Abstract: A three-phase clamp-type power meter comprises a main body suitable to be held by hand during operation, a clamp assembly to clamp around an external power line to measure the current flowing in the power line, two test terminals on the main body for connecting two external power lines to measure a voltage across them, an operating unit for generating a result from the current and the voltage measured through the clamp assembly and the two test terminals with a memory unit for storing the result, and a display unit for displaying at least one of the current, the voltage and the result.

Abstract: Radio-interrogated surface-wave technology sensor, in which the sensitive element (12) is an impedance which is electrically connected as termination to a surface-wave structure (26) of the sensor.

Abstract: A current sensing wafer fits about the blades of an AC power cord and is connectible to peripheral equipment for sensing when current is being drawn through the power cord, and thereby indicating when a power consuming device using the power cord is operating. The wafer, in a preferred embodiment, comprises an insulating substrate which has thereon a loop of ferromagnetic material. Slots for fitting about the twin blades of an AC power cord plug extend through the wafer and the loop of ferromagnetic material extends about the slots, generally in a FIG. 8 pattern. This arrangement, extending about the positive and negative conductors, creates a magnetic current in the loop. A sensor coil is integrated into the loop and includes an amplifier circuit for signaling controlled peripheral equipment that current is flowing through the AC power cord, and therefor, electrical devices using the current are operating.

Abstract: A method and a device for detecting and correcting a saturated current profile of a current transformer in a particularly simple and reliable way, initially uses a number of logic inquiries derived from sampled values of the present current signal profile to detect a start of saturation on the basis of a pattern recognition. An end of saturation is subsequently determined, likewise with the aid of a number of logic inquiries. A saturation signal is then formed from a combination of the logic inquiries. In the case of the detection of saturation, the current sampled values are discarded, and an image of the unsaturated current signal profile is reconstructed from a number of sampled values determined ahead of the time of detection of saturation.

Abstract: A current transducer includes a current transformer in which the conductor carrying the current to be monitored constitutes the primary. The transformer secondary is wound on a toroidal core. The transformer is operated below its cut-off frequency such that the output from the secondary is proportional to the differential of the current in the primary. The secondary output is integrated by an integrator to provide a measure of current in the primary and the integrator is initialized at predetermined intervals. A current measuring device for an electric machine, for example a reluctance machine, includes at least one of the current transducers.

Abstract: An integral meter and current transformer to measure single phase active and reactive energy, voltage and frequency in industrial, commercial and multi-family residential applications. The meter CT is the primary sensing element in a revenue metering system encompassing multiple meter CTs serially connected in groups in communication with data cores for collection and reporting of energy consumption. Numerous data cores may be networked to report to a central station which may be remotely interrogated over the network or dial up modem connection. The meter CT utilizes a split-core transformer with substantially overlapping fingers. Disengaging split-core sections of the meter CT enables it to be easily installed around a loaded conductor without the interruption of power to the load.

Abstract: Method for replacing a first cable (1) by a second cable (2) between a first predetermined point (1a) and a second predetermined point (1b). The cable comprising,the provision of first series impedance means (S1) close to the first end (2a) and second series impedance means (S2) close to the second end (2b) of the second cable (2), which first (S1) and second (S2) series impedance means can be switched between a state of high impedance value and a state of low impedance value,electrically connecting the second cable to the first cable (1) at the first (1a) and second (1b) points, during which operation both the first (S1) and the second (S2) series impedance means are kept in their state of high impedance value,switching the first (S1) and (S2) series impedance means to their state of low impedance value before optionally removing the first cable between the first point and the second point.

Abstract: A self-powered electrical clamp meter measures AC voltages in the range of 6 volts to 600 volts and AC currents in the range of 1 ampere to 300 amperes, and receives operating power from the source of the voltage or current being measured. The clamp meter employs first and second rectifier circuits. One rectifier generates rectified AC power from an AC voltage signal supplied by a voltage probe, and the other rectifier generates rectified AC power from an AC current signal supplied by a current probe. First and second regulator circuits generate regulated DC power from the rectified AC power, and corresponding scaling circuits generate first and second scaled voltage signals whose respective amplitudes are proportional to the output of the corresponding rectifier. A switch selects the first scaled voltage signal when a voltage is being measured, and the second scaled voltage signal when a current is being measured.

