Abstract: A method and system for providing protection for a superconducting electrical cable located in a utility power network includes detecting a fault current on the superconducting electric cable, determining the cumulative total energy dissipated in the superconducting electrical cable from the fault current and at least one prior fault current over a predetermined time period, and determining whether to disconnect the superconducting electrical cable from the utility power network on the basis of the cumulative total energy dissipated.

Abstract: The present invention is directed to a circuit and method for self-testing a protection device for use in an AC power distribution system. The device is configured to be coupled between an AC power distribution system and at least one load. The method includes the step of introducing a simulated ground neutral fault during a first predetermined half cycle half cycle of the AC power. An attempt is made to detect the introduced simulated grounded neutral fault during the first predetermined half cycle half cycle. A fault condition is signaled if the introduced simulated grounded neutral fault is not detected within a predetermined period of time.

Abstract: In the current detection circuit that detects the output currents of a switching power supply circuit, an improved current detection circuit makes it possible to detect the output current directions of power supplies solves the malfunction of the power supplies vibrating or diverging during changes in load state and during parallel operation, and thus implements stable operation. The direction of an output current I2 can be detected by using the current detection circuit 8 that has multiple switching elements S1 to S4 each operating synchronously with an inverter circuit.

Abstract: Disclosed is an apparatus and method for detecting a loss of a current transformer connection coupling a protective relay to a power system element of a three-phase power system and providing a plurality of secondary current waveforms of the three-phase power system to the protective relay. The apparatus includes a first logic circuit and a second logic configured to provide corresponding first and second binary signals in response to respective comparisons of calculated current value(s) of a plurality of like-phase digitized current sample streams to respective threshold values. The apparatus also includes a set reset flip-flop having a set input adapted to receive the first and second binary signals to provide a third binary signal. The third binary signal indicates loss of a current transformer connection when the set input is asserted and indicates no loss of a current transformer connection when the reset input is asserted.

Abstract: A drive unit for controlling drives of machine tools or production machines includes a signal electronics unit, a startup/diagnostic unit, and an interface between the signal electronics unit and the startup/diagnostic unit. The interface has a data line for data exchange between the signal electronics unit and the startup/diagnostic unit, and an electric power line independent of the data line. A switch can be provided that disconnects the signal electronics unit from a power mains or from an additional power supply, when a power failure is detected, and connects the signal electronics unit to the startup/diagnostic unit via the electric power line. This provides a simple and cost-effective approach for supplying electric power to the signal electronics in the event of a power failure or malfunction of the main power feed to the drive unit.

Abstract: Protection systems for electrical systems are described, where the electrical systems may include spot networks and/or grid networks. The various protection systems may be designed and used to detect and clear faults that may occur within the electrical systems. For example, a pair of Rogowski coils may be used to detect current along a conductors at their respective locations on the conductors, and to output corresponding signals to a multi-function, differential relay having multiple voltage and current inputs. By comparing the signals from the Rogowski coils, the differential relay may determine whether a fault exists at some point along the conductors and between the pair of Rogowski coils. Further, the relay may then, in response to the fault, trip a circuit breaker or other network protection device to address the fault.

Abstract: A system for determining whether arcing is present in an electrical circuit in response to a sensor signal corresponding to current in the circuit includes a circuit for analyzing the sensor signal to determine the presence of broadband noise in a predetermined range of frequencies, and producing a corresponding output signal. A controller processes the sensor signal and the output signal to determine current peaks and rise times and to determine, using the current peaks and rise times and the presence of broadband noise, whether an arcing fault is present in the circuit, by comparing data corresponding to the current peaks and rise times and broadband noise with preselected data indicative of an arcing fault. The circuit for analyzing and the controller are integrated onto a single application specific integrated circuit chip.

Abstract: An apparatus and method for monitoring and controlling a backup power source and one or more critical loads powered thereby is disclosed. The apparatus is constructed in the form of an electrical distribution panel that includes electronic systems for monitoring the current to the critical loads. In the event of an overcurrent condition on one or more critical load circuits, the system is able to disable power flow to the offending circuit so as to protect the remaining critical load circuits and the backup power source. The system is also provided with a means for communicating status information about the system to a remote user.

