Showing papers on "Relay published in 1996"

Functional organization of thalamocortical relays

Abstract: The thalamus has long been seen as responsible for relaying information on the way to the cerebral cortex, but it has not been until the last decade or so that the functional nature of this relay has attracted significant attention. Whereas earlier views tended to relegate thalamic function to a simple, machine-like relay process, recent research, reviewed in this article, demonstrates complicated circuitry and a rich array of membrane properties underlying the thalamic relay. It is now clear that the thalamic relay does not have merely a trivial function. Suggestions that the thalamic circuits and cell properties only come into play during certain phases of sleep to effectively disconnect the relay are correct as far as they go, but they are incomplete, because they fail to take into account interesting and variable properties of the relay that, we argue, occur during normal waking behavior. Although the specific function of the circuits and cellular properties of the thalamic relay for waking behavior is far from clear, we offer two related hypotheses based on recent experimental evidence. One is that the thalamus is not used just to relay peripheral information from, for example, visual, auditory, or cerebellar inputs, but that some thalamic nuclei are arranged instead to relay information from one cortical area to another. The second is that the thalamus is not a simple, passive relay of information to cortex but instead is involved in many dynamic processes that significantly alter the nature of the information relayed to cortex.

An on-line relay coordination algorithm for adaptive protection using linear programming technique

Abstract: An adaptive system for protecting a distribution network should determine and implement relay settings that are most appropriate for the prevailing state of the power system. This paper presents a technique for determining coordinated relay settings. The technique uses the Simplex two-phase method; Phase I determines whether the constraints selected for illustrating the conditionality between primary and back up relays are feasible, and Phase II finds the optimal relay settings. A looped distribution system, protected by directional overcurrent relays, was used for testing the technique. The tests were conducted in a laboratory environment; some results from those tests are reported in the paper.

Coordination of directional overcurrent relay timing using linear programming

Abstract: A successive linear programming methodology is presented to treat more effectively those applications where a local structure change is performed to a power system already in operation, and where the modification of the settings of already existent relays is not desirable. The dimension of the optimization problems to be solved is substantially reduced, and a sequence of small linear programming problems is stated and solved in terms of the time dial settings, until a feasible solution is reached. With the proposed technique, the number of relays of the original system to be reset is reduced substantially. It is found that there is a trade-off between the number of relays to be reset and the optimality of the settings of the relays.

Expose hidden failures to prevent cascading outages [in power systems]

Abstract: Major blackouts are rare events, but their impact can be catastrophic. A study of significant disturbances reported by NERC in the period from 1984 through 1988 indicates that protective relays are involved in one way or another in 75 percent of major disturbances. A common scenario is that the relay has an undetected (hidden) defect that was exposed due to the conditions created by other disturbances. For example, nearby faults, overloads, or reverse power flows expose the defective relay and cause a false trip, which exacerbates the situation. Given the importance of hidden failure modes in traditional relaying systems, intervention by computer-based rational control schemes is proposed in this article. Relays with high-vulnerability indices can be identified, and their vulnerable functions and failure modes identified. Countermeasures to reduce or eliminate the likelihood of the hidden failure of key relays can be provided.

Use of biased-relay feedback for system identification

Abstract: The purpose of this work is to devise a relay feedback experiment that can identify two points on the Nyquist curve from a single test at the frequencies ω=0 and ω=ω u . An identification procedure is devised accordingly for this parameter identification. The theory of equivalent gain is described, the biased relay feedback system is analyzed, and the potential problems are explored. Parametric system identification is discussed followed by the conclusion

Self-interference cancellation for two-party relayed communication

Abstract: A source transmitted signal is cancelled at the receiver (110) associated with the transmitter (104), so that the desired received signal can be extracted from a composite received signal consisting of the source signal relayed from the relay station (Relay Device) along with the desired received signal from the other user in the pair, plus additive noise. The invention takes advantage of the fact that each of the users (User 1, User 2) knows a priori the exact structure of its source transmitted signal and can estimate the channel characteristics between the relay station and itself.

