from the heater circuit, a second state indicative of current leakage from the heater circuit where the polarity of the power source is normal, and a third state indicative of current leakage from the heater circuit where the polarity of the power source is reversed.

Abstract: The present invention discloses a safe operation method for voltage reduction arc suppression of a ground fault phase of a non-effective ground system, for use in ground fault safety operation of a neutral point non-effective ground generator or distribution network. When a single-phase ground fault occurs, an external voltage source is applied at a non-effective ground system side between a bus and the ground, or between a line and the ground, or between a neutral point and the ground, or between a shunting tap of a non-effective ground system side winding of a transformer and the ground, to reduce the fault phase voltage to be lower than the continuous burning voltage of a ground arc, thereby meeting the requirements of long-term non-stop safe operation. The operation means and control method effectively prevent power outages, and improve the reliability and security of power supply.

Abstract: A mutually induced filter for filtering radio frequency (RF) power from signals supplied to a load is described. The mutually induced filter includes a first portion connected to a first load element of the load for filtering RF power from one of the signals supplied to the first load element. The load is associated with a pedestal of a plasma chamber. The mutually induced filter further includes a second portion connected to a second load element of the load for filtering RF power from another one of the signals supplied to the second load element. The first and second portions are twisted with each other to be mutually coupled with each other to further facilitate a coupling of a resonant frequency associated with the first portion to the second portion.

Abstract: Testable sealed and/or self-diagnosing electromagnetic or solid-state relays simplify troubleshooting of electrical circuits. The testable relay comprises a relay housing with terminals adapted to connect to a circuit and an opposing top wall with testable terminals formed as projections being flush with or extending from the top wall and being exposed for testing the relay by applying a multimeter device. A self-diagnosing relay comprises a relay housing with terminals adapted to connect to a circuit, and at least two light-emitting diodes (LEDs). One of the LED indicates the relay is energized, and another LED light is a diagnostic LED and indicates if the relay is damaged.

Abstract: A power pedestal includes a pedestal member including a base structured to be fixed to a platform and an enclosure extending from said base, a plurality of input power terminals mounted to said pedestal member and structured to be electrically connected to a power source, a number of output power receptacles mounted to said enclosure, a number of circuit interrupters having a ground fault detection capability and being structured to output an alarm signal in response to detecting a ground fault, a relay structured to receive the alarm signal from the circuit interrupters and to output an indicator signal, and an indicator unit structured to receive the indicator signal from the relay, the indicator unit including an indicator and being structured to illuminate the indicator in response to receiving the indicator signal.

Abstract: Provided is a power supply device which uses a simplified device configuration to reliably detect anomalies such as fused contacts, and which eliminates overcharging and secondary battery hazards caused by overcharging. The power supply device (1) is provided with: a control unit (7) for monitoring and controlling the operation of the power supply device (1), and for monitoring anomalies in the power supply device (1); a secondary battery (3) connected to the control unit (7), and for discharging electricity which has been charged; a main contact (9) connected to a battery circuit network (8) formed between the secondary battery (3) and a load (13); an auxiliary contact (10) connected in series to the main contact (9), and which is always on; and an anomaly detection circuit (11a).

Abstract: Equipment including at least one plug-in unit and a body device for receiving the plug-in unit is presented. The plug-in unit includes an electrically conductive structure (121, 122, 123) having at least one surface area capable of forming a capacitive coupling with a surface area of an electrically conductive part (130, 131) of the body device when the plug-in unit is inserted in the body device. The equipment further includes a monitoring circuit (124) for generating a signal indicative of electrical properties of a measurement circuit including the capacitive coupling and at least one galvanic contact provided by electrical connectors of the plug-in unit and the body device. The generated signal is also indicative of correctness of the installation of the plug-in unit. Thus, the correct installation of the plug-in unit can be electrically indicated and monitored.

Abstract: A rocker contact switch for a GFCI device includes a base and first and second legs extending from the base. When the base is moved, the second leg rotates to contact a conductive member to put the GFCI device in an end of life condition. The first leg is substantially prevented from moving in response to movement of the base. A test button of the GFCI device is pushed a first distance to complete a first circuit that trips the GFCI device. The test button is pushed a second distance, which moves the base of the rocker contact switch, to complete a second circuit that puts the GFCI device in an end of life condition by moving the rocker switch base.

Abstract: A power system is for a facility. The power system includes a load panel powered from a split phase electrical distribution configuration having a first line, a second line and a neutral. A two-pole circuit interrupter in the load panel receives power from the first line, the second line and the neutral, and protects an unbalanced load. The two-pole circuit interrupter is structured to trip open or open responsive to an input. A circuit in the load panel is structured to determine that the neutral is broken or missing and responsively output to the input to cause the two-pole circuit interrupter to trip open or open.