Abstract: An evaluator (210) having an input (207) for receiving a signal indicative of a channel current sensed via a sensor in a mutlichannel current sharing system, and circuitry (313, 319) coupled to the input (207) and responsive to the signal for indicating an unreliable sensing for the sensor when a low current condition occurs for a time period exceeding the switching time period of the channel current. Further, the apparatus can include an additional input (207) and circuitry (313, 319) for evaluating an additional sensor sensing an additional channel current. The low current condition is characterized by thresholds corresponding to the peak level and a valley level of the channel current over a switching time period.

Abstract: A microcontroller-based system to detect ground-fault and grounded-neutral conditions in a monitored circuit of an electrical distribution system having line and neutral conductors. The system includes a single sensor producing an output signal responsive to current flow in both the line and neutral conductors of the monitored circuit, and a microcontroller receiving the sensor output signal and initiating the generation of a circuit status signal indicating one of a normal operating condition, a ground-fault condition or a grounded-neutral condition in the monitored circuit. The microcontroller is programmed to continuously test for ground-fault conditions by evaluating the sensor output signal and, at selected intervals, test for grounded-neutral conditions by evaluating the sensor's output signal response to a microcontroller initiated ping in the sensor circuit.

Abstract: A method and arrangement for reducing stress in an electrical network. In the method and arrangement, an inrush current caused by a network component or part connected to the live electrical network is minimized, the network component or part being disconnected from and connected to the live electrical network by opening and closing a circuit breaker (3). The current of at least one phase (A, B, C) of the network component or part is measured, the breaking-off moment of the current is determined after the circuit breaker (3) is opened, the optimum closing moment (TOPTIMUM) of the circuit breaker (3) is determined on the basis of the breaking-off moment of the current, and the circuit breaker (3) is closed in such a manner that it closes at the optimum closing moment (TOPTIMUM).

Abstract: A branching unit for use in submarine systems that includes a ground termination; first, second, and third cable terminations each coupled to a power feed line of a respective submarine cable; a re-configuration relay in series between the first cable termination and the ground termination, the re-configuration relay being unidirectional and having at least one contact positioned in series between the second and third terminations, the at least one contact being closed when the re-configuration relay is de-energized; and a bypass relay in series between the second and third cable terminations, the bypass relay having a contact positioned in parallel with the reconfiguration relay and being open when the bypass relay is de-energized.

Abstract: In one embodiment, an integrated differential isolation loss detector is disclosed that generates a first temperature that is a function of a high side current and a second temperature that is a function of a low side current. A temperature sensor senses the difference between the first and second temperatures and provides an output signal that is indicative of the magnitude and the polarity of the sensed difference. A controller receives the output signal and if the difference is greater than a predetermined magnitude the high side current, the low side current, or both can be disconnected from the load. In another embodiment, an integrated differential isolation loss detector is disclosed that includes a first temperature difference generator that generates first and second temperatures where the difference between the first and second temperatures is a function of the magnitude of the high side current.

Abstract: The system is intended to provide an isolated power supply for an electrical load. It contains a generator for producing a supply signal, and a transmission path having two separate branch elements. The first branch element is designed for transmission of the supply signal (S1) in the forward direction, and the second branch element is designed for transmission of the supply signal in the backward direction, so that this results in a closed circuit for the supply signal. The two branch elements contain means for isolation. The load can be supplied by the supply signal with an electrical power of at most 100 mW.

Abstract: Protection systems for electrical systems such as substation power dividers are described. The protection systems may be designed and used to detect and clear faults that may occur within the substation power dividers. For example, a first Rogowski coil may be used to detect current along a primary conductor, and output a corresponding current signal to a multi-function, differential relay having multiple voltage and current inputs. Similarly, additional Rogowski coils may be used at each of a plurality of secondary feeders, where power from the primary feeder may be distributed to the secondary feeders using a connection bus. By comparing the signals from the first Rogowski coil and the additional Rogowski coils, the differential relay may determine whether a fault exists at some point along the conductor(s) and between the first Rogowski coils and the additional Rogowski coils, including whether a fault is associated with the connection bus.

