Abstract: A server and method detects a power transformer. The server reads power transformer data from a data converter and determines if work state of a power transformer needs to be changed from based on the power transformer data. An alert message is generated by the server and sent to an alarm computer in response to a determination that the work state of the power transformer needs to be changed. The server saves the power transformer data into a database system.

Abstract: An apparatus for testing a high-voltage equipment transformer or inductor has a filter transformer having a primary side connectable to line and a secondary side and a grounded electrostatic shield between the primary and secondary sides. A static frequency converter has a plurality of inputs connected to the filter-transformer outputs and a plurality of outputs. Respective capacitors each have one side connected to a respective one of the converter outputs and an opposite side connected star-fashion to a common ground. A matching transformer has a plurality of inputs connected to the capacitors and a plurality of outputs connectable to the transformer or inductor to be tested.

Abstract: A protective system far a power transformer having a neutral line connected to ground where large currents can flow in the neutral line due to electro-magnetic disturbances. The system includes circuitry for: (a) sensing the current level in the neutral line and whether it exceeds a predetermined threshold for a predetermined period; and (b) sensing and processing the harmonic content of the load current and determining the existence of certain relationships of the “even” and “odd” harmonics. Signals, including alarms, indicative of excessive conditions are produced. The system may also include circuitry for sensing the load current level and generating a signal alarm if the load level is above a giver) value when the harmonics and the DC current have values in excess of certain predetermined values.

Abstract: A high-voltage transformer for providing an alternating voltage in the kV range, comprising at least one secondary winding wound on a coil carrying body surrounding a transformer core, and an insulation housing encapsulating the secondary winding is provided to electrically insulate the secondary winding. Said insulation housing is walled by the coil carrying body carrying the secondary winding and by an enveloping body made of plastic and enveloping the secondary winding so that an annular gap is formed, wherein the annular gap between the secondary winding and the enveloping body is filled with an insulating fluid. The annular gap has a gap width of less than or equal to 20 mm viewed in the cross-section, and the enveloping body has a wall thickness of less than or equal to 20 mm, wherein the plastic is polypropylene, and a separate expansion volume is not provided for the insulating fluid.

Abstract: An improved internturn short circuit detection device of transformer via differential voltage comprises a single-phase transformer (TM). The single-phase transformer (TM) comprises a high-voltage coil (K) and a low-voltage coil (N). A voltage transformer (PT) is positioned at the high voltage side of the single-phase transformer (TM). Two branches of a tap (K1) of the high-voltage coil (K) are connected with the input of a first converter (Q?), and a first voltage (U1?) is obtained. The secondary side of the voltage transformer (PT) is connected with the input of a second converter (Q), and a second voltage (U1) is obtained, and the first voltage (U1?) and the second voltage (U1) are compared, and when the voltage difference is above a predetermined primary threshold value, an interturn short circuit failure of the primary side is determined.

Abstract: A method of providing transformer rating information. The method includes the steps of: (a) determining k-factors for eddy losses and stray losses related to a transformer; and (b) providing a revised rating for the transformer using the k-factors determined at step (a).

Abstract: A current transformer assembly for use in an electrical monitoring system is described herein. The current transformer assembly includes a housing including a plurality of shielding members that at least partially define a cavity therein. The housing further includes an inner surface that defines an opening that extends therethough. A first current transformer is positioned within the housing. A second current transformer is positioned within the housing and is spaced a distance from the first current transformer to facilitate reducing electronic noise interference between the first and second current transformers.

Abstract: A detecting station of a winding product and a method for detecting an inter-turn short circuit are provided. The method includes following steps. First, a high voltage pulse is input to two ends of a winding of a winding product. Next, a voltage value of an electrifying process of the winding is extracted for generating an extracting data. Finally, a time-frequency converting operation is performed to the extracting data, and a time-frequency analysis information is generated for indicating whether or not the inter-turn short circuit is occurred in the winding.

Abstract: The invention relates to a device for testing transformers, having a static frequency converter (2). The static frequency converter (2) comprises a plurality of outlets (21, 22, 23), which are connected to a filter device (6). The filter device (6) also comprises a plurality of outlets (31, 32, 33), which are connected to a matching transformer (8), and wherein the matching transformer (8) is connected to the transformer (15) intended for testing. The filter device (6) is a filter transformer (11).

