The present invention relates to resistive leakage current in a surge arrester that measures not voltage but leakage current alone in the surge arrester to obtain a resistive leakage current included in the leakage current so as to compensate for shortcomings in conventional metal-oxide surge arresters. The present invention performs a reference point detecting step (S20) to select a reference point by performing pattern analysis based on a characteristic pattern shown in a total leakage current (I.sub.T) when an applied voltage is 0V, a resistive leakage current calculating step (S30) to calculate a resistive leakage current by Fourier series-expanding the total leakage current (I.sub.T) starting at the reference point, and reference point verifying/correcting steps (S40 and S41) to correct the reference point until a characteristic pattern of the resistive leakage current (I.sub.R) according to non-linear resistance characteristics of the surge arrester (1) is shown so that the resistive leakage current (I.sub.R) is recalculated, and the present invention determines that the resistive leakage current (I.sub.R) calculated based on the completely corrected reference point is the resistive leakage current of the surge arrester (1).

An over-voltage protection system is provided for use with electrical equipment. The system includes a protection circuit having a first bus for receiving electrical power, a second bus for providing power to the equipment and two parallel surge arresters connected between the first bus and ground. A main and backup bushing are arranged in parallel between the first and second bus. The main bushing is arranged in series with a normally closed contact maintaining the main bushing in service by default. The backup bushing is arranged in series with a normally open contact isolating the backup bushing by default. The protection circuit comprises a controller for testing the insulation of the arresters and bushings. The controller is configured to selectively actuate the contacts to selectively isolate, or incorporate, the arresters and bushings in the circuit to facilitate testing and maintenance while maintaining the protection circuit operational.

The invention relates to a system and a method for monitoring the state of at least one over voltage protection component. The system has a transmission unit and a connection assembly coupled to the transmission unit. The system additionally has at least one measuring assembly coupled to the connection assembly. The at least one measuring assembly is designed to be arranged in at least one over voltage protection component. The system additionally has an analysis unit coupled to the at least one measuring assembly.

A monitoring arrangement for electrical equipment includes a first sensor for sensing a surface creeping current on a creeping path-lengthening electrically insulating housing of the equipment. A monitoring system includes electrical equipment, the monitoring arrangement, a communication device for transmitting data to a central server device, and a central server device configured to receive and evaluate the data.

An instrumented electric power voltage arrester includes a temperature sensor, wireless transmitter, and a visual over-temperature indicator. A disk shaped module, a replacement varister block, or a dummy block containing the sensor/transmitter is placed between varister blocks inside the arrester housing. A strap-on module is attached to the outside of the arrester housing. The sensor/transmitter utilizes a harvesting power supply that draws electric power for the electronics from the power line protected by the arrester. An ambient temperature sensor may be utilized to enhance accuracy. The temperature sensor/transmitter typically sends arrester monitoring data wirelessly to an RTU or handheld unit located outside the arrester, which relays the monitoring data to an operations control center that scheduled replacement of the arrester based on the monitoring data. A surge counter keeps track of the number of equipment and lightning related temperature surges experienced by the arrester.

The present invention relates to a device and method for detecting a surge arrester resistive leakage current for reducing the computational load, which may significantly reduce the computational load as the Fourier transform process need not be repeated in the process of searching to match a section to be Fourier transformed to a section in-phase with AC voltage to extract the resistive leakage current component from the Fourier series of surge arrester leakage current and enables real-time detection of the resistive leakage current by shortening the section searching process of one-period leakage current by searching for the section of one-period leakage current, which is to be initially Fourier-transformed, based on the characteristic pattern that it is repeatedly generated by application of an AC voltage. The present invention is implemented by a leakage current detection unit 10 detecting a leakage current in a surge arrester 1, a reference point search unit 20 of selecting a time when the leakage current has a highest left-right symmetry, as a reference point, a Fourier transform unit 30 obtaining a Fourier series for the one-period leakage current starting at the reference point, and a resistive leakage current extraction unit 40 correcting the reference point so that a characteristic pattern of the surge arrester resistive leakage current is shown in the sum the sine terms of the Fourier series.

Example implementations relate to circuits. For example, an implementation includes a detection circuit including a comparator circuit. The comparator circuit includes a first input terminal, a second input terminal, and an output terminal. The detection circuit also includes a reference voltage circuit to provide a set point voltage to the comparator circuit via the first input terminal. The detection circuit further includes a diode to reduce the set point voltage from a first magnitude to a second magnitude when the first magnitude is equal to or lower than a magnitude of the load voltage.

The object of the invention is an overvoltage protection apparatus with monitoring function having a parallel circuit of two branch circuits, wherein the first branch circuit has a first overvoltage protection device and a second overvoltage protection device that are connected in series, wherein the second branch circuit has a third device and a fourth device that are connected in series, wherein the first overvoltage device and the third device have a first shared voltage potential during operation, and wherein the second overvoltage device and the fourth device have a second shared voltage potential during operation, wherein a first measuring tap is provided between the first overvoltage protection device and the second overvoltage protection device and wherein a second measuring tap is provided between the third device and the fourth device, with a signal being derived from the voltage between the first measuring tap and the second measuring tap that provides state information in relation to the first overvoltage protection device and the second overvoltage protection device.

An arc detection circuit includes a current detector and arc determination unit. The current detector detects a current flowing through a transmission line which connects an electric power supply device and an electric power conversion circuit. The arc determination unit calculates, from a result of measurement of the current, an area of interest and an area for comparison. The area of interest is an area of a region of interest defined by a predetermined frequency range and predetermined time for determination. The area for comparison is an area of a portion in which detected strength exceeds a predetermined strength threshold in the region of interest. The arc determination unit determines an electric arc has occurred when a ratio between the area of interest and the area for comparison exceeds a predetermined area-ratio threshold.

The present invention performs a reference point detecting step (S20) to select a reference point by performing pattern analysis based on a characteristic pattern shown in a total leakage current (I.sub.T) when an applied voltage is 0V, a resistive leakage current calculating step (S30) to calculate a resistive leakage current by Fourier series-expanding the total leakage current (I.sub.T) starting at the reference point, and reference point verifying/correcting steps (S40 and S41) to correct the reference point until a characteristic pattern of the resistive leakage current (I.sub.R) according to non-linear resistance characteristics of the surge arrester (1) is shown so that the resistive leakage current (I.sub.R) is recalculated, and the present invention determines that the resistive leakage current (I.sub.R) calculated based on the completely corrected reference point is the resistive leakage current of the surge arrester (1).