Abstract: Disclosed herein are apparatus, methods, and systems for monitoring and detection of conditions indicative of an electrical fault for an electrical circuit or system. In one aspect, a central control can simultaneously monitor a plurality of geographically distributed electrical circuits or systems for conditions that have been predetermined to be indicative of an electrical fault or concern, and provide either some communication (e.g., a warning) or instruction (e.g., to terminate power) back to the monitored circuit/system, the owner/operator/user of the circuit/system, or both. The central control can collect, store, mine, and analyze data from the diverse monitoring of plural systems. A knowledge base can be built up over time and used to establish monitoring of the same, other circuits and systems, develop more accurate monitoring and communication of faults or concerns, and account for factors related to normal operation of a circuit or system.

Abstract: The present invention is directed to a circuit interrupting device including an actuator that provides an actuator stimulus upon the occurrence of the fault actuation signal. A circuit interrupter is positioned to electrically disconnect the first, second and third electrical conductors from each other upon the occurrence of the actuator stimulus. An automated test circuit is coupled to the circuit interrupting assembly. The automated test circuit is configured to automatically produce the simulated fault condition during a predetermined portion of an AC line cycle to determine whether the fault detection assembly is operational such that the fault detection assembly provides a fault detection signal without the circuit interrupter electrically disconnecting the first, second and third electrical conductors from each other.

Abstract: An apparatus and method is provided for identifying a faulted phase in at least one shunt capacitor bank. The apparatus generally includes a sampling circuit for sampling current or voltage signals associated with the shunt capacitor bank. A microcontroller is coupled to the sampling circuit and programmed to measure a compensated neutral point phase angle from the sampled signal, and compare the compensated neutral point phase angle with a fixed reference phase angle to identify the faulted phase of the shunt capacitor bank. The method generally includes the steps of sampling a current or voltage signal associated with the shunt capacitor bank, determining a compensated neutral point phase angle from the sampled signal, and comparing the compensated neutral point phase angle with a fixed reference phase angle to identify the faulted phase of the shunt capacitor bank. The invention also relates to an apparatus and method for identifying the location of the fault (e.g.

Abstract: A system and method for a vehicle control system is disclosed herein. The system includes an inverter circuit, a permanent magnet synchronous motor, and a crossover connected between the inverter circuit and the permanent magnet synchronous motor. The system may also include at least one current sensor installed between the inverter circuit and the permanent magnet synchronous motor. A contactor may also be connected between the inverter circuit and the permanent magnet synchronous motor and may pass or shut off electricity between the inverter circuit and the permanent magnet synchronous motor. The system may also include a control unit connected to the contactor and the current sensor. The control unit may detect a current abnormality using information from the current sensor and open the contactor if an abnormality is detected.

Abstract: The present invention relates to a ground fault detecting and controlling method for a parallel-structured high voltage system, and more particularly, such a ground fault detecting and controlling method for a parallel-structured high voltage system, in which it can be more precisely determined whether or not the system operation is emergently stopped based on individual insulation resistance values for respective items of the system, and it can be determined whether there is the possibility of temporary operation of the system in the emergency stop situation of the system operation. According to the present invention, a combined insulation resistance ground fault reference value is calculated based on individual insulation resistance values for respective items of the system, and the entire system is controlled by using the calculated combined insulation resistance ground fault reference value such that a high-accuracy ground fault detecting and controlling method can be provided.

Abstract: Disclosed are apparatus, methods, and systems for the monitoring of grounding components in an electrical system. Methods of monitoring grounding components comprise a signal or plurality of signals imposed on a ground loop circuit by a first inductive element, a second inductive element which receives the signal(s), and circuitry which compares changes in the imposed signal(s) to a baseline to calculate impedance. Active monitoring of impedance enables contractors to ensure installation of a grounding system was performed correctly, and allows a user to track changes in impedance over the life of the electrical system such that, if an impedance threshold is reached, appropriate action may be taken.

Abstract: In one implementation, a ground fault interrupt circuit is provided for a utility power connection to an electric vehicle charging unit. The ground fault interrupt circuit may include a gain amplifier having an input connected to be capable of receiving a differential current from a current sensing transformer and a comparator having an input connect to a reference voltage. It includes a rectifier circuit connected between the gain amplifier and the comparator with a charge accumulator circuit coupled between the rectifier and the comparator.

