A protection circuit is disclosed. The protection circuit includes a direct current (DC) blocking component electrically connected between a neutral of the transformer and a ground, and an overvoltage protection device electrically connected in parallel with the DC blocking component. The overvoltage protection device is constructed to repeatably and reliably provide overvoltage protection in response to a voltage at the transformer neutral above a threshold. The DC blocking component has an impedance below a predetermined value, thereby effectively grounding the neutral of the transformer. The DC blocking component is persistently maintained in connection to the transformer neutral.

A method and a device for disconnection of faults in an electric network comprising a plurality of stations connected in a loop, comprising feeding the loop from at least two feeding points from a power source, earthing a neutral point of the electric network through an impedance, detecting earth faults in a directional earth fault protection in at least one first secondary substation provided with directional earth fault protection, disconnecting a detected earth fault by a load switching device in said at least one first secondary substation provided with directional earth fault protection, detecting fault currents arising from short circuits between two or more phases in an over-current protection of a second secondary substation, and opening said loop with a circuit breaker of said second secondary substation.

The present invention provides a trip control circuit for a circuit breaker capable of breaking a circuit when a fault current occurs due to a DC current component, as well as an AC current. The trip control circuit comprises a current transformer that has a core allowing a circuit to pass through and a secondary coil for detecting a current flowing on the circuit and providing a current detection signal; an oscillation circuit section that configured to apply an electrical signal to the secondary coil to increase a slope of a hysteresis loop of the current transformer to allow the secondary coil to detect a DC current and an AC current; and a trip determining circuit section that configured to compare a current value indicated by the current detection signal with a predetermined reference current value.

In a three-level chopper apparatus, a protection switch circuit is controllable to change a current pathway through which an overvoltage is applied to a second capacitor or a first capacitor to a current pathway through which no overvoltage is applied to the second capacitor or the first capacitor.

The present disclosure is a transformer monitoring system that has a transformer monitoring device that reads a measurement on at least one node of a transformer. Additionally, the system has a processor that analyzes the measurement and compares the measurement to a threshold value. In addition, the processor transmits an alert to utility personnel if the comparison indicates that the system is not operating properly.

A method for detecting faults (4) in a three-phase electrical distribution network comprising determining a zero sequence current (21 C), a first phase current (21A) and a second phase current (21 B) at a location of the three-phase electrical distribution network, determining first filtered currents (22) by removing a frequency component from the determined currents corresponding to a fundamental frequency of the electrical distribution network through filtering out said frequency component, determining directions of the first filtered currents during a first time period (23), and comparing said directions (24) relatively to each other, and, if at least one of the determined directions is opposite with respect to at least one of the other two determined directions, signaling a detection of a fault (25).

A protected capacitor system/method implementing enhanced transient over-voltage suppression is disclosed. The system/method incorporates one or more surge suppression devices (SSDs) proximally located and in parallel with a capacitor structure to produce an overall protected capacitor structure having enhanced reliability and simultaneous ability to resist transient overvoltage conditions. The SSDs are formed from series combinations of transient voltage surge suppressors (TVSs) (metal oxide varistor (MOV), diode for alternating current (DIAC), and/or silicon diode for alternating current (SIDAC)) and corresponding shunt diode rectifiers (SDRs) and placed in parallel across a capacitor structure to locally suppress voltage transients across the capacitor structure in excess of the voltage rating of the capacitor structure. The parallel shunting TVB/SDR pairs may be integrated into a printed circuit board (PCB) assembly that is externally attached to the capacitor structure or encapsulated in an enclosure incorporating the capacitor structure.

A protected capacitor system/method implementing enhanced transient over-voltage suppression is disclosed. The system/method incorporates one or more surge suppression devices (SSDs) proximally located and in parallel with a capacitor structure to produce an overall protected capacitor structure having enhanced reliability and simultaneous ability to resist transient overvoltage conditions. The SSDs are formed from series combinations of transient voltage surge suppressors (TVSs) (metal oxide varistor (MOV), diode for alternating current (DIAC), and/or silicon diode for alternating current (SIDAC)) and corresponding shunt diode rectifiers (SDRs) and placed in parallel across a capacitor structure to locally suppress voltage transients across the capacitor structure in excess of the voltage rating of the capacitor structure. The parallel shunting TVS/SDR pairs may be integrated into a printed circuit board (PCB) assembly that is externally attached to the capacitor structure or encapsulated in an enclosure incorporating the capacitor structure.

System and method for detecting turn-to-turn faults in one or more windings of various objects are provided. In one implementation, a fault detector receives a set of current measurements associated with a transformer and uses these measurements to execute a procedure for detecting a turn-to-turn fault in the transformer. The procedure can include dividing a steady-state differential current value by a steady-state voltage value to obtain one or more compensating factors, determining a magnetizing current amplitude indicator by multiplying the steady-state voltage value by the one or more compensating factors, determining a compensated differential current value by combining the steady-state differential current value with a modifier value that incorporates the magnetizing current amplitude indicator, comparing the compensated differential current value against a threshold value, and declaring an occurrence of the turn-to-turn fault in the transformer when the compensated differential current value exceeds the threshold value.

The present disclosure relates to an earth leakage circuit breaker and a method for controlling the same. The earth leakage breaker includes a zero-phase current detection unit for detecting a zero-phase current generated in a zero current transformer formed in three-phase electrical lines; a voltage detection unit for detecting a voltage from each of the two electrical lines; a trip unit for tripping contact points between the two electrical lines and a single-phase load when a trip signal is inputted; and a control unit which, when the zero-phase current is detected by the zero-phase current detection unit, detects an electrical line in which the voltage has dropped by a predetermined level or more, and generates and outputs the trip signal to the trip unit when the electrical line in which the voltage has dropped by a predetermined level or more exists.