Abstract: A protective relay having means for adjusting a plurality of characteristic angles is disclosed. A characteristic angle is preselected to correspond to a desired reach representative of one or more zones of an A.C. high voltage transmission line desired to be protected. The adjustable characteristic angle means is interconnected to each of the one or more phases of the A.C. transmission line by a cascaded arrangement of one or more transactors and clamping means. The adjustable characteristic angle means comprises an operational amplifier, a plurality of resistors, a capacitor and selectable means for interconnecting each of the plurality of resistors one at a time to the operational amplifier. The plurality of resistors have values to correspond to the desired characteristic angles of the protective relay. The operational amplifier in combination with the plurality of resistors and the capacitor develop an output signal having a substantially constant magnitude as the characteristic angle is varied.

Abstract: A high speed relay for detecting multiphase faults using operating and polarizing signals from static transmission line protective relays provides an instantaneous estimate of the relative phase angle between relay signals without any loss of relay security.

Abstract: A method of, and apparatus for, detecting shorted turns in an electrical reactor. The impedance of the reactor, and its rate of change, are monitored. A reduction in impedance which exceeds a predetermined rate of change indicates the impedance change is due to shorted turns, and not to some normal cause, such as temperature.

Abstract: A digital protective relay system includes a read only memory (ROM) in which a program for executing calculations on a judgment formula for a predetermined protective relay function is stored. Switching of the judgement formula, from one form (e.g., over current protection) to another form (e.g., undervoltage protection), is facilitated by a setting unit and an operation mode switching unit which permit changing of judgement formula constants without changing the ROM program. The setting is used to input desired relay operation threshold values. The operation mode switching unit is used to specify the kind and sign of constants contained in a predetermined term in the judgment formula and also the kind of inequality in the formula.

Abstract: In a digital distance relay including sample-hold circuits for sampling the voltage and current of an electric power line system, analog-digital converters for converting the outputs of the sample-hold circuits into digital values, memory devices for memorizing the digital values and a program, and a central processing unit for exercising a relaying operation, there is provided a central processing unit which includes means for determining whether at least one of the digital values is greater than a predetermined value. The relaying operation of the distance relay is initiated only when the one digital value is greater than the predetermined value. A method is disclosed which includes the above determining step.

Abstract: In an impedance-measuring device for impedance protection, the phase positions of a plurality of alternating-current quantities are compared with the aid of a phase comparator. From the output signal thereof it is clear whether the impedance in a fault loop with a voltage U and a current I lies inside or outside an impedance zone, which is defined by means of a model impedance, Z.sub.k =R+jX. The comparator is supplied with input quantities corresponding to IX, U.sub.k, I and preferably also U.sub.p, where U.sub.k =U-IZ.sub.k, whereas U.sub.p relates to a voltage which is phase-shifted -90.degree. with respect to U. Quantities corresponding to IX, U.sub.p and I are each supplied to one input of a second logic component. This second logic component also has an input which is connected, via a delay element, to the output of a first logic component, the two inputs of which are supplied with quantities corresponding to I and U.sub.k, respectively.

Abstract: A digital type distance relay system comprises a sampling and hold circuit for sampling and holding the current in and voltage on a power transmission system, an A/D converter for receiving the outputs of the sampling and hold circuit through a multiplexer and converting the received analog quantities into corresponding digital quantities I and V, and a digital computer. The digital computer includes a data memory for memorizing the current I and voltage V and also a digital voltage V.sub.p having a predetermined relation to the voltage V, a setting memory for memorizing a setting value Z.sub.0 for setting a range of protection of the power transmission system, a ROM for memorizing a program for executing an arithmetic operation according to the formula .vertline.I.multidot.Z.sub.0 +K.sub.1 V.sub.p .vertline.-.vertline.I.multidot.Z.sub.0 -V-K.sub.2 V.sub.p .vertline..gtoreq.K.sub.0 as well as the constants K.sub.1 and K.sub.2 and minimum sensitivity value K.sub.0, and a CPU.

