Abstract: An apparatus for providing reverse protection to an electronic circuit is provided. The electronic circuit has a positive input terminal and a negative input terminal. The positive input terminal is coupled to a positive battery terminal via the apparatus. The negative input terminal is connected to a negative battery terminal. The apparatus includes a MOSFET transistor having a gate terminal, a drain terminal and a source terminal. One of the drain terminal and the source terminal is connected to the positive battery terminal and an other of the drain terminal and the source terminal is connected to the positive input terminal. One end of a resistor is connected to the gate terminal. One end of a pair of Zener diodes is connected to the gate terminal. The other end is connected to the source terminal.

Abstract: A MOSFET is used to protect a battery driven load against the effects of a reverse-connected battery. This invention is particularly suitable for use with loads, such as those commonly found in motor vehicles, which contain semiconductor devices that may be severely damaged by a reverse voltage. The source of the MOSFET is connected to the positive terminal of the battery, and a gate driver circuit is used to provide a gate to source voltage sufficient to turn the MOSFET on when the battery is properly connected. If the battery is connected in reverse, the gate driver turns the MOSFET off, and the intrinsic body-drain diode in the MOSFET prevents a reverse current flow through the load. In conjunction with the MOSFET, a sensing device sends out a warning signal which may be used, for example, to turn off a portion of the load if the output of the battery falls below a level necessary to maintain the MOSFET in a fully on condition.

Abstract: A transformer isolated circuit for driving a semiconductor power switch includes a transformer which is driven with a high frequency Pulse Width Modulated (PWM) signal in such a way that the constantly present PWM carrier supplies the power needed for high gate current pulses, while different duty cycles determine the "on" or "off" state of the power device under control. Transformer saturation is prevented by sensing primary current and returning it to zero once per PWM cycle. Because of the high PWM carrier frequency used, the average transformer power is low, yet the secondary side is able to deliver high pulse currents for fast "on-off" switching of the gate of even the largest N- or P-channel device, without need for auxiliary power supplies. Also included are provisions for extremely fast output current limiting, for use where short circuit protection is necessary. Discussion of a monolithic implementation is included.

Abstract: An engine-driven power generating system comprising a bridge circuit section in which a low-frequency switching elements driven alternately by low-frequency drive signals, and high-frequency switching elements driven by high-frequency drive signals during the ON period of the low-frequency switching elements are connected in a bridge network, and an inverter circuit section having a drive signal supply circuit for supplying low-frequency and high-frequency drive signals are each supplied to the low-frequency and high-frequency switching elements that form a pair; the a-c voltage generated by an engine-driven a-c generator is converted into d-c voltage that is in turn converted into a predetermined level of low-frequency a-c voltage; characterized in that an emergency relay circuit device for protecting the engine-driven power generating system against abnormal operating condition.

Abstract: A detachable operating unit for connection with a main unit comprises at least two power supply units for applying operating voltages to the detachable operating unit, the power supply units generating two different voltages, respectively; at least two power supply terminals for engaging the detachable operating unit and the main unit to receive two different voltages applied to the power supply units, respectively; a ground terminal for engaging the detachable operating unit and the main unit; a protective circuit for applying a reverse voltage in repsonse to a differential voltage between voltages of the power supply units, the protective circuit being disposed between one of power supply units which generates the operating voltage lower than that of the other power supply unit, and the ground terminal.

Abstract: A process control instrument receives a DC current from a two wire loop and has overcurrent protection and reverse current protection circuits which pass a portion of the DC current as a device current to a process controlling device. The overcurrent protection circuit includes a current sensing circuit which conducts the device current and generates an output indicative of device current. The overcurrent protection circuit also includes a current diverting circuit coupled across the two wire loop and responsive to the sensor output for diverting loop current in excess of a predetermined upper limit of device current back to the loop when the sensor output indicates the upper limit is reached. The reverse current protection circuit is coupled across the loop and includes a variable impedance which conducts the device current. The variable impedance inhibits the device current from flowing through the device when a loop potential is reversed from a predetermined polarity.