Abstract: A device for diagnosing operation status of an external control unit includes an insulation transformer, a signal generating unit, a first switch circuit constituting the external control unit connected to the secondary side of the insulation transformer, a second switch circuit connected to the intermediate tap of the primary winding of the insulation transformer, and a second switch circuit including a switch and a resistance, a detection circuit for detecting operation status of the external control unit, and a current measuring unit connected to the second switch circuit. The detection circuit includes a diode and a resistance and is connected to the secondary side of the insulation transformer. The current measuring unit measures a current flowing through the switch and/or the resistance and uses the measured current to diagnose the operation status of the external control unit.

Abstract: A current sensing assembly is provided for sensing the current travelling through a current carrying member of a pad mount distribution transformer in a meter network. A current sensor includes a slot having an open end that receives the current carrying member. The sensor includes a conductive coil disposed adjacent the slot that generates an output signal indicating a sensed current level. A retainer member includes a retainer wall that is configured to be inserted into the open end of the slot so as to define a receptacle that captures the current carrying member therein.

Abstract: A method of testing a power system component is disclosed. The method includes coupling a test set to the power system component and displaying a test form on a display integral with the test set. The method also comprises inputting at least a first test control parameter into the test form using an interface integral with the test set. The method also comprises stimulating the power system component using the test set to produce a first response of the power system component, wherein the stimulating is performed based at least in part on the first test control parameter. The method also comprises displaying a first test result in the test form on the display, wherein the first test result is based on the first response.

Abstract: A method, device and computer program product for determining at least one property of a current (Ip) running through the primary winding of a transformer operating in saturation using an unreliable detected current (Is) running through the secondary winding of the transformer. According to the invention a first reliable extreme point (EP1) of a cycle of the current in the secondary winding is detected and compared with an absolute time reference. Based on the comparison a first property of the current running through the primary winding in the form of the phase angle is then determined.

Abstract: Example methods include calculating a first number of turns of a shield winding included in an energy transfer element of a power supply. A first number of turns of the shield winding is calculated for the power supply to have a low noise current in an input conductor of the power supply. The method then includes increasing the first number of turns to a second number of turns. The power supply is then operated, which generates a first voltage waveform of a voltage between the input conductor and an output conductor of the power supply. An impedance is then inserted between the shield winding and the input conductor. The noise current is reduced by adjusting a value of the impedance until a second voltage waveform of the voltage between the input conductor and the output conductor reverses polarity to be the opposite of a polarity of the first voltage waveform.

Abstract: A system is used with a plurality of modules, each module requiring galvanic isolation from the other modules. Galvanic isolators are employed, each having an input and an output, the output galvanically isolated from the input, the output responsive to the input according to a response characteristic of the isolator. Each module has, a respective first isolator and a respective second isolator. The input of each respective first isolator and each respective second isolator for each module is disposed controllably to receive an activation signal from the module indicative of a module fault to be annunciated or to receive a test signal from the module, the test signal being smaller than the activation signal. The outputs of the respective first isolators are aggregated to a first node and the outputs of the respective second isolators are aggregated to a second node.

Abstract: A diagnostic method for determining deformations in a transformer winding including the steps of representing the winding as a lumped parameter circuit and dividing the winding into at least two sections; generating a first set of fingerprint values based on capacitive values of the winding; the first set of finger print values indicating the location and extent of radial deformation in the winding; generating a second set of fingerprint values based on capacitive values of the winding; the second set of finger prints indicating the location and extent of axial deformation in the winding and determining the location and extent of radial or axial deformation or combination of both radial and axial deformation in the winding by comparing the measured values with the first set and second set of finger print values.

Abstract: A method and system for obtaining the characteristic impedance of an electrical winding by measuring the input and output voltages and the currents within a winding across a low frequency range, and applying transmission line properties to model the winding. The characteristic impedance (Zc) is directly proportional to the capacitance of the winding, and is independent of external circuits. Thus any changes to Zc will reflect movements of the winding that would affect the capacitance. Because Zc has a smooth and robust monotonical relationship with frequency of the applied signal, the resulting curve is exponential in shape. A relative comparison between Zc curves will provide a clear indication of the overall axial or radial winding movements, or winding faults, which can be used to assess the overall health of the winding.

