Abstract: A microwave sensor includes a case 1 of an object apparatus in which a discharge may occur; the object apparatus 2; an antenna 3 which is attached to the object apparatus case 1 and receives a microwave signal generated by a discharge; a signal processing unit 4 which is connected to the antenna 3, amplifies and detects the microwave signal, and amplifies the detected video signal; and an output terminal 13 through which the video signal is output.

Abstract: An object of the present invention is to provide an insulation state measurement method and a judgement apparatus for a power conversion system, which can monitor the insulation state of an electric path with one end to which a power scarce is connected, or the power source itself in a non-use state of the power source, and can prevent an unexpected failure.A solar cell array connected to one end of an electric path is set in a non-grounded state upon operation of a change-over switch, and a measurement switch which receives an operation command from an operating circuit temporarily applies a high voltage to the electric path. A current detector detects a weak current flowing through connection lines, and supplies detection data to an insulation judgement unit. The insulation judgement unit calculates the insulator resistance on the basis of the magnitude of the applied voltage, and the magnitude of the weak current detected by the current detector.

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 wet/dry hot stick tester designed to provide a dry test of a hot stick by applying a voltage equivalent to 100 KV/ft to the hot stick, and to provide a wet test of a hot stick by applying a voltage equivalent to 75 KV/ft thereto. Output electrodes are positioned along a reading aperture provided in a housing of the hot stick tester, in which a hot stick being tested is positioned. A two tap transformer has a first input tap for providing a first voltage equivalent to 100 KV/ft to a hot stick positioned in the reading aperture during a dry test thereof, and has a second input tap for providing a second voltage equivalent to 75 KV/ft to a hot stick during a wet test thereof. An ammeter measures the leakage current through the hot stick during an applied voltage. A wet/dry switch switches the two tap transformer between the first and second input taps.

Abstract: A non-ferrous current sensor is used to continuously measure the charging current magnitude in step-graded foil and paper insulation systems and capacitive insulation systems used on high voltage measurement and control apparatus such as instrument transformers and on the condenser bushings of power transformers and circuit breakers. The low voltage measured signal is conditioned by an electronic circuit that modulates a DC signal in a system current control loop to provide continuous remote monitoring and alarm functions. Remote power is supplied to the sensor and conversion circuits through the current loop. The sensor detects changes in the charging current through the insulation ground conductor, indicating the degradation of the dielectric properties between the foil layers. The sensor and associated electronic circuitry are enclosed in a housing adaptable to be used with a capacitance tap common to high voltage measurement and control apparatus.

Abstract: A test instrument for testing magnet wire which is provided which tests, collects and permits analyzing the effect of temperature, frequency, voltage and rise time associated with magnet wire use, and more particularly, the effects of those variables on the insulation of the wire, so as to evaluate the magnet wire performance and inverter controlled dynamoelectric machine applications.

Abstract: A method of detecting a partial discharge signals occurring at an insulator, using a Frequency Spectrum Analyzer (FSA) with a monitor screen.

Abstract: A non-ferrous current sensor is used to continuously measure the charging current magnitude in step-graded foil and paper insulation systems and capacitive insulation systems used on high voltage measurement and control apparatus such as instrument transformers and on the condenser bushings of power transformers and circuit breakers. The low voltage measured signal is conditioned by an electronic circuit such that it modulates a DC signal in a system current control loop to provide continuous remote monitoring and alarm functions. Remote power is supplied to the sensor and conversion circuits through the current loop. The sensor detects changes in the charging current through the insulation ground conductor, indicating the degradation of the dielectric properties between the foil layers. The sensor and associated electronic circuitry are enclosed in a housing adaptable to be used with a capacitance tap common to high voltage measurement and control apparatus.

Abstract: A method of detecting failed disks in power-system surge arresters comprising a network of at least two parallel-coupled stacks of series-coupled ZnO varistors includes measuring differential current flow through each pair of stacks during surge voltage conditions, and comparing the current so measured with a fixed fraction of the total current carried by the arrester. Because each stack contains a like number of substantially identical varistors, current flow through the stack containing a failed disk will measurably exceed current flow through each non-defective stack. If the measured current flow through a stack is excessive relative to current flow through the remaining stacks, the excessive current flow stack is presumed to contain a defective disk. In today's technology, precision Rogowski coils or fiber-optic current sensors provide the high-bandwidth, high dynamic-range transducers necessary for the measurement of both total and differential current.

