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Showing papers on "Relay published in 1999"


Patent
16 Jun 1999
TL;DR: In this paper, an improved system, method and apparatus for control of an instantaneous flow-through fluid heater system is disclosed, which incorporates a logic control method providing modulation of power in small steps to a plurality of heating elements retaining responsiveness to closed-loop control needs without inducing light flicker.
Abstract: An improved system, method and apparatus for control of an instantaneous flow-through fluid heater system is disclosed. The control incorporates a logic control method providing modulation of power in small steps to a plurality of heating elements retaining responsiveness to closed-loop control needs without inducing light flicker. Further, the life of the coils of heating circuit electromechanical relays are extended by energizing the coils with a pulse-width-modulated drive decreasing in duty cycle and thus the latent coil heat when an increase in mains voltage is sensed. The life of the contacts of same relays are extended by inhibiting heating element triac drive immediately upon sensing loss of relay coil power, such as by an over temperature limit switch opening, thus ensuring that relay contacts open with zero heating element current. In addition to the software “watchdog timer” internal to the microcontroller, a redundant fail-safe circuit external to the microcontroller prevents a program lockup condition from leaving any heating element triac or relay drive in an energized state. A combination of control hardware and program provide self-diagnostic detection of an inoperative thermistor, stuck relay, or a failed triac or heating element. An improved means of sensing water level is disclosed incorporating a low-level, high frequency signal, allowing detection of non-conducting distilled water and the reliable detection of water in the presence of main-frequency currents as would exist in ungrounded sheathed heating elements with electrical leakage or as would exist with bare-elements.

161 citations


Journal ArticleDOI
03 Oct 1999
TL;DR: In this paper, a new concept of protection coordination by time is introduced to formulate all the system relays and system equipment operation into a set of optimization equations and constraints, and an evolutionary algorithm is applied as a constraint satisfaction optimization tool to search for the optimal relay setting.
Abstract: A typical industrial power network may consist of hundreds of pieces of equipment and even more protection relays to protect the system are required. Each protection relay in the power network needs to be coordinated with the relays protecting the adjacent equipment. The overall protection coordination is, thus, very complicated. A new concept of protection coordination by time is introduced in this paper to formulate all the system relays and system equipment operation into a set of optimization equations and constraints. Its purpose is to search for an optimal protection setting to minimize the system disturbance time as well as the time of interruption of the power supply. An evolutionary algorithm is applied as a constraint satisfaction optimization tool to search for the optimal relay setting. This method can find the best protection relay coordination, which cannot be achieved by traditional methods. This is the most significant achievement of the paper.

143 citations


Journal ArticleDOI
TL;DR: It is proved that there exist multiple fast switches if and only if the sign of the first nonvanishing Markov parameter of the linear system is positive and fast switches are shown to occur as part of stable limit cycles.

137 citations


Patent
Yasuro Shobatake1
17 Sep 1999
TL;DR: In this paper, a message relay device suitable for contructing a ultra-high-speed message relaying system is described, where a flow is detected by a prescribed condition, while a bypass channel capable of transferring messages with an amount of calculations smaller than the case of handling messages by a default channel is set up, and the message transfer belonging to the flow is switched from the default channel to the bypass channel.
Abstract: A message relay device suitable for contructing a ultra-high-speed message relaying system is disclosed. In the message relay device, a flow is detected by a prescribed condition, while a bypass channel capable of transferring messages with an amount of calculations smaller than the case of handling messages by a default channel is set up, and the message transfer belonging to the flow is switched from the default channel to the bypass channel, while providing the connection-less communications on the default channel, so that it is possible to realize the message relaying with the ultra-high throughput by relieving the large amount of calculations inherently associated with the connection-less communications.

109 citations


Journal ArticleDOI
TL;DR: The C37.110-1996 guide for the application of current transformers used for protective relay purposes was published by the Power System Relaying Committee (PSCLC) as discussed by the authors, which is a one source document.
Abstract: Relay engineers have had to rely on many sources to compile information on current transformer application. Typically, they have drawn on relay application and transformer textbooks, manufacturer publications, and standards. Recognizing the need for a comprehensive one source document, the power system relaying committee has produced the C37.110-1996 guide for the application of current transformers used for protective relay purposes.