Methods and systems for automatic testing of a relay

Abstract: A system and method for automatically testing the operation of a protective relay system is disclosed. The system and method provide for continuous testing to ensure proper operation of the protective relay system while the relay remains in service and without interrupting the normal operation of the relay. This testing is performed by storing reference data corresponding to test signals, generating test signals, sampling a specific test signal, processing that test signal through the relay and comparing the processed test signal with the corresponding reference data. Upon detection of an error in the relay, the system and method further provide for isolation of the relay from the electric power system and automatic testing of individual electrical components within the protective relay system to determine the identity of the malfunctioning component. The method of determining the malfunctioning component requires: selecting a component for testing, generating a test signal, providing the test signal as an input to the selected component, processing the test signal through the selected component and the subsequent component in the protective relay system and comparing the processed test signal with corresponding reference data. Finally, the system and method further provide for automatic correction of the malfunctioning component, if possible.

Model system tests on a new numeric method of power system frequency measurement

Abstract: A numerical technique for the evaluation of power system frequency has been implemented on a TMS320C31 digital signal processor. The frequency measuring equipment has been tested on programmable relay testing equipment, using known reference signals, and on a micromachine based power system simulator. The results show the frequency measuring equipment gives fast and accurate measurement under both steady-state and dynamic conditions. The response of the equipment to instantaneous changes in phase and amplitude is found to be undesirable if the algorithm is to be applied to frequency measuring protection relays.

Method and system for resilient frame relay network interconnection

Abstract: A method and system for resilient internetwork connection of frame relay (FR) networks and/or end systems For FR relay networks interconnected by a self-healing network, a standard protocol is provided which allows a resilient network-to-network interface NNI to automatically respond to physical interfaces failures detected by the self-healing network Switching gateways in the resilient NNI, re-route further traffic to avoid the failed physical interface In one embodiment, a simple set of interacting protocols and mechanisms control communication between FR/ATM gateways and ATM switches Each FR/ATM gateway includes interworking function (IWF) processing modules for converting user data between frame relay packets and ATM cells and for processing status signaling messages to achieve a resilient NNI Status signaling messages are used to determine when the physical interface which receives cell data differs from the physical interface over which data was sent as the result of a failure detected by the self-healing network Cell traffic can then be switched to the receive ATM physical interface or to another pre-configured back-up physical interface End-to-end resiliency is obtained between frame relay networks interconnected by a self-healing network which is not vulnerable to single point failure

Frequency relaying based on instantaneous frequency measurement [power systems]

Abstract: A frequency relay capable of under/over frequency and rate of change of frequency measurements has been implemented on a digital signal processor using an instantaneous frequency measuring algorithm. Careful attention to the filtering aspects of the relay is needed under dynamic conditions due to frequency modulation of the input signal. An algorithm for avoiding unwanted relay operation due to impulsive changes in the input signal is presented. Results are shown for simulated tests using computer-based relay testing equipment, and for overloads on a micromachine power system simulator.

Multiple altitude satellite relay system and method

Abstract: A multiple altitude satellite relay system is disclosed in which Medium Earth Orbit satellites are continuously linked with at least one Geosynchronous satellite to provide uninterrupted relaying of messages and data. The Medium Earth Orbit satellites are synchronized with the Geosynchronous satellites to produce continuous links. A parameter to achieve the synchronization involves the positions of the Medium Earth Orbit satellite relays relative to the positions of the Geosynchronous satellite relays. Another parameter to achieve synchronization involves the ratio between the orbital periods of the Geosynchronous satellite relays relative to the orbital periods of the Medium Earth Orbit satellite relays. These parameters may be further adjusted to provide continuous links above the horizon of the earth.

Optical transceiver and optical communications network for both of optical fiber transmission and free space transmission

Abstract: A cable network is constituted such that interconnectable, passive 4-terminal star couplers are connected to each other via optical fiber cables and a bi-directional optical relay amplifier. Cells each constituted by using free space transmission light are integrated by the cable network. An optical signal transmitted from or directed to a mobile station in a cell is linked to the cable network via an optical relay amplifier, which provides interface between free space transmission light and guided light. Even in a case where a barrier interposed between two mobile stations prevents a direct communication between those stations, a collision between those stations can be detected by a collision detection proxy server having functions of collision detection according to the principle of code transition rule violation and jamming signal transmission. A communication between those stations can be realized by connecting, to the cable network, a relay proxy server having a packet relay and transmitting function.