Abstract: An apparatus for testing the insulation of an insulated electrical conductor has an alternating current high voltage power source which provides a high test voltage between the electrical conductor and an electrode to reveal defects in the insulation. A high Q antiresonant circuit, tuned to a predetermined frequency, is connected in series with the electrode and power source for shunting most frequency components of the corona and noise currents to ground and for non-shunting an insulation fault voltage of the predetermined frequency resulting from an arc current due to a defect in the insulation. The fault voltage signal non-shunted by the antiresonant circuit is provided through a coupling impedance to a transmission cable having a pair of twisted wires for transmission to a remote location. Impedance matching transformers, coupled to both pairs of ends of the twisted wires, are tuned to the same frequency as the antiresonant circuit to minimize attenuation of the signal.

Abstract: The reliability of thin film insulators is determined with noise measurements which find the barrier height mean and standard deviation. A constant voltage source is applied across the thin film insulator. A low noise amplifier is connected across a resistor which is in series with the insulator. A spectrum analyzer is connected to the low noise amplifier. The power density is obtained by observing the output of a spectrum analyzer. The current spectral density is compared to a predetermined reference to detect the presence of defects in the insulator.

Abstract: An accurate dielectric breakdown prediction method and a prediction method in which accurate time dependent dielectric breakdown (TDDB) characteristics can be obtained on the basis of dielectric breakdown prediction by a step stress method are provided. In this method, dielectric breakdown is predicted on the basis of a plurality of reference currents in accordance with an applied voltage, or a reference current I.sub.cr is varied as the function of the applied voltage. In the step stress TDDB prediction, a Chen-Holland-Hu model or improved Chen-Holland-Hu model is employed. Since TDDB characteristics can be obtained from only dielectric breakdown prediction, this method is advantageous for early reliability prediction.

Abstract: To carry out a non-destructive test for testing insulation of a small-size electric machine having a coil, a surge voltage is applied to the coil of the electric machine mounted in a decompression tank whose inner pressure is kept from 15 to 25 [Torr] so as to generate glow discharge in case there exists a flaw in the coil.

Abstract: A non-ferrous current sensor is used to continuously measure the charging current magnitude in step-graded foil and paper insulation systems and capacitive insulation systems used on high voltage measurement and control apparatus such as instrument transformers and on the condenser bushings of power transformers and circuit breakers. The low voltage measured signal is conditioned by an electronic circuit such that it modulates a DC signal in a system current control loop to provide continuous remote monitoring and alarm functions. Remote power is supplied to the sensor and conversion circuits through the current loop. The sensor detects changes in the charging current through the insulation ground conductor, indicating the degradation of the dielectric properties between the foil layers. The sensor and associated electronic circuitry are enclosed in a housing adaptable to be used with a capacitance tap common to high voltage measurement and control apparatus.

Abstract: A capacitance test device has been developed for measuring the capacitance of the insulation wrap on armature bars in electromagnetic generators and motors. The test device comprises a probe having an electrode plate mounted on an inflatable bladder. The plate is formed of an elastomeric conductive material and is sufficiently flexible to make good surface contact with the insulation on an armature bar. The plate is electrically connected to a capacitance meter that is also coupled to ground as are the armature bars during testing. The bladder is initially deflated to reduce the thickness of the test device so that the device can be slid into the narrow gap between the insulated armature bars of a stator. Once positioned between the bars, the bladder is inflated with a pressure hose to press the electrode plate firmly against the surface of the insulation of the armature bar.

Abstract: A device for testing pairs of wires in a cable which includes a testing console having known means for performing tests on the wires and having a test fixture with a plurality of pins extending through a mating surface, the pins being arranged and arrayed to enter holes containing wires to by tested in a terminal fixture, the terminal fixture having holes into which wires may be inserted and held by friction, the holes opening in a terminal fixture having the holes in the same array as the array of pins in the test fixture so that when the terminal fixture and the test fixture are brought together with the same orientation the pins extending from the test fixture enter the holes in the terminal fixture and make a circuit between the testing console and the wire, and the console includes a rotating switch arrangement to bring both ends of each wire into circuit with testing equipment consecutively and one-at-a-time.

