Showing papers on "Relay published in 1981"

Satellite communications system and apparatus

Abstract: A satellite communications system, which is inherently power limited, employing spread spectrum techniques in order to trade-off bandwidth for small ground station antennas. In a one-way system embodiment a central station transmits data to a satellite for relay to a large number of small antenna receiving stations, the transmissions being spread spectrum encoded with spreading code lengths selected to provide adequate data recovery at the least sensitive station to which the transmissions are directed. Spreading codes may also function to address particular stations. In a two-way system embodiment, the central station additionally functions as a terrestrial relay station. A plurality of small antenna transmitting stations, at least one of which may be at the same site as a receiving station, transmit code division multiplexed data via the satellite to the central relay station using sufficiently long and distinct spreading codes as to permit adequate data error rates and to distinguish the transmissions of the various stations. The central relay station reformats the received data for retransmission to the satellite for relay to the receiving stations.

Method and apparatus for controlling distributed electrical loads

Abstract: An apparatus for controlling distributed electrical loads including a microprocessor based central controller coupled via a twisted pair bidirectional data line to a plurality of microcomputer based transceiver decoders. Each transceiver decoder is coupled to a plurality of relays, each relay associated with a particular load to be controlled. Override switches and sensors, coupled to transceiver decoders provide override requests and information related to ambient conditions at the site of a load. A user defined data base includes sub-sets of relays called sectors, patterns of relay states, remote switches, a time dependent schedule and condition responses. A communication protocall and arbitration scheme provide for interactive communication between the central controller and each transceiver decoder with interfacing with the operation of any other transceiver decoder. Enhanced data storage capacity is achieved through dynamic allocation of memory space for pattern data.

Hybrid D.C. power controller

Abstract: A hybrid D.C. power controller of the relay/circuit breaker type that uses a hybrid arrangement of hard contacts (4) and power FET's (18, 20) in cooperative functional combination as the arc quenching means for 270 volt D.C. power systems in low atmospheric pressure environments such as at 80,000 feet altitude in aircraft applications. Also, the relay is provided with arc horns (44c, 48b, 48c, 46c), magnetic field amplifiers (60, 62) looped stationary contacts (44, 46), arc splitters (64, 66), and gas ablating insulating members (60b, 62b, 72, 74, 64b, 66) to enable the relay to interrupt the power circuit if necessary without the help of the power FET's. The power FET's are controlled in both opening and closing the power circuit to afford arcless contact operation in normal load make-break situations. Current and voltage sensing (28, 32) and sampling (CS, VS) circuits determine when to turn the power FET's on after contact arcing has provided the required values. The power contacts (4) can be closed and opened by manual switch (TS) control and opened automatically under overload or short circuit conditions by instantaneous trip detector (ITD) control. Isolation contacts (2) in the power circuit are controlled by delay means (MMV4, MMV8) to close last and open first with respect to the power contacts.

Protective relaying system

Abstract: A protective relaying system which detects a fault in an electric power system having a circuit breaker by using a current and a voltage of the electric power system. The protective relaying system includes input conversion unit adapted for connecting the electric power system to receive a first and a second input signals corresponding to the current and the voltage and for converting the magnitude and/or the phase of the first and second input signals to produce a first, a second and a third electrical quantities. The protective relaying system also includes comparing unit connected to receive the first, second and third electrical quantities, for comparing the first and second electrical quantities to produce a first logical state signal, and comparing the third and a fourth electrical quantities to produce a second logical state signal cyclically, and for producing a logical state signal including the first and second logical state signals cyclically. The protective relaying system further includes digital data processing unit connected to receive cyclically the logical state signal, for producing a first and a second serial logical state signals and for judging whether a phase-rotation sequence of the first and second serial logical state signals equals a predetermined sequence to produce a protection relay output signal. The protection relay output signal is used to trip the circuit breaker.

