Showing papers on "Relay published in 1991"

Wireless indoor data relay system

Abstract: This invention removes the requirement of cable interconnection for local area networks (LANs) by wireless relay stations suitable for very high data rates by operation at high carrier frequencies where signal reflection and absorbtion by walls is total or requires undesirable high omnidirectional RF power transmissions. The LAN can be deployed without special installation requirements when operated with indoor transponders (U.S.Pat.4,975,926). In the preferred embodiment relay stations communicate with IR light beams, and wall and ceiling propagation blockage is overcome by low power RF structure couplers.

Arcing fault detector

Abstract: An arcing fault detector is set up to identify arcing faults and to distinguish them from other disturbances in a circuit. A plurality of electrical conditions are monitored (16, 18) and the conditions are tested against predetermined parameters for establishing a series of logical conditions relating to the presence of an arcing fault. A logic circuit (30, 34, 36, 38, 40, 46) combines the logical conditions for deciding on the presence of an arcing fault. An output signal of the logic circuit (P) is used to activate a relay (52) for interrupting the supply of electrical power to the circuit.

A practical protective relay for down-conductor faults

Abstract: A practical relay for detecting down-conductor high-impedance ground faults (HIGF) is described, with supporting theory and data from live line tests. The use of the third-harmonic current magnitude and the phase relation to the system voltage is shown to provide useful information for detecting this type of fault. By suppressing ambient harmonics and utilizing only the change in the harmonics, a fault current sensitivity of 1% of the feeder rating is shown to be feasible. Fault detection concepts include harmonic phase sequence components in the three-phase unit. Relays for both single-phase laterals and three-phase circuits are described. Redundant measurement techniques in both versions are shown to enhance the reliability of the system and to contribute to the feasibility of the noted sensitivity. >

Wireless indoor data relay system

Abstract: This invention removes the requirement of cable interconnections to local area network (LAN) nodes with wireless optical relay stations suitable for high data rates. Relay sections are equipped with IR transmitters, receivers and narrow beam optics. Manual beam alignment during the LAN installation is aided by a visible light beam of equal beam width and direction. Rotational freedom of the optical antenna systems provide precise aiming. Structure couplers extend, by low-power RF coupling through nonmetallic wall and ceilings, the wireless data transmission from a single room to rooms and building floors. Shielding and wall gaskets of the structure couplers eliminate RF radiation penetration and leakage, and therefore prevent eavesdropping and jamming.

Network traffic management.

Abstract: A network traffic management system and method for a relay-based communications network such as Frame Mode Bearer Service (FMBS) in which terminals (A and B) are linked by nodes (N) through which calls are routed, consists of setting a Recovery Needed flag at a node on detection of incorrect transmission of a frame or congestion at a node which discards the frame. The destination terminal (B) is notified by transmitting a null frame giving rise to a negative acknowledgement (NAK) received at the source terminal (A). The discarded frame is retransmitted with a Recovery flag set. At the node (N) the Recovery flag is detected and the frame is transmitted toward the destination terminal in the normal way. If the Recovery flag is not set and the Recovery Needed flag is set the frame is discarded. In this way, the rest of the network is not burdened with the transmission of frames that will be discarded by the destination terminal in any event until the discarded frame is correctly received. Furthermore, discarding frames that will not ultimately be transmitted successfully allows more accurate monitoring of successfully completed frame transmissions in order that more accurate billing of the customer can be employed.

DYNA-TEST simulator for relay testing. I. Design characteristics

Abstract: The authors describe a new digital dynamic testing (DYNA-TEST) simulator developed for protection relay applications. This simulator is capable of producing voltage and current transients that correspond to actual fault events in the power systems. Fault transients are generated either by simulating power system faults using an electromagnetic transient program or by replaying records of fault signals captured in substations by digital fault recorders. These signals are used to test protection relays. Such an approach to relay testing represents a major improvement over steady-state testing. >

Regulation of traffic load of fixed stations in a cellular radio communication network

Abstract: The process aims to constantly optimize the distribution of the radio-electric load on a radio communication cellular network between fixed relays. This is equivalent to increasing or reducing the surface of network cell when the traffic in the cell decreases or increases. Each relay transmits a field correction parameter as a function of a load indicator and fixed factors so that each mobile station corrects the radio electric field and selects the relay corresponding to the highest corrected field. The correction parameter of a relay in a given cell also depends on overload indicators relating to adjacent cells and indicators of field boundary displacements with respect to cells adjacent to the given cell.