Abstract: To locate ground faults in a normally ungrounded DC circuit a centertapped voltage divider is connected across the positive and negative buses. An oscillator controlled switch is connected between the centertap and ground which when operating modulates the ground fault currents with a square wave having a repetition rate no greater than 3 hertz. A Hall probe including a field nulling coil is clamped successively along the conductors under test. A capacitive storage circuit maintains the energization of the nulling coil at the level that provided a null indication immediately prior to actuation of a test button. The Hall probe is connected to a read-out oscilloscope which indicates the presence or absence of the square wave modulation. Fault currents as small as 1 ma can be detected.

Abstract: A withstand voltage-testing apparatus includes a high voltage generator for applying a high voltage to a work, the withstand voltage of which is to be measured. A ground conductor covers the work with an insulating material. A conductor is wound around a current transformer to connect the ground conductor and the ground. A variable resistor is connected with the output terminals of the current transformer. A digital panel meter, which includes a detector, detects a voltage generated by the variable resistor. A warning mechanism displays that work produced by the above is defective when a voltage detected by the detector is higher than a predetermined value.

Abstract: Insulation test equipment for testing high voltage electrical equipment at rated voltage levels up to above 5 kV. A multistage rectifier-capacitor voltage multiplier ladder is used to boost the test voltage to the desired level, while keeping the current and load capacity to a safe, low level. If an appreciable amount of current is attempted to be drawn, such as might occur with accidental human contact, the rectifier--capacitor ladder breaks down to limit the voltage and current to safe levels. Two separate current limit resistors are provided for both outgoing and incoming voltages of the test equipment. One is installed in the test apparatus and the other is installed on the high voltage fuse at the contact point between the motor windings and the test lead. The voltages and insulation current generated by the test equipment are monitored indirectly through opto-coupler circuits to isolate and protect the monitoring circuits and the operator.

Abstract: A method for determining transient partial discharges in the insulating medium of an electrical power transformer, for example, oil and paper, uses in one embodiment a circular plate inserted in the interior of a transformer tank which picks up partial discharge signals. These are high frequency transients which are processed by use of DC notch filters, blocking capacitors and amplified by high frequency amplifiers. The peaks of the partial discharge signal are detected by peak amplifiers, sorted by relative magnitudes, and either displayed or further processed by computer techniques for indicating incipient transformer failure.

Abstract: An insulating condition detecting apparatus for a wire-cut electrical discharge machine in which insulation between a wire electrode and a workpiece is detected without rising any other special power source than a power source for machining. A voltage between the wire electrode (6) and the workpiece (6) is detected during a period. A switching element (3) for electrical discharge, formed of a semicondctor, is turned off and a switching element for charging is turned on to charge the capacitor. When the detected voltage is lower than a reference value, it is determined that the insulation between the wire electrode and the workpiece is unsatisfactory, and a dielectric breakdown signal is outputted.

Abstract: The primary charge roller evaluator is a device to determine an accurate measurement of conductivity or leakage current of primary charge roller, from its steel shaft to outer coating. This measurement is based on the impedance of the roller, that is the in-phase resistance and the capacitive reactance of the roller. This measurement allows the user to evaluate the quality of the primary charge roller. This evaluation is then used to predict the performance of primary charge roller. Accurate conductivity or leakage currents are determined by totally enclosing the primary charge roller in conductive holders and applying a pre-measured pressure on roller for maximum contact. Humidity compensator adjusts for changes in humidity and has non-linear scale to adjust for patented characteristics of rollers.

Abstract: A non-ferrous current sensor is used to continuously measure the charging current magnitude in step-graded foil and paper insulation systems used on high voltage measurement and control apparatus such as instrument transformers and on the condenser bushings of power transformers and circuit breakers. The low voltage measured signal is conditioned by an electronic circuit such that it modulates a DC signal in a system current control loop to provide continuous remote monitoring and alarm functions. Remote power is supplied to the sensor and conversion circuits through the current loop. Alarm level thresholds and alarm time delay are embodied in a control device which may be located in a remote location, away from the high voltage equipment. Step-graded insulation systems form a capacitively divided circuit between the high potential and ground. As the dielectric between the foil layers breaks down, the total capacitance of the insulation system increases, producing an increase in the charging current.

Abstract: In an electric apparatus such as an electric power cable system, a high frequency pulse is induced on a conductive member such as a metal sheath, where partial discharge occurs in an insulation. The high frequency pulse is detected by means of a bypass lead wire, a metal foil electrode, a detecting coil, and the like provided on the electric apparatus without interrupting a live operation of the electric apparatus.

