A relay protection method against LC parallel circuit detuning faults comprises the steps of: a relay protection device samples a current of a parallel LC, that is, a reactor and a capacitor, and samples a total current flowing through the whole LC; convert the current of the reactor into a current of an equivalent capacitor; calculate amplitudes of the current of the equivalent capacitor and a current of a realistic capacitor and calculate an amplitude of the total current flowing through the LC; calculate a current amplitude ratio of the equivalent capacitor to the realistic capacitor; and when the amplitude of the total current flowing through the LC is large enough, send an alarm signal or a trip after a setting time delay if the current ratio exceeds a preset upper and lower limit range. Also provided is a corresponding relay protection device.

An exemplary electrical network in form of a ring system includes a plurality of infeed transformers which are arranged in parallel between a sourcing busbar/cable system and a ring load busbar/cable system. A junction point connects each infeed transformer to the ring load busbar/cable system. The network includes a plurality of current limiters, where each current limiter is positioned between two junction points. Upon a fault event of an infeed transformer, two current limiters on both sides of a respective junction point of the faulted infeed transformer are simultaneously tripped in order to reduce current in the ring load busbar/cable system.

Disclosed are advances in the arts with novel methods and apparatus for detecting faulty connections in an electrical system. Exemplary preferred embodiments include monitoring techniques and systems for monitoring signals at one or more device loads and analyzing the monitored signals for determining fault conditions at the device loads and/or at the main transmission lines. The invention preferably provides the capability to test and monitor electrical interconnections without fully activating the host system.

Disclosed are advances in the arts with novel methods and apparatus for detecting faulty connections in an electrical system. Exemplary preferred embodiments include monitoring techniques and systems for monitoring signals at one or more device loads and analyzing the monitored signals for determining fault conditions at the device loads and/or at the main transmission lines. The invention preferably provides the capability to test and monitor electrical interconnections without fully activating the host system.

A power distribution system for connection to an AC voltage network, having a UPS power supply unit for uninterruptible power supply with a network-side input and with at least one output to which a number of loads are connected or can be connected in parallel load circuits, wherein a protective device having an electromechanical tripping device, in particular a thermal/magnetic tripping device, and having an evaluation and tripping unit is connected in the or each load circuit, which tripping unit trips the tripping device on the basis of an electronic overload and/or short-circuit characteristic curve and on the basis of the output voltage from the UPS power supply unit.

Systems, devices, methods, and techniques are disclosed for performing calibrated measurements of current through switches in an electronic control unit. In one example, a device includes a current sensor system; a controller, operably connected to the current sensor system; and one or more switches, operably connected to the controller. The current sensor system is configured to receive a measurement of current conducted through at least one switch of the one or more switches. The current sensor system is further configured to perform a measurement of calibrated total current for the one or more switches. The current sensor system is further configured to determine a calibrated value of current for the at least one switch, based at least in part on a comparison of the measurement of current conducted through the at least one switch and the measurement of calibrated total current for the one or more switches.

A method and a device provide protection for a multi-terminal HVDC grid against faults. The method includes measuring a DC displacement voltage having a polarity and a value, determining if a short circuit fault exists by comparing the DC displacement voltage with a threshold displacement voltage and identifying a fault type based on the polarity and the value of the DC displacement voltage. The disclosed device contains a converter having a positive pole and a negative pole, a DC-switch substation, a DC line connecting the converter and the DC-switch substation and a transient fault detector. The transient fault detector contains a positive voltage sensor sensing a positive transient voltage of the positive pole and a negative voltage sensor sensing a negative transient voltage of the negative pole and a control unit which is adapted to derive a DC displacement voltage from the positive and the negative transient voltages.

A data center includes one or more racks, computing devices mounted in the racks, and an electrical power system. The electrical power system supplies power to the computing devices in the racks. The electrical power system includes one or more rack power distribution units (PDUs) and one or more floor power distribution units (PDUs) or power panels. The rack PDUs include rack-level circuit protection devices that protect the computing devices receiving power from the rack PDU from overcurrent conditions. The floor PDUs or power panels include floor-level circuit protection devices that protect the computing devices from overcurrent conditions. The rack-level circuit protection devices have a faster response time than the floor-level circuit protection devices.

A relay protection method against LC parallel circuit detuning faults comprises the steps of: a relay protection device samples a current of a parallel LC, that is, a reactor and a capacitor, and samples a total current flowing through the whole LC; convert the current of the reactor into a current of an equivalent capacitor; calculate amplitudes of the current of the equivalent capacitor and a current of a realistic capacitor and calculate an amplitude of the total current flowing through the LC; calculate a current amplitude ratio of the equivalent capacitor to the realistic capacitor; and when the amplitude of the total current flowing through the LC is large enough, send an alarm signal or a trip after a setting time delay if the current ratio exceeds a preset upper and lower limit range. Also provided is a corresponding relay protection device.

A power system having: a DC bus, a plurality of power modules, each including a capacitor, each power module being connected to the DC bus in parallel with the other power modules, a plurality of arc suppressing devices configured to short circuit the DC bus in case of a fault on the DC bus, a plurality of current sensors, each being arranged to measure current between the DC bus and a DC side of a respective power module, and a control system associating each current sensor with an arc suppressing device of the plurality of arc suppressing devices, wherein the control system is configured to, only when at least two of the current sensors simultaneously measure a current higher than a threshold current, trigger the arc suppressing device or arc suppressing devices associated with the at least two current sensors to short circuit the DC bus.