A negative sequence voltage (NSV) protection system is provided that can be added to existing equipment or included as a standalone device for detecting GFOV in electrical configurations connecting distributed energy resources to utility grids. The NSV protection system can be implemented at the low side of a distribution transformer of a typical distribution circuit or in a control system of inverter-based energy resources connected to a distribution feeder. The NSV protection system includes a passive monitoring system that outputs a trip signal when a potential GFOV is detected to occur. The trip signal can then be relayed to open the circuit breakers of a distribution circuit or to cause an inverter-based energy resource to trip offline.

A system includes a transformer rectifier unit (TRU) having three inputs, a first AC bus configured to supply power to a first of the three inputs, a second AC bus configured to supply power to a second of the three inputs, and a third AC bus configured to supply power to a third of the three inputs. The system includes a power quality sense device electrically connected to each of the first, second and third AC busses. The system includes an electrically held contactor electrically connected between the TRU and the power quality sense device. The electrically held contactor is configured and adapted to be switched ON or OFF depending on whether the power quality sense device is energized or de-energized.

A welding-type power supply that receives alternating current (AC) input power and converts the AC input power to direct current (DC) power to provide power for welding tools. The welding-type power supply is configured to detect whether single phase AC power or three-phase AC power is connected to the input of welding-type power supply. Single phase input power may be detected by sampling ripple voltage of the DC power, either synchronously with the AC input power or synchronously with a signal generated by an output of the welding-type power supply.

An electrical device includes a first terminal structured to electrically connect to a power source; a second terminal structured to electrically connect to a load; a voltage sensor electrically connected to a point between the first and second terminals and being structured to sense a voltage at the point between the first and second terminals; a switch electrically connected between the first terminal and the second terminal; and a control unit structured to detect a power quality event in the power flowing between the first and second terminals based on the sensed voltage and to control a state of the switch based on the detected power quality event.

A welding-type power supply that receives alternating current (AC) input power and converts the AC input power to direct current (DC) power to provide power for welding tools. The welding-type power supply is configured to detect whether single phase AC power or three-phase AC power is connected to the input of welding-type power supply. Single phase input power may be detected by sampling ripple voltage of the DC power, either synchronously with the AC input power or synchronously with a signal generated by an output of the welding-type power supply.

An arc detection device includes a voltage detector connected between a first wire and a second wire to detect a voltage between the first wire and the second wire, the first wire connecting a positive electrode of a DC/DC converter and a plurality of DC/DC converters and branching from the positive electrode of the DC power source into the plurality of DC/DC converters, the second wire connecting a negative electrode of the DC/DC converter and the plurality of DC/DC converters and branching from the negative electrode of the DC/DC converter into the plurality of DC/DC converters; and an arc determiner that determines an occurrence of an arc based on the voltage detected by the voltage detector.

A heating device includes a heater, an AC-voltage input section between which an AC voltage is applied, a fuse, a switcher, an AC-voltage-abnormality detector configured to detect an abnormality of the AC voltage, a controller. The controller is configured to execute a current-flowing operation in a state in which connection of a first connection terminal to a second connection terminal is a non-connecting state. The current-flowing operation is an operation in which an electrical current flows through the heater. The controller is configured to execute a connecting process in response to detection of the abnormality of the AC voltage by the AC-voltage-abnormality detector detected in the middle of the current-flowing operation. The connecting process is a process of switching a connection of a first connecting point to a second connecting point from a non-connecting state to a connecting state.

A heating device includes a heater, an AC-voltage input section between which an AC voltage is applied, a fuse, a switcher, an AC-voltage-abnormality detector configured to detect an abnormality of the AC voltage, a controller. The controller is configured to execute a current-flowing operation in a state in which connection of a first connection terminal to a second connection terminal is a non-connecting state. The current-flowing operation is an operation in which an electrical current flows through the heater. The controller is configured to execute a connecting process in response to detection of the abnormality of the AC voltage by the AC-voltage-abnormality detector detected in the middle of the current-flowing operation. The connecting process is a process of switching a connection of a first connecting point to a second connecting point from a non-connecting state to a connecting state.

To improve functional security in electric power systems, a fault detector is provided in the electric power system that is connected to the data communication bus and that evaluates streamed values of at least one process parameter. In order to detect an electric fault in the electric power system, the fault detector is arranged to send a fault present indication to the switching element when an electric fault is detected. The fault present indication is sent to and received by the switching element, before the tripping operation of the switching element is triggered upon receipt of the switching command from the automation system, and the switching element triggers the tripping operation of the switching element only when a fault present indication has been received.

A method and a system for detecting and processing one or more deviations from an acceptable electrical behavior at a point of interest in an electrical network, the system comprising a voltage sensor and/or a current sensor, a measurement-processor configured to process measurements received from the at least one of a voltage sensor and a current sensor, at least one storage for storing one or more acceptable values related to the electrical behavior at the point of interest, and a deviation-processor, the deviation processor is configured to receive one or more detected values related to the electrical behavior at a point in time at the point of interest and detect one or more deviations between the one or more acceptable values and the one or more detected values, and analyze one or more deviations between the one or more acceptable values and the one or more detected values.