A current transformer (CT) for the purpose of, for example, current measurement, that uses a power line as a first coil and a second coil for measurement purposes, is further equipped with a third coil. Circuitry connected to the third coil is adapted to inject a known reference signal to the third coil of the CT. The injected reference signal, i.e., current, generates signals in the first and second coils of the CT. The signal generated in the second coil is compared using circuitry attached thereto to the reference signal. Based on the results, and the difference between the expected results and the actual results, updated calibration parameters are determined. These provide improved accuracy when using the CT, for example for measurement of the like of current or phase of the primary coil when measurements are adjusted using the newly determined calibration parameters.

A current sensor includes an excitation detection winding configured such that an excitation signal for exciting a second magnetic core is input, the excitation detection winding detects magnetic flux flowing through the second magnetic core and outputs a detection signal indicating a measurement-target current. The current sensor includes an auxiliary winding that detects the magnetic flux and outputs an auxiliary signal indicating the measurement-target current. The current sensor includes a feedback winding wound around first and second magnetic cores, the feedback winding being configured such that a signal generated from the detection signal is input, and the feedback winding being wound to cancel out magnetic flux of the first and second magnetic cores. The current sensor includes a circuit to output an output signal indicating a level of the measurement-target current by modifying a signal output from the feedback winding based on a correction signal generated from the auxiliary signal.

A dry high voltage (HV) instrument transformer in the form of a HV current transformer includes a core casing having a secondary winding, a top housing, a primary winding, and a dry bushing, wherein the core casing comprises an insulation containing an electrically insulating material made of PES nonwoven impregnated and cured with low viscosity epoxy. The dry HV instrument transformer in the form of a HV voltage transformer includes a bottom tank housing, a cast of a primary winding module with an embedded screen surrounding the primary winding, a field grading disc, and a core, wherein the cast of the primary winding module is made of an insulating composite containing an electrically insulating material made of PES nonwoven impregnated and cured with low viscosity epoxy.

A coil wire includes a core wire and a winding wire. The winding wire is wound around a circumference of the core wire so as to form a plurality of spirals. The coil wire satisfies one of: (i) an outer surface of the core wire is exposed, and a distance between the outer surface of the core wire and an inner circumferential surface of part of the winding wire is smaller than a thickness of a first insulating film coated on the winding wire; or (ii) the outer surface of the core wire is coated by a second insulating film, and a distance between an outer surface of the second insulating film and the inner circumferential surface of part of the winding wire is smaller than a thickness of a thicker one of the first insulating film and the second insulating film.

The present disclosure relates to a bushing-type current transformer, and a switchboard having the bushing-type current transformer applied thereto, comprising: a binding plate; a bushing including a first fixing part and a second fixing part located on each of the two sides of the binding plate and each providing an accommodating space; and a current transformer fitted and fixed to the first fixing part of the bushing.

The present disclosure relates to a bushing-type current transformer, and a switchboard having the bushing-type current transformer applied thereto, comprising: a binding plate; a bushing including a first fixing part and a second fixing part located on each of the two sides of the binding plate and each providing an accommodating space; and a current transformer fitted and fixed to the first fixing part of the bushing.

A current transformer includes a first housing including a first handle portion and a first distal portion, a second housing including a second handle portion and a second distal portion, a first core mounted in the first distal portion, a second core mounted in the second distal portion, and a lock attached to the second handle portion at a pivot point, wherein the first housing is rotationally coupled to the second housing about a fulcrum point and the lock is rotatable about the pivot point into a closed position wherein the lock engages the first handle portion and prevents the first handle portion and the second handle portion from rotating towards each other.

A current transformer includes a housing including generally cylindrical outer and inner walls defining an internal chamber, a front face enclosing one end of the internal chamber, a base, and a central opening defined by the inner wall. A generally toroidal current transformer core is disposed within the internal chamber. A secondary wiring is disposed about the transformer core and is configured to generate a current in response to magnetic flux in the transformer core. A pin housing is disposed on the front face of the housing adjacent the base. The pin housing has electrically conductive pins. A test wire passes through the central opening. The secondary wiring is electrically connected to a first pair of the pins and the test wire is electrically connected to a second pair of the pins.

A current transformer includes a housing including generally cylindrical outer and inner walls defining an internal chamber, a front face enclosing one end of the internal chamber, a base, and a central opening defined by the inner wall. A generally toroidal current transformer core is disposed within the internal chamber. A secondary wiring is disposed about the transformer core and is configured to generate a current in response to magnetic flux in the transformer core. A pin housing is disposed on the front face of the housing adjacent the base. The pin housing has electrically conductive pins. A test wire passes through the central opening. The secondary wiring is electrically connected to a first pair of the pins and the test wire is electrically connected to a second pair of the pins.

The present invention refers to HV apparatus, in particular a HV dry current transformer, insulated with an insulating gel, or a voltage transformer, insulated with an insulating gel. The dry HV current transformer comprises at least two electrically conductive elements i.e. a head transformer cover, a head housing base, a core casing and a primary conductor. In the dry HV current transformer at least one of the electrically conductive elements has a coating made of solid insulating material separating the surface of the conductive elements from the insulating gel and adapted for limiting the electron emission from the conductive elements into the insulating gel. The voltage transformer comprises a bottom external housing, a bottom support flange, a core. In the voltage transformer at least one of the electrically conductive elements has a coating made of solid insulating material separating the surface of the conductive elements from the insulating gel and adapted for limiting the electron emission from the conductive elements into the insulating gel.