Abstract: A system for detecting a power cable for water treeing and other forms of deterioration based on the dielectric loss of the insulation of the cable. An AC test signal is injected to the conductor of a sample of cable to be tested. The voltage drop appearing across a resistor connected to the insulation shield layer of the cable is measured by means of a lock-in amplifier. A phase shifter adds to the voltage drop a voltage signal that is 180 degrees out of phase with the reactive component of the voltage drop. The output of the lock-in amplifier is the active component of the voltage drop that is representative of the dielectric loss of the insulation of the cable. This approach permits an accurate and reliable detection of trees even if they have not spread out evenly in the power cable, as distinct from the conventional tan .delta. method.

Abstract: Test apparatus for a high voltage cable installation includes a high AC voltage source having the frequency range intended to be carried by the cable installation and a high DC voltage source. A switch alternately passes positive and negative polarities of the DC voltage, and the AC voltage source and the alternating polarity DC voltage output from the switch are coupled while isolating the voltage sources from each other. The resulting alternating polarity DC-biased AC voltage is injected into the cable installation to produce indications of incipient faults.

Abstract: A plug for insulating electrical contacts of a male connector has a connector engaging portion for snugly coupling the plug to the connector and a head portion extending from the connector engaging portion. Bores extend axially through the connector engaging portion and only partially through the head portion, and snugly receive the contacts.

Abstract: An accurate dielectric breakdown prediction method and a prediction method in which accurate time dependent dielectric breakdown (TDDB) characteristics can be obtained on the basis of dielectric breakdown prediction by a step stress method are provided. In this method, dielectric breakdown is predicted on the basis of a plurality of reference currents in accordance with an applied voltage, or a reference current I.sub.cr is varied as the function of the applied voltage. In the step stress TDDB prediction, a Chen-Holland-Hu model or improved Chen-Holland-Hu model is employed. Since TDDB characteristics can be obtained from only dielectric breakdown prediction, this method is advantageous for early reliability prediction.

Abstract: In an apparatus for testing cable (comprising a metallic core jacketed by insulation) to detect localized defects on the insulation caused by its carbonization, the cable is moved in an axial path through an array of five ring electrodes radially spaced from that path and spaced from each other along the path by axial gaps. The first and fifth electrodes from left to right are grounded while high voltage circuits supply current to the middle three electrodes at DC voltages which causes (a) the second and fourth electrode, and (b) the third electrode to be positive and negative, respectively, relative to ground, and which voltages are high enough to produce flow of charge through the atmosphere adjacent the electrodes, and between the electrodes and the moving cable.

Abstract: Electric bus bar insulating coatings are calibrated to withstand long term outdoor exposure without failure. Manufacturing samples of the coating material are evaluated at the coating manufacturing site prior to shipment to the bus bar manufacturer. Bus bar samples coated with the material are suspended within a heated water bath and subjected to several hundred volt-amperes. The thickness of the coating is predetermined to provide accurate qualifying data for each coating sample within a reasonable time frame. Coating compositions that qualify are then applied to electric bus bar conductors by the bus bar manufacturer.

Abstract: In accordance with the present invention, an apparatus and process for convenient electrical access following application of an overcoat layer to the core of a thin film transducer for measuring core-to-coil impedance and breakdown voltage during manufacture and final testing is disclosed. The invention may employ existing process feedback circuitry at the wafer level typically severed in the machining process or the invention provides for a permanent dedicated terminal on the support structure.

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

Abstract: A device for detecting and indicating a fault current flowing through a lightning arrestor or an insulator, the current being DC or at AC mains frequency, the device being housed inside a box that is provided with a frangible window and that has a piece of metal electrically connected to an end fitting of the lightning arrestor or of the insulator passing therethrough. The device has: a transformer for transforming the current, the primary of the transformer being constituted by the piece of metal, and the secondary of the transformer being connected to a peak-limiting circuit to make pulses of current due to surges corresponding, in particular, to lightning strikes inoperative; a heating resistance fed by said transformer and constituting an igniter for a pyrotechnic composition in which it is embedded, the composition being designed to break the frangible window; and preferably indicator means suitable for being released by rupture of the frangible window.

