Showing papers on "Relay published in 1993"

PID autotuning algorithm based on relay feedback

Abstract: A PID autotuning algorithm based on relay feedback has the capability of exploring different points of the process frequency response before performing the actual tuning procedure. In addition, the algorithm minimises the amount of a prioriinformation required on the process; in fact, the user is only asked to specify the minimum phase margin required for the closed-loop system. Some experimental results, obtained by laboratory simulation, are also presented.

Adaptive out-of-step relaying using phasor measurement techniques

Abstract: Adaptive relaying proposes to provide protection functions that will adapt to changing power system conditions The adaptive out-of-step relay presented recognizes power system changes and uses a modified system impedance matrix to change relay settings An investigation of a Florida-Georgia 500 kV interconnection initially, used a simple two-machine mode to represent the interconnection After this approach is tested a three-machine Florida model will be constructed The results from the two approaches will then be compared The configuration used to implement the relay consists of two or more phasor measurement units (PMUs), which provide synchronized real-time information regarding the state of the system These PMUs are discussed and data provided by the PMUs is analyzed >

Method and apparatus for implementing self-organization in a wireless local area network

Abstract: A method and apparatus for implementing self-organization in a wireless local area network ("LAN"). Each LAN is divided into a plurality of cells. Each cell is occupied by a number of nodes and one or more relay points (RPs) for communicating information within and among cells. Two separate channels are provided. The first channel, the control channel, is common to all RPs and accessible by all nodes and is utilized for communication of control information such as signal strengths of the RPs and the operating parameters of the selected RP. The second channel, the data channel, is utilized for normal communications between the selected RP and the node, and is specific to the RP. To initiate the self-organization process, the node identifies relay points in the LAN by acquiring identification information transmitted by the relay points across a common control channel. The node selects one of the relay points for communication with the node, and issues a message over the control channel requesting that the selected relay point transfer operating parameters from the relay point to the node. In response, the operating parameters are conveyed to the node. The operating parameters of the node are conformed to those of the selected relay point so that the node can communicate in the context of the selected relay point over the data channel unique to the cell, and through the selected relay point to other nodes within the same cell or to the network.

A proposal of nanoscale devices based on atom/molecule switching

Abstract: This paper proposes a very small switching device, called an atom relay, which would supersede present metal‐oxide‐semiconductor devices for the next decade. The basic configuration of an atom relay consists of an atom wire, a switching atom, and a switching gate, with total dimensions below 10 nm, and an operation speed at more than terahertz level. The operation principle of the atom relay is that a switching atom is displaced from the atom wire by the electric field supplied from the switching gate, and the atom relay exhibits an ‘‘off’’ state. The switching characteristics of the atom relay are demonstrated by simulation, and it is shown that the electron propagation is successfully cut if a gap of about 0.4 nm is formed in the atom wire by the displacement of the switching atom. A self‐relay structure, in which the switching atom is displaced by the electric field from the atom wire itself, enables a dynamic memory cell, and the functions are ascertained by simulation. Fundamental logic circuits as NAND and NOR gate constitutions are also proposed. These logic and memory circuits can integrate a supercomputer in a 200‐μm‐square of area, with 107 gates of logic circuit and 109 bits of memory, and operate at more than 1012 Hz. The atom relay is evaluated on the basis of the characteristics necessary for integrated circuit devices, together with several nanoscale devices, and is found to be the most promising candidate device for future integrated circuits.

Travelling-wave-based protection of double-circuit lines

Abstract: Double-circuit current comparison protection (DCCCP) is an algorithm for travelling-wave-based protection of a double-circuit high-voltage line. It uses the balance between the two circuits to distingush between an internal fault and an external disturbance. To prevent incorrect trips superimposed currents are used, and the relay has to be blocked after detecting an external disturbance. The setting of relay parameters is discussed, as well as its performance. The tripping time is between 100 and 200 μs for the majority of faults. For faults around voltage zero, the tripping time is between 1 and 3 ms, depending on the amplitude of the short-circuit current. Faults close to the remote line terminal are not detected at all. Some direct lightning strokes will lead to an incorrect trip. To overcome the disadvantages of DCCCP, it is combined with travelling-wave-based differential protection in a protective scheme. Differential protection is a somewhat slower but very reliable backup. Its parameter setting is discussed, as well as its performance. The tripping time is between 1 and 3 ms. The protective scheme further contains fast reclosure, breaker-failure detection and adaptive setting for the backup relays.

