Abstract: A method and a device for directional detection of a fault on a power transmission line extending between two stations (P, Q). In one of the stations (P) there is a travelling wave model which, by means of currents and voltages measured in the station, calculates the voltage distirbution along the line. The direction to a fault is determined by monitoring changes in calculated voltages in the two stations. If a fault occurs between the stations, the voltage change occurring in a station (Q) between the voltage existing prior to a fault and after a fault can be estimated as .vertline..DELTA.Uq.vertline., and the corresponding voltage change occurring in the other station (P) can be estimated as .vertline..DELTA.Up.vertline., whereby according to the invention the difference .vertline..DELTA.Uq.vertline.-.vertline..DELTA.Up.vertline.>0 signifies a fault on the line side of the station (P), i.e. a fault lying ahead of the measuring point. A fault lying behind station P is evidenced when .vertline..DELTA.Uq.

Abstract: Apparatus for performing selective-pole trip determination is included in each protective relay of a current only monitoring protective relay system for protecting an electrical transmission segment of a power system network against faults. Current signals from the phases of the transmission segment are provided to a sequence network of the apparatus for conversion into positive and negative sequence component signals for each phase. A zero sequence component signal is also derived. A logic circuit is provided for each of the phases of the transmission segment and is governed by the corresponding sequence component signals and phase shifted variations thereof to detect a single-pole fault exclusively in the corresponding phase and generate a signal in response to the detection. An internal trip detection enables each phase logic circuit to generate its corresponding trip signal.

Abstract: A system for measuring electric power supplied through a power distribution network and, inter alia, detecting theft of power from the network, and a remote reading Hall effect based electric power meter for use therein are both described.

Abstract: A protective system for protecting elements (for example D) of an electric power system allocates a protection zone to each element. The protection zones are defined by switching points (for example 19', . . . , 24') which isolate the associated element (for example D) from the power system. Each of these switching points is associated with a transmitter/actuator unit (for example 19, . . . , 24). The transmitter/actuator units (for example 19, . . . , 24) produce "open" commands for their associated switching points (for example 19', . . . , 24') if it is determined that a fault has occurred inside the associated protection zone. The "open" commands for the switching points (for example 19', . . . , 24') are formed locally within the vicinity of each of the switching points.

Abstract: A new protective relay for determining the occurrence of a single-phase-to-ground fault and tripping the appropriate circuit breaker. At local and remote terminals of a protected line segment, three signals representative of an electrical parameter on each phase conductor are input to a local and remote protective relay. In both the local and remote protective relays, the three electrical parameter signals are manipulated to produce two evaluation signals. The two local evaluation signals produced in the local protective relay are transmitted to the remote protective relay, and the two remote evaluation signals produced in the remote protective relay are transmitted to the local protective relay. In the local protective relay the two local evaluation signals are manipulated to produce a third local evaluation signal, and the two remote evaluation signals are manipulated to produce a third remote evaluation signal.

Abstract: New logic circuitry for a directional comparison blocking protective relay scheme. A forward-reaching and a reverse-reaching protective relay located at the local and remote terminals of a protected line segment determine whether a fault is internal or external to the protected line segment. To carry out this function, the protective relays produce signals representative of fault location and communicate with each other via a communications channel. A fault detector and logic circuitry is provided at each terminal for processing the produced signals to determine the fault location and avoid tripping when the fault character changes. By using fault detectors to determine the existence of a fault, the logic at each terminal for combining the signals is simplified and security against false tripping is improved.

Abstract: A communication system for transmitting baseband digital signals on an electrical power line. A pulse generator produces digital signals which are limited to a frequency spectrum of 30 kHz to 300 kHz and applied directly, i.e., without modulation, to an electrical power line. At the receiving terminal an amplifier compensates for attenuation characteristics of the electrical power line and the received signal is then sampled to extract the information from it. To avoid interference when both a transmitting and receiving link are located at a substation, the baseband system incorporates a mimic network to mimic the interference signal erroneously picked up by the receiving link from the transmitting link located at the same substation. The mimic signal is then subtracted from the interference signal to neutralize the effect of the latter.

Abstract: Disclosed is a positive sequence undervoltage distance relay that forms a part of a relay system that provides protection for a high voltage three phase transmission line. The undervoltage distance relay provides a high speed blocking function for use with the high speed tripping functions in the protective relay system. In one embodiment the undervoltage distance relay utilizes the positive sequence components of the three phase transmission line. In another embodiment the undervoltage distance relay utilizes the line to ground (or line to line) voltages and currents of the three phase transmission line.

Abstract: In a digital protective relaying device for protecting electric power transmission line including an electric station at each end thereof, and each electric station including at least one circuit breaker to be tripped by a protective relay for protecting the own station, a digital protective relay provided with a computer is further provided at each end so as to receive electrical data in digital form from the electric stations for operating in an ordinary protective operation. As a control condition occurs in one station, the condition is sent to a digital protective relay provided at the other end of the transmission line, thereby changing the operational steps of the computer included in the protective relay.

Abstract: With heretofore known directional comparison protection systems working with fault direction detectors at both ends of a line section which is to be protected and data transmission between both end stations as well as transmitters and receivers and comparison-evaluation devices for narrowing or sectionalizing the location of the fault site with respect to the line section to be protected, the reliability of such sectionalizing procedure, especially in the case of faults near to an end station, when working with series capacitors or capacitance, is dependent upon the response of the protective gap of such capacitors. With non-response there are produced transient oscillations which can falsify the directional determination. The invention solves this problem by using distance protective relays as the fault direction detectors with line replica or image impedance, which can be switched in the sense of a zone staggering protection.

Abstract: A distance relay system for a three-phase electric power transmission line comprises means for producing positive, negative and zero sequence symmetrical component voltages from the phase voltages of the line, and means for producing positive, negative and zero sequence voltage drops from the corresponding sequence currents and impedances of the line. Zero sequence current in a parallel line and the mutual impedance between the lines may be taken into account. Predetermined ratios of the sequence voltages and changes in the voltage drops are used to produce a distance factor K corresponding to the ratio of the distance to a fault on the line and the length of the line. The single equation for K applies to all ten fault conditions that can occur on the line. A fault signal is produced when K lies between predetermined fault values. The faulted phase of single phase to ground faults may be identified. Particular expressions for K are given.