Described are curve shapes that may be implemented in a transformer protector that provide enhanced fault protection. A transformer protector curve rating structure relates response curves to the transformer size and simplifies selection of response curves implemented within a transformer protector and associated transformer.

The present subject matter describes fault detection during power swing in a power transmission system. Voltage and current measurements are obtained for each phase at a terminal of the power transmission system. Based on measurements obtained, a value of change in an impedance angle for each phase-to-ground loop and each phase-to-phase loop for each sampled value of voltage and current is calculated, where the value of change in the impedance angle is a difference between impedance angles of two samples separated by a predetermined interval. Further, the average values for change in impedance angle based on a predetermined number of values of the change in the impedance angle for each phase-to-ground loop and each phase-to-phase loop is calculated. The average values calculated are compared with a threshold of change in impedance angle and based on the comparison a fault in one or more of the phase-to-ground loops or phase-to-phase loops is detected and classified.

An example apparatus includes: a signal terminal for inputting a signal or for outputting a signal; functional circuitry coupled to the signal terminal; a positive supply rail for supplying a positive voltage; a ground supply rail for supplying a ground voltage; a first electrostatic discharge protection circuit coupled between the positive supply rail and the ground supply rail; a second electrostatic discharge protection circuit coupled between the signal terminal and the ground supply rail; an enable circuit coupled to the signal terminal and to the positive supply rail; and a common trigger circuit having a trigger output signal coupled to the first electrostatic discharge protection circuit and to the second electrostatic discharge protection circuit. Additional apparatus and methods are disclosed.

A circuit interruption device (e.g., a molded case circuit breaker) includes at least one set of contacts, a contact actuator mechanism configured to open the at least one set of contacts and a trip control circuit configured to cause the contact actuator mechanism to open the at least one set of contacts responsive to a condition satisfying a first trip criterion and to apply a second trip criterion (e.g., a lower current level trip threshold) responsive to the opening of the at least one set of contacts. The trip control circuit may be configured to apply the second trip criterion after a succeeding closure of the at least one set of contacts. The trip control circuit may be further configured to return to application of the first trip criterion after lapse of a predetermined interval following the succeeding closure of the at least one set of contacts.

A circuit interruption device (e.g., a molded case circuit breaker) includes at least one set of contacts, a contact actuator mechanism configured to open the at least one set of contacts and a trip control circuit configured to cause the contact actuator mechanism to open the at least one set of contacts responsive to a condition satisfying a first trip criterion and to apply a second trip criterion (e.g., a lower current level trip threshold) responsive to the opening of the at least one set of contacts. The trip control circuit may be configured to apply the second trip criterion after a succeeding closure of the at least one set of contacts. The trip control circuit may be further configured to return to application of the first trip criterion after lapse of a predetermined interval following the succeeding closure of the at least one set of contacts.

A method and a device for supplying energy to a low-voltage load using an electronic power supply device. The method involves: a) setting the power supply device to be able to provide an output current to the low-voltage load up to a specified peak current value upon demand; b) monitoring the output current (I.sub.L) provided to the low-voltage load by the electronic power supply device to detect an increase of I.sub.L over a threshold (I.sub.N) which is lower than the peak current value, c) if an increase of I.sub.L to an increased output current value higher than I.sub.N is detected, detecting the increased I.sub.L value and ascertaining an output current pulse duration (t.sub.Pulse) based on the increased current value; d) providing I.sub.L at the level of the increased current value for the duration of the ascertained t.sub.Pulse; and e) providing the I.sub.L at the level of I.sub.N after t.sub.Pulse has expired.

Disclosed in the present invention is a novel overvoltage protective device for lightning protection, comprising a first varistor, a second varistor, a PTC Thermistor, and lead-out terminals. The first varistor and the PTC Thermistor are connected in parallel, and then further connected in series with the second varistor to form a single port combined circuit. The surge-withstand capability of the first varistor is higher than the surge-withstand capability of the second varistor. At least one of the two lead-out terminals of the single port combined circuit is a thermally-conductive end with low thermal resistance. The second varistor is thermally coupled to the PTC Thermistor. The thermally-conductive end with low thermal resistance is thermally coupled to one or both of the second varistor and the PTC Thermistor.

The present invention increases noise immunity of an electrical leakage detection circuit. A first comparator COMP1 generates a first comparison signal indicating a comparison result between a voltage corresponding to a detected signal from a zero-phase-sequence current transformer and a predetermined first threshold voltage V.sub.TH1. A judgment circuit outputs a judgment signal indicating if there is electrical leakage based on the first comparison signal and outputs a mask signal corresponding to the first comparison signal. A mask circuit generates a latch input signal based on the judgment signal and the mask signal. An output stage comprises a latch circuit which latches a state of the latch input signal when the latch input signal is asserted. The output stage generates a drive signal corresponding to the state of the latch circuit.

A compensation filter and a method for activating a compensation filter are disclosed. In an embodiment a compensation filter includes an operational amplifier, a capacitive element, a first and a second resistive element and a current converter. The compensation filter is configured to attenuate a common mode interference in a critical frequency range.

A compensation filter and a method for activating a compensation filter are disclosed. In an embodiment a compensation filter includes an operational amplifier, a capacitive element, a first and a second resistive element and a current converter. The compensation filter is configured to attenuate a common mode interference in a critical frequency range.