School bus alarm system

Abstract: An alarm system for vehicles such as school buses which forces the driver to walk through the vehicle to silence the alarm at the end of each route so that he will detect the presence of passengers remaining on board. An ignition relay is energized whenever the ignition switch is on. An arming relay for the alarm is energized when the door switch of the bus is first activated. An override relay is also energized when the door switch is first activated. Alternative circuits for the arming relay include one set of the override relay contacts and a disable switch for the alarm located at the back of the bus. The alarm sounds when the ignition switch is turned off and can be deactivated only by depressing the disable switch at the rear of the bus.

Application of artificial neural network in protective relaying of transmission lines

Abstract: That the artificial neural network (ANN) can perform the pattern classification in excellent fashion is already established in the literature. The authors envisage the relay as a pattern classifying device. This opens a new dimension in relay philosophy which needs wide investigations. Keeping the microprocessor relay framework intact, the authors report the findings about the feasibility of using ANN in protection of transmission lines. The ADALINE model is explored for the application and is found to yield encouraging results. The input variables are quantified over the operating range which eases the arithmetics of the microprocessor. The training is performed in off-line mode and the converged weight matrix is stored for on-line use. >

The dentate nucleus is a short-latency relay of a primary auditory transmission pathway.

Abstract: Recordings of unit activity showing 4-6 ms latency responses to a click stimulus provided evidence that the dentate nucleus could function as a short-latency auditory relay. On the basis of these findings, plus fiber fillings from injections of phaseolus leucoagglutinin into the dentate, a new auditory pathway between dorsal and ventral cochlear nuclei, dentate nucleus, and rostral thalamus is proposed. The pathway could provide direct, short-latency transmissions to the motor cortex that bypass the classical auditory receptive cortex.

Power feed line switching circuit for submarine branching device and method of feeding power to submarine cable communication system

Abstract: A power feed line switching circuit for a submarine branching unit includes first, second and third electrical paths (101, 102, 103), connected e.g. in a Y-shaped connection, and first, second and third terminals (104, 105, 106) connected respectively thereto. The circuit further comprises first and second relays (107, 108) each including driving units (107L, 108L) inserted in the first and second electrical paths (101, 102) and switching units (107C, 108C) for disconnecting the corresponding terminals (105, 104) and connecting the terminals (105, 104) to the ground, respectively. A third relay (109) has a driving unit (109L) and its switching unit (109C) forms a lock-up circuit for the grounding path (110) for terminal (105). These relays (107, 108, 109) are used to control the connections between the terminals (104, 105, 106) and electrical paths (101, 102, 103), for establishing a one-end power feed line or a both-end power feed line to maintain power feed for repeaters and the submarine branching unit by the plurality of relays, even though a fault is caused in the optical marine cables for cable landing stations.

Interrupt-driven microprocessor-based overcurrent relay

Abstract: An interrupt-driven overcurrent relay for power systems using the 8085 microprocessor is presented. The relay requests processing time from the microprocessor only when a fault occurs. In this way, the microprocessor is given the opportunity to run other tasks such as diagnostic tests online during normal conditions. >

Design of a digital multi-curve time-overcurrent relay

Abstract: An algorithm for implementing a digital time-overcurrent relay on a single 8-b microprocessor is presented. Integer arithmetics is found to provide an adequate overall error performance. The relay responds to the mean value of the fault current, as do most available solid-state overcurrent relays. An extra feature has been devised in this application: the possibility of processing more than one time-current curve concurrently at low additional cost, thus offering a multioutput relay, with each output corresponding to a particular curve. As many as five or six curves, each with its own digitally-adjustable settings and independent output, can be processed simultaneously. A low-cost current-measuring circuit with response time as short as one-half cycle and a broad dynamic range is used. >

A personal computer based system for the laboratory evaluation of high performance power system protection relays

Abstract: The power system simulation system described provides a relay under evaluation with current and voltage input similar to that encountered under service and fault conditions. Using digital transient simulation programs to model power system behaviour, the facility provides an effective bandwidth of from DC to 4 kHz for both the current and voltage relay input. The relay's output is automatically monitored during the test, enabling a detailed report of its response to be produced. The application of the system is illustrated by the evaluation of a new EHV teed feeder relaying system. >

