Abstract: An inverter system which converts DC input into AC output and supplies the AC output to a load such as an FL tube detects change in a circuit current due to anomaly such as discharge without contacting with a current route. Relating to an inverter which converts DC input into AC output and supplies the AC output to a load, change in a circuit current of the inverter is detected through the medium of magnetic flux change due to the change in the circuit current caused by discharge. For example, if change in a current occurs in the circuit current of the inverter by disconnection discharge or ground-fault discharge occurring in a current route including a load of the inverter, magnetic flux change occurs in circuit wiring and a space of a core gap of a transformer of the inverter. The change in the circuit current is detected through the medium of the magnetic flux change without contacting with the circuit wiring or the transformer.

Abstract: A method for arc fault detection, includes automatically generating an output signal responsive to an input signal. The input signal is indicative of an arc fault. The output signal is configured to cause an electrical circuit to open. The output signal is generated responsive to a derived signal based upon a first threshold having a first amplitude.

Abstract: A system and method for identifying an arcing event in electrical distribution equipment. The system includes memory for storing an arcing radio frequency characteristic indicative of an arcing event generated in electrical distribution equipment and a noise radio frequency characteristic indicative of background electrical noise and a sensor for detecting radio frequency signals resulting from the arcing event and propagating wirelessly from the electrical distribution equipment. The system also includes a processor for processing the radio frequency signals detected by the sensor to extract radio frequency characteristics from the detected signals and including a comparator for comparing the extracted frequency characteristics to the arcing radio frequency characteristic and the noise radio frequency characteristic stored in memory to identify occurrence of an arcing event. The system also includes an arc alarm generator for generating an arc fault signal indicative of the occurrence of the arcing event.

Abstract: Disclosed herein is an apparatus for detecting an arc fault, which prevents a malfunction caused by a conventional current detecting method by detecting a source voltage applied onto a conductive wire to determine whether there is an arc fault, prevents a malfunction with respect to a pseudo arc signal by dividing a current detecting route into two according to the magnitude of a load current occurring onto the conductive wire to determine whether there is the arc fault by voltage detection, and lessens the danger of a fire by reducing a circuit break time according to the magnitude of the load current. A voltage detector detects the arc fault by use of two detecting routes. Each route differs in a filtering value of a filter, presence/absence of level limit, an amplification factor of an amplifier, an accumulation value of a comparator, etc. according to the magnitude of a load current occurring on a conductive wire, thereby reducing a circuit break time.

Abstract: An apparatus for repeatably generating electrical arcs for testing an electrical switching device, such as an arc fault circuit interrupter, includes a stationary electrode and a movable electrode that is moved along a path of travel by an electromechanical device under the control of a controller that receives data from either a current measuring device or a voltage measuring device to detect the initiation of an arc. The movable electrode is caused to first make physical contact with the stationary electrode, and then is moved away from the stationary electrode until an arc is detected. Additionally, the movable electrode may be moved towards and away from the stationary electrode according to a test profile to control the magnitude of the randomness of the arc.

Abstract: A method of detecting a series arc in an alternating current electrical system is provided. The method is a pattern-recognition based approach and includes passing raw current signals from a conductor in the electrical system through one or more filters to provide a filtered signal; extracting one or more features from the filtered signal; and classifying the features to a known state representative of the series arc.

Abstract: A method and an apparatus detect series and/or parallel arc faults in AC and DC systems. The method according to one embodiment inputs an AC current signal; extracts a fundamental component of the AC current signal and monitoring an amplitude variation profile for the fundamental component, thereby generating a first arc fault detection measure; detects non-stationary changes in the AC current signal applying at least one measure of order higher than one, thereby generating a second arc fault detection measure; and determines whether an arc fault exists based on the first arc fault detection measure and the second arc fault detection measure.

Abstract: A gas-insulated apparatus is equipped with multiple sensors for sensing a partial discharge signal caused by a foreign substance, and a frequency analyzing section for analyzing the frequency of the sensed partial discharge signal. A defect type judging section estimates the defect type of the foreign substance from the signal obtained through the frequency analysis or from the voltage phase distribution of partial discharge synchronized with the frequency of the voltage applied to the gas-insulated apparatus, and a location determining section estimates the defect location and signal intensity from the multiple partial discharge signals. A defect size calculating section estimates the defect size for each defect type from the signal intensity and field distribution at the defect location. Dielectric breakdown risk evaluation is performed based on the defect size and type, and the insulation failure risk is diagnosed from the partial discharge.