Abstract: A multimeter having an elongated housing with a fixed recess for receiving a current-carrying conductor is provided. The multimeter is adapted to measure various parameters including a.c. and d.c. voltage, resistance, and a.c. current. On one end of the elongated housing of the multimeter is a C-shaped current sensor mounted around the fixed recess for measuring a.c. current in the current-carrying conductor and on the other end is a pair of test leads for measuring resistance, a.c. voltage, and d.c. voltage. The current sensor and the test leads provide input signals to an analog-to-digital converter (ADC) to obtain digital samples which are displayed as measurement results according to the selected measurement mode.

Abstract: A device for non-contact, non-invasive measurement of current or power in a wire, cable or conductor includes a small coil having multiple turns with a thin ferromagnetic strip. The coil may be secured to a wand or housing adapted to be used to place the coil in close proximity to the wire, cable or conductor, whereby a voltage is induced in the coil. An amplifier and or an analog or digital signal processor is utilized to increase sensitivity. A readout indicates the magnitude of the induced voltage, and a scaling device renders the readout display indicative of the current or power in the wire, cable, or conductor. The readout may comprise a digital display, a series of light emitting devices, an oscilloscope, a digital computer display system, or a flashing light emitting device having a flash rate proportional to the magnitude of the voltage. The device may be constructed in a wand or pen-like fashion, with the coil and strip incorporated into the wand.

Abstract: The present invention is a current sensing method and apparatus wherein a current transformer producing a secondary current is disposed in communication with a conductor having a primary current desired to be sensed. A current analyzer in communication with the current transformer is adapted to estimate the primary current in the conductor based on the secondary current output waveform, even in the case where the secondary current is in saturation. In one embodiment, the current analyzer estimates the primary current in the conductor by capturing the secondary current waveform output from the current transformer, selecting a predetermined number of data points in an undistorted, region of the secondary current waveform, and estimating the primary current based on the selected data points.

Abstract: A magnetic core for a hybrid non-contact current meter having a magnetic core that is adapted for encircling a current carrying conductor wherein the magnetic core includes a first portion having a first integral toroidal section and a first pair of opposing side walls extending therefrom, a second portion having a second integral toroidal section and a second pair of opposing side walls extending therefrom such that the first portion and second portion are coupled together so to define an aperture between the first and second pairs of opposing side walls. The first and second integral toroidal sections are designed so to be void of any discontinuities within the flow path of the magnetic flux and to have a circular shape so to promote a more thorough flux saturation whereby a reduction of zero errors results and more accurate current measurement are obtained.

Abstract: A self-powered axial current sensor for generating a signal which accurately represents current in a power line includes, in one embodiment, a housing having a bus bar opening of substantially rectangular shape extending longitudinally therethrough. The housing also includes current sensor core retaining walls which define a current sensor region, and a cover base wall which defines, with one of the retaining walls, a power core region. A current sensor core and coil are located in the current sensor region and are positioned proximate the bus bar opening. The current sensor core and coil also are substantially symmetrical with respect to the center axis of the bus bar opening. The current sensor further includes a power core and a power coil located in the power core region and positioned substantially symmetrically with respect to the center axis of bus bar opening.

Abstract: The voltage transformer has a measuring element in the electrical field between an internal conductor and an external conductor of a metal-encapsulated, gas-insulated switchgear. The measuring element includes a Pockels crystal, a crystal of transparent material which, under the influence of the electric field, influences polarized light that is radiated through on account of the Pockels effect. The Pockels crystal has two parallel walls transverse with respect to the field lines. A first deflection prism, which deflects a light beam through 180.degree., is disposed on the crystal face at the high-voltage end. Several optical elements are disposed at the face on the low-voltage side. The optical elements include a light input coupler for polarized light and two light output couplers. The reflected light beam impinges on a beam splitter, which splits the light beam into two partial beams. The first partial beam radiates firstly through a quarter-wave plate and then through a first analyzer.