A Stand-alone Digital Protective Relay for Power Transformers

Abstract: The complete design of a stand-alone prototype digital protective relay for three-phase power transformers is described. The major emphasis is on the detailed description of the hardware and software of the prototype relay. The protection functions implemented include: a percentage differential protection with a second-harmonic restraint for magnetizing inrush and a fifth-harmonic restraint for overexcitation conditions, and a separate protection for high-impedance primary and secondary ground faults. The relay design is tested with the Fourier algorithm, and any other relay algorithm can be used by replacing only one subroutine. The relay hardware consists of a data acquisition board and a digital processing board which is based on the TMS320E15 processor. Sample real-time test cases are discussed. The results show that the relay never misoperated and correctly identified all the faults. >

Data communication apparatus

Abstract: Data communication units and a data communication apparatus comprising a plurality of the units which can prevent transmission collision and can transfer the transmission initiative without a token as typically required in a token-ring network. The unit has a relay unit generating a relay signal by a received signal, a transmitter generating a transmission signal comprised of its own original data, and a sending controller which selects a send signal among the relay signal and the transmission signal and generates a non-signal state by monitoring the send signal or the received signal sent through a transmission route. The sending controller is capable of transferring the transmission initiative, and includes a first timer which generates a trigger output for selecting the transmission signal after a non-signal state continued a first prescribed time TM, a second timer which starts and maintains a non-signal state for a second prescribed time TF (TF>TM) after the owner unit having the transmission initiative finishes sending, and a sending control circuit which controls a data selector to switch the send signal by the trigger output, a request-to-send signal RTS usually given by a transmission source computer, and a transmission enable signal TES produced by the received signal, and to generate a non-signal state throughout the time TF by the signal RTS reversing the polarity. Transmission collisions can be prevented by utilizing the signal TES or providing proper values for the time constant TM and TF. The transfer of the transmission initiative is performed by controlling the sending controller and the signal RTS.

Spa and pool pump and heater control

Abstract: A control for a spa and swimming pool pump and heater assembly with diverter valves, includes a selectively actuable pump and spa heater actuator or relay having a first latching circuit, and having a separate first unlatching switch or relay contact, a selectively actuable pump and pool heater actuator or relay having a second latching circuit including the first unlatching switch or relay contact, and having a second unlatching switch or relay contact in the first latching circuit. The control also includes a diverter valve actuator in parallel to one of the pump and spa heater actuator or relay and pump and pool heater actuator or relay.

Method for switching current to successive sections of the stator of a long linear motor

Abstract: When the runner of a linear motor having a long stator which is divided into sections crosses from a first section to a second section, an inverter power supply, which was providing current to the first section via a first switching unit having a relay, is initially gated out. Then the main relay contact paths in the first switching unit are opened and main relay contact paths in a second switching unit for the second section are closed. Only then is the power supply gated in again.

Addressable relay module for circuit breakers

Abstract: An addressable relay module is provided for controlling a plurality of relay outputs associated with an electronic circuit breaker system using a trip unit for monitoring system functions or network parameters. The relay module is linked to a multi-drop serial communications network through which data pertaining to system functions is relayed to and from a communications microcontroller which controls the operational status of relay contacts linked thereto. The microcontroller addresses specific ones of associated relay outputs in accordance with address information contained within the network data. The addressable relay module effectively maps the plurality of relay contact outputs linked thereto to a corresponding plurality of network device parameters received through the multi-drop network.

Interactive relay controlled power system modeling

Abstract: Four fundamental algorithms that make it possible to simulate numerous types of protective relay systems are identified. The characteristics of these fundamental modules necessary for building an embedded relay model within an EMTP (electromagnetic transient program) are discussed. A directional time overcurrent relay model is used to provide a detailed demonstration of relay model development and to illustrate the utilization of the fundamental modules. The results of using this relay model in a modeled power system reveal the power of this concept to enhance power systems education, applications engineering, and relay design procedures. >

Power feeding branching unit for submarine telecommunications systems

Abstract: A branching unit is for use in a submarine telecommunications optical cable system which employs electrical power feeding for repeaters/regenerators, in particular a system employing multiple branching units. The unit terminates three line cables (at 1, 2, 3) and a sea earth (at 4) and includes three high voltage relays A, B, C only one of which is energised at a time. When electrical power is supplied between any two line terminations, e.g. 1 and 3, an associated relay coil, eg. C is energised so that its contacts C1 isolate the third line termination, e.g. 2, and connect it to the sea earth termination 4 via contacts D1 of a relay D if the power feed direction is from 1 to 3, or via contacts E1 of a relay E if the power feed direction is from 3 to 1. Optical regenerators (not shown), for optical path switching purposes, have series connected effectively in parallel with each of the relay coils A, B, C. When any relay A, B, C is energised, i.e. the cable system is powered up, the regenerators are also powered. Zener diodes 21 and coils 29 provide surge protection for the power feed circuits 20, relay coils and rectifiers 22, 23, 24. The fourth and fifth relays D, E serve to prevent and transfer in the changeover contacts of relays A, B, C.