Abstract: The invention relates to a testing drive for examining a stepping switch or a tap changer as part of transformer tests, wherein the testing drive has a servomotor that acts on an adapter by means of a gear train, wherein the adapter can be connected to the upper gear stage of the stepping switch or tap changer during the tests.

Abstract: A circuit system includes a first circuit for receiving an input signal, a second circuit for interfacing with a user, a signal path connecting the first circuit to the second circuit, the signal path including a first isolator and a second isolator serially connected to the first isolator, and a capacitance detector that detects a change in a combined capacitance of the first and second isolators as an indicator of a breakdown of one of the first and second isolators.

Abstract: A method and apparatus for testing a transformer. A controller generates a switching signal and supplies the switching signal to a solid state switch in circuit with a test load of known magnitude, switching the solid state switch to place the test load in circuit with the transformer. A signal through or across the transformer is then measured. Methods and apparatus for testing a transformer comprise the controller and solid state switch placing a series of test loads of different known magnitudes in circuit with the transformer from the lowest magnitude to the highest, from the highest to the lowest, or both. Additionally, a test load array comprises a plurality of power resistors, a heat sink for accommodating the plurality of power resistors, and a material providing electrical insulation of the power resistors from the heat sink and thermal conductivity between the power resistors and the heat sink.

Abstract: An apparatus for testing a high-voltage equipment transformer or inductor has a filter transformer having a primary side connectable to line and a secondary side and a grounded electrostatic shield between the primary and secondary sides. A static frequency converter has a plurality of inputs connected to the filter-transformer outputs and a plurality of outputs. Respective capacitors each have one side connected to a respective one of the converter outputs and an opposite side connected star-fashion to a common ground. A matching transformer has a plurality of inputs connected to the capacitors and a plurality of outputs connectable to the transformer or inductor to be tested.

Abstract: A method includes calculating a number of turns of a shield winding included in an energy transfer element of a power supply, where the calculating is to have a low noise current in an input conductor of the power supply. The method further includes: increasing the number of turns for the shield winding; operating the power supply; and adjusting a value of a shield impedance to substantially reduce the noise current. An apparatus includes a power supply having an energy transfer element and a shield impedance. The energy transfer element includes a shield winding having an end terminated externally to the energy transfer element. The shield impedance is coupled between the externally terminated end of the shield winding and an input conductor of the power supply, where the shield impedance has a non-zero finite impedance value to substantially reduce a noise current in the input conductor.

Abstract: A method and a device for determining a humidity content of an insulation of a transformer, the insulation having a liquid. At least one dielectric property of the insulation is measured, an uncorrected humidity content of the insulation and a conductivity of a liquid which is included in the insulation is derived from a model of the insulation, said model being chosen depending on the measured dielectric property of the insulation, and the humidity content of the insulation is corrected by means of the conductivity.

Abstract: Disclosed herein is a Fourier transform-based phasor estimation method and apparatus capable of eliminating the influence of exponentially decaying DC offsets. According to a Fourier transform-based phasor estimation method according to an embodiment of the present invention, an input signal is sampled, and samples of one-cycle data of the input signal are separated into at least two sample groups. A Discrete Fourier Transform (DFT) is performed on each of the sample groups. A DC offset included in the input signal is calculated on a basis of results of the DFT on each of the sample groups, and an error caused by the DC offset is calculated using the calculated DC offset. A phasor of a fundamental frequency component included in the input signal is estimated by eliminating the calculated error, caused by the DC offset, from the results of the DFT on the input signal.

Abstract: An improved internturn short circuit detection device of transformer via differential voltage comprises a single-phase transformer (TM). The single-phase transformer (TM) comprises a high-voltage coil (K) and a low-voltage coil (N). A voltage transformer (PT) is positioned at the high voltage side of the single-phase transformer (TM). Two branches of a tap (K1) of the high-voltage coil (K) are connected with the input of a first converter (Q?), and a first voltage (U1?) is obtained. The secondary side of the voltage transformer (PT) is connected with the input of a second converter (Q), and a second voltage (U1) is obtained, and the first voltage (U1?) and the second voltage (U1) are compared, and when the voltage difference is above a predetermined primary threshold value, an interturn short circuit failure of the primary side is determined.

