Showing papers on "Relay published in 1989"

Adaptive transmission protection: concepts and computational issues

Abstract: The authors provide a basis for adaptive transmission protection, define the concept, identify its components and illustrate it with simple examples. They concentrate on the software aspects of adaptive transmission protection. They present efficient enhancements to existing, offline algorithms used in relay coordination. The authors present the results of two different approaches, multiprocessing and supercomputing, that they have proposed and investigated with the aim of developing a fast, online tool for computing relay settings in realtime. >

A digital relaying algorithm for detecting transformer winding faults

Abstract: Electric power utilities use differential relays for detecting faults in power transformers. Conventional designs of these relays use second harmonic, third harmonic or total harmonic current as a restraining quantity. This inhibits the relay operation during magnetizing inrush conditions. Initial designs of digital differential relays also used similar approaches. Most designs used the second harmonic component of the current to block trippings during the magnetizing inrush conditions. As the operating voltages and lengths of transmission lines have increased substantially, currents during internal transformer faults can contain large harmonic components. Therefore, the security of differential relays using harmonic restraint is a matter of concern. However, some recently reported algorithms do not use second harmonic restraint to block trippings during magnetizing inrush conditions. They use winding currents. In most situations, the currents in a delta winding are not readily available. The algorithms based on transformer models need equivalent circuit parameters of the transformer. The relay engineer must determine the equivalent parameters of the transformer before using these algorithms. This paper presents a new digital algorithm for detecting winding faults in single-phase and three-phase transformers. The proposed algorithm does not use harmonic component of current to block trippings during magnetizing inrush conditions. It is applicable to situations where it is and it is not possible to measure winding currents. The algorithm does not require the B-H curve data and takes hysteresis losses of the transformer into account. The algorithm was tested using a variety of operating conditions simulated on a digital computer.

Rural radiotelephone system

Abstract: A remote coverage system extends the effective coverage area of a cellular mobile radiotelecommunications (CMR) master cell. When a mobile unit assigned to the master cell moves from the master cell's coverage area into the coverage area of a satellite cell, the satellite cell sends a signal asking for a handoff of the mobile unit to it. When the handoff occurs, the MTSO exchanges signals with the mobile unit via a relay unit located at the master cell site. The relay unit relays signals between the MTSO and the satellite cell.

I/o relay interface module

Abstract: An I/O relay interface module for mounting a plurality of relays which are adapted to be connected to individual external I/O devices to be controlled or monitored by a central controller. The I/O module comprises a plurality of relay sockets for detachably receiving the relays, respectively, and a terminal section including wire terminals internally connected to the relays through the sockets for connection between the relays and the external devices. An I/O connector is provided on the I/O module for connection with the central controller to receive therefrom control signals for energizing the relays for control of the associated devices or transmit to the central controller monitor signals from the relays as indicative of the operation of the associated devices. Also included in the I/O module is an expansion I/O connector for connection with one or more additional I/O relays provided in association with additional I/O devices such that the additional I/O devices can be also controlled or be monitored by the center controller through the I/O relay interface module. Thus, the I/O interface module can be expanded to control or monitor one or more additional I/O devices through the respective relays.

Apparatus and method for relay control

Abstract: Where there is a relay controlling an AC power circuit to a load, the apparatus of this disclosure includes a sensor for observing arc at the relay contacts and a control circuit which controls the time of subsequent actuation or deactuation of the relay with respect to the alternating current power circuit so as to eliminate relay contact arcing.

Relay actuation circuitry

Abstract: The operation of an electromechanical relay is synchronized with the power line waveform where an electrical power supply is supplied from a source to an electrical load. The current voltage supplied to the load is characterized by a power line waveform. An electromechanical relay is positioned between the power supply and the load where contacts of the relay are opened and closed to interrupt and supply power to the load. A microcontroller is positioned between a power source and the electromechanical relay and actuates the relay so that the contacts are closed or opened at a preselected point on the power line waveform. Closure of the contacts at the preselected point is accelerated by supplying an increased power signal to the relay coil and thereafter returning the signal to the rated power.

