Showing papers on "Relay published in 1977"

Fundamental basis for distance relaying with symmetrical components

Abstract: The paper derives the performance equation of a high speed distance relay which is based upon the theory of symmetrical components. A single equation is shown to be adequate for handling all types of faults which are likely to occur on a three-phase power system. Errors created by system loading and fault-path resistance are considered. A numerical example illustrates the principle of operation of the relay. The relay is especially suited to a digital computer based protection system.

Control circuit for an electrical device

Abstract: A control circuit for an electrical device which includes a switch that is electrically isolated from other components. The switch is connected in series with a photovoltaic cell and relay means. The photovoltaic cell is illuminated so that closing of contacts of the switch causes actuation of the relay means. The relay means is connected to actuate the electrical device. Voltage at the switch is limited by the voltage produced by the photovoltaic cell.

Power contactor and control circuit

Abstract: The power contactor for controlling the application of power to and the character of the current to a load includes a power relay having contacts connected between a source of power and the load, such as a motor or heater, with each of the contacts being provided with arc suppression means. A steering relay is provided to control the direction of current to a motor and thus its direction of rotation or the voltage applied to a heater. A control circuit insures that the steering relay contacts remain either open or closed while power is being applied to the load. The steering relay is provided with bracer bars to prevent short circuiting between relay contacts should any welding occur therebetween. The arc suppression means for each of the power relay contacts includes a solid state device, such as a triac, in parallel therewith, and auxiliary contacts for controlling the gating current to the triac. The auxiliary contacts close prior to either the opening or closing of the power relay contacts and open just after either the opening and closing of the power relay contacts, and therefore no gating current is applied to the triac while the power relay contacts are closed.

Remote control portable wirefeed arc welding system

Abstract: A remote control unit for closing a normally open contactor in response to closing of a normally open gun switch in a portable wirefeed arc welding system having a power source including the contactor, a portable wirefeed unit, a welding gun, a ground cable interconnecting the power source and the work, an electrode power cable interconnecting the power source and the wirefeed unit and gun, and control leads interconnecting the wirefeed unit with the work and the gun; wherein a capacitor in the control unit is operable to place an override current on the ground and electrode power cables in response to closing of the gun switch, and sensing means comprising a sense relay are operable in response to such override current to effect closing of a normally open cycle hold delay relay and the contactor. The cycle hold delay relay, in turn, closes a fourth or rearming delay relay which opens the circuit to the sense relay. So long as welding current is drawn, the first control relay remains closed to hold the cycle hold delay relay closed. An interruption of welding current for two seconds causes the cycle hold delay relay to time out to open the rearming delay relay and the contactor.

Motor protective device

Abstract: An electrical device is connected to the magnetic starter of an electrical motor to protect the motor windings from a loss of power on one or more input lines of a three phase power source. The device includes two transformers each being connected across two input lines and having one input line in common with each other. The transformer secondaries are each connected in a relay circuit so that a voltage on the secondary of each transformer above a predetermined value will actuate the relay in its respective circuit. The contacts of both relays are connected in series with each other and with the magnetic starter of the electrical motor so as to actuate the magnetic starter when both relays are closed. When the voltage on any of the three input lines drops substantially below a normal operating level, one or both of these relays will open, immediately turning off the magnetic starter and shutting down the motor to prevent damage to the motor windings. The transformer primary windings are connected through a terminal strip to the power source to enable series or parallel connections to accommodate both 240 volt and 480 volt power lines.

OFF-ON-START switching system for diesel engines, and particularly automotive-type diesel engines

Abstract: To simplify the circuitry and improve reliability of pre-heat, glow-plug or the like operation while using a conventional automotive OFF-ON-START switch, a momentary-operation pre-heat switch is included in the circuit, as well as a heat-sensitive relay and a timing circuit, the heat-sensitive relay determining if pre-heating has been sufficient, and the timing relay then providing a limited time period to permit starting of the engine while still maintaining pre-heat conditions but discontinuing pre-heat conditions if starting is not commanded.

Protective arrangement for dependent switching circuits

Abstract: This invention comprises a fusible resistor in a solid astate relay comprising two solid state switches con-nected in parallel with each other, but in series with a load and a source of current. When the first of the two switches is switched on, the second switch also switches on, and con-ducts, supplying sufficient current to the load, thus reduc-ing the voltage across both switches to that of the voltage drop across the second switch. Should the second switch fall to become turned on When the first switch is turned on, there will be a higher voltage across the first switch (and the components in series with it, if any) causing excessive current to flow through the first switch, resulting in its overheating and possibly fire, particularly if the switch is encapsulated. By providing a fusible resistor in the circuit of the first switch, the fusible resistor will open at such time and disconnect the first switch from the cir-cult, preventing a possible fire or possible damage to adjacent equipment.

