Disclosed a method and system for fault location and protection of Microgrids which are operated under islanded mode by being disconnected from distribution systems under large disturbance or disaster scenarios. The disclosed method is invented to meet the protection needs for disconnected ungrounded microgrids without appropriate protection systems that are usually installed only at distribution substations. Moreover, the disclosed protection method or scheme is targeted at inverter-dominated microgrids in which fault current limiters are installed to protect inverters introduced by the increasing penetration of inverter-based distributed generators (IBDGs). Based on transient analysis and dynamic simulation of islanded ungrounded microgrids during different types of faults, it is realized that of the first terminal and second terminal sensors of the branch different types of faults can be effectively detected based on sequent components of currents flowed through terminals at faulted branches or sections, even with multiple IBGDs deployed in the Microgrids under different control strategies. The phase angle differences of zero sequence currents, and magnitude differences of negative sequence currents, and sign changes of phase currents are used to locate and protect against unsymmetrical and symmetrical faults within the islanded microgrids with lower fault currents, respectively.

Disclosed a method and system for fault location and protection of Microgrids which are operated under islanded mode by being disconnected from distribution systems under large disturbance or disaster scenarios. The disclosed method is invented to meet the protection needs for disconnected ungrounded microgrids without appropriate protection systems that are usually installed only at distribution substations. Moreover, the disclosed protection method or scheme is targeted at inverter-dominated microgrids in which fault current limiters are installed to protect inverters introduced by the increasing penetration of inverter-based distributed generators (IBDGs). Based on transient analysis and dynamic simulation of islanded ungrounded microgrids during different types of faults, it is realized that of the first terminal and second terminal sensors of the branch different types of faults can be effectively detected based on sequent components of currents flowed through terminals at faulted branches or sections, even with multiple IBGDs deployed in the Microgrids under different control strategies. The phase angle differences of zero sequence currents, and magnitude differences of negative sequence currents, and sign changes of phase currents are used to locate and protect against unsymmetrical and symmetrical faults within the islanded microgrids with lower fault currents, respectively.

An electrical apparatus configured to electrically connect to a multi-phase alternating current (AC) electrical power distribution network includes: an input electrical network including: a plurality of input nodes, each configured to electrically connect to one phase of the multi-phase AC electrical power distribution network; at least one non-linear electronic component electrically connected to the input electrical network; an impedance network electrically connected between the input electrical network and ground; and a control system configured to: access a voltage signal that represents a voltage over time at the input electrical network; determine a frequency content of the voltage signal; determine a property of the frequency content; and determine whether an input current performance condition exists in the electrical apparatus based the property of the frequency content.

An over-voltage protection circuit includes an over-voltage detection circuit, a voltage generator and a switch for providing over-voltage protection between two pins of a USB Type-C port. The over-voltage detection circuit provides an over-voltage signal according to the level of the second pin. The switch includes a first end coupled to the first pin, a second end coupled to the second pin and a control end coupled to a control signal. When the over-voltage signal does not indicate an over-voltage occurrence at the second pin, the voltage generator provides the control signal having a first level for operating the switch in a first region. When the over-voltage signal indicates an over-voltage occurrence at the second pin, the voltage generator adjusts the control signal to a second level for cutting off the switch. The switch operates in a second region after the over-voltage occurrence and before the switch is cut off.

A USB Type-C/Power Delivery controller chip includes a first pin for receiving a first voltage, a second pin for receiving a second voltage, and a third pin for coupling to the CC pin of a USB connector. The USB controller chip includes a VCONN power supply circuit having a blocking field effect transistor (BFET) coupled in series with a hot-swap field FET (HSFET) between the first and third pins, and first and second Zener diodes coupled anode-to-anode between the HSFET's source and gate. A cable detection circuit includes a BFET coupled between the second and third pins, and a Zener diode coupled between the BFET's gate and a lower rail. A power delivery physical layer circuit includes a receiver and a transmitter, each coupled to the third pin through a respective BFET, the respective BFETs each having a Zener diode coupled between respective gates and the lower rail.

A USB Type-C/Power Delivery controller chip includes a first pin for receiving a first voltage, a second pin for receiving a second voltage, and a third pin for coupling to the CC pin of a USB connector. The USB controller chip includes a VCONN power supply circuit having a blocking field effect transistor (BFET) coupled in series with a hot-swap field FET (HSFET) between the first and third pins, and first and second Zener diodes coupled anode-to-anode between the HSFET's source and gate. A cable detection circuit includes a BFET coupled between the second and third pins, and a Zener diode coupled between the BFET's gate and a lower rail. A power delivery physical layer circuit includes a receiver and a transmitter, each coupled to the third pin through a respective BFET, the respective BFETs each having a Zener diode coupled between respective gates and the lower rail.

An electrical apparatus configured to electrically connect to a multi-phase alternating current (AC) electrical power distribution network includes: an input electrical network including: a plurality of input nodes, each configured to electrically connect to one phase of the multi-phase AC electrical power distribution network; at least one non-linear electronic component electrically connected to the input electrical network; an impedance network electrically connected between the input electrical network and ground; and a control system configured to: access a voltage signal that represents a voltage over time at the input electrical network; determine a frequency content of the voltage signal; determine a property of the frequency content; and determine whether an input current performance condition exists in the electrical apparatus based the property of the frequency content.

In order to ensure safe operation of a multi-phase system, even a system including a plurality of phases, a number of phase groups is provided, which comprises some of the phases, wherein phase currents of the number of phase groups are merged in a group node to form a group sum current and a group sum current measurement value of the group sum current is captured. The current measurement values belonging to the number of phase groups are summed up to form a group sum and the group sum is compared with the group sum current measurement value to validate the phase currents of the phases in order to ensure safe operation.

A fault protection system is configured to detect a fault in an electric power system. The fault protection system obtains a differential measurement signal. The differential measurement signal may, for example, indicate, as a function of time, the difference between currents or voltages measured at two or more terminals or boundaries of a fault protection zone of the electric power system. Regardless, the fault protection system generates a fault detection signal by cross-correlating the differential measurement signal with a reference signal. The reference signal may for instance be the differential measurement signal that is expected upon occurrence of a fault. The fault protection system performs fault detection, for detecting a fault internal to the fault protection zone, as a function of the fault detection signal.

Distance protection for electric power systems disclosed herein uses an operating signal and a sequence polarizing signal made up of a supervised sequence current and a supervised sequence voltage. The polarizing signal may be determined based on the fault type and may be weighted toward sequence currents or sequence voltages depending on the power system conditions. For phase-to-ground faults, the sequence currents may include negative-sequence and zero-sequence currents. For phase-to-phase faults, the sequence currents may include negative-sequence currents. The current portion of the sequence polarizing signal may be weighted based on detection of insufficient negative-sequence current magnitude, standing unbalance, current transformer saturation, open pole, three-phase fault, and the like. The distance elements described herein provides improved protection during real-world power system conditions and changes.