108 citations


Journal ArticleDOI
TL;DR: The results are based on the formulation of relay systems as complementarity systems, and use the constructive theory of the Linear Complementarity Problem for uniqueness of solutions of linear time-invariant systems under relay feedback.

76 citations


Journal ArticleDOI
TL;DR: In this paper, a relay method for the identification of completely unknown processes for autotune purposes is presented, which does not present any convergence problem and is equivalent to the original one in terms of relative accuracy and duration of tests.
Abstract: The paper presents a relay method for the identification of completely unknown processes for autotune purposes. It is an extension of a previous technique (ATV; Li, W.; et al. Ind. Eng. Chem. Res. 1991, 30, 1530), which assumed the delay of the process to be known. By means of a maximum of three relay tests, with additional delay, models with up to five parameters can be built. The proposed procedure does not present any convergence problem and is equivalent to the original one in terms of relative accuracy and duration of tests. The application of the identification procedure to a much wider set than in the original paper shows that the model obtained from the identification presents good accuracy in the high-frequency region, while some discrepancies of different nature may be present in the low frequency. When a suitable tuning method, which exploits this characteristic, is adopted, reasonably good closed-loop performance can be achieved for proportional-integral control in all cases. The low sensitivity to experimental errors and the simple implementation make the method interesting for application in industrial autotuners.

74 citations


Patent
15 Mar 1999
TL;DR: In this paper, an electronic digital thermostat control unit comprising a linear temperature sensing element (1) connected to an A-D converter (3), a sensitivity and offset correction circuit (4), digital comparators (5, 6), digital noise filters (7, 8), a control latch (9), an output drive and protection circuit (10), and a solid state switch (11) to produce the desired output with user input in either analogue form using a potentiometer (12) or a digital form using switch with calibration and control data stored in a nonvolatile
Abstract: The present invention relates to an electronic digital thermostat control unit comprising a linear temperature sensing element (1) connected to an A-D converter (3), a sensitivity and offset correction circuit (4), digital comparators (5, 6), digital noise filters (7, 8), a control latch (9), an output drive and protection circuit (10) and a solid state switch (11) to produce the desired output with user input in either analogue form using a potentiometer (12) or a digital form using a switch with calibration and control data stored in a nonvolatile memory and a display unit (18) for displaying sensed or user set temperature. The invention further relates to the application of the said electronic digital thermostat in a multipoint temperature controller for the refrigeration and heating systems using a plurality of said electronic thermostat control units (40-44) with a logic circuit, central control unit (71), system timers and a starting relay circuit to provide application specific functions. The implementation is also shown in the form of an Application Specific Integrated Circuit (ASIC) (32) to provide reduced size and cost.

60 citations


Patent
19 Jan 1999
TL;DR: In this paper, a system for managing a distributed array of appliances includes a head-end computer having a low power main transceiver and relay units, each relay unit includes an appliance interface for communicating with the appliance, the microcomputer being also connected to the appliance interface and having program instructions for directing communication between the satellite transceiver between the appliance and the interface.
Abstract: A system for managing a distributed array of appliances includes a headend computer having a low power main transceiver and a distributed array of relay units. Each relay unit includes a low power satellite transceiver, a microcomputer connected to the satellite transceiver, the satellite transceiver being controlled by relay program instructions for detecting communications directed by the headend computer relative to the same relay unit and directing communications to the headend computer relative to the same relay unit, and for retransmitting communications to other relay units. At least some of the relay units are appliance controllers and include an appliance interface for communicating with the appliance, the microcomputer being also connected to the appliance interface and having program instructions for directing communication between the satellite transceiver and the appliance interface. Each of the relay units has a unique address associated therewith, occurrences of the unique address being detected in communications from the headend computer. Each of the transceivers has an effective range of not less than approximately 60 feet or more depending on the frequency, which can be between 66 KHz and 2.6 GHz. The transceiver can selectively operate on one of at least 16 carrier frequencies, or one of several spread spectrum channels. Also disclosed is a method for controlling a distributed array of appliances from the headend computer.