Abstract: The present invention is directed to an electrical device configured to be disposed in an electrical distribution system between a source of electrical power and an electrical load. The electrical distribution system includes at least one line hot conductor, a line neutral conductor, and a line ground conductor. The line neutral conductor is connected to the line ground conductor at a termination point in the electrical distribution system. The electrical load includes at least one load hot conductor, a load neutral conductor, and a load ground conductor. The device includes a grounding confirmation circuit that includes at least one signal generator that directs at least one test signal into a current path that includes at least the line ground conductor. The grounding confirmation circuit is configured to determine a ground continuity status of the current path based on at least one ground continuity measurement.

Abstract: The present invention is directed to an electrical wiring device that includes a plurality of line terminals configured to be coupled to a source of AC power, a plurality of feed-through load terminals, and at least one set of receptacle load terminals configured to provide the AC power to a user load via an AC power plug. A circuit interrupter assembly includes a plurality of movable interconnection members. Each movable interconnection member includes a first interconnecting contact disposed on a first side thereof and a second interconnecting contact disposed on a second side thereof. The first interconnecting contact and the second interconnecting contact are offset from one another in a direction substantially orthogonal to a direction of movement.

Abstract: An apparatus and method for providing ground fault protection to a lifting device utilizing an electromagnet and powered by a generator. The apparatus and method rectifies an AC voltage emanating from the generator source and monitors unsafe operating conditions of the generator's circuit wherein operation of the lifting device is ceased when predetermined electrical operating parameters are exceeded.

Abstract: Methods and apparatus to minimize saturation in a ground fault detection device are disclosed. An example method includes connecting a capacitor simulator to a node of the ground fault detector device to prevent saturation, and monitoring power-line conductors for ground fault conditions with the ground fault detector device. An example apparatus to simulate a saturation capacitance in a ground fault device includes a sense coil induced by power-line conductors, and at least one of an amplifier or a current detector including an input connected to the sense coil and an output connected to a ground fault detector. The example apparatus also includes a saturation capacitor simulator connected to a node of at least one of the amplifier or the current detector to prevent saturation.

Abstract: Electrical load controls are provided which include an electrical switch assembly and a fault protection device within a common housing. The switch assembly includes an actuator, and is responsive to actuation of the actuator to switch ON or OFF electricity to the load. The protection device automatically responds to a fault condition by overriding the switch assembly by automatically blocking electrical connection between phase input and output terminals and neutral input and output terminals of the load control. The actuator includes a single external interface element. In one embodiment, actuation of the actuator switches ON or OFF electricity via control of the fault protection device, and in another embodiment, movement of the interface away from the housing exposes within the housing an internal user interface for the fault protection device.

Abstract: An automotive vehicle includes a charge port integrated with the vehicle. The charge port includes electrical contacts configured to receive electrical power from an electric grid, and a fault interrupt circuit electrically connected with the electrical contacts.

Abstract: There is disclosed a circuit interrupting device with symmetrical inputs comprising a first input configured for connection to a power source or a load circuit and a second input configured for connection to a power source. There are a plurality of electrical conductors extending from the first and second inputs and a third input configured for connection to a load provided by a user. There is also a first set of transformers comprising at least one differential transformer and at least one neutral transformer connected to detect leakage current in a load circuit coupled to the first set of terminals. There is also a second set of transformers comprising at least one additional differential transformer and at least one additional neutral transformer connected to detect leakage current in a load circuit coupled to the second set of terminals.

Abstract: A system is provided including: (1) an arc fault circuit interrupter having a line side terminal and a load side terminal, wherein the line side terminal is coupled to a voltage source, and (2) a current source coupled to the load side terminal to backfeed the arc fault circuit interrupter. Numerous other aspects also are provided.

Abstract: Methods and apparatus to facilitate ground fault detection with a single coil and an oscillator are disclosed. An example ground fault detection device includes a sense coil including a secondary winding surrounding a line conductor and a neutral conductor, the line conductor and the neutral conductor forming a primary winding. The example ground fault detection device also includes a voltage oscillator connected in series with the secondary winding to drive an oscillation component, and at least one of a detector or an amplifier connected in series with the secondary winding to detect at least one of a neutral-to-ground fault or a line-to-ground fault.

Abstract: Various systems, methods and apparatus are described for detecting an excessive or faulty ground current in a conductive wire or electronic device. A ground current detector is coupled to a known earth ground to determine whether other ground lines are carrying excessive, faulty and/or leaking currents. If these types of unsafe conditions are detected, then a user can take appropriate action to locate and correct these problems.