Abstract: A motor control device controls a motor driving mechanism which drives a motor according to a motor drive signal for providing a normal drive signal and a locked condition signal. When the motor becomes overloaded while being driven by the motor driving mechanism according to the motor drive signal, the motor driving mechanism is controlled by controlling circuitry which inhibits the motor drive signal from being supplied to the motor driving mechanism. The controlling circuitry, while the motor is in the overloaded state, controls the motor driving mechanism so that power is supplied intermittently to the motor, or so that the supply of power for the regular and reverse rotation is given alternately. The controlling circuitry, when the load of the motor becomes normal, allows driving of the motor according to the motor drive signal.

Abstract: A protection device for high resistance ground faults in a power network according to the invention has a fault detection principle which is based on an indirect study of non-harmonic frequency components of the phase currents. When such a fault has occurred, a considerable change of the energy contents of these frequencies arises. This change can be detected by a device according to the invention. If by comparison (4e) between digitized input signals (I') and a harmonic Fourier model (4d) of the same signals, i.e. generation of the residuals of the system, it is found that a difference exists, and if the corresponding loss function V.sub.N (4f) for a certain time exceeeds a lower limit value - all on condition that a zero sequence current (I.sub.O) exists - then there is a high resistance ground fault on any of the phases of the network.

Abstract: The invention comprises a protective relay with selective phase selection in electric power distribution systems when there are double transmission lines (M1-P1,M2-P2) between two stations (TM, TP) and where the ends of the line are connected to a common busbar system located in each station. The protective device includes a protection unit, terminal, at both ends of each line. All the terminals (M1, M2, P1, P2) include an identical basic design for measurement of phase quantities (17), filtering (18) and A/D conversion (19); furthermore, the identical part includes a parameter estimator (20) for Fourier series expansion of measured phase signals and generation of the respective residuals. The parameter estimator cooperates with a frequency estimator (21) and a sampling regulator (22).

Abstract: A field effect transistor has its drain and source regions connected between one of the two supply pads of an operative integrated circuit, the gate of the field effect transistor being connected to the other pad such that the gate is negatively biased during reverse battery to prevent current flow through the circuit in this condition and, hence, to prevent destruction of the circuit. The FET is sized to have minimal voltage drop during normal, forward battery operation of the circuit. The FET can be implemented as either an N-channel or a P-channel device.

Abstract: A protective relay for detecting faults within a predetermined protected zone of a three phase alternating current electrical power distribution system, of the type which utilizes at least one restraint signal in conjunction with at least one operate signal to generate a net operate signal, generates an operate quantity which is related to a zero sequence component of current flowing in the power distribution system and a second operate quantity which is related to a negative sequence component of the current flowing in the power distribution system. The operate quantities are summed to form an operate signal. An adaptive restraint, which is proportional to a negative sequence component and a zero sequence component of a phase voltage of the power distribution system, is generated and utilized to provide increased sensitivity to higher resistance ground faults.

Abstract: A protective relay for detecting faults within a predetermined protected zone of a three phase alternating current electrical power distribution system generates a polarizing signal V.sub.POL which includes a signal V.sub.1 related to a positive sequence component of a phase voltage of the three phase power distribution system. A signal I.sub.1 Z.sub.R, which is a signal related to a positive sequence component of a phase current of the three phase power distribution system multiplied by a replica impedance of the protected zone of the three phase power distribution system, is also generated. The coincidence of the V.sub.POL and I.sub.1 Z.sub.R signals are compared and an operate signal is generated as a result of positive coincidence. A first restraint signal is generated as a result of negative coincidence. A second restraint signal related to V.sub.1 is also generated.

Abstract: A phase selector for identifying a faulted phase in a three-phase alternating current electrical current distribution system generates, for each of the three phases, an output signal which includes the phasor sum of a signal related to a fault component of current flowing in the phase, a signal related to a negative sequence component of current flowing in the phase and a signal related to a zero sequence component of current flowing in the phase. The phase selector also generates at least one restraint signal which includes the phasor sum of a signal related to a fault component of current flowing in one of the two other phases of the three phase power distribution system, a signal related to a fault component of current flowing in the other of the two other phases of the three phase electrical power distribution system and a signal related to the negative sequence component of current flowing in the phase.

