A selective circuit breaker, in operation connectable between a main supply line and a downstream circuit breaker, has a bypass switch in a supply line, and a controlled semiconductor switch connected in parallel to the bypass switch. A bypass switch off detection circuitry and a short circuit detection circuitry are provided for controlling the bypass switch and the semiconductor switch in accordance with a switching characteristic. The switching characteristic of the selective circuit breaker is programmable, and a short circuit current rating of the selective circuit breaker is substantially equal to a short circuit current rating of the downstream circuit breaker.

A selective circuit breaker, in operation connectable between a main supply line and a downstream circuit breaker, has a bypass switch in a supply line, and a controlled semiconductor switch connected in parallel to the bypass switch. A bypass switch off detection circuitry and a short circuit detection circuitry are provided for controlling the bypass switch and the semiconductor switch in accordance with a switching characteristic. The switching characteristic of the selective circuit breaker is programmable, and a short circuit current rating of the selective circuit breaker is substantially equal to a short circuit current rating of the downstream circuit breaker.

In an electrical distribution system including a solid-state circuit breaker (SSCB) and one or more downstream mechanical circuit breakers (CBs), a solid-state switching device in the SSCB is repeatedly switched ON and OFF during a short circuit event, to reduce a root-mean-square (RMS) value of the short circuit current. The resulting pulsed short circuit current is regulated in a hysteresis control loop, to limit the RMS to a value low enough to prevent the SSCB from tripping prematurely but high enough to allow one of the downstream mechanical CBs to trip and isolate the short circuit. Pulsing is allowed to continue for a maximum short circuit pulsing time. Only if none of the downstream mechanical CBs is able to trip to isolate the short circuit within the maximum short circuit pulsing time is the SSCB allowed to trip.

A fault protection system for an electrical power distribution system and a method of configuring and operating a fault protection system for an electrical power distribution system accepts device fault protection parameters, such as the time-current-characteristics (TCC's), of boundary devices, and selects and sets fault protection parameters for one or more fault protection devices, such as fault-interrupters, that thus coordinate with the boundary devices. Fault protection parameter selection for each fault protection device may occur automatically, and each device may reconfigure its fault protection parameters based upon changes in the electrical power distribution system, for example, as the result of fault isolation and/or service restoration.

A fault protection system for an electrical power distribution system and a method of configuring and operating a fault protection system for an electrical power distribution system accepts device fault protection parameters, such as the time-current-characteristics (TCC's), of boundary devices, and selects and sets fault protection parameters for one or more fault protection devices, such as fault-interrupters, that thus coordinate with the boundary devices. Fault protection parameter selection for each fault protection device may occur automatically, and each device may reconfigure its fault protection parameters based upon changes in the electrical power distribution system, for example, as the result of fault isolation and/or service restoration.

Fault detection, isolation and restoration systems for electric power systems using smart switch points that autonomously coordinate operations to minimize the number of customers affected by outages and their durations, without relying on communications with a central controller or between the smart switch points. Each smart recloser can be individually programmed to operate as a tie-switch, a Type-A (normal or default type) sectionalizer, or a Type-B (special type) sectionalizer. The Type-A recloser automatically opens when it detects a fault, uses a direction-to-fault and zone-based distance-to-fault operating protocol, and stays as is with no automatic opening when power (voltage) is lost on both sides of the switch. The Type-B sectionalizer does the same thing and is further configured to automatically open when it detects that it is deenergized on both sides for a pre-defined time period, and to operate like a tie-switch once open.

Electric power Fault detection, isolation and restoration (FDIR) systems using smart switches that autonomously coordinate operations to minimize the number of customers affected by outages and their durations, without relying on communications with a central controller or between the smart switch points. The smart switches typically operate during the substation breaker reclose cycles while the substation breakers are open, which enables the substation breakers to reclose successfully to restore service within their normal reclosing cycles. Alternatively, the smart switch may be timed to operate before the substation breakers trip to effectively remove the substation breakers from the fault isolation process. Both approaches allow the FDIR system to be installed with minimal reconfiguration of the substation protection scheme.

A fault type determination method and device of a terminal unit for automation used in a power distribution network are disclosed. The method includes: for each line of incoming lines and outgoing lines of a distribution device, recording the number of faults occurring on the line; after a fault occurs, determining, according to the current and/or voltage on each line, whether automated reclosing is executed, and recording the number of executed automated reclosings; in a fault type determination period, for each line, if the number of faults occurring on the line is greater than the maximum number of automated reclosings allowed by the transformer substation side, or the fault is a repeat fault, then identifying the fault on the line as a permanent fault.

A fault type determination method and device of a terminal unit for automation used in a power distribution network are disclosed. The method includes: for each line of incoming lines and outgoing lines of a distribution device, recording the number of faults occurring on the line; after a fault occurs, determining, according to the current and/or voltage on each line, whether automated reclosing is executed, and recording the number of executed automated reclosings; in a fault type determination period, for each line, if the number of faults occurring on the line is greater than the maximum number of automated reclosings allowed by the transformer substation side, or the fault is a repeat fault, then identifying the fault on the line as a permanent fault.

This application relates to methods and apparatus for fault protection in a DC power transmission network or grid that aid in determining the location of a fault in the network. The method involves, in the event of a fault, controlling at least one current limiting element of the network so as to limit a fault current flowing to below a first current level which is within the expected current operating range of the network in normal operation, i.e. a safe level. The fault current is then controlled to maintain a non-zero level of fault current flow and the characteristics of the fault current flow at different parts of the network are determined by fault current detection modules. The location of the fault is then determined based on the determined characteristics.