Relay performance in DSG islands

Abstract: During field tests to confirm the existence of ferroresonant conditions in distribution system generators (DSGs), a number of voltage and frequency relays were installed and their performance monitored while exposed to the highly distorted waves resulting from these conditions. While the general performance of relay groups was satisfactory, certain problem areas became apparent. The field tests and evaluation method are described, the test results are reported, and the problem areas are discussed. >

Electrical safety interlock and pulse-type reset circuit for a vacuum cleaner system

Abstract: A safety interlock circuit for a vacuum cleaner system is disclosed for interrupting the flow of current through conductors of a vacuum hose and handle assembly whenever an electrical attachment accessory is disconnected from the handle assembly during operation of the vacuum A pulse-type reset circuit is also disclosed for re-enabling current flow through the conductors of the vacuum hose and handle assembly after the electrical attachment accessory has been reattached to the handle assembly The safety interlock circuit of the preferred embodiment comprises a relay coil, a plurality of normally open relay contacts, and a current sensing resistor, all connected in series with an AC power source and a motor of the electrical attachment accessory A voltage doubler is also connected in parallel with the current sensing resistor for supplying a DC voltage to the relay coil The safety interlock circuit operates to interrupt current flow by opening the normally open relay contacts whenever the relay coil is de-energized The pulse-type reset circuit comprises a momentary contact pushbutton reset switch, a plurality of transistors, a capacitor, and a plurality of optical-electrical coupling devices The pulse-type reset circuit operates to supply a pulse of current to the relay coil to temporarily energize the relay coil to thereby close the normally open relay contacts, thereby allowing current flow through the current sensing resistor and allowing the voltage doubler to apply a voltage across the relay coil to sustain operation of the motor

Directional comparison blocking protective relay system

Abstract: A directional comparison relaying system includes forward looking pilot relays at each terminal of a protected line segment and monitors which detect predetermined incremental changes in line currents and voltages indicative of a fault. These predetermined incremental changes in current or voltages, which can be detected before the pilot relays respond, generate local blocking signals which are transmitted to the other terminal as remote blocking signals over a two-way communications channel. Trip signals for tripping circuit breakers at the associated terminals are generated from forward fault signals produced by the pilot relays but are blocked by the presence of either a local or remote blocking signal. However, the forward fault signal cancels the local blocking signal and the corresponding remote blocking signal at the other terminal so that when both pilot relays see an internal fault, the circuit breakers at the two terminals are tripped simultaneously. Either a reverse direction distance relay or a reverse ground current relay and a zero sequence current monitor, generate a transient blocking signal which maintains the local blocking signal and its corresponding remote blocking signal at the other terminal, and blocks a trip signal during transient fault clearing in other line segments to prevent overtripping.

Apparatus for providing distance protection and distance measurement for a high voltage transmission line

Abstract: A protective relay for detecting faults in electrical power distribution system generates a signal Δi(t) which is substantially equal to the magnitude of the power distribution system current i measured at a first time subtracted from the magnitude of the power distribution system current i measured at a second time, the second time occurring later than the first time. The signal Δi(t) is utilized to generate measurement of the distance of a fault to the relay and is also utilized to generate operate signals if the fault occurs within the zone protected by the relay.

Control procedure for electromechanical relay - using circuit to reduce coil current and maintain switched state after response

Abstract: The operation of an electromechanical relay (REC) is controlled by a circuit (SK) isolated from the load circuit (LK) that has a load resistor (LR) and power supply (VL). The control circuit has a control module (ST), supply (VB), switch (S), shunt resistor (RS) and a current reducing stage (SV) that can be a resistor bridged by a switch or a switching transistor. The circuit operates such that if the voltage (VB) and the coil current (IREL) exceed predetermined minimum values, the current is reduced and the armature maintained in a responded condition until a fall to a lower value occurs. ADVANTAGE - Achieves fast response and allows operation at varying voltage.

Hybrid contactor for DC airframe power supply

Abstract: A contactor (12) for controlling connection of a DC power supply to an electrical load (14) in includes a series circuit (19) disposed between a nonground DC potential and a load having first (20) and second (22) relays each having a pair of contacts (26), the first relay and the second relay having a conducting state when the pair of contacts are closed and a non-conducting state when the pair of contacts are open which control current flow between the DC power supply and the load with the states being controlled by control signals applied to the relays; a semiconductor switch (24) having a conductive state controlled by a control signal to turn on the semiconductor switch to connect the semiconductor switch in parallel with the contacts of the first relay and a non-conductive state controlled by a control signal to turn off the semiconductor switch to disconnect the terminals of the semiconductor switch; a fault sensor (50) coupled to the load for generating a signal in response to the load drawing current exceeding a threshold to cause the second relay to open to disconnect the load from the power supply; and a control signal generator (28) for generating the control signals of the switches.

