A fault finder for locating faults along a high voltage electrical transmission line. Real time monitoring of background noise and improved filtering of input signals is used to identify the occurrence of a fault. A fault is detected at both a master and remote unit spaced along the line. A master clock synchronizes operation of a similar clock at the remote unit. Both units include modulator and demodulator circuits for transmission of clock signals and data. All data is received at the master unit for processing to determine an accurate fault distance calculation.
Protective relay apparatus for providing a compensated fault impedance measurement for the determination of a better estimate of fault location along a transmission line is disclosed. In a power system network including local and remote generating sources disposed at respective ends of a transmission line segment of the transmission line, the protective relay apparatus is disposed at the local end of the line segment to measure the fault impedance for use in determining fault location. However, load flow conditions rendered by the generating sources interact with a fault which contributes resistance substantially to the fault impedance of the transmission line to cause an erroneous component in the fault impedance measurement rendering the determination of an erroneous fault location. The protective apparatus disclosed generates a signal as a measure of this erroneous component and compensates the fault impedance measurement as a function of the erroneous component signal, a predetermined impedance characteristic of the transmission line segment, and the fault impedance measurement to provide the compensated fault impedance measurement.
A device and a method for locating partial discharges in a conductor rod of a dynamo-electric machine are provided, the conductor rod being provided with an exterior electrical insulation. A first and a second sensor are embodied so as to detect a signal which is generated by the partial discharge and spreads along the conductor rod. The first and second sensor are disposed at a distance from each other on the conductor rod in order to emit a partial discharge output signal that represents a specific moment of detection. The partial discharge output signals of the first and second sensor are fed to an evaluation unit which is embodied so as to locate the partial discharge on the conductor rod.
A system for detecting a fault in a power line (1) includes, in the power line (1), a first circuit (4) capable of attenuating signals within a first frequency band, which is centered on a first frequency, substantially more than it attenuates signals outside the first frequency band, and, a second circuit (5) connected to the power line (1) on one side of the first circuit (4), the second circuit (5) being capable of extracting signals within a second frequency band that includes the first frequency. The relative levels of two signals extracted by the second circuit (5), are detected and signalled, the two signals being at respective frequencies which the first circuit is capable of attenuating by different relative amounts.
A method for location of a fault on a transmission line in a network for distribution and transmission of electric power uses a travelling wave model of the transmission line positioned in measuring stations (P, Q) at either end of the transmission line, to obtain the voltage distribution along the transmission line, seen from both station P and station Q. A voltage .DELTA.U.sub.Qp is generated as the difference between the voltage in station P, calculated in the travelling wave model in station Q, and the corresponding voltage one period/half period earlier. A voltage .DELTA.U.sub.Pp is generated as the difference between the voltage, calculated in the travelling wave model in station P, and the corresponding voltage one period/half period earlier. The corresponding voltage differences .DELTA.U.sub.Pp and .DELTA.U.sub.Qq are calculated for station Q. The voltage difference .DELTA.P is then generated as the difference between .DELTA.U.sub.Qp and .DELTA.U.sub.Pp and the corresponding voltage difference .DELTA.Q is generated as the difference between .DELTA.U.sub.Pq and .DELTA.U.sub.Qq. The fault distance PF is then obtained as PF=.DELTA.P.PQ/(.DELTA.P+.DELTA. Q), where PQ is the distance between the stations.
In a digital protective relay system for protecting an electric power system, a first digital operation device receives digital data on the electrical quantities of the power system and performs an operation on the digital data to produce an intermediate result, which is then stored in a memory unit. A second digital operation device reads the intermediate result from the memory unit and performs an operation on the intermediate result to produce a final result. The memory unit is so connected as to permit writing by the first operation device only, and to permit reading by the second operation device only.