57 citations


Journal ArticleDOI
TL;DR: The magnitude and phase estimate algorithms in phasor-based microprocessor relaying are nonlinear and the term "frequency response" needs to be clarified when it is used to characterize nonlinear relay algorithms.
Abstract: The magnitude and phase estimate algorithms in phasor-based microprocessor relaying are nonlinear. The characteristics of the nonlinear relay algorithms cannot be analyzed using the frequency response concept defined for studying linear time-invariant (LTI) systems. The term "frequency response" needs to be clarified when it is used to characterize nonlinear relay algorithms. The paper clarifies and then investigates the magnitude responses of deterministic relay algorithms and Kalman filter relay algorithms. The deterministic relaying algorithms studied in the paper include Mann-Morrison, Prodar, full cycle DFT, half cycle DFT, Cosine filter, and least square. In the Kalman filter relay algorithms, two-state and three-state Kalman filter models are considered. Finally, the effect of the signal statistic property on the frequency responses of the Kalman filter relay algorithms is studied.

57 citations


Patent
01 Sep 1999
TL;DR: An electromechanical relay drive system which prolongs relay life by ensuring operation of the relay in a manner to make and break contact between the contact electrodes at a zero crossing point of the switched waveform is described in this paper.
Abstract: An electromechanical relay drive system which prolongs relay life by ensuring operation of the relay in a manner to make and break contact between the contact electrodes at a zero crossing point of the switched waveform. Relay aging and environmental variations are dynamically compensated upon each actuation of the electromechanical relay to ensure proper timing of the energization and de-energization of the relay to ensure switching at the zero crossing point. Additionally, the drive system described compensates for variations in the actual contact operation during actuation for the positive and negative half cycle of the switched waveform. Furthermore, the system of the instant invention alternately energizes and de-energizes the electromechanical relay during the positive and negative half cycles of the switched waveform to prevent metal deposition from one contact electrode to the other. This system calculates the appropriate delays on a dynamic historical perspective by sensing slope changes of the coil voltage and current.

Patent
23 Jul 1999
TL;DR: In this paper, an electro-optically driven relay system for switching the application of energy to a load (5) was provided. But the relay system was not designed to handle a large number of switches.
Abstract: There is provided an electro-optically driven relay system ( 10 ) for switching the application of energy to a load ( 5 ). The subject relay system ( 10 ) comprises: a switch unit ( 100 ) operable responsive to a control signal; an electro-optic current generating unit ( 200 ) connected to the switch unit ( 100 ) for generating the necessary control signal responsive to an actuation signal; and, primary and supplemental drive units ( 300, 400 ) connected to the electro-optic current generating unit ( 200 ) for collectively generating the actuation signal. The primary drive unit ( 300 ) is operable responsive to a first input signal; and, the supplemental drive unit ( 400 ) is operable responsive to a second input signal to augment the actuation signal for at least a predetermined time duration. The switching response of the switch unit ( 100 ) is thereby accelerated.

Patent
15 Dec 1999
TL;DR: In this paper, a photocontroller with a sensor for determining the presence of daylight, and a relay, responsive to the sensor, for de-energizing a lamp during periods of daylight.
Abstract: A photocontroller diagnostic system including a photocontroller with a sensor for determining the presence of daylight, and a relay, responsive to the sensor, for de-energizing a lamp during periods of daylight. The diagnostic subsystem is responsive to the photocontroller, and includes a microprocessor programmed to verify the operability of the relay and/or the sensor and programmed to transmit a signal representative of the operability of the relay or the sensor.

Patent
15 Oct 1999
TL;DR: In this paper, a differential relay for protecting a power apparatus portion of a power system, such as a bus line, includes a circuit for determining the presence of an external fault, and maintains security by avoiding a tripping action of the relay for said external faults.
Abstract: A differential relay for protecting a power apparatus portion of a power system, such as a bus line, includes incoming and outgoing power lines on which incoming and outgoing currents are present. The incoming and outgoing currents of each phase are applied through current transformers and then through filtering and normalizing circuits prior to application to the differential relay. The differential relay includes a circuit for determining the presence of an external fault, and maintains security by avoiding a tripping action of the relay for said external faults. Further, the relay includes circuits which in response to the external fault evolving to an internal fault alters the operation of a portion of the relay, by increasing the gain for the restraint current, enabling a directional element for supervision of the differential relay, and for extending the immediate post-fault value of restraint current, and adding a time delay for a selected period of time, all of which are used to identify an external fault evolving into an internal fault.

