An earth fault detection apparatus includes a switch group configured to switch between a first measurement path including a battery and a capacitor, and a second and third measurement paths including the battery, a positive/negative-side insulation resistance, and the capacitor; a reference resistance and a test switch; and a control unit calculating a first reference value based on each charging voltage in a case where the test switch is opened and the capacitor is charged, and calculating the insulation resistance with reference to a conversion map created to correspond to an electrostatic capacitance between a power supply line and ground, wherein the control unit calculates a second reference value based on each charging voltage in a case where the test switch is closed and the capacitor is charged for a shorter time, and estimates the electrostatic capacitance with reference to a predetermined test conversion map.

An earth fault detection apparatus includes a switch group configured to switch between a first measurement path including a battery and a capacitor, and a second and third measurement paths including the battery, a positive/negative-side insulation resistance, and the capacitor; a reference resistance and a test switch; and a control unit calculating a first reference value based on each charging voltage in a case where the test switch is opened and the capacitor is charged, and calculating the insulation resistance with reference to a conversion map created to correspond to an electrostatic capacitance between a power supply line and ground, wherein the control unit calculates a second reference value based on each charging voltage in a case where the test switch is closed and the capacitor is charged for a shorter time, and estimates the electrostatic capacitance with reference to a predetermined test conversion map.

A ground fault detection device includes: a detection capacitor; a switch group for switching between a first charging path connecting the battery and the detection capacitor, a second charging path connecting the battery, a negative side insulation resistance and the detection capacitor, a third charging path connecting the battery, a positive side insulation resistance and the detection capacitor, and a measurement path for measuring a charging voltage of the detection capacitor; and a controller configured to calculate the insulation resistance based on a charging voltage measured value of the detection capacitor which exists after charging each of the charging paths, wherein after measurement of the charging voltage of the second charging path, the controller is configured to cause the switch group to switch to the third charging path before switching to the first charging path.

A ground fault detection device includes: a detection capacitor; a switch group for switching between a first charging path connecting the battery and the detection capacitor, a second charging path connecting the battery, a negative side insulation resistance and the detection capacitor, a third charging path connecting the battery, a positive side insulation resistance and the detection capacitor, and a measurement path for measuring a charging voltage of the detection capacitor; and a controller configured to calculate the insulation resistance based on a charging voltage measured value of the detection capacitor which exists after charging each of the charging paths, wherein after measurement of the charging voltage of the second charging path, the controller is configured to cause the switch group to switch to the third charging path before switching to the first charging path.

The invention relates to a method, a device (10) and an arrangement (1) for monitoring alternating current electric apparatuses (3), like e.g. power distribution transformers. The inventive method relies on an inductor antenna (11, 11′) suitable to detect the electromagnetic field at the frequency of the alternating current the apparatus (3) to be monitored is supplied with arranged in the vicinity of but distant to the apparatus (3) to be monitored and comprises the steps: —Detecting the electromagnetic field radiated by the electric apparatus (3) to be monitored; —Digitizing the detected electromagnetic field to obtain EMF-data; —Running a Fast-Fourier-Transformation on the digitized EMF-data to obtain FFT-transformed data; and—Monitoring the magnitudes of the FFT-transformed data at least at the frequency of the alternating current the apparatus (3) to be monitored is supplied with and its third harmonic for anomalies. The inventive device (10) and arrangement (1) are configured to perform the inventive method.

An underwater storage tank having a flexible multilayer tank containing a working liquid is provided. The flexible multilayer tank has at least one internal electrical insulating layer in contact with the working fluid, at least one external electrical insulating layer in contact with sea water, and at least one intermediate electric conductive layer sealed between the at least one internal electrical insulating layer and the at least one external electrical insulating layer. At least one first electrical connection means is connected to the at least one intermediate electric conductive layer, the least one first electrical connection means being electrically connectable to an electrical grounded measurement instrument to assess physical integrity of the flexible multilayer tank.

The present description concerns a circuit (5) for monitoring the operation of a component (1) associated with equipment (3), comprising: at least one device (100) for measuring one or a plurality of physical quantities associated with the operation of the component; and a circuit for calculating a value representative of a remaining lifetime of a component, said monitoring circuit (5) being linked to the equipment.

Provided are an electrical tree test device for a silicone rubber material for a cable accessory and a method for preparing a sample. The method includes: adding a semi-conductive silicone rubber into xylene, performing spraying on a surface of a silicone rubber insulation sample sheet, performing a curing processing, cutting the sample sheet into a high-voltage electrode with a triangular longitudinal section end, then adhering the high-voltage electrode on the surface of the silicone rubber insulation sample sheet, and performing a high temperature vulcanization to obtain a silicon rubber sample sheet; placing the silicon rubber sample sheet into a mold, injecting a high temperature vulcanizable liquid silicone rubber mixture, and performing the high temperature vulcanization, to obtain a sample; and performing cutting at a position distanced from a tip of the high-voltage electrode by 2 mm, and adhering a ground electrode of a flat plate-like structure at the cross section/

The present disclosure relates to a coaxial lead structure and method for radiating a GIS partial discharge UHF signal outward. The structure includes a GIS cavity, a circular hole provided on the GIS cavity, a medium cylinder provided at the circular hole and sealing the circular hole, a thin cylindrical metal lead that extends into and is fixed to the medium cylinder, and a ground lead connected to the thin cylindrical metal lead. According to the present disclosure, a relatively strong signal may be obtained outside a coaxial lead structure, and detection of a partial discharge UHF signal at this position may increase the detection sensitivity by one time compared with the detection methods of built-in and external disc insulators.

A partial discharge (PD) detection system includes a node including a sensor configured to capacitively couple to a shield layer of a cable of an electric power line. The sensor is configured to collect, from the cable, sensor data indicative of an alternating-current (AC) electrical signal in the cable. The system further includes a high-pass filter configured to filter out low-frequency signals from the sensor data, and processing circuitry configured to detect, based on the filtered sensor data, a PD event at a location on the cable that is local to the sensor.