Tamper detection methods and apparatus for load management terminals

Abstract: Apparatus and methods are claimed for detecting tampering with a load management terminal, wherein the terminal has a load control relay coupled to a power line for selectably decoupling the load from the power line. One embodiment of the claimed apparatus for detecting tampering comprises a current sensor coupled to the load control relay for sensing whether load current is flowing through the load control relay contacts when the contacts are closed. A timer is provided for measuring elapsed time during which no current is sensed flowing through the closed contacts. An indicator provides an indication of tampering when the elapsed time measured by the timer exceeds a pre-determined time limit. Preferably, in this embodiment, the current sensor comprises a voltage detector coupled to the control coil of the relay for detecting whether an AC voltage has been induced in the control coil by the load current. In another embodiment, a voltage sensor is provided for sensing whether voltage is present across the contacts of the relay when the contacts are open. In yet another embodiment, a suitable resistance is connected to the power line in parallel with the load thermostat to ensure at least a nominal current flow through the load control relay at all times. Tampering is indicated when an interruption in the continuous current flow is detected.

EMTP transient modeling of a distance relay and a comparison with EMTP laboratory testing

Abstract: A method to test the transient performance of a sampled-data relay is given. A model of one measuring unit of a digital relay is created on a personal computer. The simulations are compared with laboratory results obtained by applying digitally generated waveforms to the actual relay. Computer modeling of the digital relay is done within the models version of the Transient Analysis of Control System (TACS) subsection of the ElectroMagnetics Transient Program (EMTP). The input filter, analog-to-digital converter, Fourier fundamental frequency detector, and the relay measuring principle of one digital microprocessor-based relay are modeled. An actual 115 kV 150 mile long transmission line is simulated using the EMTP. >

Protection and recovery of telephone line interface circuits

Abstract: An automatic protection and recovery method for a telephone line interface circuit is described. The interface circuit monitors current on the line, and in the event of a fault producing an excessive current a protection relay interrupts a connection of the interface circuit to the line, and the interface circuit monitors common mode voltage on the line. The interface circuit is reconnected in response to the monitored voltage being below a relatively high threshold. If a second interruption results, the interface circuit is then reconnected in response to the monitored voltage being below a lower threshold. If a further interruption results, the interface circuit enters a ground fault recovery process. The method facilitates protection and rapid recovery from arbitrary fault conditions on the telephone line.

One time programmable switched-output controller

Abstract: A one time programmable (OTP) electronic switched-output controller apparatus comprises a plurality of switched-output relays which may be power relays, signal voltage relays, dry switching relays or any combination thereof. A power section receives AC line power and provides at least one internal operating DC voltage and provides line AC power to any power relays and to the related power outputs when the relay are actuated. An A-D converter provides DC voltage for internal operation and to any DC voltage relays. A one time programmable microcontroller, which has outputs connected to the relay coils, is programmed before installation in the switched-output controller apparatus to cause actuation of the relay coils in accordance with a preestablished operating protocol. The apparatus is shown connected for receiving RS232 signals and has an internal modem for receiving external signals over a telephone line. A relay enables switching between the RS232 and modem inputs. Provision is also made to receive other external signals, for example, from temperature or pressure sensing devices. A corresponding method of manufacturing the OTP switched-output controller apparatus is disclosed.

Digital bus-zone protection

Abstract: A numerical bus-zone protection scheme that overcomes the drawbacks of analog units was designed and constructed. Both high- and low-impedance measurement schemes for us protection relays were investigated. For the numerical bus protection designed, low impedance measurement schemes are used. The basic hardware structure used in the digital bus-zone protection scheme and two modes of realizing breaker fail protection are described. Hardware and software self-monitoring, design tests and operational experience, and customer training are briefly discussed. >

Polyphase current monitor and control system

Abstract: A solid state sensing and control device for monitoring either D.C. or A.C. currents of one or more phases that is ideal for protecting motors and other A.C. loads. The programmable monitoring device can detect an overload or an emergency and virtually instantaneously interrupt motor current to prevent burnout and reduce the danger of fire. High current conductors leading to the motor (or other load) are mechanically routed through current sensing coils. An LCD visible through the cabinet top displays menu information and data. Programming and command control are initiated by pressing one or more of a plurality of light buttons disposed beneath the cabinet that comprise OPIC transmitter-receiver pairs. An instrumentation amplifier is associated with each sensing coil, and the circuitry preferably outputs two amplified analog signals from each coil, the amplitude of the first being proportionately higher than the second. Preferably the CPU switches between the latter signals to automatically select a proper range. The CPU activates a relay field to activate a control relay that in turn activates remote relays associated with the load to be controlled. The relays disconnect current to the load when an error condition or an overload is measured.