Abstract: An exemplary automatic hi-pot test apparatus (20) includes a high voltage supply (21), a transmission device configured for transmitting an electronic device (26) to be tested, a connecting device electrically connected to the high voltage supply and configured for moving and electrically connecting with or electrically disconnecting from the electronic device, a controller (28) for controlling the connecting device and the transmission device, and a detector (27) for detecting the presence of the electronic device. When the detector detects the presence of the electronic device, the detector sends a corresponding detecting signal to the controller, such that the controller stops the electronic device and drives the connecting device to electrically connect with the electronic device whereby a hi-pot test can be performed.

Abstract: The invention relates to a method for inputting an information signal into a power cable which is connected to a voltage supply and which includes at least one or more conductors, a dielectric provided around the conductors and a conductive earth sheath arranged wholly or partially around the dielectric, the method incluging inputting a pulse-like information signal at a first position via the earth sheath in order to produce a corresponding pulse-like information signal which is propagated to a second position in the dielectric of the power cable.

Abstract: Certain exemplary embodiments include a method, which can include automatically generating an output signal responsive to an input signal. The input signal can be indicative of an arc fault. The output signal can be configured to cause an electrical circuit to open. The output signal can be generated responsive to a derived signal based upon a first threshold having a first amplitude.

Abstract: An apparatus for repeatably generating electrical arcs for testing an electrical switching device, such as an arc fault circuit interrupter, includes a stationary electrode and a movable electrode that is moved along a path of travel by an electromechanical device under the control of a controller that receives data from either a current measuring device or a voltage measuring device to detect the initiation of an arc. The movable electrode is caused to first make physical contact with the stationary electrode, and then is moved away from the stationary electrode until an arc is detected. Additionally, the movable electrode may be moved towards and away from the stationary electrode according to a test profile to control the magnitude of the randomness of the arc.

Abstract: A system and method for managing power delivered to a processing chamber is described. In one embodiment power is delivered to the processing chamber with a power cable, the power cable storing energy and including a first and second conductors, the first conductor having a first voltage polarity relative to the second conductor. The voltage polarity of the first conductor is reversed relative to the second conductor and at least a portion of the stored energy in the power cable is provided to the plasma chamber while the polarity of the first power cable is reversed.

Abstract: A power equipment includes a first internal abnormality detection apparatus comprising a first antenna accommodation pipe which is connected to a first connection pipe formed in a enclosed container and which accommodates a first antenna therein, and a first signal detection circuit which is connected to a first antenna and which detects an electromagnetic wave signal emitted when any abnormality has occurred within the enclosed container.

Abstract: There is here disclosed a method and apparatus for detecting the occurrence of arcing of a conductor by monitoring the current on an AC power line. The signal detected is split and directed along four separate paths to generate four signals having separate characteristics which represent the current in the line. A first path is for a signal representative of the current flowing in the line. A second path is for a signal having a pulse for each occurrence of a positive step change in current that is significant and has a di/dt value above a predetermined value. A third path is for a signal having a pulse for each occurrence of a negative step change in current that is significant and has a di/dt value above a predetermined value. A fourth path is for a signal having a voltage level representative of the broadband noise signal on the line. Using at least one of five different methods in combination with one of three input signals, a reference signal designated as “SINE” is generated.

Abstract: System and method for detecting partial discharge arcing phenomena in a power network distribution system which employs a mobile receiving assemblage including a wideband antenna, a computer controllable wideband radio receiver deriving an amplitude detected output and a global positioning system providing system position data. The amplitude detected outputs are digitized and treated with a digital signal processor based analysis including fast Fourier transforms extracting narrowband signal frequencies that are harmonically related to the network fundamental frequency. The narrowband signal frequencies are analyzed for peak amplitudes which are summed to derive maintenance merit values related to the arcing phenomena.

Abstract: Certain exemplary embodiments comprise a method, which can comprise automatically generating an output signal responsive to an input signal. The input signal can be indicative of an arc fault. The output signal can be configured to cause an electrical circuit to open. The output signal can be generated responsive to a derived signal based upon a first threshold having a first amplitude.