Actuating device for movable parts for closing of apertures in vehicles and vehicle roof utilizing same

Abstract: Actuating device for movable parts, such for closure parts for apertures in vehicles, having a reversible direct current drive motor, a polarity reversing actuating switch in the motor circuit for applying direct current to the motor circuit with a polarization corresponding to the desired motor rotational direction; a relay with a switch contact in the motor circuit which is in series with the polarity reversing switch; and further, having a position responsive switch connected with the relay control circuit for actuating the relay in a reference position of the movable parts, for the purpose of deactivating the drive motor by opening the switch contact. The relay is a direct current relay, which, upon application of a first or second voltage level at its control circuit, closes or, respectively, opens the switch contact. Connected with the relay control circuit, there is an electronic relay actuating stage with a storage capability, with stage, upon closing of the polarity reversing actuating switch in either direction, at least when the movable part is in the reference position, has applied a setting signal to an input thereof, in response to which setting signal the relay actuating stage applied the first voltage level to the relay control circuit, at least until the movable part has left the reference position.

Control for automatically starting a diesel engine

Abstract: Electrical control apparatus for automatically starting a Diesel engine. The apparatus includes start, preheat and run relays which respectively control the energization of a starting solenoid, glow plugs, and a fuel solenoid. The energization of the start, preheat and run relays is controlled by a control module which drives the preheat relay as soon as the control module is energized. The glow plug preheat time is measured, and the run and start relays are respectively energized just prior to, and at the termination of the preheat time. Engine cranking time and speed are monitored, dropping the start and preheat relays when the engine starts, and also when the engine speed fails to reach certain thresholds within first and second predetermined periods of time. The run relay continues to energize an electrical circuit which includes an engine reset switch and a low oil pressure switch. The engine reset switch de-energizes the control module, and thus the run relay, in the event the engine fails to start.

Relay control method and apparatus for a domestic appliance

Abstract: A relay control for a cooking appliance having a heating element includes a sensor for detectirg the occurrence of an arc upon a change of state of a relay coupled between the heating element and a power supply. Upon detecting an arc, the sensor provides a timing signal which is coupled to a microprocessor that controls the energization and deenergiza­tion of the relay. The microprocessor is responsive to the timing signal from the sensor to determine the time delay between the last energization/deenergization of the relay and the changing of the relay's state. From the time delay, the microprocessor determines a delay constant. Subsequently, the microprocessor energizes the relay at a time after the detection of a zero crossover point of the power supply signal, wherein the time is equal to the determined delay constant to cause the relay to change state at or slightly before a zero crossover point of the power supply signal. The sensor may take the form of an optical sensor, such as a phototransistor, mounted inside the housing of the relay or outside of, but within optical range of, the housing, in which case the housing would be transparent to the optical wavelength of an arc. Alternatively, the sensor may include an electromagnetic or RF pick-up coil for sensing an electromagnetic or RF signal in the radio frequency (RF) range radiated upon the generation of an arc. Such an RF pick-up coil may be mounted inside the housing of the relay or outside of the housing but within the range of the housing, in which case the housing would be formed of materials that would not interfere with the RF signal from an arc. Alternatively, the sensor may be a vibration sensor, such as a piezoelectric transducer, capable of detecting vibra­tions associated with the opening or closing of the relay contacts.

Overcurrent protection relay with communications

Abstract: An apparatus for protecting an electrical power system supplying electrical power to an electrical load comprises a transformer for sensing an operating condition of the electrical power system and for producing an analog signal representative of the operating condition, and a microcomputer for periodically sampling the analog signal and for converting the analog signal into a series of digital signals. The microcomputer includes circuitry for deriving a digital value representative of a square root of the series of digital signals and circuitry for processing the digital value over time to determine a processed value which is a function of both the sensed operating condition and time. A circuit breaker is responsive to the microcomputer for disconnecting the power system from the load in the event that the processed value is not within preset limits. The microcomputer also generates a relay signal representative of the status of the relay and the relay includes an output port responsive to the relay signal, for communicating the status of the relay to a remote station.