Defrost cycle controller

Abstract: A defrost controller for a refrigerator/freezer including one or more of the following features: (1) a timer module that can serve as a real time, cumulative time or variable time defrost timer; (2) an algorithm to control defrosting in view of frequent power outages; (3) a power up defrost cycle; (4) a default reaction to loss of compressor run information; (5) a simple manufacturing test initiator; (6) a test initialization via thermostat actuation; (7) a relay power supply which supplies two different energization voltages; (8) a relay energization signal which decays rapidly from a voltage in excess of the relay rated voltage to a voltage within the relay rated voltage; and (9) respective relay energization sequence to overcome light contact welding.

Vehicle security system

Abstract: A vehicle security system including a key switch, a first relay, a second relay, a first timer, a second timer, a warning device, and a push-button switch. The key switch activates and deactivates the system. Once the key switch is in an operative position and the system is activated, the vehicle's ignition switch in an operative position activates the second relay. Operation of the second relay, or of a vehicle door switch, activates the first relay which starts the first and second timers. The first timer initiates a first timing delay and, at the end of this timing delay, activates the warning device. The warning device warns the driver that the alarm sequence has been initiated. The push-button switch initiates an engine standby mode. The second timer initiates a second timing delay and cuts off the engine unless a standby mode is initiated before the end of the second timing delay.

Mobile communication network

Abstract: The present invention concerns a mobile network (MCN) for setting up a communication path between a mobile terminal (MT) and a telecommunication network (FTN). This path may include a radio access link (ICMRN) between the mobile terminal and a relay station (RS) and a relay link (GCFN/GCRN) between this relay station and a fixed base station (FBS). The hand-over decision in the present mobile communication network is based on measurement data relating to the radio access links (DCMRN/ICMRN) as well as to the relay links (GCFN/GCRN) included in the possible paths corresponding to the mobile terminal. In this way, the relay links (GCFN/GCRN) may be of different types and/or have varying characteristics. Allowing such flexibility for these relay links is tantamount to providing a mobile network (MCN) which can be adapted to a great variety of environments of the mobile terminal (MT) and which can to a large extent be integrated with the telecommunication network (FTN).

Method and apparatus for enhancing relay life

Abstract: An electronic control for gas furnaces controls a two speed main blower fan and an induction draft fan based on 24 volt input signals from a room thermostat, a high limit and an ignition control including a gas valve. The input signals are coupled to input ports of a microprocessor through current limiting resistors and to AC ground through pull down resistors. AC ground is also connected to the IRQ port of the microprocessor. Output ports of the microprocessor are connected to a relay driver which in turn is connected to relays for energizing and de-energizing the fans. The control calibrates itself on a continuing periodic basis to read the AC inputs synchronously at the peak of their wave and can switch the relays asynchronously based on the Real Time Clock of the microprocessor or can be switched synchronously by providing a selected delay so that contact engagement and disengagement occurs at or near the zero crossing of the AC line voltage wave form. When used with resistive loads the relays are switch in response to a signal from the microprocessor which is delayed based on the mechanical switching time constant of the relays to provide contact closure and opening at the selected point on the AC line voltage wave form. An alternate embodiment shows a feedback network used to calibrate the specific delay period for each relay upon initialization. When used with inductive loads contact closing can be effected synchronously and contact opening asynchronously.

Relay feedback method for tuning of nonlinear pH control systems

Abstract: For easier implementation of nonlinear pH controllers, we propose an on-line tuning method using the relay feedback with hysteresis. Since just two or three parameters are sufficient to characterize pH processes for practical applications (Williams et al., 1990; Lee et al., 1992), we parameterize pH processes with three parameters and then identify them with the relay feedback testing. The relay feedback method is very popular in on-line tuning of PID controllers (Astrom and Hagglund, 1984; Seborg et al., 1989). This on-line tuning method would reduce the efforts to obtain titration curves with off-line experiments

Testing dynamic characteristics of overcurrent relays

Abstract: Test methods for determining the dynamic characteristics of an overcurrent relay are discussed. By dynamics is meant the response of the relay to a current of varying magnitude. The test method, originated by IREQ, is used by Hydro Quebec to determine the ability of new relays to coordinate with the installed base of induction relays. Concurrent with this work, working group G7 of the Power System Relay Committee for the IEEE Power Engineering Society is completing a standard for inverse time-overcurrent characteristics which define equations for microprocessor relays based on the physics of induction relays. The authors discuss the correlation between the dynamic tests of induction relays and the proposed standard equations for reset and trip characteristics of microprocessor-based relays. >

Method and system for traffic management in cell relay networks

Abstract: A combination of an end-to-end closed-loop rate control mechanism for controlling the flow of cells entering a cell relay communication network from an end system, along with a segment traffic control mechanism for protecting the segment against misbehaving or malfunctioning destination end systems provides a novel, more efficient traffic management system and method for cell flow regulation in a cell relay communication network.