Abstract: The invention is based on feeding the closed bodies to be evaluated to a station for the application of high voltage for the formation of the arc across the inner space of the body and capturing the arc formed by means of a CCD camera which will compare, adjustably, the luminous intensity of the arc created within the body subjected to checking with a threshold value determining whether the luminous intensity is above or below the threshold, which will be the rejection threshold, rejecting the bodies which do not comply with the predetermined threshold value, separating them from the whole of the accepted bodies.

Abstract: A test apparatus tests an arc fault circuit breaker with an arc fault generator having an input and an output. The test apparatus includes a first electrical connector electrically connected to the load side of an arc fault circuit interrupter. A second electrical connector is electrically connected to the input of the arc fault generator. A third electrical connector is electrically connected to the output of the arc fault generator. A plurality of fourth electrical connectors are electrically connected to one or more of a plurality of masking loads. A fifth electrical connector is electrically connected to another load. A two pole, plural position rotary selector switch provides a plurality of different configurations of at least the arc fault generator and the one or more masking loads downstream of the load side of the arc fault circuit breaker.

Abstract: Certain exemplary embodiments described herein comprise a method comprising a plurality of activities comprising: discriminating an arcing condition from a non-arcing broadband signal, and, in response to detecting an arcing condition, outputting a trip signal to a circuit breaker controlling a predetermined alternating current circuit associated with the arcing condition.

Abstract: Method and apparatus for detecting or suppressing electrical arcing or other abnormal change in the electrical impedance of a load connected to a power source. Preferably the load is a plasma chamber used for manufacturing electronic components such as semiconductors and flat panel displays. Arcing is detected by monitoring one or more sensors. Each sensor either responds to a characteristic of the electrical power being supplied by an electrical power source to the plasma or is coupled to the plasma chamber so as to respond to an electromagnetic condition within the chamber. Arcing is suppressed by reducing the power output for a brief period. Then the power source increases its power output, preferably to its original value. If the arcing resumes, the power source repeats the steps of reducing and then restoring the power output.

Abstract: An insulation degradation diagnostic device (1a) comprises a current transformer (7a), a first amplifier (15), a first high-pass filter (17), a low-pass filter (19), a second amplifier (20), a second high-pass filter (21), and a discharge judgement section (30). The current transformer (7a) has a filtering function, with an amount of attenuation of ?60 dB or less and a slope characteristic of ?5 dB/oct or less at a commercial frequency and detects a current flowing through a grounding conductor (5). The first amplifier (15) amplifies a current signal from the current transformer (7a). The first high-pass filter (17) removes a low frequency component from an amplified current signal. The low-pass filter (19) removes a high frequency component from a current signal from which the low frequency component has been removed. The second amplifier (20) amplifies a current signal from the low-pass filter (19) to a predetermined level.

Abstract: A device and a method for locating partial discharges in a conductor rod of a dynamo-electric machine are provided, the conductor rod being provided with an exterior electrical insulation. A first and a second sensor are embodied so as to detect a signal which is generated by the partial discharge and spreads along the conductor rod. The first and second sensor are disposed at a distance from each other on the conductor rod in order to emit a partial discharge output signal that represents a specific moment of detection. The partial discharge output signals of the first and second sensor are fed to an evaluation unit which is embodied so as to locate the partial discharge on the conductor rod.

Abstract: A method for triggering a partial discharge acquisition from an energy generating device is described. The method includes generating a power source sensed signal by sensing electromagnetic energy output from the energy generating device, producing an present flux density trace from the power source sensed signal, and determining a lack of variation in timing from at least one of the present flux density trace and a comparison between the present flux density trace and at least one prior flux density trace.

Abstract: A computerized electricity system for connecting loads to a power source, including: (a) an arc fault detecting sub-system having at least one module including: (i) a relay unit, electrically associated with a particular load, for connecting and disconnecting to a power source; (ii) a current source for measuring a current being delivered from the power source to the load, to produce a current measurement; (iii) an analog circuit for receiving the current measurement from the current sensor, and for producing an analog signal based on the current measurement, and a second signal for indicating a potential arc fault event, and (iv) a digital circuit for receiving the second signal from the analog circuit and producing data, and (b) a processing unit connected to each module, so as to receive data corresponding to the analog signal, and the data from the digital circuit, the processing unit for identifying the arc faults, and wherein the processing unit is configured to command the relay unit to disconnect the

Abstract: New methods are used for detecting arcs in a plasma process that is fed by, for example, a freely oscillating AC generator with an output signal of the AC generator for supplying power. The method includes measuring or determining a reference value that is based on a time response of the output signal or of an internal signal of the AC generator relating to the output signal. The methods also include comparing the reference value with a threshold value and detecting an arc when a predetermined result of the comparison is obtained.