Application of df/dt in power system protection and its implementation in microcontroller based intelligent load shedding relay

Abstract: Several practical intelligent setting schemes that consider the effect of df/dt are suggested and simulated for a power system operating in an underfrequency situation. Considerations for df/dt relay setting are discussed. These intelligent setting schemes have made a positive improvement in the underfrequency condition. As an extension of these new intelligent control schemes, a microcontroller based intelligent under/over frequency relay is introduced. With its advanced hardware and intelligent software, this microcontroller has the advantages of high flexibility, less cost, and high communication ability. >

Relay tester having a circuit to sense the voltage spihe caused by the armature movement

Abstract: A computerized relay tester is provided which comprises a bar code reader, a test circuit for determining an actual value of an operational characteristic of the relay, and a memory for storing reference values for the operational characteristic for a plurality of relays. The test circuit is operative to automatically measure the actual voltage or current values at which "pickup" or "drop away" occurs in the relay under test, by sensing an inductive voltage "spike" caused by movement of the relay armature. Based on signals from the bar code reader, a reference value for the particular operational characteristic under test are retrieved from memory. The actual value is then compared with the reference value to determine whether the relay is functioning properly, and the relay tester outputs an indication of the operational state or condition of the relay.

Design of a microprocessor-based overcurrent relay

Abstract: The authors describe the design of a microprocessor-based overcurrent relay that is suitable for protecting distribution and subtransmission networks. A modified technique for modeling the time-current characteristics is described. The proposed design is implemented using a Texas Instruments TMS320C25 digital signal processor. Some details of the hardware and software of the relay are presented. A digital overcurrent relay is also described. Test results indicate that the overcurrent relay accurately emulates the desired time-current characteristics. >

Adaptive relaying for protecting a distribution system-a feasibility study

Abstract: The feasibility of an adaptive relaying system for a distribution network is examined. A reduced version of the City of Saskatoon distribution network has been selected for this study. Overcurrent and directional overcurrent relays are used to protect the system. The scope of the work includes changing relay settings and relay pick-up currents in an online mode as operating conditions of the system change. The system changes considered are the loads and generation level changes and line and transformer outages over a period of several days. Relay coordination and communication software which are essential for implementing an adaptive relaying system are discussed. A laboratory model for an adaptive relaying system is presented. It is shown that by using microprocessor-based relays and appropriate software, as well as communication aids, an adaptive relaying concept can be implemented. >

Battery power cut-off circuit

Abstract: A power cut-off circuit comprises a voltage monitoring circuit and an over-ride circuit (25), the voltage monitoring circuit comparing a portion of the battery voltage with a fixed reference voltage by way of a comparator (26) which, upon change of state, de-energises a relay coil of a relay (14) and thereby disconnects the power to most of the vehicle, but not to the starter motor circuit (11), and the override circuit (25) monitors override inputs in response to override conditions, and re-energises the relay coil in response to an override input, in turn restoring the previously disconnected power.

Automation system for safe operation of mining equipment - has duplicated control units with watchdog circuits to identify faults and operate brakes

Abstract: An automation system for use in mining applications is configured with two subsystems (1, 11) that provides a measure of redundancy for safe operation. The systems are interconnected (3) by a communication link (3) and each has an output to a watchdog circuit (4, 4') which in the event of a fault condition, opens contacts (5a, 5b) to cause a relay (6, 6') to drop out and operate the winding brake. The contacts of the relay control solenoid valves (8a, 8b) are connected into the braking circuit. ADVANTAGE - Registers both hard and software faults before critical situation occurs. Can automatically shut off part of installation if passive component fails, e.g. resistor, capacitor, diode or relay and whole system as well is active component is faulty, e.g. cutting machine, conveyor belt, wagon brakes or drive.