When a fault in an energized power distribution cable flashes over, the surge draws charge from both sides of the line. The fault thus produces a pair of current surges that propagate from the fault in opposite directions along the line. These oppositely-directed current surges create pulsed electromagnetic fields of different directions which, in turn, induce voltages of different polarities in a receiving antenna positioned along the line. The polarity of the first such voltage pulse induced in the antenna indicates the direction from the antenna to the fault. In one embodiment, the line is repeatedly "thumped," causing flashovers to recur at the fault. By moving the antenna along the line until the polarity of the initial received pulse inverts, the precise location of the fault can be determined. In another embodiment, direction-indicating fault current indicators according to the present invention are permanently placed at numerous locations in an operating AC power distribution system, in anticipation of a fault. When a fault occurs, the polarity of the first received electromagnetic fault pulse at each device indicates the respective direction from the device to the fault.

Method and apparatus for pin-pointing faults in electric power lines

A power line communications filter has an input terminal, an output terminal, and a common terminal. A transformer has primary and secondary windings, each having one end connected to the respective input and output terminals, and another end connected to a common connection. The windings are wound on a high permeability magnetic core in such a way as to promote flux leakage and with a winding polarity such that flux cancellation occurs when current flows through the windings in series. A capacitor is connected between the common terminal and the common connection of the primary and secondary windings. The capacitor has a large impedance at low frequencies such that low frequency current flows through both the windings in series and flux cancellation occurs.

Non-saturating, flux cancelling diplex filter for power line communications

An insulation state detecting device includes a positive side input terminal connected to a positive side power line of a high voltage DC power supply, a negative side input terminal connected to a negative side power line of the high voltage DC power supply, a ground electrode, a controller that detects insulation states between the positive side power line and the negative side power line and the ground electrode based on a charge voltage of a flying capacitor, and an equilibrium state forming circuit that promotes an operation of transiting a charge state of a positive side electrostatic capacitance between the positive side power line and the ground electrode and a charge state of a negative side electrostatic capacitance between the negative side power line and the ground electrode from non-equilibrium states to equilibrium states.

Insulation state detecting device

A method and system diagnose and measure partial discharge on-line in a power transmission system. A first wideband directional clamp-on detector detects pulses corresponding to partial discharge transmitted via a transmission line. A second wideband directional detector detects pulses corresponding to partial discharge output from at least one bushing tap of a high voltage device. The first and second pulses are nulled and then added and/or subtracted, and a diagnostic and measurement system analyzes the results to determine whether the high voltage device and/or an external source produces partial discharge, determine the type of discharge, and measure the level of discharge. For analysis of internal partial discharge, external partial discharges are rejected. The diagnostic and measurement system simultaneously analyzes multiple phases of the output of the high voltage device, while the device is energized. A method and system also diagnose and measure partial discharge off-line in a high voltage device. An output from at least one bushing tap of the high voltage device is split into AC and high frequency components which are synchrod in a diagnostic and measurement system. The diagnostic and measurement system simultaneously analyzes multiple phases of the output of the high voltage device.

System and method for diagnosing and measuring partial discharge

According to the invention, there is provided an apparatus for monitoring degradation of insulation of an electrical installation that can constantly monitor its electric equipments and cables for degradation of insulation under hot-line conditions. Said apparatus comprises: a first sensor for detecting a progressive wave generated by a partial discharge taking place at a location where the insulation is degraded in the power transmission paths; a second sensor for detecting the phase of said generated progressive wave as well as external noise; a third sensor for detecting a reference signal for determining the direction of said progressive wave; and a measurement section for processing the signals from the first sensor, second sensor and third sensor; wherein said measurement section determines existence or non-existence of degraded insulation by comparing the phases of the signals from the first sensor and the third sensor when it detects a progressive wave generated at a location where degradation of insulation of an electric cable or an electric equipment is taking place, and it also determines if the signal from each of the second sensor represents an external noise or degraded insulation and detects the phase of degradation if degraded insulation is involved.