Abstract: An arc fault detector, as a stand alone device or in combination with a circuit interrupting device such as a ground fault interrupter (GFCI), protects from potentially dangerous arc fault conditions. The device utilizes a line side or load side series connected inductance having an air or magnetic core to generate the derivative di/dt signal of the arc current in the conductor. The derivative signal is fed to an arc fault detector where it is analyzed for the presence of arcing. The device can have two series connected inductors inductively coupled to each other such that the signal from one inductor is inductively coupled into the other inductor for coupling to the arc fault detector.

Abstract: In the measurement of partial discharge, a voltage detected by an antenna is input to a spectrum analyzer and a phase difference between an operating voltage and a power supply of the spectrum analyzer is obtained by phase domain analysis using the spectrum analyzer. Based on the phase difference and the voltage phase shift associated with the input impedance of a signal converter circuit, the time axis displayed on the screen of the spectrum analyzer is compensated. After the compensation has been carried out, the voltage detected by the antenna is input into the spectrum analyzer and the partial discharge pattern which synchronizes with the operating voltage is measured by phase domain analysis using the spectrum analyzer.

Abstract: In order to determine whether arcing is present in an electrical circuit, a sensor signal corresponding to current in said electrical circuit is processed. The sensor signal is filtered to determine the presence of noise in a predetermined frequency range and produce a corresponding filtered signal. The corresponding filtered signal is compared to a reference threshold voltage to generate an output signal potentially indicative of arcing. A selection is made of one from a plurality of available threshold voltages as the reference threshold voltage for use in the comparing operation. The detection operation supports either or both branch feeder arc fault detection and/or series arc fault detection.

Abstract: A circuit breaker for locating an arc fault for a protected circuit includes separable contacts interrupting the protected circuit and an arc fault detector determining an arc fault in the protected circuit. An analog to digital converter circuit measures a value of peak arc current at the arc fault detector. Another analog to digital converter circuit provides a peak line-to-neutral voltage. A memory provides an arc voltage operatively associated with the value of peak current. A microprocessor determines a distance from the arc fault detector to the arc fault from the value of peak arc current, a wire resistance per unit length or a wire conductance per unit length, the peak line-to-neutral voltage and the arc voltage.

Abstract: A tester for an arc fault circuit interrupter that can selectively simulate and apply electrical arc faults and nuisance loads to at least one device under test (DUT). The tester includes a power supply, a test controller, and test circuitry coupleable to a DUT. AC power input is provided to the DUT and the power supply, which regulates the AC power input to a DC level for powering the test controller. The test circuitry full wave rectifies AC current returning from the DUT, and the test controller controls a switch in the test circuitry. When the switch is on, the AC current flows through the DUT, the full wave rectifier, the load, and the switch to ground. To simulate an arcing condition, the test controller turns the switch on and off at random intervals. To simulate a nuisance load condition, the test controller turns the switch on and off at periodic intervals. In this way, proper operation of the DUT can be verified under both arcing and nuisance load conditions.

Abstract: A system for identifying a selected electrical circuit of interest from a number of electrical circuits, by locating a circuit interrupter connected to interrupt the flow of electrical power from an electrical power supply to the selected circuit of interest. The system includes a remote portion configured to detect when the selected circuit is energized, and in response to generate a wireless signal indicative thereof to a receiver portion located in the vicinity of the circuit interrupter. In response to the wireless signal, the receiver portion is configured to generate an alert indicative to an operator that the flow of electrical power is not interrupted to the selected circuit. By switching the circuit interrupter between the ON and OFF positions, the operator is able to determine from the alert at the receiver portion whether the selected circuit interrupter is connected to control the flow of electrical power to the electrical outlet, load, fixture, or wiring of interest.

Abstract: An adapter module for detecting an electronic fault condition in an electronic circuit is disclosed wherein the adapter module may include electrical fault indicator circuitry. In general, the electrical fault indicator circuitry may include ground fault indicator circuitry, line fault indicator circuitry, or ground and line fault indicator circuitry. The adapter module may also include a magnetic device capable of detecting a magnetic field between the electrical fault indicator circuitry and an electrical circuit module. The electrical circuit module may include a switch such as a circuit breaker, a relay, or a magnetically sensitive switch. The magnetic device may include a Hall effect device or a magnetic core.

