A direct current circuit breaker, including: n in number circuit breaker modules connected in series, one energy-absorbing and voltage-limiting module connected in parallel to the n in number circuit breaker modules, and a trigger module. The n in number circuit breaker modules each includes a mechanical switch and a commutation branch circuit which are connected in parallel; each commutation branch circuit includes a charging commutation module and a commutation capacitor which are connected in series; the charging commutation module is configured to charge up the commutation capacitor and produce reverse current to cut off the mechanical switch; the one energy-absorbing and voltage-limiting module is configured to absorb energy stored in inductive elements of power systems after a fault current is cut off, so as to limit voltage and protect the mechanical switch, and n is a positive integer greater than or equal to 1.

A direct current circuit breaker, including: n in number circuit breaker modules connected in series, one energy-absorbing and voltage-limiting module connected in parallel to the n in number circuit breaker modules, and a trigger module. The n in number circuit breaker modules each includes a mechanical switch and a commutation branch circuit which are connected in parallel; each commutation branch circuit includes a charging commutation module and a commutation capacitor which are connected in series; the charging commutation module is configured to charge up the commutation capacitor and produce reverse current to cut off the mechanical switch; the one energy-absorbing and voltage-limiting module is configured to absorb energy stored in inductive elements of power systems after a fault current is cut off, so as to limit voltage and protect the mechanical switch, and n is a positive integer greater than or equal to 1.

An electrical system includes an operation MEMS switch operable in on and off states to enable and disable current flow to a load and a fault interruption MEMS switch positioned in series with the operation MEMS switch. The fault interruption MEMS switch is operable in on and off states to enable and disable current flow to the electrical load, with operation of the fault interruption MEMS switch in the off state disabling current flow to the load regardless of the state of the operation MEMS switch. A fault sensor control system operate to sense a system variable, analyze the system variable to detect if a fault is affecting the electrical system and, upon detection of a fault, switch the fault interruption MEMS switch from the on state to the off state to interrupt current flowing through the operation MEMS switch to the load.

An electrical system includes an operation MEMS switch operable in on and off states to enable and disable current flow to a load and a fault interruption MEMS switch positioned in series with the operation MEMS switch. The fault interruption MEMS switch is operable in on and off states to enable and disable current flow to the electrical load, with operation of the fault interruption MEMS switch in the off state disabling current flow to the load regardless of the state of the operation MEMS switch. A fault sensor control system operate to sense a system variable, analyze the system variable to detect if a fault is affecting the electrical system and, upon detection of a fault, switch the fault interruption MEMS switch from the on state to the off state to interrupt current flowing through the operation MEMS switch to the load.

In one example, an arc fault circuit interrupter (AFCI) is provided. The AFCI may include a plurality of current arc signature detection blocks configured to output a plurality of corresponding current arc signatures, and a processor. The processor may be configured to receive each of the plurality of current arc signature from each of plurality of current arc signature detection blocks, respectively, and generate a first trigger signal. The processor may be further configured to assess each of the current arc signatures, determine whether an arc fault exists based on the assessment, and generate the first trigger signal if an arc fault is determined to exist. A method for detecting an arc fault is also provided.

In one example, an arc fault circuit interrupter (AFCI) is provided. The AFCI may include a plurality of current arc signature detection blocks configured to output a plurality of corresponding current arc signatures, and a processor. The processor may be configured to receive each of the plurality of current arc signature from each of plurality of current arc signature detection blocks, respectively, and generate a first trigger signal. The processor may be further configured to assess each of the current arc signatures, determine whether an arc fault exists based on the assessment, and generate the first trigger signal if an arc fault is determined to exist. A method for detecting an arc fault is also provided.

A method of determining a fault in a protected zone of a power line comprises obtaining measurements at a measurement point at one end of the power line, processing the measurements in a number of parallel processing branches comprising at least two parallel processing branches, wherein the processing in each branch comprises filtering the measurements in a corresponding low pass filter for obtaining a corresponding set of filtered measurements, wherein the cut-off frequencies of the low pass filters in these parallel processing branches differ from each other, performing reach calculations on the filtered measurements for obtaining corresponding reach point quantities, and comparing the reach point quantities with corresponding thresholds. Finally, it is determined that there is a fault within the protected zone if any threshold is crossed.

A system and method for protection of an electrical grid. A respective one of the substations of the system including: a first directional protective relay to generate a signal operating on the electrical power line between the respective one of the substations and a remote one of the substations; a cyber health module to receive remote signals from two remote directional protective relays and output a reliability signal based on consistency of the remote signals and a status of the communication channels being operational; a circuit breaker to interrupt electrical power flow when directed; and a comparison circuit to receive signals and to direct the circuit breaker to interrupt electrical power flow when the reliability signal from the cyber health module indicates consistency, the first directional protective relay indicates fault, and at least one of the remote directional protective relays indicate fault.

A load abnormality detecting circuit for an inverter to detect abnormality of a load during an operation of the inverter which has a switching element and a phase synchronizing loop controlling an output frequency to be a resonance frequency of the load, the load abnormality detecting circuit includes a phase shift detection part that detects a phase shift between an output voltage and an output current which are applied from the inverter to the load and sends an abnormal load signal based on the detected phase shift. The switching element including a self-arc-extinguishing element and a reflux diode connected in reversely parallel to the self-arc-extinguishing element. The phase shift detection part detects advance and delay of a phase of the output current with respect to the output voltage.

A downhole power supply and method for supplying downhole power are disclosed. In some embodiments a downhole power supply includes a source power supply including a supply cable coupled to an electric energy source. The downhole power supply further includes at least one downhole distribution network to which the supply cable is configured to couple the electric energy source. The at least one downhole distribution network includes, multiple load supplies providing regulated power levels to multiple downhole loads and a network controller configured to individually connect and disconnect each of the load supplies in response to a failure within the downhole distribution network.