Abstract: An electrical service distribution board is accommodated in a housing, has a feed conductor that is inserted into the housing and has outgoer conductors that lead to individual loads. Electrical service devices with different protection tasks, such as fault current protection, short circuit or over-current protection and the like, which can be connected to the feed conductor and to the outgoer conductors by a plug connection via a connection system which contains connection conductors connected to them. A mounting plate is providing for holding the service devices, with the connection conductors disposed underneath the mounting plate and the mounting plate having openings into which plug elements which are disposed on the service devices can be inserted.

Abstract: Electric arc monitoring is effected by exploiting the discovery that electric arcs are fractal phenomena in that all essential information that signifies “arc” is contained in each fractal subset. These fractal subsets are logarithmically distributed over the arc spectrum. Monitoring of arcs is most advantageously effected on a fractal subset (16) of low logarithmic order where the amplitude is higher pursuant to the 1/f characteristic of electric arcs, where cross-induction among neighboring circuit is lower, and where travel between the arc (12) and the arc signature pickup (23) is longer than at the high frequencies customary for electric arc detection. Fractal subset transformation (17) reduces the danger of false alarms. Arc signature portions may be processed in out of phase paths (242, 342) or treated as modulated carriers (42) for monitoring.

Abstract: In an electro-mechanical distribution system having plural units each comprising a valve/switch and dual sensors, a computer is associated with each unit so as to process sensor information and control the valve/switch. According to the control logic, a unit is either in normal mode or fault mode. The fault mode begins with a transient waiting period and may continue on to a series of steps. A step waiting period (wherein the valve is closed) may be followed by the step testing period (wherein the valve is closed) of the same step; a step testing period may be followed by the step waiting period of the next step. Fault mode is triggered if at any time during normal mode either sensor detects a fault condition. Normal mode is triggered if at any time during fault mode both sensors concurrently detect a normal condition.

Abstract: A sense circuit and a system including a sense circuit are disclosed. The sense circuit is configured to measure and change in current with respect to time and/or a change in voltage across a portion of a substrate.

Abstract: A network protector relay controls a circuit breaker connected between polyphase feeder and network busses. A circuit samples polyphase circuit breaker current and network voltage to generate digital polyphase current and voltage samples. A microcontroller generates positive sequence current and voltage vectors from the current and voltage samples. A first trip algorithm trips the breaker in response to the positive sequence current vector being in a first trip region of a first trip characteristic with respect to the positive sequence voltage vector. The first trip characteristic is defined by a reverse trip setpoint and a first positive angle. A second trip algorithm trips the breaker in response to the positive sequence current vector being in a second trip region of a second trip characteristic with respect to the positive sequence voltage vector. The second trip characteristic is defined by the reverse trip setpoint and a second negative angle.

Abstract: A fault protection system whose trip logic considers power magnitude and direction at first and second points on a conductor is provided. Under normal operating conditions, power flows in the same direction through first and second points on the conductor. Under faulted conditions, a differential power condition exists; that is, the power flowing at a first point on the conductor is of different magnitude and/or direction than the power flowing at a second point on the conductor. The trip logic identifies the differential power condition as the result of a fault between the first and second points on the conductor and causes a protective device on each side of the fault to trip open, thus isolating the fault.

Abstract: A method and system for controlling power to a cranking subsystem in a device having a power source is disclosed. The method and system include providing at least one switch and providing at least one controller. The switch is coupled with the power source. The at least one controller is coupled with the switch. The at least one controller is for controlling the at least one switch to be open or closed based on a signature of a behavior of a portion of the device. Thus, power is controlled to the portion of the device based on the signature of the portion of the device. In one aspect, the method and system include monitoring a portion of the device to determine a behavior of the portion of the device. In this aspect, the method and system include comparing the behavior of the portion of the device to a signature for the portion of the device.

Abstract: An arc fault detector system detects arcing faults in an electrical distribution system by monitoring one or more conductors and producing an input signal representing one or more electrical signal conditions in the circuit to be monitored. This input signal is processed to develop signals representing the electrical current flow through the monitored circuit and broadband noise signal components. The system analyzes these signals to determine whether an arcing fault is present, and if so, outputs a trip signal which may be used directly or indirectly to trip a circuit breaker or other circuit interruption device.