Abstract: A sensor for picking up partial discharges in an electrical equipment tank filled with a dielectric fluid includes an antenna responsive to the electromagnetic waves generated by such partial discharges. In the sensor, the antenna is formed by two electrodes that are separated from each other by a dielectric resonator. With this arrangement, the sensor has improved sensitivity in the UHF range, while being of dimensions that are considerably smaller than dimensions of a conventional antenna for use in the UHF range.

Abstract: An arc fault detector includes a shunt resistor deployed in a protected circuit, an arc discriminator sensing voltages across the shunt resistor and producing an arc indication deduced from current variations associated with parallel and series arc faults, a signal transformer buffering the arc detection signal and producing a pulse, a switch transient detector sensing a voltage differential across load switches and producing a pulsed switch transient signal when the voltage differential across load switches exceeds a reference value, a line interrupter, such as a static relay, a switch controller including logic gates generating a trip signal based on predetermined criteria, and a manual switch for resetting the line interrupter. An embodiment comprises a voltage sensing coil enveloping a toroidal core to detect current variations in conductors passing through the core.

Abstract: A RF current transformer sensor includes a first sensor portion and a second sensor portion. The first and second sensor portions are configured to define a fixed opening for receiving a test object. The RF current transformer sensor is capable of detecting current pulses between the first sensor portion and the second sensor portion for sensing partial discharges from the test object. Further disclosed is a method of partial discharge sensing.

Abstract: Methods and systems for reliable arc detecting in systems having power signals that experience decay or increase in amplitude. One embodiment of a system for detecting electrical arcs by monitoring an alternating current power supply comprises a sampling circuit which samples electrical signals. It further comprises a delay circuit which receives the sampling circuit output and stores a time history of the output over an interval including a past, present and future versions of the history. Causal/non-causal logic compares the present version with the past and future versions to determine which will be used as an arc monitoring version to compare the present version to for arc monitoring. A dynamic processing module compensates for any amplitude differences between the present version and the arc monitoring version. An arc monitoring circuit analyzes the present version and adjusted arc monitoring version to determine if an arc signal is present.

Abstract: A partial discharge sensing system and method for conducting testing inside an enclosure includes a partial discharge sensor, an access port, and a signal cable. The partial discharge sensor is permanently installed at a test location inside the enclosure. The access port is configured so that an analyzer can be connected to the access port from an exterior of the enclosure. The signal cable operably connects the partial discharge sensor and the access port to enable an analyzer connected to the access port from outside the enclosure to interface with the partial discharge sensor for generating test data.

Abstract: The invention provides a method of detecting partial discharges in an electrical appliance insulated in a receptacle and a system of diagnosing the state of the appliance using this method. With the help of an UHF antenna placed in the receptacle of the appliance, the method includes analyzing the spectrum (RS1) of the electromagnetic signal picked up by the antenna and of identifying within the spectrum one or more frequencies of interest (B1, B2), for each of which the signal has an amplitude greater than a predetermined threshold value. To identify the frequency/frequencies of interest, the spectrum of the signal received by the antenna is compared with a reference spectrum (RS2).

Abstract: Proportional-delayed zero-crossing frequency-drift estimator devices are provided. Given N-number of time samples, the current zero-crossing time estimation technique uses only two zero-crossing time samples for repetition-rate estimation. The term “zero-crossing point” refers to the point where a sinusoidal waveform varies from a positive to a negative value and crosses the zero value in the process. The proportional-delayed zero-crossing frequency-drift estimator devices employ four zero-crossing time samples by utilizing both proportional zero-crossing points for current information and delayed zero-crossing points for past information so that the noises in the time samples will be smoothed out making a less noisy estimation.

Abstract: The present invention relates to a simple detector for partial discharge with the acoustic emission technique, which provides essentially with an acoustic emission sensor being set on a power equipment. Still, the output of the acoustic emission sensor is connected with a preamplifier and a bandpass filter in turn and the output of the bandpass fitted up with a comparator. The signals of square waves generated by the comparator can be transmitted to a microprocessor as concurrently as a counter in the microprocessor can be used to count up times for partial discharge by seconds; then, the resulted times can be displayed. Consequently, it is convenient to determine whether the power equipment is necessarily maintained by means of counting up times for partial discharge.

