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 directional relay for providing indication of the direction of a fault on an electric power transfer network has an adder (9), a subtractor (10) and filters (11) which receive signals from voltage and current transformers (6,7) and derive signals related to fault-induced forward and backward transient waves on the network. To ensure reliable operation even when the relay is close to a low impedance element such as a generator (2), the forward wave related signal is delayed in a delay unit (12) by an amount equal to the propagation time of the wave along the section protected by the relay, before the difference between its square and that of the backward wave related signal are integrated (16) to derive the fault direction signal.

Abstract: A pseudo-random measuring signal whose spectrum is constituted by lines of predetermined frequencies spaced apart from each other is applied to a system to be characterized, and one or, successively and one by one, a plurality of lines of the spectrum of the measuring signal are selected for making a comparison in phase and amplitude between the input and the output of the system; for a non-linear system, one or, successively and one by one, a plurality of lines of the spectrum of the measuring signal are eliminated at the input of the system, and the phase and/or amplitude of the corresponding line is measured at the output of the system.

Abstract: A monostable circuit of a voltage-to-frequency converter supplies feedback pulses to balance the input signal to a first integrator. These same pulses are supplied to a second integrator where they are compared with reference pulses from a crystal-controlled clock. Any drift in the pulse-width of the feedback pulses is corrected by a control signal applied to the monostable circuit by the second integrator to vary its quasi-stable period appropriately. Thus the precision of the converter is improved without disturbing its asynchronous properties.

Abstract: An electronic watthour meter for connection in a two-wire power distribution circuit comprises a shunt connected in one of the wires and an electronic circuit comprising a transconductance multiplier, a V to F converter and a reversible counter. The DC power supply of the electronic circuit is referred to the wire containing the shunt, which wire is always live, so that the electronic circuit "floats" electrically on this live wire. The first input of the multiplier can therefore be directly connected across the shunt, and the second input is connected via a high value resistance to the other wire so as to receive an input current representative of the voltage between the wires. To eliminate the effects of drift in the multiplier, the polarity of the input current to the multiplier and the direction of counting of the counter are periodically and simultaneously reversed by a square wave signal of 1:1 mark space ratio. The electronic circuit is implemented using LSI techniques.

Abstract: A measurement shunt comprises a resistance provided with first and second voltage terminals and intended to provide a voltage representative of an electric current passing through it, and an inductance connected to at least the first of said voltage terminals to produce between first and second measurement terminals a voltage free of error voltages induced in said resistance, even in the presence of a variable magnetic field. The resistance is essentially constituted by a plate (12) of electrically conductive material, the first and second voltage terminals (26,28) are disposed on the same edge of the plate at spaced apart points thereon, and the inductance comprises at least one open loop (36a) at least partly formed from an electrically conductive material extending from its first and second ends respectively disposed in the vicinity of the first and second voltage terminals, towards the interior of the surface of the plate in a plane having, at least approximately the same direction as the plate.

Abstract: In a tape transport apparatus comprising notably a floating roller (12) tangent to reels (5, 6), and an elastic endless belt (11) extending between the floating roller (12) and the reels (5, 6) to form a first loop (11a) surrounding the floating roller (12) and a second loop (11b) engaging on an arc of the periphery of each of the reels (5, 6) to maintain the tension of the accessible portion of the tape (7), this second loop (11b) extending around at least one return roller (13, 14), the invention provides that at least return roller (14) is directly driven by drive means (18, 19), whereby the peripheral speed of the driven return roller (14) and the peripheral speed of the floating roller (12) are maintained in a ratio slightly greater than 1, so as to ensure better tensioning of the tape on the take-up reel.

Abstract: A tape entrainment device especially for a magnetic recorder, comprising a roller (11) tangential to the periphery of each of the reels (9 and 10) and an endless belt (12) which passes between the roller and the reels and engages an arc of the periphery of each of the latter.The roller, which entrains the tape by friction by means of the belt on which it bears, is integral in rotation with an element (24 and/or 26) which is entrained on the one hand in rotation about its own axis and on the other hand is forced mechanically to move relative to the support along a circular path as close as possible to the path of the roller.

Abstract: A device for measuring a quantity such as the electric power in a polyphase alternating current network including at least two phase conductors and a reference conductor, of the type comprising two measuring devices which are associated respectively with the two phases and the outputs from which are connected to a summation device.A supply circuit connected to one of the phases is associated with the corresponding measuring device, and a device connected to the other phase ensures the supply to the other measuring device and to the summation device, the supply circuit and the supply device being connected through a high-impedance tie circuit, the summation device being supplied if at least one of the phases is under voltage with respect to the reference conductor.

Abstract: A switch-tuned filter comprises a capacitive filter and a resonant filter both receiving an input signal to be filtered. The resonant filter comprises a gyrator the frequency response of which depends on circuit parameters in two circuit paths therein. A tuning switch is arranged to select the values of the parameters in each of these circuit paths. The output signals of the gyrator and the capacitive filter are combined to form the filtered output signal. The circuit can be used as an equalizer in a magnetic tape recorder.