Abstract: A protective circuit arrangement includes at least two power contactors that have main make contact elements arranged in enable circuits. Each main make contact element of a power contactor is connected in series to a main make contact element of another power contactor in each respective enable current circuit. A respective coil circuit make contact element is provided in the coil current circuit of each coil of each power contactor, whereby the coil circuit make contact elements can be jointly actuated. The main make contact elements of each power contactor are disposed between two respective auxiliary contact units which each have a respective make contact element and a respective break contact element, and which are respectively configured as positively driven contacts. The make contact elements of all auxiliary contact units arc connected in series in a first indicator circuit, and the break contact elements of all auxiliary contact units are connected in series in a second indicator circuit.

Abstract: A circuit configuration has a first semiconductor switch and a first protection circuit. The protection circuit has a second semiconductor switch whose load path is connected between a control terminal and a load path terminal of the first semiconductor switch. The second semiconductor switch is switched on by a comparator circuit, in each case for a predefined time period, in dependence on a comparison between a load path voltage and a reference voltage, or between a load path current and a reference current.

Abstract: A distribution control system includes in each of feeder terminal units a controller that updates a value in a latest current value storage area of a memory, every time a current value is detected at a sampling interval. If a distribution line fault takes place, that is, if the detected current value exceeds a reference value, each controller stores the current value in a fault current value storage area of the memory as a fault current value. The feeder terminal units each supply the information about the fault current to a control center through a substation remote terminal unit so that the control center identifies a fault section from the information for detecting the fault section.

Abstract: This invention is to provide a transforming system capable of satisfactorily protecting the equipment of a substation even if a aerial electric power lines is struck directly by an intense electric shock of a large energy, such as an electric shock of a waveform similar to that of a thunderbolt stroke having a long duration of wave tail. So, this invention, a transforming system comprises, a lightning arrester, a ground fault device installed near a service entrance through which the power lines are led in, a voltammeter placed on the gas-insulated switchgear, and a control device receiving a signal from the voltammeter and providing a signal for controlling the grounding device. And when detecting of said thunderbolt arising in said aerial electric power line, a control device which order said ground fault device to make the ground fault condition.

Abstract: A method for protecting a zone in a power system, which has a number of transmission lines connected to power sources and a number of transmission lines connected to a number of loads, where the power sources and the loads are arranged outside the zone. Continuously measuring all the incoming currents (Iin) to the zone, continuously measuring all the outgoing currents (Iout) from the zone, and continuously calculating the differential current (Id) according to Id=Iin−Iout.

Abstract: A power distribution system includes circuits each having an electronic circuit breaker as a protection for short-circuits and/or overloads, and a clocked power supply unit. The clocked power supply unit is connected to the circuits and feeds power to the circuits. The electronic circuit breaker has a power stage and an adjustable current limiting device connected to the power stage. The adjustable current limiting device, in the event of an overload, when a first adjustable current threshold is exceeded, turns off the power stage after a first adjustable disconnection time has expired, and in the event of a short circuit, after a second adjustable current threshold has been exceeded, turns off the power stage after a second disconnection time has expired.

Abstract: An electrical power distribution system and automatic bus transfer switch therefor, consisting of two pairs of insulated gate bipolar transistors (IGBTs) connected in series in a back-to-back circuit configuration with respective semiconductor diodes connected across the current conducting terminals thereof so as to provide a static AC switch configuration which implements a fight-through bus transfer switch wherein only one pair of switches is rendered conductive at any one time, wherein one transistor and a diode across the other transistor of the same pair conduct in each half cycle of the AC power waveform, and thus provide power to one or more load(s) from either of two AC sources, a primary AC source or an alternate AC source.

Abstract: A network protector includes a coil drive circuit for the trip actuator which operates as a current limiter to protect a trip coil with limited impedance at the upper limit of network voltage while assuring operation at network voltages of less than 10% rated voltage. A comparator provides gate drive current to a FET connected in series with the trip coil as long as coil current is below a reference voltage proportional to a specified maximum value of coil current. When the specified value of coil current is reached, the FET is latched off until the network protector is tripped open again.