Relay control circuit

Abstract: A relay control circuit is disclosed in which a timer circuit is actuated by a reference clock pulse in synchronism with an AC voltage supplied by a commercial power supply. An output signal of the timer circuit causes current to flow in the coil of the relay thereby to close the contact of a relay. The invention further comprises a polarity-reversing device for reversing the polarity in accordance with the variations in the output signal of the timer circuit. The reference clock pulse is applied to the timer circuit through the polarity-reversing device.

Linebreak detection system

Abstract: A pipeline break detection system wherein a rate timing device is activated in response to a predetermined pressure drop in the pipeline to direct a signal and activate the on-delay cycle of an energy-blocking device, such as a relay switch in an electric circuit. The timing device then commences an off-delay cycle, and if such cycle continues to completion, it cancels the countdown of the on-delay relay. However, if the pipeline experiences a further like pressure drop, before the timing device completes its cycle, it will be recharged and remain activated to keep the on-delay relay actuated. If the pipeline pressure fails to level off to allow the rate timer relay to close, and the on-delay relay is thus enabled to complete its timed cycle, the relay closes to deliver an electrical signal.

A digital rate-of-change underfrequency protective relay for power systems

Abstract: A digital relay is described for power systems application which responds both to frequency and to rate of change of frequency. Its application is in the operating situation of load suddenly in excess of generation, either because of sudden unexpected added load or because of generator or other equipment failure; and its function is the initiation of preplanned emergency load shedding. Advantages of the relay are its sensitivity to generation-load imbalance, and its relative simplicity.

Using the computer to set transmission line phase distance and ground back-up relays

Abstract: The size and complexity of modern power transmission systems, plus the recent advances in computer technology, have made the manual calculation of relay settings impractical. Although the settings of many relays can be best handled by programmable calculators or minicomputers, one relay at a time, the time interval coordination required for phase distance and directional ground overcurrent relays dictates that a systems approach be used. The data and calculations inherent in considering a system of reasonable size require that a large core computer be utilized. Several programs have been developed to perform this function. The unique approach taken in developing the program outlined in this paper was to provide the engineer, with a knowledge of the system under study, the power to interact with the computer in making decisions of how to best make compromises to optimize system protection and reliability.

Distance protection performance during simultaneous faults

Abstract: The paper considers the performance of both unswitched and switched distance protection schemes using polarised-mho relays on systems subjected to simultaneous faults. The disturbances considered are flashoverfaults to earth, cross-country earth faults and open-conductor plus earth faults on a double-circuit 132 kV transmission system. Consideration is also given to protection performance for double earth faults separatedby a star-delta transformer. Differences in protection philosophies of British and Continental relay manufacturers are highlighted and a comparison is given for switched schemes employing overcurrent starter units.

Condition responsive thermostat control apparatus

Abstract: An ambient room illumination responsive control automatically changes the setting of a thermostat with ambient illumination. A thermostat has a pair of temperature responsive switches connected in series with control leads and a controller to low voltage A.C. power. A bypass relay has contacts connected in parallel with one of said switches. An illuminating sensor has a photoresistor in series with a resistor connected across leads with a common node connected to the gate of a controller rectifier. A capacitor timing unit is connected in one embodiment to produce a pulsed input. The rectifier is connected in series with a winding of the bypass relay and the timing unit across the thermostat leads. The rectifier conducts to open the relay contacts and insert the second switch in circuit. A second relay winding is connected across the control leads in series with a diode and a timing network to reset the relay and close the contacts. The time constants of the two timing circuits where employed insure proper operation of the set and reset branch circuits. A separate remote pulse control may be provided.

Elevator safety device

Abstract: An armature of an electric motor for an elevator car is controllably driven by a three-phase source through a semiconductor converter controlled with a difference between a command and an actual car speed signal. A relay for sensing a ripple current from the converter is serially connected to a tuned filter across the armature. When a break occurs anywhere in a circuit with the motor armature, the sensor relay is deenergized and connects an emergency braking circuit across the armature. Alternatively the sensor relay may be connected via the filter to a reactor connected to the converter.