Abstract: A device and method for dynamically determining an impedance of a network is disclosed. The device includes at least a processing system for measuring a network voltage and network current when said network is determined to be in a first state, measuring a network voltage when said network is determined to be in a second state, estimating said impedance value dependent upon said measured voltages and current, adapting said estimated impedance based on at least one prior impedance value and storing at least said adapted impedance.

Abstract: A radio frequency (RF) sensor that measures RF current includes a substrate that has an inner perimeter that defines an aperture. A conductor extends through the aperture. Sensor pads are arranged on the aperture and are connected to form two sensor loops. The loops generate an electrical signal that represents RF current flow through the center conductor. Additionally, a plurality of circular conductive rings may be included in the RF sensor to generate a signal representing the voltage of the conductor.

Abstract: The invention provides a property monitoring apparatus comprising a test current output circuit capable of varying an output current, a test current value computing means for computing a current value of a test current output from the test current output circuit, a test current control means for performing feedback control of the test current value computed via the test current value computing means to a target value, a measurement current detection circuit for measuring an output current value of the current transformer or the voltage transformer when the test current controlled to the target value via the test current control means is supplied, for storing a relationship between the output current value of the current transformer or the voltage transformer and the test current value for each target value by varying the target value of the test current via a predetermined pattern, and computing a correction coefficient for correcting a property of the current transformer or the voltage transformer based on t

Abstract: A method, device and computer program product for determining the change in insulating ability of the insulation provided between two objects of an inductively operating element, where at least one of the objects is a winding. The device includes an analyzing unit, which obtains a first frequency spectrum associated with a frequency response to a signal of varying frequency, where the signal of varying frequency can be applied to a first object of the inductively operating element and the frequency response is obtainable from a second object of the inductively operating element, compares the obtained first frequency spectrum with a second reference frequency spectrum, detects a peak in the obtained first frequency spectrum that does not appear in the second reference frequency spectrum, analyzes the shape of the detected peak, and determines the change in insulating ability based on the analyzed shape.

Abstract: A device and method for monitoring the condition of an electrical power transformer in an electrical power grid synchronously measures current and voltage data at both a high voltage side of the transformer and a low-voltage side of the transformer and computes from this measured data corresponding transformer impedance data. These measurements and computations are repeated continuously in real time at a rates up to 30 Hz to provide a sequence of real-time transformer impedance data. An alarm signal is generated if a mean of the sequence of real-time transformer impedance data changes significantly.

Abstract: Disclosed is an insulation deterioration detection device that can accurately detect insulation deterioration in multiple motors by a simple circuit configuration. When detecting insulation deterioration, one end A of a smoothing capacitor is connected via a first switch to ground, and the other end B is connected via a second switch to motor windings; in this condition, link voltage is measured by a voltage measuring circuit provided in a converter unit, and the measured link voltage value is transmitted to a microcomputer in each inverter unit via serial communication. Current flowing via motor insulation resistance Z1, Z2 is measured by a current measuring circuit provided in each inverter unit, and the microcomputer calculates the value of the insulation resistance Z1, Z2 from the link voltage value and the current value.

Abstract: This invention concerns a system for monitoring a transformer which comprises multiple terminals. The system includes multiple measuring devices and a transformer monitoring device. Each measuring device is arranged adjacently to a terminal of the transformer. Each measuring device includes a housing, a processing unit, a terminal to connect the processing unit to a sensing means to sense an electrical magnitude at the terminal of the transformer, and a data transmission terminal to transmit data between the processing unit and the transformer monitoring device. The transformer monitoring device, which is connected to the multiple measuring devices, is designed to determine, from a combination of the data from the multiple measuring devices, a present state of the transformer.

Abstract: The present invention relates to low voltage electrical equipment testing technique, more particularly, to a low voltage and intense current phase-controlled switching on equipment, comprising: a frame, at least an vacuum arc extinguish chamber, at least a permanent magnet control device and at least a intelligent phase choosing controlled module, with the vacuum arc extinguish chamber and the permanent magnet controlled device mounted on the frame, wherein the vacuum arc extinguish chamber comprises at least a movable contact and a isolated pull rods connected to the movable contact, and the permanent magnet controlled device comprises electromagnetic coils, movable iron cores and output shafts connected to the movable iron cores, and a transmission system is arranged to connect to the isolated pull rod and the output shaft, with the intelligent phase choosing controlled module electrically connected to the electromagnetic coils of the permanent magnet controlled device.