High-power solid state relay employing photosensitive current augmenting means for faster turn-on time

Abstract: A high-power solid state relay uses optically-controlled shunt and series solid state switches between a photodiode array and an output device to provide enhanced turn-off and transient immunity characteristics and an optically-controlled charging network connected to the switched load to enhance the turn-on characteristics of the relay.

A differential line protection scheme for power systems based on composite voltage and current measurements

Abstract: A differential feeder protection that utilizes voltage and current signals is described. This approach obviates the need for relay bias to compensate for capacitance spill current, thus improving the relay sensitivity. From a practical point of view, the scheme has been designed to simplify the digital hardware requirements and reduce the bandwidth requirements for signal transmission over a fiber-optic link. >

Antenna switch for transmit-receive operation using relays and diodes

Abstract: A four port antenna switch (300) for switching a receive port (320) and a transmit port (310) between a remote antenna port (330) and a standard antenna port (340) is provided. The switching actions of the receive port (320) between the remote antenna port (330) and the standard antenna port (340) is provided by a relay (350) under the control of a relay controller (352, 354, 400). The switching of the transmit port (310) between the standard antenna port (340) and the remote antenna port (330) is provided by diode switches (360, 370) under the control of diode switch controllers (332, 324, 312, 314, 400). The switching actions of the relay (350) and the diode switches (370, and 360) is complementary to each other, wherein sufficient isolation between the receive port and the transmit port is provided. In this arrangement, a low power relay may be used because the relay only switches low level received signals, and the high power transmit signals are switched by the pins.

EHV series capacitor banks: a new approach to platform to grounds signalling, relay protection and supervision

Abstract: Series capacitor banks for transmission systems above 145 kV, are normally erected for technical and economical reasons on fully insulated platforms per phase. Several methods have been used to realize the relay protection for series capacitor banks erected on platforms. One of the first designs used in the 1950's utilized protection relays and auxiliary power equipment on the insulated platforms. Signal communication was carried out by mechanical contact devices, which transmitted on/off signals from platform level to ground. In the late 1960's, the mechanical contact devices were replaced by fibre optics. The protection relays, together with electronic equipment and auxiliary power equipment, were still located on the insulated platforms. However, to give the relay protection of series capacitors the same simplicity as for ordinary substations, a new concept was introduced in the early 1970's. A number of signals were transmitted between EHV potential and ground via a modified current transformer. The relay protection and control equipment was located in the control room. The new Protection and Supervision system includes the advantages and excludes the disadvantages of the foregoing systems. The new system comprises optical current transformers, and a microprocessor-based protection, supervision and control system, located in the control room. Optical fibres connect the current transducers on the platform with the equipment in the control room. Auxiliary power to the current transducers is transmitted by light from ground level.

Thieved vehicle indicator

Abstract: PURPOSE:To make it possible to readily indicate a thieved vehicle to a person outboard of a vehicle by providing an hidden switch in an automobile, which is turned on when the driver alights from the automobile and which energizes a voice generating device, a video recognizing device or the like through a delay circuit when a key switch is turned on. CONSTITUTION:A plurality of hidden switches 1a are provided at positions which are known by the driver alone but are unknown by the others, and are connected to a switch circuit 1, and a series circuit consisting of a self-sustaining and releasing switch 1c and a contact 1b of a relay 1d is connected to the switch circuit 1, bypassing the switches 1a. When a main switch 6b in an existing circuit 6 is closed under the closing condition of the hidden switches 1a, a delay circuit 2 is energized by a power from a battery 6a so that a voice generation device 3, a video recognizing device 4 and a speed restraining device 5 are actuated after a predetermined time elapsing. With this arrangement, it is possible to indicate a thieved vehicle by means of audio or video information while preventing the thieved vehicle from running away at a high speed.