Proceedings ArticleDOI
01 Jan 1999
TL;DR: A frequency-domain method for input-output analysis of a class of relay feedback control systems based on the notion of the locus of a perturbed relay system, which specifies the response of a linear plant to its non-symmetric pulse waveform input in a closed-loop system.
Abstract: This paper proposes a frequency-domain method for input-output analysis of a class of relay feedback control systems. The approach is based on the notion of the locus of a perturbed relay system. The proposed locus specifies the response of a linear plant to its non-symmetric pulse waveform input in a closed-loop system and, consequently, comprises transfer properties of the relay system. Formulae for loci calculation are derived. The techniques of computing of the parameters of limit cycles and the gain of the relay employing the notion of the locus are given.

Journal ArticleDOI
TL;DR: In this paper, the authors describe an analog cum digital model used for real-time assessment of system performance, including SVCs, HVDC, ASC and CSC can be modelled fully digitally by computer simulation and transient realtime data injection as well as by an analog method using physical simulation with original converter controllers.
Abstract: Environmental pressures, right of way problems for new transmission lines, large scale system interconnection and increasing power demand especially in developing countries call for new transmission technologies. Use of FACTS and HVDC is gaining momentum. Relaying problems in such systems require a sophisticated approach and numerical technology using high grade processors offers a promising solution. To establish the performance of such relays which are designed more as powerful schemes rather than as a conglomeration of individual relays, detailed testing is required using an elaborate real-time simulator model. These tests are not only necessary during design and development but also are required by the utilities as a part of their acceptance. Highlighting the requirements of a hybrid real-time simulator including the complete spectrum of power system dynamics, this report describes an analog cum digital model used for real-time assessment of system performance. SVCs, HVDC, ASC and CSC can be modelled fully digitally by computer simulation and transient real-time data injection as well as by an analog method using physical simulation with original converter controllers for performance evaluation of numerical relays under real system conditions. As an example of the use of this simulator, tests on a numerical EHV-line relay are described and the relay performance is analyzed.

Patent
28 Sep 1999
TL;DR: In this paper, a modular emergency stop device including a switch unit and a control unit is presented. But the switch unit's housing and the controller's housing are adapted to be selectively coupled together and uncoupled from each other.
Abstract: A modular emergency stop device including a switch unit and a control unit. The switch unit includes a switch which converts from a normal state to an emergency state when an emergency stop is necessary and a housing for the switch. The control unit includes a controller which controls a power source for a machine and a housing for the controller. The switch unit's housing and the control unit's housing are adapted to be selectively coupled together and uncoupled from each other. The switch is operably coupled to the controller when the housings are coupled together whereby the controller may appropriately control the machine's power source when the switch is converted to the emergency state. To replace the switch, the switch's housing is uncoupled from the controller's housing to remove the switch unit and a new switch unit is coupled to the controller's housing.

Journal ArticleDOI
TL;DR: Two new methods for obtaining frequency response and step response models for processes operating under relay feedback control are described, based on the frequency sampling filter model structure and a recursive least-squares estimator.

Patent
Keiko Tanigawa1, Koji Tsukada1, Toru Hoshi1, Hiroshi Kanai1, Toshimitsu Hayashi1 
18 Feb 1999
TL;DR: In this article, an audio gateway is provided for receiving an internet relay request and a number called in a call from a telephone via the internet, and relay operations are performed with the selected destination audio data gateway.
Abstract: An audio gateway is provided for receiving an internet relay request and a number called in a call from a telephone via the internet. An audio data gateway is selected using the number called, and relay operations are performed with the selected destination audio data gateway. The relay audio data is multiplexed for streams based on multiple relay requests having the same relay destination so that the relay audio data in these streams are multiplexed into a single relay stream.