Abstract: A current transformer comprises a magnetic core having a closed central opening, at least two conductors extending through the central opening and positioned symmetrically within the magnetic core, and at least one set of winding turns wound around the core in a balanced configuration with respect to the at least two conductors.

Abstract: The invention relates to a device for testing transformers, having a static frequency converter (2). The static frequency converter (2) comprises a plurality of outlets (21, 22, 23), which are connected to a filter device (6). The filter device (6) also comprises a plurality of outlets (31, 32, 33), which are connected to a matching transformer (8), and wherein the matching transformer (8) is connected to the transformer (15) intended for testing. The filter device (6) is a filter transformer (11).

Abstract: A method for fault detection in a power transformer/autotransformer and/or interconnected power lines, which are within the zone protected by the differential protection, and particularly suitable for detecting turn-to-turn faults in power transformer/autotransformer windings. All individual instantaneous phase currents of the protected object are measured, individual phase currents as fundamental frequency phasors are calculated, the contributions of the individual protected object sides negative sequence currents to the total negative sequence differential current are calculated by compensating for the phase shift of an eventual power transformer within the protected zone, the relative positions of the compensated individual sides negative sequence currents in the complex plane are compared, in order to determine whether the source of the negative sequence currents, i.e.

Abstract: A method and system for measuring and compensating for a leakage current in a high voltage transformer. Such a method and/or system include the use of a primary winding and a secondary winding, which can be provided on a core of a soft-magnetic material. A current transformer can be placed about the leads to both the terminals of the primary winding. The current transformer can be utilized to reliably measure the leakage current flowing from the secondary winding to the primary winding through one or more amplifiers to a ground terminal. The leakage current flows back to the transformer secondary winding through a low-side current sense resistor. The total current monitor signal can be generated by the low-side current sense resistor and the leakage current measured by the current transformer is vector-subtracted from the total current monitor signal. The result is a current monitor signal fully representative of the high voltage transformer's actual load current.

Abstract: A method and apparatus for characterizing a three phase transformer (3) using a single phase power supply (1). Pairs of input terminals (H0-H3) of the transformer are sequentially energized for each energization and the voltage between pairs of output terminals (x0-x3) of the transformer are measured. Measured voltages are processed in order to characterize the winding configuration of the transformer. Either simultaneously or subsequently the presence of neutrals on the primary and/or secondary side of the transformer are identified to enable the winding configuration to be further characterized. Subsequently any phase displacement of the transformer is determined.

Abstract: This invention relates to a nulling current transformer. More particularly, this invention relates to a nulling current transformer for accurately detecting current and giving an improved response, accuracy and stability using toroidal current transformer technology along with active components. This invention finds particular application in switchgear devices such as residual current devices and metering operations. The nulling current transformer is implemented in a closed magnetic core having at least one primary winding inductively coupled thereto. A secondary winding is also inductively coupled to said magnetic core, the secondary winding being responsive to any magnetic flux generated in said magnetic core. A separate tertiary winding is also inductively coupled to said magnetic core, the tertiary winding being responsive to any magnetic flux generated in the magnetic core.

Abstract: A method of testing a power system component is disclosed. The method comprises coupling a test set to the power system component and displaying a test form on a display integral with the test set. The method also comprises inputting at least a first test control parameter into the test form using an interface integral with the test set. The method also comprises stimulating the power system component using the test set to produce a first response of the power system component, wherein the stimulating is performed based at least in part on the first test control parameter. The method also comprises displaying a first test result in the test form on the display, wherein the first test result is based on the first response.

Abstract: Methods and apparatus for analyzing electrical insulation of an electrical machine are provided. The method includes receiving a first signal that includes a plurality of partial discharge pulses from the electrical machine and a plurality of noise pulses, receiving other signals that includes information relative to at least one process parameter associated with the electrical machine, determining the plurality of partial discharge pulses from the plurality of noise pulses, identifying characteristics of the plurality of partial discharge pulses relating to the location and character of partial discharges in the electrical machine, and determining a condition of the electrical insulation using the identified characteristics and the received information relative to at least one process parameter.

