A switching apparatus for an electric grid includes first and second electric terminals, each having first and second electric branches having a plurality of switching devices. The first electric branch includes a first switching device switchable between open and closed states, which is driven by a current flowing along said first switching device and without receiving an external control signal or an external power supply, said first switching device switching from said closed state to said open state, when the current flowing along said switching apparatus exceeds a corresponding predefined threshold value or when the changing rate of the current flowing along said switching apparatus exceeds a corresponding predefined threshold value or upon a combination of these two conditions. A second switching device is connected in series with the first switching device and is switchable between closed and open states upon receiving a corresponding input control signal.

A current cut-off device for high-voltage DC current includes: between a primary point and an intermediate point, a primary diversion member and, in parallel, a primary surge protector; a secondary mechanical switch between the intermediate point and the secondary point; a main resonator whose terminal is linked to the secondary point; a main oscillation switch; a main surge protector, in parallel with a main capacitance of the main resonator; wherein the main oscillation switch includes three terminals linked respectively to the primary point, to the intermediate point and to the other terminal of the main resonator; the changeover switch can switch at least between three direct, inverting and isolated states.

The present disclosure provides a DC mechanical circuit breaker that can utilize two switches, one of which can generate zero-crossing with an alternate oscillatory circuit for the other one, which can be a conventional zero-crossing-based AC breaker and can be used in the main circuit. This is different from the conventional single-switch commute-and-absorb method currently used. The present disclosure shows that disclosed circuit breaker improves the fault current extinction and significantly reduces the voltage rate-of-change while creating the current zero-crossing faster compared to the available technology. Thus, disclosed circuit breaker is capable of interrupting high DC currents with minimal arc through a less expensive AC circuit breaker. Simulation and hardware results are provided to show the efficiency of the disclosed circuit breaker.

A hybrid circuit breaker includes a semiconductor circuit breaker, connected between a first output end of a converter of a power supply or a source branch and a first end of a damping module; a first mechanical circuit breaker, connected in parallel to the semiconductor circuit breaker, an energy absorber, connected in parallel to the semiconductor circuit breaker, and a controller coupled to the semiconductor circuit breaker and the first mechanical circuit breaker, and when a current flowing through the converter is greater than a safe current, the controller is configured to control the first mechanical circuit breaker to be disconnected, and control the semiconductor circuit breaker to be closed.

A circuit breaker includes a circuit breaker housing, an air-gap switch disposed within the housing, and a first visual indicator configured to provide an indication of an open state and a closed state of the air-gap switch. The first visual indicator includes a first window that is formed as part of the circuit breaker housing, and first and second indicator elements disposed within the circuit breaker housing. The first indicator element is configured to move into position behind the first window as the air-gap switch is placed into the open state and thereby provide a visual indication of the open state of the air-gap switch. The second indicator element is configured to move into position behind the first window as the air-gap switch is placed into the closed state and thereby provide a visual indication of the closed state of the air-gap switch.

Embodiments of a modular direct current interconnection device (MDCID) include at least three operation branches, at least one transient branch, and a local controller. Each of the operation branches includes a first terminal coupled to a common node and configured to transmit DC current in a normal mode. The transient branch is coupled between second terminals of different ones of the at least three operation branches and configured to provide a transient DC current path in a fault clearance mode. The local controller is coupled to the operation branches and the transient branch and the local controller is configured to control operation of the operation branches and the transient branch.

A direct current circuit breaker includes: a positive supply line between a positive input terminal and a positive output terminal; a negative supply line between a negative input terminal and a negative output terminal connecting a direct current load to a supply; a series connection of a first galvanic separation switch and a bypass switch in the positive supply line, and a second galvanic separation switch in the negative supply line; a semiconductor switch element connected parallel to the bypass switch; and a series connected inductor in the positive supply line. The first and second galvanic separation switch, the bypass switch, and the semiconductor switch element are controlled using a processing unit.

Various examples are provided related to direct current circuit breakers and their control methods. In one example, among others, a hybrid direct current circuit breaker (DCCB) includes an ultrafast mechanical switch (UFMS) connected in series with a commutating switch (CS) or auxiliary circuit breaker (ACB); a main breaker (MB) including a series of η semiconductor switching stages in parallel with the UFMS and CS or ACB; and control circuitry that can turn off individual switching stages in a defined order in response to opening contacts of the UFMS. The switching stages can be turned off based upon a dielectric strength across the contacts as they open. In another example, a method includes opening contacts of an UFMS connected in series with a CS or ACB; and turning off individual switching stages of a series of η semiconductor switching stages connected across the UFMS and the CS or ACB.

A high-voltage direct current cut-off device, includes: a primary mechanical switch and a secondary mechanical switch placed successively between a primary point and a secondary point but either side of an intermediate point, a primary surge arrester arranged parallel with the primary switch, a secondary surge arrester arranged electrically parallel with the secondary switch. The secondary surge arrester is arranged electrically between the intermediate point and the secondary point, and in that the device comprises a capacitive buffer circuit electrically in parallel with the assembly formed by the primary switch and the secondary switch, and electrically in parallel with the assembly formed by the primary surge arrester and the secondary surge arrester, wherein the capacitive buffer circuit comprises an activation switch and a buffer capacitance.

A changeover apparatus for interruption-free changeover between two energy supply systems includes: at least one first outer conductor section and one second outer conductor section; a first mechanical bypass switch arranged in the first outer conductor section; a first semiconductor circuit arrangement connected in parallel with the first mechanical bypass switch; a first measuring device for recording a first voltage and/or a first mains frequency, which first measuring device is connected to the first outer conductor section; a second mechanical bypass switch arranged in the second outer conductor section; a second semiconductor circuit arrangement connected in parallel with the second mechanical bypass switch; and an electronic control unit for actuating, in a predeterminable manner, the first mechanical bypass switch, the first semiconductor circuit arrangement, the second mechanical bypass switch, and the second semiconductor circuit arrangement. The first measuring device is connected for communication with the electronic control unit.