Abstract: An arc fault detector, as a stand alone device or in combination with a circuit interrupting device such as a ground fault interrupter (GFCI), protects from potentially dangerous arc fault conditions. The device utilizes a line side or load side series connected inductance having an air or magnetic core to generate the derivative di/dt signal of the arc current in the conductor. The derivative signal is fed to an arc fault detector where it is analyzed for the presence of arcing. The device can have a series connected inductor on each of multiple conductors of a power distribution network for phase/neutral or multi-phase arc detection.

Abstract: A portable circuit interrupter shutoff testing device and method, including a high current switch controlled by a timing circuit that allows current to flow through the switch and a small series resistance (in order to trip the instantaneous-trip function of the interrupter, as opposed to the overload-trip) for a short time period relative to the sine wave of the electrical power. A button activates the timing circuit which in turn activates the switch and current flows limited by the internal resistor of the device. By limiting the on time of the device to one of a few half cycles, the user can test if the circuit interrupter responds as quickly as specified by the manufacturer. A method includes receiving a stimulation indication, and selectively connecting an electrical load is sufficient to trigger the instantaneous-trip function of the circuit-interrupter.

Abstract: A method of detecting and localizing a source of partial discharge in an electrical apparatus placed in an enclosure containing an acoustically-conductive fluid.

Abstract: A partial discharge detection test link and system is disclosed to detect partial discharge of a power cable accessory. The power cable accessory includes a first accessory component and a second accessory component connected to each other. The partial discharge detection test link is a permanent or temporary substitute for a conventional service link, connects directly across the power cable accessory and includes a conductor member and a partial discharge sensor. The conductor member has an electrically conductive element and an insulation surrounding and extending along the electrically conductive element. The electrically conductive element is electrically connected directly between the first and second accessory components. The partial discharge sensor is disposed about the conductor member and has the electrically conductive element as a primary winding and a secondary winding with the insulation positioned between the primary and secondary windings.

Abstract: A technique for detecting defects in aircraft wiring, such as for detecting partial discharges or arcing in wiring or cables is disclosed. A high frequency current transformer (HFCT) is fixingly positioned in contact with a wire so that the wire is encircled by the HFCT. Partial discharges from a damaged wire so encircled will induce a current in the HFCT proportional to the current of the discharge. The HFCT includes a conductive coil-like pattern formed onto a flexible insulating material. The insulating material has slits between each coil-turn. The HFCT also includes a core of flexible material fitted between the coil-turns through the slits.

Abstract: A method and an apparatus for detecting a partial discharge in a high-voltage transmission and distribution system include detectors which are respectively attached to a power cable and an antenna, such that a first signal and a second signal at a predetermined frequency are extracted using resonators. The first signal is supplied to a differential amplifier via a delay circuit. The second signal is supplied to the differential amplifier via a regulator that includes a variable delay circuit and a variable amplifier. The output from the differential amplifier is demodulated in a demodulator. The signal from the demodulator is supplied to an MPU via an A/D converter to determine the amount of adjustment in phase and amplitude which is to be supplied to the regulator. Then, control is provided such that the output from the differential amplifier is minimized in the absence of partial discharges.

Abstract: Certain exemplary embodiments comprise method, the method comprising a plurality of activities comprising: for each of a plurality of potential arcing events associated with an alternating current: sensing the potential arcing event; identifying an amplitude-duration pair associated with the potential arcing event; assessing the plurality of amplitude-duration pairs; and determining if the plurality of potential arcing events corresponds to an arcing condition.

Abstract: An apparatus for detecting an arc fault.

Abstract: An apparatus (10) for detecting the occurrence of partial discharge in electrical equipment, such as high voltage transformers. The apparatus comprises a detecting means including an ultrasonic transducer (11) mounted at one end of an electrically insulating elongate rod (13). The ultrasonic transducer (11) is adapted to detect ultrasonic pulses or waves generated by the occurrence of a partial discharge in the electrical equipment. A radio frequency (RF) transducer (17) is also utilized to detect radio frequency (RF) pulses or waves also generated by the partial discharge. The rod (13) can be mounted in the wall of the electrical equipment and so provide a mechanism for adjusting the position of the detecting means within the electrical equipment. The apparatus is also removable from the electrical equipment and re-locatable to other equipment.