A method, system and apparatus of fault detection in line protection for a power transmission system. A voltage (u) at a measurement point on an electrical line is obtained. The measurement point is a point at which a protection device for the line protection is installed. A current (i) at the measurement point is further obtained and a differential value of the current is determined. Then, a voltage (u.sub.q) at a setting point on the electrical line is determined from the voltage (u) at the measurement point, the current (i) at the measurement point and the differential value of the current (i) according to a time domain lumped parameter model for the electrical line. The voltage change between the determined voltage at the setting point during the fault period and a voltage at the setting point determined during a pre-fault period can be further determined. The fault detection can be performed based on the determined voltage change and a fault threshold. It can ensure voltage determination accuracy and detection reliability with a low sampling rate. Moreover, the solution can work right after the fault inception, almost no waiting time is required, and thus it may achieve a super-fast line protection.

The present subject matter describes fault detection during power swing in a power transmission system. Voltage and current measurements are obtained for each phase at a terminal of the power transmission system. Based on measurements obtained, a value of change in an impedance angle for each phase-to-ground loop and each phase-to-phase loop for each sampled value of voltage and current is calculated, where the value of change in the impedance angle is a difference between impedance angles of two samples separated by a predetermined interval. Further, the average values for change in impedance angle based on a predetermined number of values of the change in the impedance angle for each phase-to-ground loop and each phase-to-phase loop is calculated. The average values calculated are compared with a threshold of change in impedance angle and based on the comparison a fault in one or more of the phase-to-ground loops or phase-to-phase loops is detected and classified.

Methods and systems provide an indication that a loose connection and/or fault occurred in a breaker box or other electrical connecting device. The method includes calculating normal resistance for circuits within a breaker box when a current drawing load is present, and monitoring increases in voltage drop of the circuits to detect whether the increase is due to increased current flow or a faulty connection.

Systems, methods, and computer-readable media are disclosed for impedance-based broken conductor detection in electric distribution systems. Upon the detection of a broken conductor, the affected overhead line will be de-energized before it hits the ground. An example method may include determining, during a first time period, a first impedance value measured by a first IED, and may further include determining, during a second time period that after the first time period, a second impedance value measured by the first IED. The method may further include determining a first ratio based on dividing a difference between the first impedance value and the second impedance value by the first impedance value, and may further include determining that the first ratio deviates from a threshold setpoint, and determining that a broken conductor condition occurs based on the first ratio deviating from the threshold setpoint.

A method for generating an error signal indicating an error type of an error in a multi-phase electrical energy supply network. Measured values describe a current operating state of the network. The measured values are transmitted to a protection device. An evaluating device evaluates every possible loop of the network that can be affected with respect to the recognition of the error type of an error, by using the measured values. In order to be able to more reliably recognize the error type even under different network conditions, the measured values and/or values derived from the measured values are evaluated using at least two different protection criteria, for every possible loop. Each of the protection criteria is suitable for indicating an error type of an error present in the evaluated loop, and the error signal is generated in consideration of all available evaluation results of the protection criteria.

A power supply protection circuit is a circuit that controls a protection switch provided on a power supply line connecting a direct current power supply and a load circuit. The power supply protection circuit includes: circuitry connected to the protection switch; and a controller that switches an operation state of the circuitry between a first state and a second state. The first state is an operation state in which driving of the protection switch is enabled when the protection switch is a first semiconductor switch having a control terminal connected to a semiconductor layer of a first conductivity type. The second state is an operation state in which driving of the protection switch is enabled when the protection switch is a second semiconductor switch having a control terminal connected to a semiconductor layer of a second conductivity type that is different from the semiconductor layer of a first conductivity type.

A method for identifying a location of a fault in an electrical power distribution network that includes identifying an impedance of an electrical line between each pair of adjacent utility poles, measuring a voltage and a current of the power signal at a switching device during the fault, and estimating a voltage at each of the utility poles downstream of the switching device using the impedance of the electrical line between the utility poles and the measured voltage and current during the fault. The method calculates a reactive power value at each of the utility poles using the estimated voltages, where calculating a reactive power value includes compensating for distributed loads along the electrical line that consume reactive power during the fault, and determines the location of the fault based on where the reactive power goes to zero along the electrical line.

A method for identifying a location of a fault in an electrical power distribution network that includes identifying an impedance of an electrical line between each pair of adjacent utility poles, measuring a voltage and a current of the power signal at a switching device during the fault, and estimating a voltage at each of the utility poles downstream of the switching device using the impedance of the electrical line between the utility poles and the measured voltage and current during the fault. The method calculates a reactive power value at each of the utility poles using the estimated voltages, where calculating a reactive power value includes compensating for distributed loads along the electrical line that consume reactive power during the fault, and determines the location of the fault based on where the reactive power goes to zero along the electrical line.

Distance protection for electric power delivery systems that include an unconventional source is disclosed herein using apparent impedance independent of memory and cross-phase polarizing. The apparent impedance may be compared with an offset distance operating characteristic. Fault direction is determined by using zero-sequence ground directional logic for phase-to-ground faults. For phase-to-phase faults, fault direction is determined using weak-infeed directional logic. Fault direction may further use incremental quantity directional principles. The distance protection may further determine a faulted loop using voltage logic. The distance protection may select between traditional distance protection and the methods described herein based on the current feeding the fault.

Methods and devices for insulation monitoring of an ungrounded IT power supply system having at least two phase conductors includes determining an insulation resistance separately for each phase conductor using a separate response value. In one embodiment of the invention, relevant current and voltage distributions are calculated. In another embodiment, a change time window is set within which a second response value is activated. In yet another embodiment, an option of shutting down/continuing operation of the IT power supply system is offered.