Current Transformer and Relay Performance in the Presence of Geomagnetically-Induced Currents

Abstract: Transient fluctuations in the earth's magnetic field are caused by solar flares or other solar phenomena. These geomagnetic field disturbances cause quasi-dc geomagnetically-induced currents (GIC) to enter a power system at grounded neutral points. The GIC is usually of sufficient magnitude to cause half-cycle saturation of large power transformers. GIC's in excess of 100 amperes have been measured in transformer neutrals, and GIC's of over 200 amps per phase can be expected on some autotransformers. This paper presents the results of studies investigating the effects of GIC upon current transformer and relay performance. The average CT flux density and CT error are examined in the presence of GIC. The effect of GIC upon CT remanence is also presented. The transient performance of the CT is studied to determine the reduced time-to-saturation from a combination of GIC and DC fault offset. Relay performance is considered in two categories (1) relay misoperation resulting from erroneous CT response, and (2) relay misoperation resulting from GIC interaction with large power transformers, notably differential protection

Method and circuit for controlling a hybrid contactor

Abstract: A method and circuit for minimizing DC current offset generated by the voltage-integrating property of an inductive load. First, second and third hybrid contactors connect first, second, and third output lines of an AC power source to first, second, and third input lines of an inductive load. Each hybrid contactor includes a pair of relay contacts in parallel with a semiconductor switching unit having two antiparallel-connected silicon-controlled-rectifiers. A latching circuit and several delay circuits are used to turn on and off the hybrid contactors; the timing of the turn-on points is controlled relative to a zero-crossing of a voltage from the AC power source such that minimal DC offset current occurs.

A Microcomputer Based Ultra-High Speed Distance Relay: Field Tests

Abstract: This paper describes the field tests of a microcomputer based Symmetrical Component Distance Relay (SCDR). A brief review of the relay operating principle is followed by a description of the field tests conducted by staging faults on a 765 kV transmission line on the AEP system. Performance of SCDR during these tests is analyzed. A newly developed Ultra-High-Speed (UHS) mode of operation for the SCDR is presented, and the performance of the relay in the Ultra-High-Speed mode is illustrated with the data gathered during the field tests.

Diagnostic monitor system for heat pump protection

Abstract: A method and apparatus for monitoring the protective circuit associated with a heat pump system wherein both the high pressure switch on the condensor side of the compressor and the low temperature switch on the evaporator side of the compressor are continuously monitored by a low voltage rectifier circuit that relays a signal to a second lock-in relay circuit which in turn initiates and maintains a signal light indicating which switch caused the heat pump system to turn down. Such a device is an inexpensive yet reliable method of diagnosing problems and dangerous conditions with minimum risk to the heat pump.

Piezoelectric relay with oppositely bending bimorphs

Abstract: The invention relates to a piezoelectric relay in which a bimorph is used as a flexible element. First, second and third relay contacts (14), (14') and (14") are disposed coplanar with the third relay contact sandwiched between the first and second relay contacts. First and second flexible members (11) and (11'), each of which is supported as a cantilever, are displaced in directions opposite to each other when an electric field is applied to one. The first flexible member (11) displaces the first and second relay contacts (14) and (14'), and the second flexible member (11') displaces the third relay contact (14"). Thus, the first and third relay contacts (14) and (14") and the second and the third relay contacts (14') and (14") are turned on or off in response to the different polarities of the applied electric field.

Diode assisted relay contactor

Abstract: A switching circuit having hybrid contactors connects the three output lines of a 3 phase AC power source to three input lines of a load, such as a motor and the like. A single pair of relay contacts is used to directly connect one output line of the AC power source to one input line of the load, whereas each of the other two phases of the AC power source are supplied to the load by one of a pair of pilot relay contacts in series with a diode-shunted one of a pair of master relay contacts. Only two extra pilot relays are used to provide a reversing function. The switching circuit further includes a zero-crossing detector, a phase-sequence detector, a control circuit including four flip-flops arranged in a tumble-down chain and a single distribution circuit having a data select circuit. The control circuit causes the making and breaking of the contacts at particular times, and in a sequence, such that arcing is prevented.

Broken rail/bond detectors

Abstract: A track circuit receiver is driven by the signal across an impedance bond and operates a relay to disconnect the signal so causing the relay to cycle. In series with the receiver input is a signal from the center tap of the impedance bond, which is normally at earth potential and does not affect the relay cycling. In the event of a rail break a significant output is obtained from the center tap, which either cancels or replaces the original receiver input signal but on a permanent basis uncontrolled by the relay. The relay therefore ceases to cycle in either event and thus provides a break indication.