Abstract: A differential protection device comprising: differential current measuring means, processing means connected to the measuring means and comprising operating rating selection means and time delay selection means to select tripping curves, actuating means, and test means connected to the measuring means. In the protection device the test means are associated with the operating rating selection means and with the time delay selection means to select a minimum or reduced operating rating and to select a minimum or reduced time delay when said test means are actuated.

Abstract: A device and method to determine the presence of a ground fault that distinguishes between the capacitive portion of the currents to ground, and the resistive portion of the currents to ground by ascertaining aspects of the voltage and residual current waveforms.

Abstract: Various systems, methods and apparatus are described for detecting an excessive or faulty ground current in a conductive wire or electronic device. A ground current detector is coupled to a known earth ground to determine whether other ground lines are carrying excessive, faulty and/or leaking currents. If these types of unsafe conditions are detected, then a user can take appropriate action to locate and correct these problems.

Abstract: In a first aspect, a ground fault circuit interrupt (“GFCI”) device is provided for use with an AC power system that includes a line conductor, a neutral conductor and a transformer. The line conductor and the neutral conductor are each coupled between a source and a load, and the neutral conductor is coupled to ground at the source. The transformer includes a first primary winding coupled in series with the line conductor, a second primary winding coupled in series with the neutral conductor, and a secondary winding. The device includes a grounded neutral fault detector circuit coupled to the secondary winding. The grounded neutral fault detector circuit: (a) drives the secondary winding with a multi-frequency AC signal, (b) monitors a multi-frequency load signal in the secondary winding, and (c) provides a first detection signal if the monitored load signal exceeds a predetermined threshold. Numerous other aspects are also provided.

Abstract: A circuit breaker apparatus may be used to interrupt overcurrent and ground fault in a circuit. The circuit breaker apparatus may include an overcurrent coil for tripping the circuit breaker apparatus, a voltage coil also for tripping the circuit breaker apparatus located proximate to the overcurrent coil, and ground fault electronics connected to the voltage coil and structured to detect a ground fault in the circuit when the ground fault exceeds a threshold level. The ground fault electronics can be structured to send a trip signal to the voltage coil when a ground fault is detected, and the voltage coil can be structured to trip the circuit breaker apparatus when it receives the trip signal from the ground fault electronics.

Abstract: A circuit breaker includes for each neutral and phase power conductor, a current sensor sensing an alternating current flowing in a corresponding power conductor, a comparator determining whether the sensed alternating current is positive or negative, a rectifier rectifying the sensed alternating current to provide a rectified current value, and an analog-to-digital converter converting the rectified current value to a signed digital value having a positive sign. A processor cooperates with the comparators and the analog-to-digital converters and includes a routine that changes the positive sign of the signed digital value to a negative sign if the sensed alternating current is negative, adds the signed digital value for each power conductor to provide a sum, and employs the sum to determine whether to output a ground fault signal. The processor further cooperates with an operating mechanism to trip open separable contacts responsive to the ground fault signal.

Abstract: A circuit is disclosed for disconnecting a power source upon the detection of a leakage. The circuit comprises a disconnect switch for disconnecting the power source. A primary circuit controls the disconnect switch. A secondary circuit senses a leakage current. An optical switch interconnects the primary circuit and the secondary circuit for opening the disconnect switch upon the secondary circuit sensing a leakage current. The circuit is suitable for use as a leakage current detection and interruption circuit for completely electrically disconnecting and isolating the power source and the primary circuit from the secondary circuit.

Abstract: The invention refers to a method and an apparatus (1) for protecting people against leakage currents while using appliances such as home appliances or the like. The apparatus (1) is provided with a differential switch (20) normally open and a differential current transformer (39) which generates a signal proportional to the leakage current, an elaboration unit (50) interfaced with the latter acquires said signal and keeps the switch (20) closed until a dangerous condition is met, corresponding to an acquired signal having a magnitude greater than a limit value.

Abstract: A circuit interrupter includes band pass filters cooperating with a current sensor to output bands having different, non-overlapping ranges of frequencies, peak detectors cooperating with the filters to detect corresponding peak current values, envelope detectors cooperating with the filters to detect corresponding occurrences from the bands being within corresponding predetermined magnitude ranges, a counter counting the occurrences, and a processor providing and disabling series arc detection when sensed current is greater than a first predetermined value. The processor determines tallies responsive to peak current values exceeding corresponding thresholds, determines series arcing from sensed current being less than the first predetermined value for a predetermined time, the tally for a current half-cycle being nonzero, and a count for the current half-cycle being different than the count for an immediately previous half-cycle of like polarity by at least a second predetermined value.