Abstract: A distance protective relay employing phase angle comparator measurement is provided with an improved polarizing signal. In one embodiment, a phase distance relay is provided with a two-component polarizing signal which includes one component representative of a faulted transmission line voltage and a second component representative of the product of a predetermined constant and the positive sequence component of the faulted transmission line voltage. One preferred polarizing signal for a phase AB phase distance relay is V.sub.POL =V.sub.AB +KV.sub.AB1, where K is approximately 0.3. Such a polarizing signal results in improved relay operation under certain fault conditions, especially under steady state conditions. In another embodiment, a ground distance relay is provided with a two-component polarizing signal. For, example, one preferred polarizing signal for a phase A ground distance relay is V.sub.POL =V.sub.A +KV.sub.AJ, where K is approximately 0.3. Other embodiments are disclosed.

Abstract: In a method and a system for protecting an electric power system, a signal useful for the protection is produced through operation on a digital data q.sub.m indicative of an instantaneous value at a first time point of an AC electrical quantity and another digital data given by 1/2{axq.sub.m-n -(2-a)xq.sub.m-n+l } where q.sub.m-n and q.sub.m-n+l represent data indicative of instantaneous values of an AC electrical quantity, at a time point in advance of the first time point by an angle of .alpha..degree. (0.ltoreq..alpha..ltoreq.180), and at a time point lagging behind the first time point by an angle of (180-.alpha.).degree., respectively, and a equals to .alpha./90.

Abstract: A system for rapidly detecting short circuits on power transmission lines in electrical power systems is provided to protect the power network from the effects of short circuits within the system. The instant invention provides a system for detecting multi-phase faults and causing three-phase tripping when required and also detecting single-phase faults and providing a control signal to trip the single-phase that is faulted. Signals proportional to system voltages are applied to a memory circuit to produce signals indicative of the steady-state condition of the circuit. Three other signals indicative of the voltage drops of the transmission line phases are produced by applying a signal proportional to the instantaneous current flow through each phase to replica impedance circuits. For each phase, the difference between the voltage drop and the system voltage is multiplied by a polarizing memory voltage.

Abstract: In a protective relaying apparatus for an electric power transmission system and the like there is provided a nonvolatile memory device in which various values required for protection of the system are written electrically. An input device designates addresses in the memory device and memorizes values in the addresses under control of a control device. A digital processing device carries out the protective operations for the electric power transmission system based on the values thus set in the non-volatile memory device.

Abstract: The invention relates to protective apparatus used on AC power lines. An embodiment of an apparatus for putting the invention into practice comprises impedance sensing means having an impedance characteristic defining at least three distinguishable zones in its RX diagram, and being arranged to produce respective different signals, one for each zone, indicating the zone in which the sensed impedance lies. The movement of the point representative of the apparent impedance of the line across these zones is different according to whether the movement is due to loss of synchronism between the generators supplying the line or due to power oscillations. A logic circuit is provided to detect this difference in movement.

Abstract: At an end (11) of a power transmission line (10), a fault detecting system monitors variations resulting from a fault in voltage and current being transmitted through the line and calculates the distance between the end and location (20) of the fault by the use of the variations and a line constant inherent to the line, such as that given by the characteristic impedance and the propagation constant, to thereby locate the fault with a sufficient accuracy by directly using the commercial frequency and without affected by the impedance that accompanies the fault. The system can calculate the fault impedance from the distance and those backward impedances seen at the end and an opposing end (12) of the line backwardly of the location of fault.

Abstract: A method and apparatus for fault direction determination is disclosed wherein a capacitor is connected in series in a line or network having a relay arrangement or scheme possessing directional and distance characteristics. To prevent faulty tripping of the relay arrangement, caused by the effect of the series capacitance in the line, the relay arrangement is structured such that the integrity of the directional characteristics thereof is maintained. Positive tripping of the relay is maintained, especially in the event of near faults which usually are most affected by the action of the series capacitance.

Abstract: A circuit arrangement for determining the reactance of a power transmission line in the event of a short circuit from first and second measurement valves proportional to the short circuit current and voltage respectively, in which, in order to perform this determination, in a very short time, the circuit arrangement contains a phase shifter in which, from the first measurement variable an auxiliary measurement variable which lead the first measurement variable approximately by a phase angle corresponding to the phase difference between the current and voltage in the case of a metallic short circuit is formed and switches used to couple the auxiliary measurement variable and the second measurement variable to an evaluation arrangement for determining the phase angle and to an arrangement for storing the maximum value of the measurement variables which two arrangements are followed by a computer which computes the reactance from the phase angle and stored maximum values.