Abstract: High resistance ground faults on a transmission line of an electrical power transmission network are detected with the aid of a device comprising a travelling wave model of the line located in measuring stations (P, Q) at either end of the line, which permits the voltage distribution along the line, seen both from P and from Q, to be obtained. A voltage .DELTA.U.sub.Qp is formed as the difference between a votlage in station P, calculated in the travelling wave model in Q, and the corresponding voltage one period earlier. A voltage .DELTA.U.sub.Pp is formed as the difference between a voltage calculated in the travelling wave model at P and the corresponding voltage one period earlier. The corresponding voltage differences .DELTA.U.sub.Pq and .DELTA.U.sub.Qq are calculated for station Q. The voltage difference .DELTA.P is then formed as the difference between .DELTA.U.sub.Qp and .DELTA.U.sub.Pp, and the corresponding .DELTA.Q is formed as the difference between .DELTA.U.sub.Pq and .DELTA.U.sub.Qq.

Abstract: In a short-circuit distance relay for protecting a single-channel power transmission system with power supplies installed at two ends thereof, when there exists any resistance at a fault point on the power transmission line, an error is induced in measurement of the distance up to the fault point by a voltage drop component flowing through the fault-point resistance from the remote-end power supply. In order to eliminate such error in measuring the distance, the relay of this invention computes the impedance up to the fault point from the information including a positive-phase voltage and a positive-phase current in a normal state of the power transmission system, and also a positive-phase voltage, a positive-phase current and a negative-phase current in a faulty state of the system, whereby the fault-point resistance is rendered unconcerned with the distance to consequently avert the measurement error.

Abstract: An electronic protective relay which offers a very sensitive detection of a reverse power condition of a three-phase alternating current generator for the protection against generator motoring is disclosed. A current signal is generated from a current transformer coupled to one phase of the ac generator; and a voltage signal is generated from a potential transformer coupled across the one phase and another phase of the generator. A current input circuit is operative to maintain the phase angle between the voltage and current signals over a wide variation of input current, e.g. from one milliamp to 75 amperes. In addition, a phase-rectification type multiplier affords a relatively simple, but effective method for detecting the power flow direction of the generator. Once the power flow is determined to be in the reverse direction and above a preselected magnitude, a signal indicative of a potential generator motoring condition is geneated.

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 phase comparison type ground distance relay for a predetermined phase of three-phase AC transmission line includes a phase coincidence detector responsive to phase coincidence between an operating signal and a plurality of polarizing signals. Zero suppression networks are utilized for deriving second and third polarizing signals in order to improve discrimination between internal and external faults; thereby increasing the reliability of the relay operation and the security of the protection system. The second polarizing signal comprises that portion of a signal which exceeds a predetermined threshold value and which is related to the product of a signal proportional to the net current flowing in all three phases of the power system and the positive sequence replica impedence of the transmission line.

Abstract: A method and apparatus for detecting a fault and also the direction of a fault in electric lines, wherein voltage (Su) and current step signals (Si) corresponding to the transient components in the line voltage and line current are derived; the instantaneous values of these step signals (Su, Si) define, in a co-ordinate system formed by the step signals (Su, Si) themselves, a point which passes through a line of motion (B) after the occurrence of a fault; and if the point transgresses a triggering boundary (AI, AII, AIII, AIV) in the co-ordinate system the fault is detected. In this event the direction of the fault is found from the quadrant (QI, QII, QIII, QIV) in which the transgression takes place.

Abstract: In an electrical power distribution system, line disturbances produce voltage and current travelling waves, or step-change signals, that are phase-shifted 90.degree. relative to each other. A simulation signal is derived from the current step-change signal and is in phase with the voltage step-change signal. The two in-phase signals are combined and compared with established limit values to determine when a fault occurs.

