A method for detecting faults in a low voltage three-phase network including: checking if any of three phases of the three-phase network satisfies first conditions for a predetermined duration of time; if at least two phases satisfy the first conditions, detecting an inter-phase fault by checking if the current level in at least two phases exceed a threshold and if the corresponding current flows are in the same direction; if only one of the three phases satisfies the first conditions, for the phase which has satisfied the first conditions, checking if a second condition is satisfied and, in a positive case, detecting a mono-phase fault.

An integrated circuit breaker includes a solid state switching module (SSWM) configured to receive and switchable control a line power (LP) for a given phase, and output a first switched power (SP) to a load. A first sensor (LPS) senses LP currents. A second sensor (SPS) senses SP currents. A power module controls operating states of the SSWM based upon LPS and SPS reading(s). The LPS and/or the SPS may also sense temperatures. The power module includes a high voltage domain, isolated from a low voltage domain, that includes a gate driver coupled to the SSWM and a high voltage controller providing drive signals to the gate driver. The low voltage domain includes an LP monitor and an SP monitor that detects anomalous LP and/or SP conditions and communicates error signals to the high voltage domain and to users for reporting, diagnostic, and/or other purposes via an external communications module.

A system for preventing ground fault in a three-phase electric transmission line system caused by a line break, includes: the transmission lines, a programmable relay protection system, including a plurality of relay devices on each line, programmed to include: preset parameter ranges of at least two electric operating conditions, at least one high sensitivity instantaneous undercurrent and at least one high sensitivity condition selected from line differential overcurrent and negative sequence overcurrent (and combinations thereof), the preset ranges being acceptable operating parameter ranges; monitoring; permitting closed circuit operation when all of the lines show that the two operating conditions are within the preset acceptable operating parameter ranges; tripping a circuit breaker on a broken line when that line shows that the two operating conditions are outside the preset parameter ranges; and shutting down power to the broken line before it otherwise causes a ground fault or other short circuit.

A control system and method for tie point fault interrupter and sectionalizing recloser devices in an electrical grid feeder. The technique enables automated sectionalizing reclosers equipped with three-phase current sensing and single- or three-phase voltage sensing, and able to detect pulse-closing operations, to isolate faults and restore load based on pulse count rather than requiring source re-energization and waiting for loss of voltage timers. The system includes a fault interrupter initiating a pulse-testing sequence upon detecting loss of voltage, where a number of preliminary pulses are used to distinguish transient faults from persistent faults, and pulses are counted by the sectionalizing reclosers to determine which of these devices should open. An alternate configuration is disclosed for reinitializing faults, including the fault interrupter closing if initial pulse testing indicates no fault, and subsequent cycles cause a sectionalizing recloser adjacent the fault to open, allowing the fault interrupter to close and hold.

Systems and methods may be used to determine fault types and/or directions even during a loss of potential by receiving, at one or more processors, an indication of a pre-fault power flow direction for a power delivery system. The one or more processors then determine a fault direction during a fault for the power delivery system using current vector angles and the pre-fault power flow direction.

This application relates to methods and apparatus for handling a fault associated with a voltage source converter (VSC) for exchanging electrical power between an AC system (101, 102) and a DC system (106-1, 106-2). The VSC (104) is connected to the AC system via an interface apparatus, comprising a transformer (107) with a set of primary windings (202) for coupling to a plurality of AC phases (A, B, C) of the AC system. In embodiments of the disclosure the set of primary windings having a neutral point (N) and the interface apparatus includes a fault module (301) having an energy storage element (302) connected in parallel with a resistive element (303) between the neutral point of the set of primary windings and a reference voltage, such as ground. The fault module does not interfere with normal operation but in the event of a phase-to-ground fault on the secondary side of the transformer, can induce earlier zero-crossing in the AC phases than otherwise would be the case, thus allowing AC breaker (108) to open with a reduced arcing time.

A system for preventing ground fault in a three-phase electric transmission line system caused by a line break, includes: the transmission lines, a programmable relay protection system, including a plurality of relay devices on each line, programmed to include: preset parameter ranges of at least two electric operating conditions, at least one high sensitivity instantaneous undercurrent and at least one high sensitivity condition selected from line differential overcurrent and negative sequence overcurrent (and combinations thereof), the preset ranges being acceptable operating parameter ranges; monitoring; permitting closed circuit operation when all of the lines show that the two operating conditions are within the preset acceptable operating parameter ranges; tripping a circuit breaker on a broken line when that line shows that the two operating conditions are outside the preset parameter ranges; and shutting down power to the broken line before it otherwise causes a ground fault or other short circuit.

A hybrid load protection apparatus (1) comprises a primary power supply path (1A) provided between an input terminal (2) and output terminals (2, 3) and a controllable mechanical switch (5A) connected in series with a primary coil (4A-1) coupled inductively to a secondary coil (4A-2) providing a voltage, U.sub.A, corresponding to a current rise speed of the electrical current flowing through the primary path (1A). The voltage, U.sub.A, is applied directly to a driver input (IN) of a first driver circuit (6A) to trigger automatically a switch-off of the mechanical switch (5A) within a first switch-off period (Δt1) to interrupt the primary power supply path (1A), A secondary power supply path (1B) is provided in parallel to the primary path (1A) and having a further coil (4B) connected in series with a semiconductor power switch (5B). wherein a second driver circuit (6B) associated with the secondary path (1B) detects an increasing electrical current, I, flowing through the secondary path (1B) caused by the interruption of the primary current path (1A) on the basis of a voltage drop (ΔU.sub.4) generated by the further coil (4B) and a non-linear voltage drop (ΔU.sub.5) along the semiconductor power switch (5B) applied as a sum voltage (U.sub.B) directly to a driver input (DESAT) at a high voltage side of the second analog driver circuit (6B) to trigger automatically a switch-off of the semiconductor power switch (5B) within a second switch-off period (Δt2) to interrupt the secondary power supply path (1B).

The invention relates to fluid drive systems used in fluid wells and brake systems for permanent magnet wellhead direct drives. The braking controller connects or disconnects a brake resistor from a back EMF. A variable frequency drive (VFD) drives the motor and communicates with the control circuitry of the brake controller. The control circuitry monitors the brake resistor and depending on the rotational speed and direction of the motor and operating state of the VFD, disconnects or connects the brake resistor. If the direction of the motor is in reverse and above a threshold speed, it connects the brake resistor. If the direction of the motor is in reverse and below the threshold speed, the control circuitry dissipates stored back EMF through the brake controller. The amount of stored back EMF corresponds to the time to empty a pump.

A virtual electronic circuit breaker having an electrical relay and a control circuit, the control circuit including a load and wire protection (“OC”) detection unit, a microprocessor and a driver. The OC detection unit is configured to monitor a power flow and the electrical relay is effective to control it. The driver is effective to cause the relay to stop the power flow upon receipt of a deactivation command. The OC detection unit is effective to cause the driver to receive a deactivation command if the OC detection unit senses that a short circuit condition or an overload condition exists. The microprocessor of the control unit is configured so as to be capable of, at least, receiving input from the OC detection unit and sending output to the driver.