Multi-mode control logic circuit for solid state relays

Abstract: For providing an interface between a low level input control signal and a power switch, a control logic circuit is presented for permitting operation of a solid state relay in any one of a plurality of modes of operation including operation as either a normally open relay, a normally closed relay, or a latching relay, and also to make possible combinations of such relays for operation in parallel with a second relay operating in or out of phase with a first relay The control logic circuit includes logic gates with means for selective interconnection of external terminals to set the operation in the desired mode as well as to permit one relay to be responsive to the condition of another

Protective relay circuit providing a combined distance and overcurrent function

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 R - Z F ) is applied. The quantity I is the current in the line, Z R is a replica or reference impedance corresponding to the lines being protected and Z F is the line impedance to the fault from the relay measuring point. IZ 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 R - Z 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. The protective relay circuit may be used on series-capacitor compensated lines as well as on uncompensated lines. When the protective relay circuit is used on a compensated line, the a-c threshold level of the level detector is set to be a function of the breakdown voltage of the spark gap protecting the series compensating capacitor.

Electrical power supply fault detecting system

Abstract: To detect system ground faults and shorted alternator output winding turn-to-turn faults, the series combination of a resistor and the operating coil of an electrical relay having a normally closed contact pair is connected between the neutrals of two parallel connected polyphase alternator output winding groups, the junction between the resistor and operating coil is connected through a resistor to ground and the normally closed relay contact pair is connected in series in the alternator exciting field winding energizing circuit. To detect open diodes in the main polyphase diode bridge type full-wave rectifier circuit, an auxiliary polyphase full-wave rectifier circuit having the operating coil and normally closed contacts of two relays in series in each leg is provided. Upon the failure of a diode of the main rectifier circuit, sufficient current to operate the corresponding relay in the auxiliary rectifier circuit is diverted therethrough. Upon the operation of one of the auxiliary rectifier circuit relays, the magnitude of the energizing potential supplied to the alternator exciting field winding is reduced and upon the operation of more than one of the auxiliary rectifier circuit relays, the alternator exciting field winding energizing circuit is interrupted.

Circuit fault detection apparatus for railroad track circuit redundant connections

Abstract: Continuity detector apparatus is coupled into duplicate conductors connected in parallel between each rail of a track section and an energy source or occupancy receiver of an associated track circuit to detect and register a fault in either parallel conductor and to indicate need for corrective action to restore the operational security provided by the duplicate circuit paths. In one form, each detector is a two-winding relay with one winding inserted in series in each of the duplicate circuit paths so poled that equal track current flows in opposite directions in the winding, when both conductors are unbroken to hold the relay released. Any interruption of either parallel conductor causes the relay to pick up to register the fault and transmit a corresponding indication. In a second form, a different transformer winding is connected with each conductor. An alternating current voltage of selected frequency is applied to the other winding of one transformer which, if both track conductors are complete, causes a current to flow in a loop including each conductor. This produces an output from the other winding of the other transformer which is applied through a filter and amplifier to hold energized the detector relay. A break in either conductor interrupts the loop, deenergizing the relay which releases to register the fault and activate an indication to signal a need for repairs.

Safety test circuit for combustion control apparatus

Abstract: A safety test circuit for a combustion control apparatus. This safety test circuit is used to check the off-failure of a safety transistor actuating a safety relay which acts to stop the operation of controlled units in the event of mal-combustion or the like, and also to check the on-failure of a control transistor actuating a control relay which controls the controlled units. An operation instruction signal and the collector potential of the safety transistor are applied to a logic circuit including a flip-flop and logic gates so that the off-failure of the safety transistor can be driven to check, utilizing the electrical signal propagation delay time of the elements constituting the logic circuit, before the propagation delay time has elapsed. The logic circuit is also used for similarly checking the on-failure of the control transistor. A check signal may be additionally applied to the logic circuit so that these transistors can be tested during the continuous operation of the combustion control apparatus.

Motor control circuit

Abstract: A motor control circuit for preventing automatic restarting of an electric motor following an interruption of electric current flow therethrough. An electric motor incorporates winding means and a series automatic reset thermal overload protector. Current flow to the motor is normally controlled by current supply switch means in series with the motor across electric power input terminals. A first relay device is switched by external actuation of a normally open start switch to switch the current supply switch means to its conductive state for starting the motor. A second relay device connected across a pair of motor terminals is energizable in response to current flow through the motor. A restart prevention switch connects in series with the current supply switch and motor across the electric power terminals. The restart prevention switch is coupled to both the first and second relay devices and is controlled thereby for permitting current flow to the motor therethrough either while the start switch is being actuated, or while the motor is operating, the restart prevention switch otherwise being in its current blocking state.

Thermal overload protection unit for electrical machines - has excess load relay to develop electric analogue of rotor temp.

Abstract: The thermal overload protection unit operates via an excess-load relay that takes the electric machine out of circuit in the event of overloading. It is partic. suitable for a synchronous motors protection where rotor temps. can build up to high values during start up and speed build-up to the normal running speed of the motor. The excess load relay simulates the heating effect in the motor armature by an electrical parameter(s), and in addition a speed related magnitude is supplied to the relay to adjust the response of the protection unit as a whole.