Abstract: The invention concerns a method of direct measurement of a parameter characterizing a fault on an electricity line 1, such as the distance x or the resistance R.sub.d of the fault, the method being based on Ohm's Law including the line inductance L and the resistances R, R.sub.d. The signals respectively associated with the variation of current i(t) and of voltage v(t) at the measuring point M are operated upon by transfer functions the ratio of which is equal to:(2/.tau.) tan .omega..tau./2,.tau. corresponding to the propagation time of a wave over double the distance between the measuring point M and a zone boundary P. The method thus takes into account the distributed capacitances C of the line.

Abstract: A protective relay which hardly makes maloperation in itself regardless of mixing of low-order higher harmonics in its at least two sinusoidal input signals comprises a first and a second phase detection comparator generating two different-phase square signals indicative of the phase difference between the sinusoidal input signals, a first and a second timer receiving the square signals generated from the first and second phase detection comparators respectively and generating their output signals as a result of comparison between a first period of time and one of the periods or the period of presence or absence of the square signals, a third timer receiving the same square signal as that applied to the first timer and generating its output signal as a result of comparison between a second period of time and the other period or the period of absence or presence of the square signal, a fourth timer receiving the same square signal as that applied to the second timer and generating its output signal as a result

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: An electrical distribution system has parallel connected generators powered by variable speed engines. Loads connected with each generator are interconnected through an electrical distribution bus. Constant speed drives have inputs connected with the engines and outputs directly connected with the generators. The connections between the constant speed drive outputs and the generators are characterized by the absence of overrunning clutches used in prior systems. An improved electrical protective circuit senses a flow of electrical power from the distribution bus to a generator, driving the generator as a motor. If the power flow to the generator is excessive, the bus tie breaker is opened disconnecting the generator from the bus.

Abstract: A power flow detector for connection to power supply lines includes a phase difference-to-pulse width converter for producing pulse signals for which the pulse width corresponds to the phase difference between the load voltage and load current of the power supply lines. The output of the phase difference-to-pulse width converter is integrated and the integrated voltage is compared with a reference voltage. The power flow direction is determined by whether the integrated voltage is larger than or smaller than the reference voltage.

Abstract: A protective relay system for opening local and remote circuit breakers of a protected line segment when a fault occurs thereon. The protective relay system includes local and remote fault detectors for producing local and remote blocking carrier signals, respectively, for transmission to the other terminal when a fault is in the forward direction from the terminal. Reception of a blocking signal blocks tripping of the circuit breaker at the receiving terminal. When the fault is internal, the blocking signals are transmitted for only a short duration, sufficient to allow the protective relays at both terminals to detect the internal fault. When transmission of the blocking signals stops, the trip coils at both terminals are energized because the relays at both terminals see the fault in the forward direction and do not receive the blocking signal. For an external fault the relays at the terminal from which the fault is seen in the forward direction transmit a blocking signal to the other terminal.

Abstract: Protective relay apparatus for detecting the direction or distance to a fault from the measuring point on an ac electrical power transmission line using current and voltage deviation signals. The deviation signals represent the changes induced by the fault from the steady-state pre-fault magnitudes. Trajectories are plotted on an X-Y plane using the voltage deviation signal as the X-axis coordinate and the differentiated current deviation signal multiplied by the line reactance to the balance point as the Y-axis coordinate. Due to the use of the differentiated current deviation signal, the trajectories are straight lines. The threshold boundaries for determining the distance to or direction of the fault are time-varying lines of unit slope representing the pre-fault voltage at the fault point.

Abstract: A power converting device including at least one power converting element, and a protection circuit monitoring the switching characteristics of the power converting element and for protecting the power converting element during switching thereof, including a first circuit coupled to detect a reverse voltage applied to the power converting element, a second circuit coupled to the first circuit for receiving the detected reverse voltage and for integrating the detected reverse voltage to produce a reverse voltage/time integral signal, and a third circuit coupled to receive the reverse voltage/time integral signal for producing a decision signal only when the amplitude of the reverse voltage/time integral signal exceeds a first prescribed value, the decision signal indicates that the power converting element is extinguished.