Abstract: A protective relay circuit includes a first a-c level detector or bi-polar threshold circuit to which a polarizing signal V.sub.POL is applied. An output is provided from the first a-c level detector only when the magnitude of V.sub.POL exceeds a predetermined value. Also included is a second a-c level detector or bi-polar threshold circuit to which an operating signal V.sub.OP is applied. An output is provided from the second a-c level detector only when the magnitude of V.sub.OP exceeds a predetermined value. The output of the first level detector is compared in a coincidence circuit with the output of the second level detector. The detection of coincidence for a predetermined time period, as measured by a characteristic timer, results in an output signal for use in controlling operation of a trip coil of a circuit breaker.

Abstract: By switching-in a trip boundary, which excludes the load range in the complex impedance plane, of a directed or non-directed end or final stage of a measuring system of a distance protection apparatus, it is possible to eliminate faulty or spurious triggering of the protection apparatus, notwithstanding a possible improper excitation. The functional reliability of the protection apparatus is thus improved and there is possible monitoring of fault functions where, in each case, there is logically coupled a "yes" or "no"-type output response of the measuring system with a "no" or "yes"-type excitation output by means of appropriate and comparison logic circuitry.

Abstract: Apparatus is provided for sensing and responding to short circuit faults, in particular in three phase alternating current supply lines for direct-on-line starting three phase squirrel cage induction motors. Line current in each line is sensed by a respective current transformer and signals representing both the amplitude and phase of each line current are produced. Line-to-line or line-to-neutral voltage for each phase is also sensed, by photo-electric isolator circuitry, and signals produced representative of the respective phases of these voltages. Logic circuitry is used to produce from the signals representative of current and voltage phases three phase difference signals in the form of currents each varying substantially directly with the difference between the respective current and voltage phases of the respective line.

Abstract: Directional relay and method for monitoring at least one A.C. power transmission line to determine the position of a fault on the line with respect to a measurement location thereon.According to a representative embodiment characteristic parameters, typically the respective phases, of a first signal representing the difference of complex voltages after and before the occurrence of the fault and of a second signal representing the line current after the occurrence of the fault, are compared, the result of the comparison providing the desired indication.

Abstract: A method of, and apparatus for, monitoring faults at electrical lines, wherein there are formed a multiplicity of detection signals, and threshold monitoring the phase angle between timewise successive detection signals. According to a first aspect of the invention none of the detection signals has a magnitude equal to the line voltage signal. As a further aspect one of the detection signals can comprise an external signal. A still further feature contemplates that one of the detection signals is a difference signal formed by the line voltage signal and an external signal.

Abstract: A distance-selective short-circuit monitoring device with a low response time (FIG. 3, FIG. 5) results from sequence detection of first and second monitoring signals (US.sub.1, US.sub.2) which are selectively allotted to the zero cross-overs of detection signals (Ud.sub.1 -Ud.sub.4) which determine a polygonal triggering zone, the selective allocation being in accordance with the sign of the signal change rate, and by counting the alternations between first and second monitoring signals (US.sub.1, US.sub.2) within a predetermined monitoring interval (Tu), the duration of which corresponds at least approximately to a half-period of the mains frequency.

Abstract: A method of, and apparatus for, the distance-selective monitoring of faults at electrical lines by means of a quadrilateral trigger or trip region. There are formed at least two reference signals of at least approximately the same phase and from each of these reference signals and the line voltage there is formed a respective difference signal. Each difference signal experiences a separate comparison with a related threshold phase angle in order to determine whether the monitored fault lies within or without the trip region.

Abstract: In a digital distance relaying system the principle of comparing the amplitude values of alternating current quantities is used. In one example, amplitude values of V and V-IZ are compared and in the other example the amplitude values of V-IZ and IZ are compared for determining the operating point of the relay system.