Control circuit for electrical appliances

Abstract: A circuit for controlling a ceiling-type fan includes a switch or relay for controlling the fan, connectable to the fan. A logic circuit produces an output signal for controlling the switch or relay from an input signal generated by momentarily interrupting the power applied to an input to the logic circuit. A diode and capacitor isolate the power supply connections of the circuit to maintain the supply voltage during the momentary power interruptions. In one embodiment the control circuit controls the on-and-off switching of the fan, as well as its speed, together with on-and-off switching of a light associated with the fan. In one embodiment the forward and reverse directions of the fan are controlled as well.

Recognition and Self-Organization of Nodes into DTDMA Nets

Abstract: An effective relay management solution applicable to multiple terminal ground-to-ground or ground-to-air line-of-sight communication environments is described. Algorithms are developed which enable terminals first to recognize the existence or availability of other terminals, and second, to self-organize a community of terminals rapidly into local nets without the need for a master control terminal. Computer simulation results show how a static or dynamically changing user geometry can be managed. Network connectivity is provided automatically and the system protects itself against the loss of a master user by not requiring one.

Stability of limit cycles in feedback systems containing a relay

Abstract: The stability of limit cycles in feedback systems containing a relay is investigated in the paper. A necessary and sufficient condition for limit-cycle stability as well as a second necessary condition are derived. The conditions are used in conjunction with the exact limit-cycle solution which is readily found for relay systems. An approximate version of these two conditions, using the describing-function solution for the limit cycles, is also proposed. Extensive simulation results are given to substantiate the theory developed.

Motor protection control circuit

Abstract: A protection device and circuit for a fluid pump or the like including a motor control relay MS for actuating relay contacts MS-1, MS-2, MS-3 that control the communication of power to a drive motor 10a, and a manual reset motor protection device 24 that deenergizes the control relay in response to sensed malfunctions. The motor protection device comprises a manual reset motor protector 40 having switch contacts 42 connected in series with the motor control relay and a tripping coil 44 which, when energized, opens the switch contacts. A current shunt path 46 including serially connected pump assembly mounted sensors 48, 50, normally shunts current around the tripping coil and is interrupted in the event of a sensed malfunction, causing the energization of the tripping coil which opens the switch contacts and deenergizes the drive motor. The switch contacts must be manually reclosed to reactivate the pump assembly. The impedance of the tripping coil and the motor control relay are selected so that should the switch contacts fail to open in response to energization of the tripping coil, the impedance of the tripping coil will reduce the voltage on the control relay below its seal-in value, thereby deenergizing the control relay.

Apparatus for controlling distributed electrical loads

Abstract: An apparatus for controlling distributed electrical loads including a microprocessor based central controller coupled via a twisted pair bidirectional data line to a plurality of microcomputer based transceiver decoders. Each transceiver decoder is coupled to a plurality of relays, each relay associated with a particular load to be controlled. Override switches and sensors, coupled to transceiver decoders provide override requests and information related to amibient conditions at the site of a load. A user defined data base includes sub-sets of relays called sectors, patterns of relay states, remote switches, a time dependent schedule and condition responses. A communication protocall and arbitration scheme provide for interactive communication between the central controller and each transceiver decoder with interfacing with the operation of any other transceiver decoder. Enhanced data storage capacity is achieved through dynamic allocation of memory space for pattern data. This divisional application is particularly directed to an improvement in the transceiver decoder permitting it to accumulate data from switch actuations and then transmit this accumulated data to the central controller whenever the transceiver decoder can gain access to the twisted pair data line.

Vital DC source ground fault detector apparatus

Abstract: A pair of transistors, alternately activated by a low frequency generator, alternately connect the positive and negative terminals of the monitored DC source to the common bus of the ground detector apparatus Each produces a fault current signal flow through any ground fault existing on the other source terminal, with the return circuit including a permanent ground rod, the input of a comparator, and apparatus common An opposing reference current signal of preselected level is applied to the comparator input, at the same time as each fault signal, from a current pump network driven by the low frequency generator If each reference current signal is larger than the corresponding fault current signal, the comparator output is a square wave signal of alternate plus and minus pulses which is applied to a negative voltage generator network controlled by contacts of two synchronizing relays alternately driven by the low frequency generator If the comparator square wave output is synchronized with synchronizing relay operation, a registry relay is held energized to indicate the absence of ground faults on the source If either or both fault current signals are greater than the corresponding reference current signal, the output is either of one polarity or is not synchronized with the relays so that the registry relay is deenergized and releases to indicate a ground fault condition