Sequence based network protector relay with forward overcurrent protection and antipumping feature

Abstract: A digital network protector relay samples the polyphase current, network voltage and phasing voltage at 16, and preferably 32, times per cycle so that up to the seventh and fifteenth harmonics, respectively, are eliminated from the sequence calculation used to make trip and close decisions. The relay also provides metering, forward overcurrent protection, and an anti-pumping feature, the latter of which locks the circuit breaker out if a selected number of breaker operations is exceeded during a given time interval. Sequential sampling of the polyphase current and voltages by a single analog to digital converter reduces the cost of the relay. In order to accommodate metering and extraction of the fundamental components of the current and voltages for the sequence calculations, the polyphase current and network voltage are sampled sequentially in a first order for a given number of cycles and then in a second reverse order for the same given number of cycles.

Frequency Relaying Based on Instantaneous Frequency Measurement

Abstract: A frequency relay capable of under/over frequency and rate of change of frequency measurements has been implemented on a digital signal processor using an instantaneous frequency measuring algorithm. Careful attention to the filtering aspects of the relay is needed under dynamic conditions due to frequency modulation of the input signal. An algorithm for avoiding unwanted relay operation due to impulsive changes in the input signal is presented. Results are shown for simulated tests using computer based relay testing equipment, and for overloads on a micromachine power system simulator.

Self-monitoring line interface circuit

Abstract: A line circuit whose circuit components are selectively controllable by a microprocessor/DSP to provide normal BORSCHT functions or to be selectively tested without need for an electromechanical relay to isolate the line circuit from the loop conductors. The conventional line transformer is advantageously replaced by a loop current feed resistor network and either a high voltage or a lower voltage battery may be connected to provide loop current to the resistor network through a current regulator circuit and battery switch circuit. In normal operation, an ac feedback path, which includes the line receive amplifier, increases the terminating impedance above the dc value of the feed resistors so the loop termination resistor network may match the characteristic impedance of the loop at the audio frequencies employed. In the testing mode, the microprocessor/DSP selectively applies or denies power to the line driving and receive amplifiers as well as to a level shifting circuit interposed between the codec analog output and the input to isolate or include these components or to provide a codec loop-back path. The condition of the dc feed resistors and protective fuses, the condition of the loop closure detector and of the ringing generator are reported to the microprocessor/DSP over the same terminal normally used for reporting the on-hook and off-hook status of the loop.

A novel approach for interactive protection system simulation

Abstract: This paper presents a new approach for interactive power network protection system simulation. In the new approach, power system transients are simulated using an Electromagnetic Transients Program (EMTP), while protective relays can be modeled using any high-level language or commercially available software package, such as MATLAB. The interactions between power systems and relays are implemented by using an "interaction buffer". Using this technique, the EMTP can be run in single-step, multiple-step or mixed mode. This new approach makes the protection system simulation quite efficient, flexible and accurate.

Surge-resistant relay switching circuit

Abstract: In a relay switching panel, a switching circuit operates to selectively connect and disconnect resistive, capacitive and inductive loads to an AC power source with substantially no arcing. The switching circuit comprises a pair of relays, preferably connected in parallel, with one of such relays having a triac, connected in series therewith. With the relays open, an air gap isolates the power source and the load. In closing the relays in sequence, one relay provides a conductive path from the power source to the triac. After a suitable delay to allow the relay contacts to stabilize in the closed position, the triac is triggered to provide a conductive path from the power source to the load, and a large current surge flows to the load. After the current surge has subsided, the second relay is closed to provide a direct conductive path between the power source and the load. Next the first relay and the triac are removed from the circuit to ensure full conduction through the second relay. Another sequence of opening and closing the relays and the triac in a particular order can be employed to provide substantially arcless switching during turn off. As a result of this arrangement, the switching circuit is low cost, compact and reliable over an extended period of time.