Telephone operated heating, ventilating and/or air conditioning

Abstract: A unit for providing heating, ventilation, and/or air conditioning (HVAC, 15) is controlled by one or another thermostat (17a, 17b) in response to a switch (21) the setting of which is controlled by dual tone multiple frequency signals sent from a regular telephone (26) over ordinary phone lines (27). The functions of ring detection and answering a call (28) as well as tone detection (30) may be provided by selected modules (34-38) or by an answering machine (83). A switch used to select one of the thermostats may comprise a stepping relay (21a) a bistable toggle relay (21b), or a bistable relay 21c. The phone control switch apparatus may selectively apply power to an outlet (91) for running a self-contained HVAC such as an air conditioner (94) or a heater (95).

Combined use of definite and inverse time overcurrent elements assists in transmission line ground relay coordination

Abstract: In some cases the coordination of ground time overcurrent relays in transmission line protection applications can be difficult. The combined use of definite and inverse time overcurrent characteristics sometimes provides significantly improved protection speed and sensitivity. Two cases are discussed where the use of hybrid characteristics has achieved improvements. The application of hybrid characteristics is limited by difficulties in dynamic coordination. The technology to overcome the dynamic problems would appear to be technically feasible. >

Reverse/forward bias tester for relay and diode packages

Abstract: A tester for individually testing diode packages, double pole relays and single pole relays includes a circuit contained within a housing, which circuit connects the diode package or relay being tested to a source of 12-volt direct current and transmits the direct current through the diode package, or relay, to an array of indicator lamps under the control of one normally open and two normally closed switches. A forward and reverse bias switch controls the direction of current through the diodes of the diode package and the internal diode of the relays to determine if the diodes and internal diode are oriented properly and conduct current properly.

Load drive circuit

Abstract: The invention relates to a load drive circuit which is able to detect an "on" fault of a switch element for controlling power to a load, and reliably interrupt the load current. A monitoring sensor is provided which generates an output when energy is supplied to the switch element of the switch circuit from outside the circuit, and a received signal level of the energy is a high level with the switch element "off", but does not generate an output when a received signal level of the energy is a low level with the switch element "on". Through logical processing of the output of the monitoring sensor and a load drive signal for driving the switch element, using a logical sum operating circuit and a self-hold circuit, the relay contact points can be prevented, at the time of an "on" fault of the switch element, from following the load drive signal, and from "hunting".

A neural network based back error propagation relay algorithm for distribution system high impedance fault detection

Abstract: The paper presents a novel FFT based relaying scheme for electric utility-radial distribution high-impedance fault detection. The scheme utilizes a multi-layer feedforward neural network as a fault classifier that maps the discriminant harmonic vector of the three phase residual voltage, current and power magnitudes and phases into fault logic 1 detection. The scheme utilizes only low order harmonics, namely second, third and fifth of the residual voltage, current and power at the substation feeder transformer secondary side.

Monitoring circuit for computer controlled safety devices

Abstract: The invention relates to a monitoring circuit for computer-controlled safety devices. The monitoring circuit described here is an arrangement which initially holds safety-relevant loads switched off by means of a safety relay (K) until a self-test of the controlling computer has been completed within required time conditions. A holding capacitor (C1) is connected in parallel with the drive path of the safety relay (K), which holding capacitor (C1) can be charged via a charging circuit (R1, V1) when the safety relay (K) is in the quiescent position (Nc), and, after charging has been completed, moves the relay into the operating position, subject to simultaneous application of a drive signal from the microprocessor, only when specified connection conditions for the safety-relevant loads are met. A remanence relay can be used as the safety relay (K) for defect locking. The monitoring circuit according to the invention uses the difference between the pull-in voltage and the tripping voltage of the safety relay (K).

Safety charging connector for automobiles

Abstract: A safety charging connector is provided for connecting two batteries of two automobiles The safety charging connector comprises four contact terminals each for contacting a different electrode of one of the two batteries, a relay switch for rendering conduction among the contact terminals, and a control circuit for controlling the conduction of the relay switch; the control circuit includes four sub-circuits each of which is serially connected between the relay switch and one of the four terminals