Abstract: A device is provided for monitoring through-fault current in an electric transformer on an electrical power system. The device generally includes a magnitude calculator for calculating the magnitude of current (e.g., a root means square value of current or magnitude of a fundamental of current) based on the current through the electric transformer. A through-fault energy calculator is further provided which is coupled to the magnitude calculator for calculating a through-fault energy value based on the magnitude of current or the calculated current through the transformer. An accumulator is coupled to the through-fault energy calculator for accumulating a plurality of through-fault energy values, and an alarm coupled to the accumulator for indicating that the accumulated through-fault energy values exceed a selected threshold.

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: An inverter circuit includes a power supply which outputs an alternating current voltage, an inverter transformer having one primary coil connected to an output terminal of the power supply and pairs of secondary coils which supply an alternating current high voltage, induced by the one primary coil, to pairs of discharge tubes and a plurality of balance transformers having primary coils serially connected between respective pairs of the pairs of secondary coils of the inverter transformer, and having secondary coils corresponding to the primary coils of the plurality of balance transformers, wherein the secondary coils of the plurality of balance transformers are serially connected to form a loop.

Abstract: A noncontact voltage sensor is housed in a container comprising a container body having an opening on one side and an insulation cover body for sealing the opening. A plate type electrode insulated from a ground is housed in the container. The cover body side is opposed to a charging part of such as cables of an aerial line. A voltage is induced in the plate type electrode due to aerial electric charges between the charging part and the plate type electrode in the container, allowing detection of the voltage in the charging part. The cover body of the noncontact sensor is made of a fluorine containing resin such as an ethylene tetrafluoride resin to prevent a water film from forming on the outside surface of the insulation cover body and causing deterioration of the detection.

Abstract: Method and device for measuring a dielectric response of an electrical insulating system, wherein a first measurement result is determined by a frequency domain method and a second measurement result is determined by a time domain method, whereupon the first measurement result and the second measurement result are combined to form an overall measurement result as the dielectric response. Standard types of measurement methods, for example the FDS and PDC methods, may be used as measurement methods for the frequency domain and the time domain.

Abstract: A method of supervising the operation of a plurality of current transformers arranged in respective groups and connected to a protection relay forming part of a three-phase electrical power system includes determining a current ratio at an output of each group of current transformers, comparing each current ratio with a predetermined high ratio, comparing each current ratio with a predetermined low ratio, and generating a fault indication when the current ratio at one location exceeds the predetermined high ratio and the current ratio at the or each other location remains below the predetermined low ratio.

Abstract: A current transformer test method implemented using a test device, is useful to verify proper CT installation and operation, and does not rely on the generator (or other system) to be in a state of relatively high assembly. The test device allows a current transformer to be tested by supplying an alternating current (AC) signal to a primary winding of the current transformer to thereby induce an AC signal in a secondary winding of the current transformer. The test device is used to simultaneously monitor the phases of the supplied AC signal and the induced AC signal so that a determination can be made as to whether the current transformer secondary winding is properly installed relative to the current transformer primary winding, and to simultaneously monitor the current magnitudes of the supplied AC signal and the induced AC signal so that the turns ratio of the current transformer can be determined.

Abstract: Disclosed is an apparatus and method for detecting a loss of a current transformer connection coupling a protective relay to a power system element of a three-phase power system and providing a plurality of secondary current waveforms of the three-phase power system to the protective relay. The apparatus includes a first logic circuit and a second logic configured to provide corresponding first and second binary signals in response to respective comparisons of calculated current value(s) of a plurality of like-phase digitized current sample streams to respective threshold values. The apparatus also includes a set reset flip-flop having a set input adapted to receive the first and second binary signals to provide a third binary signal. The third binary signal indicates loss of a current transformer connection when the set input is asserted and indicates no loss of a current transformer connection when the reset input is asserted.

Abstract: An apparatus for sensing the current in a power line of a power system and systems incorporating the apparatus are disclosed. The apparatus may comprise an enclosure providing a window operable to permit the passage of the power line therethrough. The apparatus may further comprise an active current transformer set within the enclosure and operative to produce a scaled version of the current. The apparatus may further comprise an amplifier coupled with the active current transformer and operative to reduce the phase shift and ratio error between the current and the scaled version of the current. The apparatus may further comprise a powering current transformer set within the enclosure and operative to receive power from the power line on a primary winding and deliver power on a secondary winding.