Electrical control system for relay operation responsive to thermostat input having improved efficiency

Abstract: A temperature control system is shown in which a thermostat circuit is combined with a power supply to produce a higher anticipator current for a W1 signal while reducing power consumption and heat generation of the circuit. A first relay power signal is provided by an unbalanced bridge rectifier (D1, D2, D3, D4, D7, D8) while current drawn through the anticipator resistor (AR1) by means of an additional bridge rectifier circuit (D7, D8, D9, D10) is merged with the first relay power signal. In a second embodiment, an unbalanced bridge rectifier (D1, D4, D7, D2, D3, D8) has an output connected to a first stage relay power signal line as well as to second and third relay power signal lines. A second stage of the power supply includes a first additional bridge rectifier (D5, D6, D7, D8) connected to the second relay power signal line that drives current through the W1 anticipator while in a third stage of the power supply a second additional rectifier (D20, D21, D7, D8) is connected to the third relay power signal line and draws current through the W2 anticipator. Each stage of power adds more capacitance (C12, C11, C10) as the power requirements increase.

Keypad entry electronic combination lock with self generated combination

Abstract: A combination lock and particularly an electronic combination lock used on a container that is typically housed within an enclosure having a door which further has a lock and a security switch indicating that the enclosure door has been opened may, be provided with a device to shunt a security signal around the switch associated with the enclosure door to shut off, override, or cancel the security switch signal. The lock may be provided with a shunt relay which effectively connects a signal from a voltage source to a monitor or alarm when the combination lock is opened, thereby signaling the monitor that the enclosure door was opened by an individual having the authorized combination for the combination lock. This indicates that the person opening the enclosure lock has a legitimate authorization to access the locked container within the enclosure and that the opening of the enclosure door may be reasonably ignored. Upon the locking of the combination lock and the closing of the enclosure door a brief alarm signal indicates that the combination lock has been locked and the enclosure closed.

Parallel micro-relay bus switch for computer network communication with reduced crosstalk and low on-resistance using charge pumps

Abstract: A micro-relay replaces electromechanical and solid-state opto-isolated relays in a computer network. The micro relay is an integrated circuit containing several bus switches in parallel. Each bus switch can make or break a connection. The bus switch is an n-channel MOS transistor with the source and drain connected to different network busses. A bus enable input causes the connection to be made or broken. The bus enable input is separately buffered for each gate of each MOS transistor to prevent crosstalk between bus switches. Since the MOS transistor stops conducting when the source is at a voltage level of the power-supply voltage minus the threshold voltage, a boosted voltage is applied to the gate of the MOS transistor to allow conduction even when the source is at the power-supply voltage level. The boosted voltage is generated by a charge pump. A substrate bias is applied to the transistors to prevent crosstalk from undershoots. Buffers for the gates of the bus switches are inverters that are connected to the boosted voltage rather than the power supply, and to the substrate voltage rather than ground. Thus the gates are driven to the boosted voltage or to the substrate voltage. For reduced crosstalk when the connection is broken, two transistors in series are used for each bus switch, with the intermediate node being pulled to ground when the bus switch is disabled, shielding the two transistors and the two network busses on opposite sides of the bus switch. An external capacitor is used to reduce noise from the charge pump.

An investigation into the use of adaptive setting techniques for improved distance back-up protection

Abstract: Changes in power system operating conditions adversely affect the reach point accuracy of distance relays. This paper discusses adaptation of the settings of distance relays within an integrated digital hierarchical protection system for the optimisation of relay performance. Specific reference is made to adaptation of the zone 3 setting to ensure optimal relay performance over a wide variety of operating conditions. Results illustrating the performance of adaptive methods compared to conventional fixed setting are presented for an application study of the North Wales 400 kV transmission network, UK.

Coordination of overcurrent directional relays in meshed networks using the Simplex method

Abstract: In this paper, the authors formulate the coordination problem of a set of directional overcurrent relays installed in meshed power networks. After analysing the topology of the network to identify the primary/back up pairs, the coordination problem is organized in terms of a linear programming problem to be solved using the Simplex method. As a result, this application gives the instantaneous relay settings, the relay pick up taps and the time dial settings. The methodology is illustrated using a small power network mainly conceived for didactic purposes.