Abstract: A fault indicator for detecting the occurrence of a fault current in a monitored conductor includes a rotatably mounted indicator flag. The flag is positioned in either a reset indicating or a fault indicating state by a magnetic pole piece, which is magnetized in one magnetic direction or the other by momentary application of a current in one direction or the other to an actuator winding on the pole piece. An auxiliary magnetic circuit comprising an auxiliary pole piece magnetized by the actuator winding, a reed switch and a bias magnet magnetically aligned to oppose the reset magnetic orientation and reenforce the trip magnetic orientation of the magnetic pole piece provides contact closure upon occurrence of the fault current.

Abstract: A monolithic inductor (20, 20') is formed over a silicon or other substrate (22). The inductor (20, 20') includes at least one coil (62, 78) arranged so that its axis (58) is parallel to the substrate (22). Other inductive features, such as other coils (64, 70, 72) or planar spirals (74, 76) are arranged in series with the coil (62, 78) to guide magnetic flux lines away from the substrate (22). In one embodiment, a common thin film coil core (60) made from a magnetic material is provided for two coils (62, 64). The coil core (60) provides a continuous magnetic material flux path through the two coils (62, 64). In another embodiment, an axis (58) of the coil (78) is located between the plane in which two spirals (74, 76) are located and the substrate (22) to guide magnetic flux lines (82) away from the substrate (22).

Abstract: An arrangement for securing a current transformer to an electric utility meter housing. The arrangement includes a utility meter base plate which forms a portion of the electric utility meter housing. The utility meter base plate includes (i) a first central axis and (ii) a transformer receptacle defined therein. The transformer receptacle has an opening and a first retention surface. The arrangement also has a current transformer assembly including (i) the current transformer and (ii) a wall member affixed to the current transformer. The wall member defines an annular channel having a second central axis, and the current transformer is positioned within the annular channel. The transformer assembly also includes a tab having a second retention surface. The tab extends from the wall member.

Abstract: The invention concerns an electrical current sensor comprising a magnetic circuit (3), with an air gap (3a), a winding (4) on the magnetic circuit in which a current to be measured flows, a magnetic field detector (5) arranged in the air gap, and a support plate (2) carrying an electrical circuit (6) configured to amplify an output signal from the magnetic field detector. The support plate (2) comprises a main part (21) and a lateral extension (23), the entire unit having an area cut away from the overall rectangular shape of the plate. The turns (4a) of the winding (4) are arranged at that area in such a way that the thickness of the sensor depends on the transverse dimensions of the winding.

Abstract: A clamping mechanism for mounting a circuit condition monitoring device to electrical cables of various diameters includes a core member comprising a plurality of laminations arranged in a generally rectangular configuration. A spring spanning the core member is anchored at one end to the core at a point near the housing of the monitoring device and at the other end is attached to a bridging member affixed at the opposite end of the core near the housing. This allows the spring to expand less as it transverses the bridge in order to accommodate different power cable diameters.

Abstract: An electrical energy meter is provided with snap fit interlocking parts that eliminate the need for screws or fasteners. The current sensor, located within the meter, has a plurality of current conductors and a notched blade attached to each current conductor that functions as an interlocking component to the meter base without the need for additional fasteners. A circuit board used by the meter is attached to a plurality of integral posts projecting from the base and the periphery of the circuit board has a pair of spaced notches for connection to the ends of a radial communications antenna without the requirement for additional hardware.

Abstract: An integrated circuit includes a sensor which is arranged in the vicinity of a conductor in the circuit and is capable of measuring the current through the conductor. This sensor, for example constructed as a coil, is capable of determining whether a connection which includes the conductor is in order. It can thus be tested notably whether the possibly multiple supply connection of the integrated circuit is appropriately connected to an external connection terminal.