Patent
03 May 1999
TL;DR: In this paper, the authors described a handover method for a digital cellular mobile radio system, where the cell is associated with a base transceiver station comprising a plurality of relay stations including the current and target relay stations and geographically distributed within the cell.
Abstract: A method is described of handing over calls between two relay stations, respectively a current relay station and a target relay station in the same cell of a digital cellular mobile radio system, the cell being associated with a base transceiver station comprising a plurality of relay stations including the current and target relay stations and geographically distributed within the cell. Each relay station comprises at least one antenna connected to at least one transmit/receive device. Each relay station has a plurality of traffic channels and a plurality of associated signaling channels. A call being set up for a mobile station is allocated, from the channels of the current relay station, at least one current traffic channel and at least one current associated signaling channel. The plurality of relay stations shares at least one particular traffic channel, constituting a shared traffic channel, which is reserved at least partly for handover. The method includes a first handover phase in which the shared traffic channel is a first target traffic channel. The first phase includes the following successive steps: sending by the mobile station of at least one test message to the plurality of relay stations via the shared traffic channel, and selection by the system of the target relay station from the plurality of relay stations, in accordance with at least one predetermined selection criterion based on at least one parameter associated with the quality of reception of the at least one test message. The method also includes a second handover phase with a traffic channel associated with the target relay station as a second target traffic channel.

Patent
03 Dec 1999
TL;DR: In this article, a relay test set of reduced size and weight includes a small, highly efficient voltage and current source, which is used to reduce the size of the power source needed to inject the correct voltage or current into the secondary inputs of a protective relay.
Abstract: A relay test set of reduced size and weight includes a small, highly efficient voltage and current source. The test set incorporates a Class D switching amplifier design that greatly reduces the size of the power source needed to inject the correct voltage and current into the secondary inputs of a protective relay. To further reduce the size, weight and cost of the relay test set, a single voltage amplifier is used to drive both voltage and current secondary inputs of a protective relay. In so doing, this test set then becomes both a voltage transformer and current transformer simulator utilizing a single voltage power source at reduced size, weight and cost. To make the power source variable while maintaining accuracy, a microcomputer module is used to monitor both current and voltage being injected into the protective relay. This microcomputer may also automatically run the required relay tests and route the voltage or current to the appropriate inputs of the protective relay by direct control of a relay matrix.

Journal ArticleDOI
TL;DR: In this paper, the performance of an Elman recurrent network-based relay to determine the fault direction on a transmission line on fault data recorded in the field is described, which uses samples of voltage and current signals to learn the hidden relationship existing in the input patterns.
Abstract: Summary form only given as follows. Performance of an Elman recurrent network-based relay to determine the fault direction on a transmission line on fault data recorded in the field is described in this paper. The network uses samples of voltage and current signals to learn the hidden relationship existing in the input patterns. Studies show that the proposed network is able to identify the fault direction correctly and rapidly. Results obtained indicate that the proposed network is robust, fast and accurate.

Journal ArticleDOI
01 Jan 1999
TL;DR: In this article, the authors describe the design and evaluation of a protection relay for wind farms with fixed-speed induction generators, which provides short-circuit protection for a mediumvoltage collection circuit and the medium-voltage (MV) and lowvoltage windings of the generator-transformers connected to it.
Abstract: The paper describes the design and evaluation of a protection relay for wind farms with fixed-speed induction generators. The relay provides short-circuit protection for a medium-voltage collection circuit and the medium-voltage (MV) and low-voltage (LV) windings of the generator-transformers connected to it. The ability to protect the generator-transformers allows a significant reduction in wind farm construction cost, since the MV fuses normally used to protect the generator-transformers are not required. The authors discuss how the operating characteristic for the protection was designed, implemented in a processor-based relay and then tested using a wind farm simulator and test set. A selection of test results are to illustrate how the relay performs occur on the protected collection LV terminals of a generator-transformers or on the utility network. The paper also discusses how the relay performed when installed at the Cemmaes wind farm in Wales for a 12 month site trial.

Journal ArticleDOI
TL;DR: This paper presents an analysis of a class of two-relay feedback systems, motivated by the idea of estimating a relay-type nonlinearity on the feedback path of a plant by adding another relay, using Poincare's method.

Patent
01 Jul 1999
TL;DR: In this paper, a caching method for caching network contents of a packet transfer network including a packet relay for relaying accesses of clients to servers supplying contents, and a network contents cache device are disclosed.
Abstract: A caching method for caching network contents of a packet transfer network including a packet relay for relaying accesses of clients to servers supplying contents, and a network contents cache device are disclosed. Accesses from the clients to the servers are monitored by the said packet relay to determine a cache priority on the basis of a product of relaying path lengths from the packet relay to the server and frequency of access from the client to the servers and the network contents cache device preferentially caches a response to the access to the server having higher cache priority.