Relay driving circuit for a latch-in relay

Abstract: A relay driving circuit for a latch-in type magnetic relay having an excitation coil, generating a set current and a reset current of opposite polarity for the coil. A capacitor is provided between the input terminals of the circuit in series with the coil. A set switch is connected in series with the coil and the capacitor, and a reset switch is connected across the series combination. An input voltage level detector is provided to make the set switch conductive, thereby applying the input voltage to the excitation coil and the capacitor to provide the set current. As the input voltage decreases below the trigger level, the detector makes the reset switch conductive to allow the capacitor to discharge current in the opposite direction through the excitation coil. The circuit includes a disable switch responsive to the capacitor being charged to a voltage level sufficient to provide the reset current, the disable switch setting the set switch to a non-conductive state to thereby prevent the capacitor voltage from being reversely applied.

Fail-safe valve relay driver circuit for gas burners

Abstract: A fail-safe gas valve driver circuit controlling the gas supply line of a gas burner, which circuit in its essential circuit elements (FIG. 1) includes an appropriate switching means (S1) effectively feeding a pulsed DC wave form into the rest of the valve relay driver circuit, operatively consisting only of a capacitor (C1) in series with a gas valve relay (K1), which in turn is in parallel with a diode (D1). In operation, the valve relay coil is energized by charging the capacitor with the switch connected to a positive DC voltage source (V dc ; FIG. 1A), and then grounding the positive end of the capacitor (switch connected to ground) applying a negative voltage across the coil of the relay (FIG. 1B). When the capacitor is again connected to the positive DC voltage source by the switch, the current in the relay coil is sustained by the diode (FIG. 1C). The switch is operated at a sufficiently high rate so the current in the relay coil has insufficient time to decay significantly during the charging cycle of the capacitor before being replenished during the capacitor discharge cycle. With this circuitry the gas supply valve (G.V.) will always go to, or be maintained in, a closed position, regardless of what component(s) of the valve relay driver circuit might fail or deteriorate. Any inadvertent supply of gas to the burner due to any component failure is avoided without any component redundancy. Two exemplary, transistor switching circuits are described (FIGS. 2 & 3).

Radio fax transmission

Abstract: Disclosed is an audio-to-radio and radio-to-­audio signal converter and method for interfacing a facsimile machine with a radio transmitter-receiver having a microphone input, an audio output and a push-­to-talk relay. The converter provides a first circuit for inputting the output signal of a facsimile machine to the microphone input of a radio transmitter-receiver; a second circuit controlled by the output signal of the facsimile machine for operating the push-to-talk relay of the radio transmitter-receiver; and a third circuit connected to the audio output of the transmitter-receiver for amplifying the audio output signal, and inputting the resultant signal to the facsimile machine. A fourth circuit provides a null feedback that keeps the stronger audio signals from being amplified which may trigger the push-to-talk relay.

Rapid pressure rise circuit

Abstract: An electronic relay control circuit is provided for liquid cooled electric power transformers. The control circuit senses the rate of change of internal tank pressure and operates its relays in response to a sudden pressure increase. Relay control connections are provided for operating transformer trip and annunciator circuits. The relay response is field adjustable.

Signal processing system

Abstract: PURPOSE:To allow an intermediate relay station to branch and insert an additional bit easily by devising the system such that a specific additional bit is arranged in the same string at equal intervals even after converting the string to some string. CONSTITUTION:In the case of inserting an additional bit to a data signal inputted from a carrier terminal station equipment, processing framing and applying conversion to a string for the transmission to a radio line, the length of a subframe to a prescribed position whose additional bit is inserted is formed to be a product among the number of strings before string conversion, the number of strings after string conversion and an optional natural number. Thus, the specific additional bit is branched or inserted easily in the intermediate relay station and the equipment of the intermediate relay station is simplified and the cost is reduced.

Solid state optical relay

Abstract: A solid-state, four terminal optical relay has a current regulator with two input pins, and an output switch with two output pins. The relay includes an optical isolator assembly so that the current which causes switching of the relay is optically, rather than electrically, transmitted to an output switch driver. The relay includes an internal current overload detect and latch circuit which operates if the relay is switched on into a shorted load, or if a short is switched in across the load while the relay is on. The current overload detect and latch circuit is sufficiently fast to permit the relay to be continuously pulsed into a shorted load without damage to the relay.

Relay for detecting a current disturbance and asserting an output

Abstract: An apparatus for detecting a power system disturbance. The apparatus may be a current rate-of-change relay for qualifying system-separation transfer-trip commands.