Abstract: A current sensor for sensing alternating current in a current-carrying conductor includes a substantially C-shaped magnetic core having first and second ends with a gap therebetween. A current sensing element, which includes a microresonant element, is positioned proximate the gap between the first and second ends of the magnetic core such that the element oscillates when exposed to an alternating magnetic field. A biasing coil is attached to the micro-resonant element for carrying a bias current. The micro-resonant element resonates, or vibrates, at a standard oscillating frequency when no current is present in the biasing coil, and resonates at a modified oscillating frequency when current is present in both the biasing coil and the current-carrying conductor. The magnitude of current in the current-carrying conductor is determined as a multiple of the product of a ratio of the standard oscillating frequency and the modified oscillating frequency, and the bias current.

Abstract: The alternating current sensor has a transformer-like iron core structure, the circuit in which the current to be measured is connected to the primary winding (current input winding), the secondary winding includes two independent units, namely output current winding and exit measuring winding. The conductor for the output current winding is of high stability with low temperature coefficient of resistance. Nearly the entire induced current in the secondary side flows in the output current winding, finally the induced voltage in the measuring winding is detected by the voltage meter. By this scheme those disadvantages of the conventional alternating current sensor such as high temperature rise, resistance variation caused by increased temperature coefficient of the conductor and the load resistance effect are minimized to achieve the aim of high accuracy alternating current measurement.

Abstract: The measuring device is intended for a metal-enclosed, gas-insulated high-voltage installation. It contains at least one sensor (10, 11), arranged in an enclosure tube (3) of the metal enclosure which is filled with insulating gas, and at least one electronic evaluation device (23, 23'), which processes output signals of the sensor (10, 11). The evaluation device (23, 23') and a plug-and-socket device (28, 28') connecting the evaluation device to an output of the sensor (10, 11) are arranged in a two-part metal housing. One part of this housing is formed by a hollow metal flange (26), integrally formed on the outer surface of the enclosure tube (3), and the region of the enclosure tube (3) rimmed by the hollow flange (26). The other part of the housing is a housing element (27) which is depressed in the shape of a trough and is fastened to the hollow metal flange (26) of the enclosure tube (3) by its edge, which delimits the trough opening.

Abstract: An apparatus senses signals on conductors and includes a ceramic sensor body. A plurality of antenna elements are formed in the ceramic sensor body. Each antenna element includes a conductor sensing end and forms an array having a substantially planar face that is to be placed adjacent to conductors to be sensed. Each of the antenna elements further comprises a central electrode and a surrounding shield electrode spaced from the central electrode. A signal processor is connected to each antenna element and receives the signal output from each antenna element and processes the received signals for determining the presence of signals passing to the conductors. The central electrode and surrounding shield electrode are formed of a hardened, conductive paste received within the ceramic sensor body.

Abstract: An apparatus for monitoring the current flow through a variable load such as various lengths of heater cables. The apparatus can detect a wide range of currents so that the size of the load can vary.

Abstract: The measuring device is intended for a metal-enclosed, gas-insulated high-voltage installation. It contains at least one Rogovski coil (10), which is arranged in an enclosure tube (3), filled with insulating gas, of the metal enclosure and serves to detect the current in a current-carrying conductor (9), led through the enclosed tube (3), and a measuring electrode (11), which surrounds the conductor (9) and serves to detect the voltage of the conductor (9). The current conductor (9) is rigidly connected to a current-conducting cast armature (13) of an insulator (14) fastened to the enclosure tube (3). In the measuring device according to the invention, a defined field geometry is maintained in the interior of the enclosure tube (3) even over long periods and under changing loads. Consequently, the sensors, in particular the voltage sensor containing the measuring electrode (11), can transmit output signals of high measuring accuracy.