Abstract: A megohm tester for determining resistance utilizing a relaxation oscillator which generates output pulses, at a rate dependent on an unknown resistance detected at a test site within an electronic apparatus, which can then be compared to known values provided as standards.

Abstract: An apparatus for providing a quantitative measurement of high frequency corona discharges from electrical devices operating at high voltages, including an alternating current power source for providing a test signal variable in amplitude and frequency, a high pass filter to reject power source cyclical components and to isolate corona discharge components, an adjustable gain amplifier, and a power meter providing a quantitative readout of the amplitude of corona discharges integrated over a preselected time period. Electromagnetic shielding of individual assemblies comprising the test equipment allows corona detection without emissions or interference from external sources.

Abstract: Disclosed is a ground fault detection apparatus for an operating, normally ungrounded supply system, the apparatus having a periodically grounded center tap of a test impedance that is connected across conductors of the system, and detector circuitry including a charge balance circuit having low gain and wide dynamic range that measures the amplified voltage output of a Hall effect current sensor. A preferred implementation of the circuit has a charge transfer variable oscillator. A pair of microprocessor-controlled counters that are responsive to the oscillator precisely measure the average frequency of the oscillator over intervals that are automatically maintained at approximately one second in duration, the microprocessor calculating the fault current as the difference between current measurements taken with and without the center tap grounded.

Abstract: In an electric apparatus such as an electric power cable system, a high frequency pulse is induced on a conductive member such as a metal sheath, where partial discharge occurs in an insulation. The high frequency pulse is detected by means of a bypass lead wire, a metal foil electrode, a detecting coil, and the like provided on the electric apparatus without interrupting a live operation of the electric apparatus.

Abstract: An electrical generator inspection system comprises an electro-magnetic core imperfection detector that provides an analog signal representative of fault currents detected between adjacent laminations of a stator core; an analog-to-digital converter coupled to the detector for converting the analog signal to a digital signal; a digital filter coupled to the output of the converter for digitally filtering the digital signal to remove noise therefrom; and means for storing predetermined signal criteria and for comparing the filtered digital signal to the predetermined criteria to determine the location of the insulation defects along the stator core. In one embodiment, the system further comprises means for storing the filtered digital signal in a memory.

Abstract: An impending failure of an electronic circuit caused by aerosol deposition is detected by using a test circuit including a plurality of conducting paths, aerosol deposition enhancement means, controllable means to control the aerosol deposition enhancement means, conducting path isolation sensing means to measure the isolation of the conducting paths and control means to supply a control signal to the controllable means and warn of impending test circuit failure responsive to conducting path isolation. In addition, the apparatus includes deliquescence enhancement means which is controllable and responsive to the control signal from the control means.

Abstract: A testing voltage of 800 to 5000 volts is applied to a measuring electrode constructed of carbon fiber brushes. This testing voltage is regulated to the desired value by means of a control circuit. Sparkover pulses travel through a filter to an output, with the response level of the testing voltage being regulated accordingly. Thus the test is reliable without highly electrically or mechanically stressing the test object.

Abstract: A reference AC signal having a frequency of about 4-10 Hz is injected into a line of a DC electrical network for performing insulation measuring in a processing unit. The AC signal is measured in a mixed bridge having a first resistive dividing bridge connected in parallel with a second capacitive dividing bridge between the line and the ground. The intermediate output points of the first and second bridges are joined together and connected in an input of the processing unit. The impedance and the dividing ratio of the two bridges cause the DC voltage measured at said input to be low in relation to the value of the AC voltage measured at the output of said mixed bridge.

Abstract: A charging current flows through an insulation for insulating two conductors of an electric apparatus by applying an alternate current voltage thereto. A direct current component of the charging current is detected, and is amplified by biasing a direct current voltage to the alternate current voltage. An insulation deterioration of the electric apparatus is determined by an absolute value of the amplified direct current component.

Abstract: In order to enable measurement of insulation resistance values of a number of electronic parts such as chip capacitors with high accuracy and without the reducing measurement efficiency of characteristics, such as the capacitance, capacitance values of chip capacitors which are held by respective holding portions of a turntable are first measured in a capacitance measuring position during intermittent feeding of the turntable. When an insulation resistance measuring region is filled with those of the chip capacitors whose capacitance values have been measured the turntable is stopped. In this stopped state, a plurality of chip capacitors being located in the insulation resistance measuring region are simultaneously charged and subjected to the measurement of insulation resistance values.