Abstract: A ground distance relay employing phase angle comparator measurement is provided with additional input signals. In one embodiment, a two input ground distance relay is provided with two additional input signals. In this embodiment, the first two input signals comprise an OPERATE SIGNAL of the form IZ-V and a POLARIZING SIGNAL of quadrature shifted form. The third input signal comprises a #2 POLARIZING SIGNAL which is related to the zero sequence voltage at the relay. The fourth input signal comprises a CURRENT SUPERVISION SIGNAL which is related to the zero sequence current at the relay. These four input signals are directed to coincidence and timer circuitry. The presence of these four inputs provides improved relay security against undesirable relay operation for several existing problems. For example, additional security is provided for situations in which a single line to ground fault occurs at or just beyond the relay balance point where fault resistance may cause undesirable relay operation.

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.

Abstract: A method of, and apparatus for, locating a fault on a line, wherein current and voltage signals weighted relative to one another are formed from measurement signals corresponding to the line current and line voltage at a measurement location and after superimposing are used for a phase detection. At least one of the current signals or voltage signals is multiplied by a weighting factor at least approximately devoid of phase shift. From mutual relatively weighted current- and voltage signals there is determined the phase angle of a sinusoidal component of at least one auxiliary signal -- corresponding to the sum or difference of a respective pair of mutually relatively weighted measurement currents and measurement voltages -- in relation to a reference phase position which can be correlated to a reference location at the line.

Abstract: Provided is a digital fault-location calculation system which comprises first means for obtaining data including voltage and current information of a power transmission system subjected to fault-location calculation, a computer, and second means coupled between the first means and the computer for transferring the obtained data to the computer from the first means. The computer has at least two functions, one of which is the detection of occurrence of a faultin the transmission line and the other is the calculation of distance from the point of installation of the system to the fault point, in response to the data transferred through the second means and in accordance with predetermined processes. The distance to the fault point is computed by the other function of the computer only upon the detection of occurrence of a fault in the transmission line by the one function of the same.

Abstract: The protective relay circuits herein provide a combined distance and overcurrent type of function. The protective relay circuit includes an a-c level detector or bi-polar threshold circuit to which the quantity I (Z.sub.R - Z.sub.F) is applied. The quantity I is the current in the line, Z.sub.R is a replica or reference impedance corresponding to the lines being protected and Z.sub.F is the line impedance to the fault from the relay measuring point. IZ.sub.F is equal to V, the voltage input to the relay. An output is provided from the a-c level detector only when the quantity I (Z.sub.R - Z.sub.F) exceeds a predetermined value. The output of the level detector is compared in a coincidence circuit, or AND gate, with a polarizing signal. The detection of coincidence for a selectable predetermined time period, as measured by a characteristic timer, results in an output signal for use in controlling operation of the trip coil of the circuit breaker.

Abstract: A starting relay for a power transmission line protection system.Where long line sections have to be protected, confusion can arise between normal heavy loads and distant faults having comparable line impedance. The invention provides a starting relay which limits operation of the normal distance relay to conditions within the starting relay characteristic, this being derived by phase and amplitude monitoring of the load at the relay station. The characteristic accepts heavier line currents at potentially normal phase angles than at abnormal phase angles.Certain unbalanced faults do however exhibit normal phase angles and these are detected by substantial line voltage drops. A described combination of phase, current and voltage detectors thus covers substantially all faults.The starting relay finds particular application in a carrier-blocking fault detection scheme employing duplicates of the basic characteristic.

Abstract: A static circuit comprising an input transformation circuit responsive to current or voltage derived from an electric power system to be protected for producing a first pair of electric quantities having a phase difference of .theta. and a second pair of electric quantities dephased by .phi. from the first pair of electric quantities respectively, a pair of multipliers for the producing products of the first and second pair of electric quantities, and an adder or subtractor for producing the difference of these products.

Abstract: A protective relay arrangement for an A.C. power system wherein the occurrence of a fault is detected by monitoring the phase or amplitude relation between at least one pair of signals which, when a fault occurs in the system, are functions of a current and/or voltage which would have occurred in the power system if the or each emf source in the system had a value equal to the pre-fault voltage at the point in the system where the fault has occurred.