A ground monitoring tester for an AC power network, the tester comprising: a processor configured to repeatedly conduct impedance measurements of the ground of said AC power network at a point between a neutral reference point and the ground, wherein the processor is configured to conduct the impedance measurements repeatedly at intervals such as between 2 milliseconds and 2 minutes, indefinitely (i.e. without a time limit ending the measurements), whether or not the appliance or system is operational and whether or not there is an indication of a problem in the ground of said AC power network, wherein each of the impedance measurements is based on a voltage differential between a sequence of voltages including a first voltage without an internally generated reference current and a second voltage with an internally generated reference current, and at least one indication output based on the impedance measurements of the ground.

A ground monitoring tester for an AC power network, the tester comprising: a processor configured to repeatedly conduct impedance measurements of the ground of said AC power network at a point between a neutral reference point and the ground, wherein the processor is configured to conduct the impedance measurements repeatedly at intervals such as between 2 milliseconds and 2 minutes, indefinitely (i.e. without a time limit ending the measurements), whether or not the appliance or system is operational and whether or not there is an indication of a problem in the ground of said AC power network, wherein each of the impedance measurements is based on a voltage differential between a sequence of voltages including a first voltage without an internally generated reference current and a second voltage with an internally generated reference current, and at least one indication output based on the impedance measurements of the ground.

The invention provides a transformer short-circuit protection method and a transformer short-circuit protection device. The transformer short-circuit protection method includes: acquiring output voltages of a plurality of output lines of at least one winding on a low-voltage side of a transformer; and determining a short circuit according to the output voltages, and sending a protection signal when the short circuit is determined.

The invention provides a transformer short-circuit protection method and a transformer short-circuit protection device. The transformer short-circuit protection method includes: acquiring output voltages of a plurality of output lines of at least one winding on a low-voltage side of a transformer; and determining a short circuit according to the output voltages, and sending a protection signal when the short circuit is determined.

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.

An intelligent transformer monitoring system to detect and monitor random failures in distribution transformers due to improper usage and poor maintenance is provided. The intelligent transformer monitoring system includes a GSM-GPRS, a measurement and instrumentation module, a control relay module, a Trivector energy measurement, and a GPS module. The GSM-GPRS includes microcontroller along with GSM_GPRS modem in order to execute remote communication on GSM-GPRS. The Measurement and Instrumentation module includes eleven temperature measurement channels with 8-digital temperature sensors and 3-RTD. The control relay module includes 4 SPDT relays to execute output controls such as load trip and cooling motor etc. The GPS module acquires the latitude, longitude and time data from the satellite for location sharing. The Power supply module is an AC/DC SMPS power supply to convert 240V/415V AC to 12 VDC for the intelligent transformer monitoring system.

An intelligent transformer monitoring system to detect and monitor random failures in distribution transformers due to improper usage and poor maintenance is provided. The intelligent transformer monitoring system includes a GSM-GPRS, a measurement and instrumentation module, a control relay module, a Trivector energy measurement, and a GPS module. The GSM-GPRS includes microcontroller along with GSM_GPRS modem in order to execute remote communication on GSM-GPRS. The Measurement and Instrumentation module includes eleven temperature measurement channels with 8-digital temperature sensors and 3-RTD. The control relay module includes 4 SPDT relays to execute output controls such as load trip and cooling motor etc. The GPS module acquires the latitude, longitude and time data from the satellite for location sharing. The Power supply module is an AC/DC SMPS power supply to convert 240V/415V AC to 12 VDC for the intelligent transformer monitoring system.

The present disclosure relates generally to an overvoltage protection assembly, and an electrode useable in pairs in such an overvoltage protection device. In various aspects, at least one electrode is made from a single piece of conductive source material to ensure its strength, reliability, and ease of manufacture. Still further, the electrode has a specific geometry selected to enhance electromagnetic effects experienced during high voltage, high current overvoltage events in a way that quickly relocates and dissipates an arc formed at a gap between an electrode pair, to ensure repeatable, reliable performance of the overvoltage protection device.

The present disclosure relates generally to an overvoltage protection assembly, and an electrode useable in pairs in such an overvoltage protection device. In various aspects, at least one electrode is made from a single piece of conductive source material to ensure its strength, reliability, and ease of manufacture. Still further, the electrode has a specific geometry selected to enhance electromagnetic effects experienced during high voltage, high current overvoltage events in a way that quickly relocates and dissipates an arc formed at a gap between an electrode pair, to ensure repeatable, reliable performance of the overvoltage protection device.

An intelligent electronic device (IED) may obtain a residual flux of each phase of a transformer. The IED may determine a maximum difference (DIF) signal based on the residual flux and the prospective flux associated with potential close POWs of the corresponding phase. The TED may select a closing POW that results in a minimum DIF signal. The TED may send a signal to close a ganged switching device of the transformer at a time based on the selected closing POW.