Abstract: An integrated circuit includes a sensor which is arranged in the vicinity of a conductor in the circuit and is capable of measuring variations of the current through the conductor. This sensor, for example constructed as a coil, is capable of determining whether a connection which includes the conductor is in order. It can thus be tested notably whether the possibly multiple supply connection of the integrated circuit is appropriately connected to an external connection terminal.

Abstract: A self-powered powerline sensor includes a core layer for wrapping about an a.c. powerline; a winding layer, including of a plurality of windings to be energized by the a.c. powerline, disposed about the core layer; means for sensing a condition in or about the a.c. powerline; and means, powered by the windings, in communication with the means for sensing, for transmitting a signal representative of the sensed condition over the a.c. powerline.

Abstract: A fault indicator for indicating the occurrence of a fault current in an electrical conductor is mounted on the test point of an elbow connector of the type commonly used in power distribution systems. An integral collar assembly encircles the connector housing to capacitively couple the fault indicator circuitry to the system conductor within the connector. The collar assembly includes an inner magnetic core which establishes the coupling and an outer core which shields the inner core from magnetic fields resulting from fault currents in adjacent conductors.

Abstract: A system that monitors and controls electrical power consumption that will be retrofitted to a typical consumer electrical power arrangement (typical arrangement-electrical feed line from a provider, a meter, a circuit breaker and individual input wiring to a plurality of electrical devices, appliances and outlets). The system includes a control unit which receives information from an electromagnetic pickup device from which real time electrical consumption is determined over very short periods of time. The control unit has a main data processing and storage processor for retaining information and it may include a communication microprocessor for sending signals to corresponding modules. The electromagnetic pickup device uniquely measures the electromagnetic flux emanating at each output wire from each of the individual circuit breakers in a breaker box. The modules have filters which release electrical power to the individual electrical devices, appliances and outlets at a controlled, economic rate.

Abstract: An electrical device is capable of sensing both AC and DC current which is flowing through an electrical circuit. The electrical device bifurcates the current into separate paths, wherein impedance of each path has a constant relationship to each other. In a further embodiment, the electrical device includes a current sensor for measuring current flowing through the circuit. The sensor is of a type which does not introduce insertion loss.

Abstract: Inductive current sensor and electrical apparatus incorporating this sensor. The magnetic circuit of the sensor comprises a separable part carrying the detector element and is made of a material having a permeability lying between 5 and 100. The circuit reduces the influence of spurious gaps and external interference on the current sensor for the electrical apparatus.

Abstract: A current determiner having an output at which representations of input currents are provided having an input conductor for the input current and a current sensor supported on a substrate electrically isolated from one another but with the sensor positioned in the magnetic fields arising about the input conductor due to any input currents. The sensor extends along the substrate in a direction primarily perpendicular to the extent of the input conductor and is formed of at least a pair of thin-film ferromagnetic layers separated by a non-magnetic conductive layer. The sensor can be electrically connected to a electronic circuitry formed in the substrate including a nonlinearity adaptation circuit to provide representations of the input currents of increased accuracy despite nonlinearities in the current sensor, and can include further current sensors in bridge circuits.

Abstract: The invention concerns magnetic sensors and, particularly, a magnetic sensor arrangement for use in an electrical measuring device. In the device, magnetic sensors are provided within recesses formed in the arms of the device. The recesses are typically formed within laminations and act so as to shield the magnetic sensors from interference, whilst enabling them to detect a magnetic field of an electrical conductor placed between the two arms.

Abstract: A method and sensor for accurately measuring DC current includes an electromagnetic circuit component, such as a current transformer, having a saturated state and an unsaturated state which generates a DC current based on the DC current being measured. The current transformer includes a first circuit for generating the DC current being measured. A second circuit is electromagnetically coupled to the first circuit to generate a constant DC offset current so as to minimize error at low levels of the measured DC current. A third circuit is electromagnetically coupled to the first circuit for generating a third DC current representative of the first DC current. The first DC current is then measured based on the third DC current. The measured first DC current is then adjusted based on the added second DC current. A sampling circuit is operatively coupled to the third circuit component for sampling the third DC current during a sampling interval.