Apparatus for monitoring degradation of insulation of electrical installation

A method of and apparatus for the detection of insulation deterioration in an electrical power supply system utilizes the detection of a progressive wave generated by a corona discharge or partial discharge due to such insulation deterioration. Sensing of said progressive wave may be effected by an apparatus comprising: a first coil having two primary windings, wound with the same number of turns and in the same direction, and a secondary winding, the primary and secondary windings being wound on a core whose magnetomotive force and magnetic flux density are roughly proportional to each other; a second coil composed of a primary winding and a secondary winding both wound on a core whose magnetomotive force and magnetic flux density are roughly proportional to each other; and an impedance circuit. Determination of the position of insulation deterioration may be effected by comparing the phase of the progressive wave at a reference point in a common bus with the phase of the progressive wave in each of the power supply lines branching off from the common bus.

Method of and apparatus for assessing insulation conditions

A signal discriminator adapted to discriminate a signal with a specific frequency out of a current composed of two or more superimposed components with different frequencies. One type of signal discriminator disclosed includes a first coil composed of a primary and a secondary winding wound with the same number of turns and in the same direction on a core whose magnetomotive force and magnetic flux density are roughly proportional to each other, a second coil composed of a primary and a secondary winding wound on a core whose magnetomotive force and magnetic flux density are roughly proportional to each other, and an impedance circuit. Another type of signal discriminator is composed of a first winding with short-circuited ends and a second winding for detecting signals both wound on an annular core having an approximately linear BH characteristic with the magnetomotive force and the magnetic flux density roughly proportional to each other. Also disclosed is a method of obtaining the high frequency component of the signals transmitted through a signal line which is passed through said annular core.

Apparatus for and method of discriminating signals

A method of and an apparatus for judging whether a signal of insulating deterioration generated by any deterioration in insulation of an object of measurement is superimposed on the current flowing through this object. Disclosed first is a method of ascertaining the power supply line in a power supply system with two or more power supply lines whose insulating performance has deteriorated by detecting the progressive wave generated by the corona discharge or the partial discharge generated in the section concerned of the line by any deterioration in insulation thereof. Secondly, a method is disclosed of locating the position where the progressive wave has been generated by comparing the phase of the progressive wave at a reference point provided in a common line with each of the phases of the progressive wave in a plurality of power supply lines branching off from the common bus. Disclosed further is an apparatus for carrying out the above methods equipped with a first coil composed of two primary windings wound with the same number of turns and in the same direction and a secondary winding, the primary and secondary windings being wound on a core whose magnetomotive force and magnetic flux density are roughly proportional to each other; a second coil composed of a primary winding and a secondary winding both wound on a core whose magnetomotive force and magnetic flux density are roughly proportional to each other; and an impedance circuit.

Method for assessing insulation conditions

A signal discriminator adapted to discriminate a signal with a specific frequency out of a current composed of two or more superimposed components with different frequencies. One type of signal discriminator disclosed includes a first coil composed of a primary and a secondary winding wound with the same number of turns and in the same direction on a core whose magnetomotive force and magnetic flux density are roughly proportional to each other, a second coil composed of a primary and a secondary winding wound on a core whose magentomotive force and magnetic flux density are roughly proportional to each other, and an impedance circuit. Another type of signal discriminator is composed of a first winding with short-circuited ends and a second winding for detecting signals both wound an an annular core having an approximately linear BH characteristic with the magnetomotive force and the magnetic flux density roughly proportional to each other. Also disclosed is a method of obtaining the high frequency component of the signals transmitted through a signal line which is passed through said annular core.

Signal discriminator and method of signal discrimination

An apparatus for judging whether a signal of insulating deterioration generated due to deterioration in insulation of an object of measurement is superimposed on the current flowing through this object. An apparatus equipped with a first coil composed of two primary windings wound with the same number of turns and in the same direction and a secondary winding, the primary and secondary windings being wound on a core whose magnetomotive force and magnetic flux density are roughly proportional to each other; a second coil composed of a primary winding and a secondary winding both wound as a core whose magnetomotive force and magnetic flux density are roughly proportional to each other, and an impedance circuit.

Junji Suehiro

Papers

Method of and apparatus for assessing insulation conditions

Apparatus for and method of discriminating signals

Method for assessing insulation conditions

Signal discriminator and method of signal discrimination

Apparatus for assessing insulation conditions