Electric motors control system

Abstract: This system for controlling the operation of several electric motors notably for blinds and similar devices comprises a plurality of decentralized control devices each associated with one motor and controlled from a central control means via a common control line. Each decentralized control device comprises, for each direction of rotation of the motor concerned, a relay and, for each motor, control means connected in parallel to the common control line. The control means for each relay comprise a switch connecting the common line to the middle point of the pair of inverters controlling the two directions of rotation of the motor. The front contact of each inverter controls the energization of the corresponding relay and the back contact of each inverter controls the self-energization of the relay of the other inverter via a self-energization contact provided on the other relay.

Over-current protective apparatus for a power circuit

Abstract: A solid state relay structure for use with different alternating current motors having a range of full load current and service factor ratings. The relay includes a rectangular housing and bores extending through the housing through which conductors to the motor are passed. The rear end of the housing is spaced from the panel on which the relay is mounted so the conductors may be looped through the bores when portions of the looped conductors are passed in the space between the rear end of the relay and the panel. The solid state components of the relay are encapsulated in the interior of the housing and are connected to switches, terminals, and a light emitting diode located at the front of the housing so the relay may be easily programmed for use with motors having different ratings. The terminals and operating and test instructions, located at the front end of the relay, provide a convenient arrangement for wiring the relay in its control circuit and information to program the relay.

Decentralized mounting method for path-selective relay

Abstract: PURPOSE:To make it possible to employ a short-life relay, and to make narrow the range of trouble influence by decentralizing and mounting a path-selective relay on each trunk package.

Digital output control circuit

Abstract: There is shown a digital output circuit wherein digital data from a computer based controller is applied as input signals to a set of holding latches which are, in turn, enabled by control circuitry such as by response to address signals. The digital data stored in the several holding latches are applied as input signals to a corresponding number of relay driver circuits. The relay driver circuits are, in one aspect of the invention, coupled to selectively operate output control relays in accordance with the data signals applied to the driver circuits therefor. In another form, the driver circuits are connected directly to an output circuit without the intervention of relays. Selective control is provided for establishing the relay output signal in a latched or holding mode or in a controlled time momentary closure mode. In the momentary closure mode the time is established by a data controlled counter. Additionally, a protective circuit is provided which prevents the output circuit from issuing a spurious output signal during a power-up or power-down interval.

Mailbox signalling device

Abstract: A device for signalling when a remote receptacle such as a rural mailbox has been opened. The device includes a switch that is closed by the opening of the box, a relay actuated thereby, a hold-in circuit established by the relay, a signalling means such as a buzzer or a light or both that is energized when the relay is actuated and a reset switch in the hold-in circuit for disabling the relay and the signalling means.

Earth leakage detection in compensated power networks - uses superimposed AF signals and reactive power relay detector

Abstract: A method is used for determining earth leakage direction in compensated power networks. It involves phase analysis of voltages and currents of frequency higher than the power frequency using a reactive idle power relay. It is designed to enable faulty conductor identification and thus decisions on preventive measures. The higher frequencies are superimposed on the network using external audio frequency sources and would not normally occur in the network. The superimposed signals are single phase and are applied to the neutral terminal for defined test periods via a filter.

Fault current protection circuit - has summator transformer, amplifier for fault signal and triggering relay override

Abstract: A fault current protective circuit consists of a summing current transformer. The primary windings of the transformer are formed by the lines of an AC or three-phase supply. There is a frequency generator produces a bias magnetisation in the summing current transformer via a bias magnetising winding. The secondary winding is connected to an amplifier which amplifies a pulse given off by the secondary winding when there is a fault on the line. A triggering relay is connected in the amplifier circuit. The current in the line (1) of the AC supply can be interrupted by a circuit breaker (2). The circuit breaker is actuated by a switching mechanism (3). The switching mechanism is triggered by the relay (6). The summing current transformer (4) has another secondary winding (5) which is connected directly to the triggering relay (6) thereby overriding the amplifier (7).

Safety device for concentrically contrlling address

Abstract: PURPOSE:To obtain a safety device for concentrically controlling an address which are simple and surely operable, by adequately connecting a keep relay to a switch which operates and release a relay.

System for land seismic cable fault location

Abstract: A system for locating discontinuities in land seismic geophone cables, which cables have plural sections with electrical connectors at the ends of each section. One of the connectors of each section has a relay incorporated with it, and includes a circuit for connecting a short circuit between all of the plural geophone circuit conductors. The short circuit connection is made when the relay is actuated, and the relay is actuated upon command from a recording station.