Abstract: A highly accurate electromagnetic-induction-type conductivity and dielectric constant meter is obtained by using a calibration box (instrument) and a structure as below. The conductivity and dielectric constant meter employs an electromagnetic inductive probe which includes a primary transformer composed of a toroidal core with a wound primary coil, a secondary transformer composed of a toroidal core with a wound secondary coil, an electrostatic shield shielding the transformers, and cables that connect the probe to a meter. To eliminate the electrostatic capacity produced by causes other than electromagnetic induction, the structure of the probe is symmetrical. In a first embodiment, the secondary transformer is placed between two parts of the primary transformer, which has two cores of the same shape that are placed symmetrically.

Abstract: A measuring device for measuring time varying differential-mode currents flowing in first and second conductive groups includes a low reluctance magnetic circuit including first and second portions defining first and second openings positionable to surround the first and second conductive groups. The magnetic circuit comprises a twisted loop which cancels common-mode flux produced by common-mode current flowing in the first and second conductive groups.

Abstract: A method and apparatus for detecting and indicating the number of times a CRT unit arcs. The apparatus is constructed of a ferrite split toroid core wound with wire which is coupled around the focus lead and/or ground lead of a CRT through which a current spike will occur during an arcing event. The wound wire is coupled to a current pulse detector which in turn is coupled to a monostable mode timer and counter for counting the number of arcing events. The counter is coupled to a display device for displaying the number of times the CRT has arced.

Abstract: A magnetic core for a non-contact clamp-on current sensor having a magnetic core that is adapted for encircling a current-carrying conductor wherein the magnetic core includes a first portion having a first integral toroidal section and a first pair of opposing side walls extending therefrom, a second portion having a second integral toroidal section and a second pair of opposing side walls extending therefrom such that the first portion and second portion are coupled together at the first and second pairs of opposing side walls so to define an aperture therebetween for receiving a current carrying conductor and measuring the line current therein. The first and second integral toroidal sections of the magnetic core are designed so to be void of any discontinuities within the flow path of the magnetic flux and so to have a circular shape which promotes a more thorough flux saturation.

Abstract: The invention relates to a method for detecting partial discharges occurring in a cable, wherein the cable has an earth screen with a helical structure, comprising the following steps of: arranging at least one detection coil round the cable for detecting electromagnetic pulses travelling along the cable; applying a potential difference between the core and the earth shield of the cable; and analyzing pulses generated by possible partial discharges in the at least one detection coil in order to determine the location and quality of the partial discharge having caused the pulse, wherein the detection coil is adapted to process signals with a frequency higher than 100 MHz. It has been found that with coils comprising only such a limited number of turns the signal detected by the coil is a much better representation of the form of the electromagnetic pulse travelling along the cable.

Abstract: A remote non-invasive current sensing apparatus for sensing current being carried through a conductor located beneath or on top of a surface. First and second magnetic field sensor elements are placed in operative connection with the surface. There is no requirement to insert the sensor element within the current line by cutting the line or to encircle/enclose the conductor within a coil or other element. The second magnetic field sensor is located a predetermined distance from the first magnetic field sensor. The outputs of the magnetic field sensors are amplified and then provided to a processor which calculates the amplitude of the current in the conductor and the distance of the conductor is from the surface.

Abstract: A noise suppressor for engagement over a cable or ribbon, has a pair of ferrite core halves held in a pair of case halves which are closed around the cable or ribbon. The noise suppressor has a pair of case portions made of resilient material, each case portion having opposite side walls and a floor for defining a space with an open top for receiving a ferrite portion, and ends for passing the conductor. Hinges and latches or latches only hold the case portions together in a closed position around a conductor with the open tops of the case portions facing each other. Ferrite portions are in each case portion, each ferrite portion having a channel and at least one face. The faces engage each other and the channels merging when the case portions are in the closed position for passage of the conductor through the channel. A raised platform on the floor of each case portion is made as one piece with the case portion and extends into the space and into engagement of the ferrite portion.