Starting device for an internal combustion engine, especially of a motor vehicle, with a redundancy circuit

Abstract: The starting device for starting an internal combustion engine includes a starter motor (12) with a pinion for cranking the internal combustion engine; a voltage source (40) for the starter motor; a starter relay (14) for connecting and disconnecting the voltage source to and from the starter motor and an electronic relay (32) for triggering the starter relay according to control signals from the motor controller (50). The electronic relay (32) is mounted on the starter motor or in the starter relay. The electronic relay (32) includes a power module (34) with a redundancy circuit including two transistors (144', 144") coupled with each other by a logic circuit for preventing starter operation when one of the two transistors is defective.

Solid state/electromechanical hybrid relay

Abstract: A hybrid or combination solid state/electromechanical relay circuit combines the advantageous features of solid state and electromechanical relays but avoids their disadvantageous features. An electromechanical relay includes a coil and a pair of contacts which close in response to energization of the relay coil; this pair of contacts being coupled between the load and the ac source. The relay coil is coupled through a switch to a source of dc coil voltage and is also connected to ground. A triac has its first and second main electrodes coupled in parallel to the pair of contacts of the electromechanical relay between the ac source and the load. A capacitor has one lead connected to the first lead of the relay coil and a second lead connected to the gate of the triac. On application of power to the coil, the capacitor charges through the triac, mining it on prior to the coil voltage of the relay reaching its design pick-up voltage. Then during switch dormancy, the coil-energized relay contacts carry the load. Likewise, upon opening of the switch, the capacitor supplies gating current to the gate of the triac device prior to opening of the relay contacts. The make or break current is carried by the triac, but the steady state current is carried by the relay contacts. The capacitor can be optically coupled to and electrically isolated from the triac device, through a bi-directional LED arrangement, and either a phototransistor pilot stage or a phototriac.

Relay protection operation for faults on Nyseg's six-phase transmission line

Abstract: This paper describes the performance of the protection system used for the first commercially operated six-phase transmission line in the world-New York State Electric & Gas's 93 kV (phase to phase and phase to ground) line from Goudey Station to Oakdale substation (USA) during faults in the winter of 1993. The paper briefly describes the basics of the High-Phase Order Transmission Demonstration Project and the integration of available state of the art microprocessor based relays, with a programmable logic relay (designed for the protection of conventional three-phase systems) in a hierarchical six-phase protection system. The operation of the protection system during two faults on the line in January and February 1993 is reported. The modeling of the six-phase line in a conventional three-phase short circuit study program is also considered and a comparison between the measured and calculated fault currents is presented.

Smart messages and smart macros for telecommunications relay service (trs) and operator services for deaf (osd)

Abstract: A telephone call is received at a relay center for routing to a forward party. A platform at the relay center can detect a call processing event in the relay center during processing of the telephone call. The relay center platform generates a context-dependent message based on the call processing event for review by the communications assistant. The communications assistant reviews and sends the message to a relay party using a message button. The relay center platform can automatically transmit messages to the caller, the forward party, a third party, and the communications assistant based on detected call processing events. The message button condenses responses to commonly occurring processing events discerned during call routing. The platform can automatically enter data determined from call processing into blanks in stored message templates. Such stored message templates can be activated and executed in response to detected call processing events.

Discrete step remotely adjustable matching circuit for MRI RF coils

Abstract: An RF coil tuning circuit is disclosed in which two banks of parallel capacitive branches are provided. Each capacitive branch includes a fixed value capacitor, a relay and a PIN diode connected in series. An impedance of the tuning circuit is adjusted to the optimum VSWR=1 condition by first switching the eight PIN diodes to learn which open/closed condition applies the fixed value capacitors in the optimum combination. Then, the PIN diodes are all closed and the optimum combination is applied using the open/closed states of the relays.

A micromechanical relay with a thermally-driven mercury micro-drop

Abstract: We present a mercury-contact micro-mechanical relay. While microrelays have been introduced to MEMS on several occasions, all are based on solid contacts, leaving the same contact problems faced by macroscale mechanical relays. The goal of our device is to use mercury to eliminate surface degradation, signal bounce, and high resistance at contacts common in solid contact devices. Descriptions of the design and fabrication of a micromechanical relay with a thermally-driven 25 /spl mu/m mercury micro-drop are presented, including the technique for formation of mercury droplets, as well as some data on the switching performance of the relay. Video demonstration of the actuation sequence will be presented.