An apparatus and a method for operating an electric power network are disclosed. The electric power network is a compensated network arranged to be compensated by an arc suppression coil. An indication for an occurrence of an earth fault in the electric power network is received and the arc suppression coil is tuned away from resonance with respect to a resonance point of the electric power network, while the earth fault is present in the electric power network, to increase fault current in the electric power network for tripping one or more relays in the electric power network.

A load center comprises a common instantaneous tripping unit that works on a principle of solid state switching. The load center further comprises a plurality of branches of branch circuit breakers each of which is coupled to the common instantaneous tripping unit via a corresponding high power connection and a corresponding low power connection such that the common instantaneous tripping unit feeds the plurality of branches at the same time. The common instantaneous tripping unit interrupts a short circuit fault in an interruption time which is significantly reduced thus reducing or eliminating chances for a personal injury during the short circuit fault.

A load center comprises a common instantaneous tripping unit that works on a principle of solid state switching. The load center further comprises a plurality of branches of branch circuit breakers each of which is coupled to the common instantaneous tripping unit via a corresponding high power connection and a corresponding low power connection such that the common instantaneous tripping unit feeds the plurality of branches at the same time. The common instantaneous tripping unit interrupts a short circuit fault in an interruption time which is significantly reduced thus reducing or eliminating chances for a personal injury during the short circuit fault.

Systems, methods, techniques and apparatuses of ground fault protection are disclosed. One exemplary embodiment is a power switch being structured to receive a load current from a power source at a source-side and selectively output the load current from a load-side to a load; a first voltage measuring device structured to measure a first voltage of the source-side while the power switch is conducting the load current; a second voltage measuring device structured to measure a second voltage of the load-side while the first voltage measuring device is measuring the first voltage; and a controller structured to determine a source-side-to-ground voltage based on the first voltage, determine a load-side-to-ground voltage based on the second voltage, determine a ground fault is occurring, and determine a direction of the ground fault relative to the power switch by comparing the source-side-to-ground voltage and the load-side-to-ground voltage.

Disclosed is a system that reduces fault currents in a power grid, thereby reducing the risk of unintentionally igniting a fire when an object comes in proximity to a high voltage power line. The circuit comprises an isolation transformer, a neutral connection, a current compensating device, and an automatic recloser or other circuit interrupting type protection system. The isolation transformer may comprise a delta-delta or delta-zigzag transformer with a one-to-one ratio between the input and output voltages and phase angle. The current compensating device is connected to the neutral and configured to redirect a substantial portion of a fault current to ground through the isolation transformer neutral instead of the fault itself. The current compensating device may comprise an arc suppression coil tuned to match the capacitance of the three phase outputs, or an inverter.

A method for identifying an outgoing circuit having an earth fault in a three-phase power supply system, wherein a zero voltage and zero currents of outgoing circuits are measured and stored, where a space vector representation of the zero voltage and an active component of the space vector representation of zero currents are determined and, after determining an earth fault at a first time, a second time at which the space vector representation of the zero voltage has a local minimum and a third time at which the space vector representation of the zero voltage has a local maximum are determined, where the trapezoidal sum of the active component of the space vector representation of the zero currents is determined and used to determine the outgoing circuit having the earth fault via comparison with a predefined variable threshold value, an earth fault being determined if this threshold value is exceeded.

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 virtual electronic circuit breaker having an electrical relay and a control circuit, the control circuit including a load and wire protection (“OC”) detection unit, a microprocessor and a driver. The OC detection unit is configured to monitor a power flow and the electrical relay is effective to control it. The driver is effective to cause the relay to stop the power flow upon receipt of a deactivation command. The OC detection unit is effective to cause the driver to receive a deactivation command if the OC detection unit senses that a short circuit condition or an overload condition exists. The microprocessor of the control unit is configured so as to be capable of, at least, receiving input from the OC detection unit and sending output to the driver.

A motor drive includes a rectifier bridge, which rectifier bridge is connected to an DC link, which is connected to an inverter bridge having phase outputs configured to be connected to an elevator motor, as well as a drive control controlling the semiconductor switches of the inverter bridge. The inverter bridge has upper semiconductor switches of the upper side connected to plus of the DC link and lower semiconductor switches of the lower side connected to minus of the DC link, the upper semiconductor switches are semiconductor switches without desaturation- and/or over-current protection whereas the lower semiconductor switches comprise a desaturation- and/or over-current protection, or vice versa. The drive control includes an earth fault control circuit which is configured to establish an earth fault test, in which each single semiconductor switch comprising a desaturation- and/or over-current protection is switched through, only one at a time, over a test time period, whereby the earth fault control circuit is configured to enable start of the motor drive only if the earth fault test has not lead to a tripping of the desaturation- and/or over-current protection of one of the semiconductor switches.

A method and a device for detecting faults and for protection of electrical networks, the electrical networks being fed from a transformer station through a first three-phase switching device with circuit breaker, a distribution network and feeders. A second three-phase switching device with circuit breaker is connected before the feeders. The circuit breaker of the second switching device, has parallel-coupled damping impedances and is connected in series between the first three-phase switching device and the feeders when a short circuit current is detected. At least one of the damping impedances has deviating properties compared to the others, so as to create a negative sequence current detectable in the electrical networks. The damping impedances are bypassed by the circuit breaker of the second switching device after a predetermined period of time.