Abstract: An apparatus for detecting a defect in an insulator formed therein with an axially extending hollow section; having a hold section 2 for holding the insulator, a first electrode 3 inserted in the hollow section 1a of the insulator 1, and a second electrode provided outside of the insulator 1. An electric discharge structure 10 produces an electric discharge between the first and second electrodes 3, 5, a path recognizes 11, 12, 13 for recognizes whether the electric discharge passes through a predetermined path, and a discriminating structure 14 for discriminates whether the insulator 1 is satisfactory, in accordance with a signal from the path recognizes.

Abstract: A system for measuring partial discharges comprises a plurality of acquisition circuits each including a signal shaping circuit delivering a signal value, a multiplexer enabling the signal values provided by the various acquisition circuits to be delivered in succession on a common path, an acquisition trigger circuit responding to the existence of an acquisition command signal provided when the input level of at least one of the acquisition circuits exceeds a defined threshold and defining an acquisition command signal, and a signal treatment and storage system responding to the acquisition command signal and then performing an acquisition cycle during which it stores the values of the signals provided by the various acquisition circuits via the multiplexer.

Abstract: In order to detect if there is a fault in a cable (6), three signals are applied to the cable (6) by a suitable transmitter (FIG. 1). Two of the signals are of high frequency and the other signal is of low frequency equal to an integer multiple of the difference between the frequencies of the high frequency signals. Aerials (10a, 10b) of a receiver (FIG. 2) detect the high frequency signals and the receiver processes those high frequency signals to determine a frequency signal. This is then compared in a comparison circuit (31) with the low frequency signal detected by ground probes (22,23) of the receiver (FIG. 2). At a fault in the cable (6), e.g. where the outer insulation is damaged, the conductor of the cable (6) is shorted to ground and this causes a change in a phase between the signals. Thus by moving the receiver along the cable (6), there will be a change in place at or adjacent the fault which will be detected by the receiver (FIG. 2) allowing the fault to be located.

Abstract: Device for verifying the tightness of a network of cables with metal sheathing or metal part. This device comprises a central measurement unit (UC) connected to rack units (UBo1, UB2) controlling the assemblies of cables of the network (C1, C2) to which they are connected via terminal boards. The assemblies are disconnected from ground at the head of the network of the assembly of cables (C1, C2) and the insulation resistance with respect to ground of this assembly of cables is measured. The resistance is compared with an adjustable standard resistance. The electrochemical couple generated by a lack of tightness, which is associated with an alarm is also measured. The rack unit (UBo1) at the head of the network is associated with at least one rack unit (UBe1) located at the end of the cable or assembly of cables (C1) in which signals are detected and analyzed.

Abstract: A method of determining the percentage gas content of an insulating glass window unit or the like comprises the steps of applying a voltage to opposed panes of the unit, progressively increasing the voltage, monitoring the voltage and recording the magnitude of the voltage at which a continuous discharge occurs, or is about to occur, between the electrodes and converting the magnitude to a number indicative of the percentage gas content of the gas between the panes.

Abstract: An automatic insulation tester tests the insulation resistance of electrical equipment when the electrical equipment is inoperative. The automatic insulation tester is automatically rendered operative when the electrical equipment is inoperative, and is automatically rendered inoperative when the electrical equipment is operative. The automatic insulation tester applies a voltage on the order of the rated voltage of the electrical equipment to the electrical equipment and measures and displays the insulation resistance of the electrical equipment. When the insulation resistance falls below a predetermined value, an indicator is activated, and remains in an activated state until the insulation resistance of the electrical equipment rises above the predetermined value and the automatic insulation tester is manually reset.

Abstract: The present invention is a method and apparatus for testing the condition of insulating systems. The insulating system is charged up by a dc voltage and then discharged. The return voltage appearing after discharge is assessed and the quotient of the peak value of the return voltage and the charging voltage is measured. According to the invention the charging is done in time-interval of 10.sup.-3 -10.sup.4 seconds, with a ratio of charging to discharging time in the range of 0.1-100. The measurement cycle is repeated several times with other charging/discharging times, but with the same charge/discharge ratio. The resulting spectrum of values may be compared with a reference whereby the state of the insulating system can be assessed. An apparatus for implementing the method the apparatus for implementing the said method consists of a high voltage source, a switching circuit and voltage measuring units.