Abstract: Protective relay apparatus and method for determining the faulted phase conductor of a three-phase ac electrical transmission line. The voltage and current on each conductor are measured and the steady-state ac electric power signal removed. The resulting filtered-voltage signals are multiplied by the characteristic admittance of the transmission line and then combined with the filtered-current signals to produce three current signals representative of the current on each conductor caused by an incident traveling wave and three current signals representative of the current on each conductor caused by a forward traveling wave. A comparator compares the six current signals to provide an indication of the direction to the fault and to provide an enable signal when the fault is on the protected line segment. The three incident-wave current signals are filtered to provide a modal signal representing the total current produced on the transmission line by a first propagational mode of the incident traveling wave.

Abstract: A process and device useful in the protection of AC current circuits, particularly of parallel lines supplied at both ends, provided with protection relays at both ends of the line against susceptibility to false triggering as a result of transient signal components and signals disturbances, and particularly useful in providing stepped protection upon initial disconnection at one side of a line after occurrence of a short circuit against the change of energy direction with reversal of the fault direction detected in the protection relay of the sound line on crossing the triggering range of the appropriate characteristics curve, which also leads to false triggerings in multi-system protection relays because of transient switching inaccuracies.

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: In circuitry for generating tripping and blocking signals for the protection of electrical power supply network components as a result of the occurrence of faults, the blocking signals are selected from each phase of the electrical power supply network to prevent tripping in each phase for faults occurring behind the protected component. A sequence detector includes a partial detector for each phase of the electrical power supply network and includes logic circuitry responsive to respective tripping and blocking signals generated for each phase of the electrical power supply network in dependence on whether the fault lies ahead or behind the protected electrical component, respectively. Each logic circuit includes a gate and a delay circuit responsive to the output of the gate. The output of the delay circuit in the tripping logic circuit is input to the gate in the blocking logic circuit and vice-versa.

Abstract: Protective relay apparatus and methods for detecting direction to a fault from a measuring point on an A.C. electrical power transmission line using current and voltage deviation signals which may include traveling wave transients, and for providing both directional and distance information from the same signals after traveling wave transients have been removed. Fault generated current and voltage deviations from the steady-state, prefault magnitudes are used to generate trajectories in one embodiment by differentiating the current deviation and using it as one coordinate, and by using the voltage deviation as the other coordinate. A forward fault produces a straight line trajectory which crosses the origin between the second and fourth quadrants, and the reverse direction fault produces a straight line trajectory which crosses the origin between the first and third quadrants.

Abstract: This invention relates to methods and apparatus for detecting the occurrence of a fault on a conductor or transmission line and for protecting the conductor or line in accordance with the determination of fault. The instantaneous value of the voltage (V) and current (i), or the modal components of that voltage and current in the case of a polyphase line, are formed into two functions S.sub.1R and S.sub.2R, which are of the general form V-iR and V+iR respectively where R is a replica of the surge impedance of the line. Superimposed components of these functions are derived by continuously subtracting the steady-state value of each function from its instantaneous value. The sequence in which the functions obtain a value outside a predetermined band of values is monitored to provide an indication of the existence and direction of a fault with respect to the measuring point. Trip and block signals are generated for operating circuit breakers.

Abstract: In directional wave detector apparatus for electrical power line relay protection devices determining the direction to a fault, the current and voltage of the travelling waves generated by a fault point are combined at a measuring point and the sign of the combined signal is determined. A tripping or blocking signal is emitted depending on whether the sign of the combined signal indicates that the fault lies within or outside the range protection of the relay protection device.

Abstract: A circuit interrupter includes a digital trip unit containing a microprocessor. The circuit interrupter also includes current transformers for sensing current flow through the contacts of the interrupter and for providing operating power to the trip unit. The current transformers monitoring current flow through the breaker and control potentiometers receiving operator-entered values of the product of line voltage and power factor are connected to the microprocessor to supply it with the values needed to compute real power flow through the interrupter and to display the numeric value of this power flow. The power flow is compared to an operator-entered limit value of peak demand power, and an alarm signal is generated whenever power flow exceeds the limit value peak demand. Integration capability is also provided to calculate energy flow through the contacts in megawatt hours and to present the numeric value of this energy flow.

