A gapped resonant current transformer that has a pre-determined gap in a split-core. The invention eliminates the need for a magnetic flux shunt between the primary and secondary windings. Further, the sensitivity to the clamping force holding the two halves of the split-core is reduced as well as temperature effects on the core. Finally, excess heat is removed from overload (saturation) by circulating power back into the line.

Electrical current transducer (2) of a closed-loop type for measuring a primary current (I.sub.P) flowing in a primary conductor (1), comprising a fluxgate measuring head (7) and an electronic circuit (16) including a microprocessor (18) for digital signal processing. The measuring head includes a secondary coil (6) and a fluxgate detector (4) comprising an excitation coil and a magnetic material core. The electronic circuit comprises an excitation coil drive circuit (14) configured to generate an alternating excitation voltage to supply the excitation coil with an alternating excitation current (I.sub.fx), the secondary coil (6) connected in a feedback loop (12) of the electronic circuit to the excitation coil drive circuit (14), the electronic circuit further comprising a ripple compensation circuit (26, 28) configured to compensate for a ripple signal generated by the alternating excitation voltage.

In order to demagnetize a transformer core (13, 23) a demagnetization device (40) is detachably connected to a primary side (11) of a transformer (10, 20). An alternating signal is fed to the primary side (11) in order to demagnetize the transformer (10, 20).

In order to demagnetize a transformer core (13, 23) a demagnetization device (40) is detachably connected to a primary side (11) of a transformer (10, 20). An alternating signal is fed to the primary side (11) in order to demagnetize the transformer (10, 20).

A circuit for sampling current includes a current transformer, a reset resistor, a diode, a sampling switch, and a current sampling resistor. The current transformer includes a primary winding and a secondary winding. The reset resistor and two ends of the secondary winding are connected in parallel. The sampling switch, the diode, and the current sampling resistor are connected in series and then connected to two ends of the reset resistor in parallel. The primary winding is for connecting to a circuit to be sampled. When a current flows through the primary winding and the circuit to be sampled and the sampling switch is turned on at a negative AC half cycle, the circuit for sampling current samples the current flowing through the circuit to be sampled.

A circuit for sampling current includes a current transformer, a reset resistor, a diode, a sampling switch, and a current sampling resistor. The current transformer includes a primary winding and a secondary winding. The reset resistor and two ends of the secondary winding are connected in parallel. The sampling switch, the diode, and the current sampling resistor are connected in series and then connected to two ends of the reset resistor in parallel. The primary winding is for connecting to a circuit to be sampled. When a current flows through the primary winding and the circuit to be sampled and the sampling switch is turned on at a negative AC half cycle, the circuit for sampling current samples the current flowing through the circuit to be sampled.

Provided is a plug for use as a disconnector for current transformers. Two types of short circuits are provided in the plug. A first short circuit is used for diverting overvoltages by short-circuiting the electrical contacts in the plug. A second short circuit is provided for short-circuiting electrical contacts in the plug when the plug is not contacted. The short circuits are designed in such a way that the first short circuit is used as a fuse when the second short circuit fails.

Provided is a plug for use as a disconnector for current transformers. Two types of short circuits are provided in the plug. A first short circuit is used for diverting overvoltages by short-circuiting the electrical contacts in the plug. A second short circuit is provided for short-circuiting electrical contacts in the plug when the plug is not contacted. The short circuits are designed in such a way that the first short circuit is used as a fuse when the second short circuit fails.

A current transformer and a direct current source based on a current transformer are disclosed. In an embodiment, the current transformer includes two output ends; a first winding and a second winding connected in series between the two output ends; a main core; a bypass core, arranged to be magnetically coupled with the main core. The first winding is wound on a part of the main core and a part of the bypass core, and the second winding is wound on apart of the bypass core. In an embodiment, the current transformer also includes a high-frequency bypass, connected in parallel with the first winding, and used to filter a high-frequency signal. The high-frequency bypass provides a low-impedance path for a high-frequency signal in a primary conductor under measurement, such that the bypass core with the second winding presents less obstruction to the main core, thereby reducing heating.

A power cable assembly includes a power cable extending between a first end and a second end having a hot conductor and a neutral conductor. The power cable assembly includes a circuit protection device along the power cable between the first and second ends. The circuit protection device has a ground fault circuit interrupt (GFCI) device configured to sense a current difference on the hot and neutral conductors to initiate a triggering event. The circuit protection device has a high-power relay device connected to the GFCI device. The high-power relay device is connected to the hot conductor and is configured to open the hot line when the triggering event is initiated by the GFCI device.