A medium-voltage switchgear system includes a three-phase circuit breaker having first, second and third single-phase vacuum interrupters connected between respective first, second and third single-phase inputs and first, second and third single-phase outputs. Magnetic actuators are connected to first, second and third single-phase vacuum interrupters, which are configured to receive an interrupt signal and in response, actuate the respective vacuum interrupter connected thereto into an open circuit condition. A controller circuit is connected to each of the first, second and third magnetic actuators and generates an interrupt signal in response to a detected single-phase overcurrent or fault on a single-phase circuit and interrupt that single-phase circuit on which the single-phase overcurrent or fault occurred and maintain power on the remaining two single-phase circuits over which a single-phase overcurrent or fault was not detected.

A network service and transformer safety protector on a secondary side of a network transformer tank system. The network service and transformer safety protector is positioned between the network transformer and a secondary network distribution system and is configured to connect and disconnect a transformer from the secondary network. The network service and transformer safety protector is attached to the outside of the transformer tank.

A circuit breaker comprises a switch and an actuator comprising a displaceable shaft mechanically connected to a movable contact in the switch. A Thomson coil is adapted to displace the shaft in a first direction, and a disconnecting device is connected in series with the switch and that is adapted to open during an interval when current is extinguished. An energy storage is provided being a separate part from the shaft and being adapted to store energy when the shaft moves in the first direction and to release energy to displace the shaft in a second direction, comprising a mass-spring arrangement with a body, a first spring between the shaft and one end portion of the body at a side facing the shaft and a second spring at a first end portion connected to a side of the body facing from the shaft and at second end portion being fixed. The movement of the body continues undisturbed to achieve a time interval wherein a current is extinguished. A current-interrupting arrangement for a circuit breaker is provided that has a simple mechanical construction and which can handle the problem at closing-in into a permanent fault in an adequate way.

A fault interrupting switching device that is part of a transformer in an underground residential power distribution circuit and provides fault isolation and restoration. The switching device includes a vacuum interrupter having a fixed terminal and a movable terminal, where the fixed terminal is electrically coupled to a transformer interface and the movable terminal is electrically coupled to a connector interface. A control rod is coupled to the movable terminal and an actuator assembly is coupled to the control rod and is operable to move the control rod to open and close the vacuum interrupter. An electronics assembly electrically is coupled to the movable terminal, and includes a high voltage capacitor and an energy storage capacitor, where the high voltage capacitor provides power to operate the actuator when the vacuum interrupter is open and the energy storage capacitor provides power to the electronics assembly when the vacuum interrupter is closed.

A switching device that is part of a transformer in an underground residential power distribution circuit and provides fault isolation and restoration. The switching device includes a transformer interface for coupling the device to the transformer and a connector interface for coupling the device to a connector. The device also includes a vacuum interrupter having a fixed terminal and a movable terminal, where the fixed terminal is electrically coupled to the connector interface and the movable terminal is electrically coupled to the transformer interface. A control rod is coupled to the movable terminal, an actuator assembly is coupled to the control rod and is operable to move the control rod to open and close the vacuum interrupter. A capacitor is electrically coupled to the fixed terminal, and provides an interface for power line communications signals, voltage sensing, help determine power flow direction and help determine the distance to a fault.

A switch assembly that is part of a transformer in an underground residential power distribution circuit and that provides fault isolation and restoration. The switch assembly includes first and second switching devices each having an outer housing, a transformer interface electrically coupled to the transformer, a connector interface electrically coupled to a first connector and a first vacuum interrupter having a fixed contact and a movable contact, where the fixed contact is electrically coupled to the connector interface and the movable contact is electrically coupled to the transformer interface. A control board controls the first and second switching devices, where the control board is responsive to voltage signals from capacitors in the first and second switching devices.

A method for isolating a fault in an underground power distribution network. The network includes a power line, a plurality of transformers electrically coupled to and positioned along the power line, a first recloser connected to one end of the power line and a second recloser connected to an opposite end of the power line, where each transformer includes an upstream switching device and a downstream switching device, and where power is provided to both ends of the power line through the first and second reclosers and one of the switching devices is a normally open switching device. The method includes detecting overcurrent by some of the switching devices, detecting loss of voltage by some of the switching devices and sending clear to close messages to some of the switching devices to open and close certain ones of the switching devices to isolate the fault.

A transformer assembly including a transformer that is part of an underground residential power distribution circuit and that provides fault isolation and restoration. The transformer assembly includes an enclosure enclosing a primary winding and a secondary winding. The transformer assembly also includes first and second switching devices mounted to a panel of the enclosure, where each switching device includes an outer housing, a transformer interface electrically coupled to the primary winding, a connector interface electrically coupled to a first connector and a vacuum interrupter having a fixed contact and a movable contact. The fixed contact is electrically coupled to the connector interface or the transformer interface and the movable terminal is electrically coupled to the other connector interface or the transformer interface.

A method for isolating a fault in an underground power distribution network. The network includes a power line, a plurality of transformers electrically coupled to and positioned along the power line, a first end switch connected to one end of the power line and a second end switch connected to an opposite end of the power line, where each transformer includes an upstream switching device and a downstream switching device, and where source power is provided to both ends of the power line through the first and second end switches and one of the switching devices is a normally open switching device. The method includes detecting overcurrent in the network from the fault, opening certain ones of the switching devices in response thereto, detecting loss of voltage as a result of the open switching devices and opening or closing certain ones of the switching devices to isolate the fault.

Disconnect switches include a housing, a fixed main contact in the housing, a movable main contact in the housing in cooperating alignment with the fixed main contact, a first actuator coupled to the movable main contact, and a second actuator coupled to the housing. The second actuator is configured to apply a motive force to the housing that is in a direction opposing a motive force applied by the first actuator to the movable main contact.