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: A method for the directional detection of faults on power transmission lines is described.According to one embodiment applied to a link comprising several lines in parallel each provided, towards each of their respective ends, with a directional relay, the indications from all of these relays in response to the detection of a fault on the link, are combined to determine the presence or the absence of the fault on the lines under consideration. In particular, this method is applicable to lines compensated with series capacitors at the beginning of the line.

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 protective relaying system for detecting and clearing high impedance faults on a polyphase electrical distribution circuit. First and second ratio ground relays are located at first and second circuit breakers, respectively. The first circuit breaker is located at the substation, and the second circuit breaker is remote from the substation, usually operating with a reclosing relay. A zero sequence directional relay, located at the second circuit breaker, coordinates the ratio ground relays by adjusting the trip delay time of the second circuit breaker according to the flow direction of a zero sequence quantity at the second circuit breaker.

Abstract: In circuitry for generating tripping and blocking signals for the protection of electrical components in an electrical power supply network as a result of the occurrence of faults therein, respective tripping and blocking outputs for each phase of an electrical power supply network are generated such that double or triple pole tripping is prevented unless the presence of an actual second tripping signal is detected subsequent to the detection of a first tripping signal. The respective tripping signals and blocking signals for each phase of the electrical power supply network are generated in dependence on whether the fault lies ahead or behind the electrical component to be protected, respectively, in response to measurement of the voltage and current associated with transient waves generated by faults in each electrical power supply network phase.

Abstract: A network protector relay produces a close signal entirely from sequence components based on the magnitude and phase relationships between the positive sequence component of the phase-to-ground voltages on the network side of the protector and the positive sequence component of the phasing voltages. The close signal may be inhibited by either the presence of the negative sequence component of the phase-to-ground voltages on the network side of the protector or if a trip contact is closed. The trip contact will be closed under certain specified conditions which make it advantageous to prevent manual closing of the contacts.

Abstract: By forming current jump or surge signals and voltage jump or surge signals, in accordance with the changes as a function of time of the line current and line voltage in relation to the steady-state course of the current and voltage and comparison of such jump or surge signals with a threshold value, dependent upon the other jump or surge signal, or an appropriate threshold value function, there can be derived trip boundaries in the surge signal plane. Exceeding such trip boundaries in a direction from the inside towards the outside can be utilized as a fault criterion for producing a trip signal.

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: Circuitry for generating tripping and blocking signals for the protection of electrical components included in electrical power supply networks as a result of the occurrence of faults therein provides multiphase pole tripping in the event that, after a single pole tripping has been executed, a new single phase fault occurs in any of the remaining phases of the electrical power supply network. Respective tripping and blocking signals are generated for each phase of the electrical power supply network in dependence on whether the fault lies ahead or behind the electrical component to be protected, respectively, in response to measurement of the voltae and current associated with transient waves generated by faults associated with each electrical power supply network phase.

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: In a protective system which operates in response to a plurality of state quantities, for example voltage and current, one of which being a digital code signal having a long code length and transmitted over a transmission circuit, the density of the code errors of the digital code signal is detected. A plurality of state quantities are processed by a processor including first means responsive to the digital code signal and second means not responsive to the digital code signal. Either one of the first and second means is selected according to the density of the code errors.

Abstract: A solid state, reverse power flow detector and control circuit which samples the line voltage and current, once each cycle. The voltage sampling circuit includes a pulse generator providing a voltage pulse of short duration at a given time or phase angle in each cycle. The voltage signals are applied to an SCR through a gate operated by the current signals. In one embodiment, the gate comprises a single transistor. With forward or no current, the gate does not allow the voltage signals to reach the SCR. When current reverses, the gate allows the voltage signals to trigger the SCR. The SCR turns on a transistor energizing a relay, after a brief delay. The relay acts to set the regulator or other device in power reverse condition. When current again is forward, the relay is deenergized and the device returned to the forward condition.

Abstract: A directional relay for a polyphase electric power transmission system wherein the direction of a fault from the relaying point is determined by determining the sense of the variation of the zero or negative sequence voltage of the system between the relaying point and the fault point.