Patent
01 Jul 1999
TL;DR: A car battery jumper cable for coupling an effective or charged power source to a battery (failed or not charged) accurately, which includes a relay switching circuit connected to the power source and the battery by two current conductor pairs, is described in this article.
Abstract: A car battery jumper cable for coupling an effective or charged power source to a battery (failed or not charged) accurately, which includes a relay switching circuit connected to the power source and the battery by two current conductor pairs, first and second voltage polarity recognition circuit respectively connected to the power source and the battery by a respective voltage conductor pair to recognize the polarity of the power source and the battery, a logic recognition circuit, which produces a control signal subject to the polarity of the power source and the battery, and a driving circuit controlled by the control signal from the logic recognition circuit to drive the relay switching circuit, enabling the two poles of the power source to be accurately coupled to the two poles of the battery.

Patent
17 Jun 1999
TL;DR: In this article, a triode AC switch and the relay are provided in parallel with the resistance for limiting the rush current caused by switching of a power switch between a rectifier diode bridge and a smoothing condenser.
Abstract: A rush current limiting device capable of restraining increased power consumption and heat generation caused by resistance for limiting rush current, and effectively limiting rush current caused on any conditions has. A resistance for limiting rush current caused by switching of a power switch between a rectifier diode bridge and a smoothing condenser. A triode AC switch and the relay are provided in parallel with the resistance. The on-operation of a power switch is monitored by the input monitoring circuit, and an triode AC switch is turned on at the zero crossing point of input signals after the on-operation by the zero crossing circuit to short-circuit the resistance. After a delay of the relay due to sensitive time, the relay is turned on by a relay driving circuit, and the triode AC switch is turned on.

Patent
24 Sep 1999
TL;DR: In this article, a relay device and a communication device capable of realizing the contents protection procedure between devices that are not connected to the same network are disclosed, so that there is no need for a device on the first network or a device/service/sub-unit on the second network to account for the other network that is connected via the relay device.
Abstract: A relay device and a communication device capable of realizing the contents protection procedure between devices that are not connected to the same network are disclosed. A relay device and a communication device are so configured that between a device/service/sub-unit on the second network and a device on the first network which are a pair that is carrying out transmission or reception of contents to be protected, a device on the first network or a device/service/sub-unit on the second network can carry out the contents protection procedure while recognizing the target of the contents protection procedure as the relay device, so that there is no need for a device on the first network or a device/service/sub-unit on the second network to account for the other network that is connected via the relay device.

Patent
23 Jun 1999
TL;DR: In this article, the relay destination search section searches for data in the relay FAX data memory and obtains the address of a relay apparatus candidate, and the adjacent district number search Section searches for the number of an adjacent district and continues the search based on the district number.
Abstract: The Internet facsimile apparatus in the present invention is provided with data memories such as telephone book data memory, relay FAX data memory and adjacent district number memory. Its collation section collates the telephone number of the recipient with the data of the telephone book memory, then the relay destination search section searches for data in the relay FAX data memory and obtains the address of a relay apparatus candidate. If there is no appropriate relay apparatus in the same district, the adjacent district number search section searches for the number of an adjacent district and continues the search based on the district number. In this way, when carrying out image transmission using the Internet facsimile apparatus as a relay apparatus, the nearest Internet facsimile apparatus suitable for use as a relay apparatus is automatically selected.

Patent
07 Dec 1999
TL;DR: In this article, the authors proposed a power switching controller for detecting whether the light is present and for sequently switching the contact states of the first relay and the second relay depending on the result of the light detection to reduce the commercial alternating current through the first and second lines.
Abstract: The present invention relates to a device for the automatic shut-off of equipment's stand-by power which can switch on or off the power for a set of electric and electronic appliances and can reduce the power consumption in a state of waiting for use. The invention provides a device for the automatic shut-off of equipment's stand-by power which particularly comprises a first relay for switching contacts of the first line, a second relay for switching contacts of the second line, and a power switching controller for detecting whether the light is present and for sequently switching the contact states of the first relay and the second relay depending on the result of the light detection to thereby allow or cut off the commercial alternating current through the first and second lines.