Abstract: A modulator for injecting signals into a polyphase power transmission system includes a bridge of four thyristors for each phase. The thyristors of each bridge are connected so that when the thyristors of two opposite arms are ignited simultaneously they produce a signal at the output from the modulator of opposite sense to the corresponding signal when the thyristors of the two other opposite arms are ignited. The thyristors of the adjacent arms are controlled in opposition and coupled by an induction coil having two windings which, through the back EMF generated by mutual inductance, causes the extinction of one of them when the other is ignited. The energy stored in the induction coil at the time of the extinction phase is dissipated as heat in a resistor provided for this purpose in a loop which does not contain the supply.

Abstract: A system for identifying which of the phases of an N-phase electric-power transmission network has experienced an electrical disturbance. For each phase there is produced a first signal representative of the transient variations of an electrical parameter of the respective phase, or of a linear combination of at least two of these parameters. A set of N second signals is generated from the product of two linear combinations of at least N-1 signals selected among the first signals. The sum of all coefficients for each linear combination is set to zero, with each of the second signals being related to a given phase. Each of the second signals is then integrated to produce a set of N third signals associated with the respective phases. A fourth signal is generated by combining all of the N first signals in a symmetrical manner with respect to all of the first signals, such that the fourth signal is independent of the associated phases.

Abstract: This invention relates to a tape transport for use with a transducer to transport tape along a predetermined path extending past the transducer, comprising two capstans, each disposed at a respective end of the predetermined path; two rollers, each disposed adjacent a respective one of the capstans and arranged to guide tape beyond the respective end of the path in partial wrapping engagement about its respective capstan; two motors each coupled to a respective one of the capstans; and a control circuit coupled to the motors and arranged to control operation thereof to drive the capstans at differing torques whereby to induce a controlled tension in tape extending along the path. One of the motors is driven by an independent source of signals, and the other is driven so as to be dependent, in part, of the operation of the first motor.

Abstract: A ripple control relay is arranged (i) to delay implementation of a received command until the end of a predetermined time interval following reception of the command; (ii) to delay implementation as in (i), and to implement the complementary command automatically after a further predetermined interval; or (iii) to repeat the sequence as in (ii) cyclically.

Abstract: An electronic watthour meter for connection in a two-wire power distribution circuit comprises a shunt connected in one of the wires and an electronic circuit comprising a transconductance multiplier, a V to F converter and a reversible counter. The DC power supply of the electronic circuit is referred to the wire containing the shunt, which wire is always live, so that the electronic circuit "floats" electrically on this live wire. The first input of the multiplier can therefore be directly connected across the shunt, and the second input is connected via a high value resistance to the other wire so as to receive an input current representative of the voltage between the wires. To eliminate the effects of drift in the multiplier, the polarity of the input current to the multiplier and the direction of counting of the counter are periodically and simultaneously reversed by a square wave signal of 1:1 mark space ratio. The electronic circuit is implemented using LSI techniques.

Abstract: A function generator (25) receives the signal (svm) representing the speed of rotation of a motor (13) and works out EN=CN+f (vm), f (vm) being a single-valued and monotonic function of the real speed vm of the motor and CN being worked out by computer means (24) so that: CN=EN-f (VM), VM being the nominal value of the speed of rotation of the motor. The latter is fed by a signal which is a function of EN. The reference information f (VM)=IC is worked out from an item of error information which is a function of the deviation between the real speed (vb) and reference speed (vp) of a tape (10) driven by the motor, the rate of variation of IC having a maximum value limited in absolute value.The device is suitable for subordinating the rate of travel of a tape carrying sound to the frequency of a pilot signal.

Abstract: The present invention refers to capacitive voltage transformers.In accordance with one embodiment a capacitive voltage transformer has two capacitors connected in series between a point on a high voltage line and a reference point such as earth and two impedances connected in series with the two capacitors.A medium voltage electromagnetic detector is connected between the common point of the two capacitors and the common point of the two impedances. An electronic voltage detector is connected to the terminals of the series circuit formed by the two impedances, the values of the latter being selected in order that the instantaneous voltage at the terminals of the electronic detector is always a constant fraction of the voltage taken off between the line and the reference point.Application to the operation of highspeed static protections from a capacitive voltage transformer having a medium voltage electromagnetic circuit.

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: A capacitive voltage transformer of the type having voltage divider capacitors and an electronic amplifier connected to one of the divider capacitors includes circuitry for isolating the voltage divider capacitors in the event that primary power to the voltage divider is interrupted. The circuitry measures and compares the voltage at a terminal of one of the divider capacitors and the current through the divider. If primary power to the voltage divider is interrupted, the capacitor voltage remains high while the divider current goes to zero, and the circuitry acts to isolate (such as through relay controlled switches) the divider capacitors from the electronic amplifier. This prevents any distortion from appearing in the voltages across the divider capacitors and prevents transients from developing at the input to the electronic amplifier.

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.