Power relay with assisted commutation

Abstract: The contacts of a power relay are shunted by a gateable semiconductor device to assist in the commutation of contact-destroying arcs upon making and breaking of the power relay contacts; current-detection apparatus, such as a current-sensing transformer and the like, are utilized in the conductors connecting the relay contacts and the gateable switching device to an input from an A.C. source. Control electronics receive the outputs of both current-sensing apparatus to gate the shunting device into conduction during relay contact closure and separation, in a manner to minimize the current passing through the shunting device and therefore to minimize the energy dissipated therein.

Minimum power, feedback controller, transmit/receive switch

Abstract: A transmit/receive switch incorporating a latching relay in a feedback circuit so that the relay is energized only when it is commanded into a different mode (transmit or receive) than it is in, and the energization is removed as soon as the relay switches into the correct mode.

Static distance relays with improved polarizing signal

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 POL =V AB +KV 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 POL =V A +KV AJ , where K is approximately 0.3. Other embodiments are disclosed.

Electronic control system

Abstract: An electronic control system particularly suited for use with an automatic fuel dispensing system uses a centrally located computer to supply serial polling signals to various sub-stations. At the sub-stations, the polling signals are decoded into signals used to control the operation of specific system relays operated by the system. The status of the decoded polling signals as well as the operating status of the relays is supplied back to the computer for verification. A time-out control circuit continuously monitors the input polling signals applied to the relay terminal. If activity does not appear on the input signal line at the terminal after a pre-established time interval, all of the system relays at that terminal are turned off or rendered inoperative, irrespective of the status of the relay control signal obtained from the output of the polling signal decoding circuit. As a consequence, if the remotely located computer should fail to properly operate for any reason, the system is placed in a "fail-safe" standby condition of operation.

A Subsynchronous Oscillation Relay - Type SSO

Abstract: The philosophy and design of a subsynchronous oscillation (SSO) relay are discussed. The relay utilizes a unique technique for detecting extremely low magnitudes of subsynchronous current. Special logic is used to determine if the currents represent a potential danger to a turbine-generator. A procedure for selecting relay settings is described.

Low energy relay using piezoelectric bender elements

Abstract: A remote disconnect coupler 18 for accomplishing switching at the end of a transmission line 12 between a test apparatus 24 and normally connected equipment 20 in response to signals from a remote command apparatus 16 includes a piezo-electric switch actuator 26 and command identification apparatus 28. In preferred forms the identification apparatus times reswitching and accomplishes snap switch action with oscillatory switch actuators 150 and dual switch actuators 116, 120.

Programmable sequence control method and devices

Abstract: A programmable sequence control apparatus including a first memory device for storing sequence program instructions, an input/output device, a relay ladder operation device for executing logic operations for a relay ladder circuit having n rows and m columns (wherein n and m are positive integers) in accordance with the program instructions, and a control device for delivering control signals to the relay ladder operation device, is so constructed that the control device includes a memory device for storing contact data and branch data for one column j (wherein j=1, 2, . . . , m) of the relay ladder circuit temporarily, the relay ladder operation device includes first and second registers of a series-in and parallel-out mode which receive and store the contact data and the branch data for the column j, respectively, a third register normally operable in a parallel-in and parallel-out mode, and a gate circuit including logic elements for executing logic operations for the column j based on the parallel delivered outputs of the first and second registers and a third register storing the operation results for the preceding column (j-1), and the relay ladder operation device repeats the aforementioned operation for all of the columns of the relay ladder circuit.

Application of Subsynchronous Oscillation Relay-Type SSO

Abstract: A subsynchronous resonance relay which will protect against Torsional Interaction, Torque Amplification, and Induction Generator Effect has recently been developed. This paper describes the theory and rationale applied to select the appropriate settings for the newly developed relay. An example is employed to effectively demonstrate the methods applied. This example in conjunction with a description of some tests provides a good indication of the level of protection and security provided by the relay. Ref. I describes the newly developed relay in detail.