Abstract: An arc fault circuit interrupter includes separable contacts, an operating mechanism, a current sensor sensing current flowing through the contacts and outputting a sensed current, and a processor determining and storing peak values of the sensed current for plural half-cycles. The processor provides arc fault detection, determines whether a first predetermined plurality of half-cycles occur in succession and correspond to non-unity power factor, and responsively inhibits the detection for a first predetermined time, and whether a second predetermined plurality of half-cycles occur in succession, each with smaller peak amplitude than that of an immediately preceding half-cycle of like or differing polarity, and responsively inhibits the detection for a second predetermined time.

Abstract: A control circuit of Ground Fault Circuit Interrupter (GFCI), includes a load connection circuit used to connect power end and load end while transferring AC thereof, a creepage detection circuit, a trip control circuit and a trip circuit, and further includes a self-diagnosis current generation circuit, a self-diagnosis display circuit and a first switch duct. When the input AC in positive half-cycle, one of the said trip circuit and the self-diagnosis display circuit is electrically connected, while another should be electrically connected while the input AC in negative half-cycle, so without manpower-provided simulated signal, the control circuit of GFCI can be self diagnosed of creepage protection function, for the feedback of the stand or fall circs in time.

Abstract: A circuit is disclosed for disconnecting a power source upon the detection of a leakage current comprising a power cable having an insulated first and a second wire. The power cable has a conductive shield surrounding the first and second wires with a drain wire electrically contacting the conductive shield. A disconnect switch is interposed between the power source and the power cable. A primary circuit controls the disconnect switch. A secondary circuit is connected to the drain wire for sensing a leakage current between the conductive shield and one of the first and second wires. An optical switch interconnects the primary circuit and the secondary circuit for opening the disconnect switch upon the secondary circuit sensing a leakage current.

Abstract: An arc fault circuit interrupter includes separable contacts, a neutral conductor, an operating mechanism structured to open and close the separable contacts, at least one current sensor structured to sense current flowing through the separable contacts and output a sensed current value; and a processor. The processor includes a first routine structured to provide parallel arc fault detection, a second routine structured to provide series arc fault detection, and a third routine structured to enable the first routine and disable the second routine for a predetermined time when the sensed current value is greater than a predetermined value and to enable the second routine and disable the first routine for the predetermined time when the sensed current value is less than the predetermined value.

Abstract: A ground fault circuit interrupter device is described.

Abstract: A self testing fault detector having a line side and a load side and a conductive path there between, said apparatus is provided. The self testing fault detector includes a controller, adapted to perform periodic status tests on a protection circuit of the self testing fault detector without interrupting power to the load.

Abstract: The present disclosure relates to resettable circuit interrupting devices and apparatus capable of being tested and reset from remote locations, and in particular to portable circuit interrupting devices and apparatus capable of being tested and reset from remote locations.

Abstract: An interrupter circuit is disclosed for interrupting power in a power cable from a power source. The power cable comprises an insulated line wire and an insulated neutral wire with a conductive shield surrounding the line wire and the neutral wire. A non-insulated drain wire contacts the conductive shield. An outer insulating layer is molded about the conductive shield. A disconnect switch is interposed between the power source and the power cable with a disconnect switch driver controlling the disconnect switch. A sensing circuit is connected between the drain wire and the disconnect switch driver for sensing a leakage current between the conductive shield and one of the insulated line wire and the insulated neutral wire for opening the disconnect switch for disconnecting the power cable from the power source.

Abstract: A non-invasive underground arc fault detection apparatus is for an underground electrical conductor. The apparatus includes an electric circuit having an opening for admitting the electrical conductor therethrough. The electric circuit includes one or two transducers adapted to output a first signal representative of current flowing in the electrical conductor and a second signal. An arc fault detection circuit cooperates with the electric circuit to output a third signal derived from the first signal. The third signal is representative of an arc fault of the electrical conductor. An audible annunciator cooperates with the arc fault detection circuit to annunciate the third signal. A power supply cooperates with the electric circuit and is adapted to power the arc fault detection circuit and the annunciator from the second signal.

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

Abstract: A tester for verifying the integrity of insulation in a branch circuit of a power distribution system. Two test circuits are included; the first providing an insulation test; and a second, a shared/grounded neutral test. In the insulation test, a 500-volt ac output limited to 5 milliamps is selectively applied to the pairs of wires of the branch circuit. If an output current of greater than 3 milliamps is recorded, an insulation failure is noted and the operator proceeds to the second test which applies a pulsed 3 volt, 1 ampere current-limited voltage across the suspected leads. One of the suspected leads is monitored with a portable ammeter to detect any pulse current.