Abstract: A signal representative of a rectified current supplied by a current sensor is applied to the input of a correction circuit. The form of the input signal of the correction circuit, deformed with respect to the form of a theoretical signal, is corrected so as to reduce the errors of the rms or mean current values. The output signal of the correction circuit is equal to the input signal if the difference between the output signal and the input signal is lower than a limiting value. In the opposite case, the output signal is equal to a variation signal equal to the limiting value. Application to measuring devices and trip relays.

Abstract: A current sensor for detecting AC current through a load impedance of an electrical circuit. Sensor components are fabricated within a multilayer board so that a board can be made to comprise a plurality of independent sensors. The sensor includes a transformer circuit including a primary coil which is electrically coupled in series with the current path of the electrical circuit. This primary coil includes at least one current path element, in the form of a conductive strip constructed so as to add minimal resistance and inductance to the electrical circuit. The transformer secondary comprises at least a first electrically conductive coil inductively coupled to at least a part of the current path, and preferably a second electrically conductive coil inductively coupled to a second part of current path of the electrical circuit.

Abstract: A device is provided for measuring electric current having at least one probe sensitive to magnetic flux arranged in the air gap of an annular core through which at least one conductor of a current to be measured is intended to pass. A compensation winding is wound of the core and a measuring resistor is connected in series with the compensation winding. A circuit is provided for regulating the supply current to the compensation winding regardless of the direction of the current to be measured. The circuit is controlled by the output signal of the sensor which is sensitive to magnetic flux.

Abstract: A clamping mechanism for mounting a monitoring device to an electrical cable includes a core assembly formed by a plurality of laminations secured together and arranged in a generally rectangular configuration. A spring spanning the core is anchored at one end to the core at a point near the housing of the monitoring device and at the other end is attached to a bridging member affixed at the opposite end of the core near the housing. This allows the spring to expand less as it transverses the bridge in order to accommodate different power cable diameters.

Abstract: There is disclosed a methodology for measuring the magnetic field strengths of fundamental and harmonic frequencies associated with a.c. electrical current flows over a protracted period of time; and, particularly, in hostile environments. A preferable application calls for the determination of the field strengths associated with electrical currents flowing in a.c. power, distribution lines of utilities. The monitoring instrument is positioned in relation to the power lines to be monitored, typically at the base of a pole immediately adjacent the pole of the power line or on a power line supporting pole itself. In order to provide for long term, powering of the monitoring device, d.c. power is developed utilizing the a.c. power that is present. The conversion from a.c. to d.c. is effected at a distance sufficiently far from the monitoring instrument so as not to have any consequence on the readings that are being taken.

Abstract: Apparatus for electrical line communication that includes a coupler at each of two or more locations along a pair of lines, the coupler having capacitive circuits serially connected with an air-core transformer. The capacitive circuit is designed to resonate with the air-core transformer at a preselected frequency. A transmitter, receiver and modem may also be provided at each location. The apparatus incorporates a novel phase linear coupler which eliminates noise and is matched resistively to the characteristic impedance of the line at a preselected frequency. This apparatus therefore linearizes communication on the line and allows high speed data and voice communication over long distances.

Abstract: A method for measuring the current in an AC power transmission network, where a measurement quantity is obtained by means of a current transformer and digital samples are converted. To prevent faulty detection of the current due to a decaying DC component of the current transformer, two initial auxiliary measurement quantities that are normal to one another are formed from the digital samples by means of at least two FIR filters, and together with two additional auxiliary measurement quantities that are normal to each other, are used to produce a measured value corresponding to the amplitude of the current. The additional auxiliary measurement quantities are produced from samples formed from an older measurement quantity obtained earlier by a quarter period of the current to be measured. The differential angle is formed from the two measurement quantities. An output signal is generated from the two measured values in an evaluation device when the measured values exceed preset threshold values.