Various embodiments of the present invention are directed to a first trip unit that is configured to be coupled to a power distribution system arranged in a Zone Selective Interlocking (ZSI) arrangement. The first trip unit includes an Input/Output circuit including a ZSI input terminal and a ZSI output terminal, a heartbeat signaling module configured to transmit a second signal to a second trip unit in a lower-level zone than the first trip unit, responsive to the normal condition, a first monitoring module configured to monitor a first signal received by the first trip from a third trip unit in a higher-level zone, responsive to the normal condition, and a second monitoring module configured to detect the fault condition. Related systems, devices, and methods are also described.

Methods, systems, and computer readable mediums for protecting and controlling a microgrid with a dynamic boundary are disclosed. One method includes detecting a fault in a microgrid that includes a dynamic point-of-common-coupling (PCC), in response to determining that the microgrid is operating in a grid-connected mode, isolating the fault by tripping a microgrid side smart switch and a grid side smart switch that are located immediately adjacent to the fault, initiating the reclosing of the grid side smart switch, and initiating the reclosing for the microgrid side smart switch via resynchronization if the grid side smart switch is successfully reclosed, and in response to determining that the microgrid is operating in an islanded mode, isolating the fault by tripping a microgrid side smart switch that is located immediately adjacent to the fault, and initiating the reclosing of the microgrid side smart switch.

A method of operating an electrical power distribution system including a plurality of circuit protection devices and an additional circuit protection device communicatively coupled by a communications network is described. The method includes transmitting, by each circuit protection device of the plurality of circuit protection devices, an electrical current communication to the communication network, the electrical current communication including an indication of an electrical current detected by the transmitting circuit protection device formatted according to a network communication protocol of the communication network. The additional circuit protection device receives the electrical current communications from the plurality of circuit protection devices and determines, based on the received electrical current communications, whether a ground fault condition exists in the electrical power distribution system.

Unique systems, methods, techniques and apparatuses of a distribution system are disclosed. One exemplary embodiment is an alternating current (AC) distribution system including a first substation including a first transformer and a protective device; a first distribution network portion coupled to the first transformer; a second substation; a second distribution network portion; a DC interconnection system coupled between the first distribution network portion and the second distribution network portion; and a control system. The control system is structured to detect a fault in the first transformer or the transmission network, isolate the first distribution network from the fault, determine a set point of the DC interconnection system, and operate the DC interconnection system using the set point so as to transfer a portion of the MVAC from the second distribution network portion to the first distribution network portion.

A method of preventing disjunctions in a power distribution unit having a plurality of output connectors is disclosed. A power level of each of the output connectors is sensed. It is detected that the power level of a given output connector exceeds a fixed power limit. In response to the detection, a delivery of power by the given output connector is stopped while maintaining a delivery of power by a remainder of the output connectors. Power delivery may be resumed in response to receiving a user command to rearm the given output connector. A power distribution unit adapted to prevent disjunctions is also disclosed.

According to an embodiment of the invention, a data transmission device that includes a communicator and a controller is provided. The communicator is connected to a network and communicates with another device via the network. The controller transmits, from the communicator to the other device, a data set including data of at least one item in the case where the data of the at least one item has changed from the state of previous interval; and the transmitted data set includes the data having the changed state. The controller acquires the data of the at least one item at a first interval, and performs the transmitting of the data set to the other device at a second interval or at a frequency less than the second interval by updating the data of the at least one item at the second interval; and the second interval is slower than the first interval.

A control system and method for a feeder, or portion of the distribution grid, which enables fault location, isolation and service restoration without communications between the feeder switches. The method uses definite time coordination between feeder switches and local measurements to determine which switches should open or close in order to isolate the fault and restore service downstream of a faulted section. Time-current characteristics and feeder topology are shared with all switches in the feeder prior to a fault event. When a disturbance occurs, a timer is started at each switch. When a switch measures voltage loss in all three phases, it stops its timer. Each switch evaluates the timer values and, when a particular switch determines based on the time-current characteristics that the immediate upstream switch opened to isolate the fault, that particular switch also opens. Power upstream of the particular switch is then provided by an alternative source.

Unique systems, methods, techniques and apparatuses of a power grid control system. One exemplary embodiment is a nested microgrid system comprising a first microgrid including a network controller, a second microgrid, a third microgrid, a first restoration path selectively coupled between the second portion of the first microgrid and the second microgrid, and a second restoration path selectively coupled between the second portion of the first microgrid and the third microgrid. The network controller is configured isolate the first portion of the first microgrid from the second portion of the first microgrid, calculate weighting factors for the first and second restoration paths, select the first restoration path using the first weighting factor and the second weighting factor, and couple the second portion of the first microgrid to the second microgrid using the first restoration path.

An electrical system includes first, second and third busses; a first interrupter electrically connected between the first and second busses; at least one of a shorting apparatus operatively associated with the first or second bus, and the first interrupter comprising a trip coil; a current sensor to sense a fault current flowing in the first bus and responsively output a first signal; a number of light sensors to sense an arc flash operatively associated with a number of the first, second or third busses and responsively output a second signal; a second interrupter electrically connected between the second and third power busses and output a third signal; and a circuit to invert the third signal to provide a fourth signal, and to operate the at least one of the shorting apparatus and the trip coil responsive to an AND of the first, second and fourth signals.

The present disclosure provides a system-level protection system and method for sub/super-synchronous resonance/oscillation. The system includes a centralized protection coordinator arranged in a control center and a plurality of distributed protection relays arranged in a plurality of transformer substations or wind farms. Each distributed protection relay is configured to acquire a sub/super-synchronous impedance of the wind farm. The centralized protection coordinator is configured to acquire the sub/super-synchronous impedances measured by the plurality of distributed protection relays, to obtain a sub/super-synchronous aggregate impedance of the system according to a preset circuit topology and the sub/super-synchronous impedances, and to generate a system-level protection signal when the sub/super-synchronous aggregate impedance does not meet a stable condition. Each distributed protection relay is further configured to initiate a system-level protection according to the system-level protection signal.