Abstract: A system for distributing DC power to a plurality of optical network units in a fiber-to-the-curb communication system is provided. The system includes an AC-DC rectifier coupled to at least one local power hub. The local power hub includes a bulk DC-DC converter coupled to the AC-DC rectifier and a plurality of active current limiters coupled to a plurality of power outputs from the DC-DC Converter. Each of the active current limiters supplies current limited power to one of the optical network units in the fiber-to-the-curb system.

Abstract: An integrated fault circuit includes a fault switch interposed between an input power source and an electronic subsystem power bus. A power converter is connected to the electronic subsystem power bus and converts power derived therefrom to at least one voltage output to supply power to an electronic subsystem and at least one fault protection output controlling the fault switch. A fault detection circuit is operatively connected to detect an out of range current on the electronic subsystem power bus and has at least one fault detection output connected to the power converter. When the out of range current is detected on the electronic subsystem bus, the fault detection circuit instructs the power converter, via the at least one fault detection output, to open the fault switch, thereby isolating the input power from the electronic subsystem bus.

Abstract: A differential protective relay and method for a microprocessor-based bus differential protective relay that ensures fast and sensitive operation under internal fault conditions and offers improved stability during external fault and other non-internal fault conditions. The method uses a two-slope differential characteristic to cope with small CT transformation errors without reducing relay sensitivity. The method can also use a saturation detector to switch dynamically between the 1-out-of-2 and 2-out-of-2 operating mode depending whether or not the CTs saturate. In a 2-out-of-2 operating mode, both the differential and directional elements must confirm a fault for the relay to trip. In a 1-out-of-2 mode, if saturation is not detected, the relay can trip without checking the fault direction.

Abstract: An obstacle detection system for vehicular environments including a monitoring sensor system and a mounting system is disclosed. An installer can make aiming adjustments, in the factory or field, to account for tolerance stack-up. The system includes a housing for mounting the monitoring sensor system to minimize cross-talk and interference between transmitter and receiver sections, to limit sensor system movement, and to enable gross and fine aiming adjustments. In one embodiment, a circuit board is disposed within a cradle assembly which, in turn, is mounted in or integral to the housing to position the obstacle detection sensor as necessary. The cradle in one embodiment is an enclosure for the circuit board. The sensor housing is mounted to the interior vehicle trim, door panel, and/or door sheet metal and ensures consistent mounting regardless of interior trim or factory installation variations. Integral adjustment mechanisms are incorporated for adjusting the orientation of the sensor system.

Abstract: The electrical distribution device comprises a main part comprising main breaking means, at least one secondary part comprising at least one secondary breaking device, and an electrical power distribution line connected between the main and secondary parts. The secondary part comprises secondary control means enabling opening of at least one secondary breaking device if a current flowing in said breaking device is lower than a preset opening current threshold. A distributed electrical installation comprises at least one such device. An electrical protection process for an electrical distribution device comprises an opening step of the secondary breaking means when a current flowing in these means is lower than a preset opening current threshold following detection of a fault.

Abstract: A device comprising a fault detector and communications module. The communications module can transmit and receive information and data via a commercial two-way wireless system, which may include two-way paging technology. The inventive device is capable of measuring imbalance currents in a remote capacitor bank, and if the imbalance current exceeds a set threshold the inventive device communicates this information, and/or other information, to an electric utility control center. The communications module is mounted using a standard utility meter socket, thereby allowing the communications module and an associated adaptive capacitor control to be stacked and mounted on the same meter socket to provide an integral unit. A two-way infrared communication port is also provided.

Abstract: A safety device for a number of electrical loads that are connected to a supply line between a high-side path and a low-side path. The loads are activatable individually by way of drivers provided in the low-side path. A fuse is provided in the high-side path (2a) and causes, in the event of a defect in at least one driver, a permanent interruption in the high-side path.

Abstract: When directional overcurrent protection relays are included at the load end of a set of parallel feeders fed from an AC power source, a minimum fault-current threshold is specified based on the potential of a phase-to-phase fault at the source to cause a relay to operate misleadingly. This threshold is, for plain (transformerless) feeders, approximately 50% and, for transformer feeders, approximately 85% (nominally 86.7%) of rated pre-fault load current. These thresholds can, however, be ignored if the relay outputs are processed in a 2-out-of-3 circuit, so that a relay on one phase will only operate its associated circuit breaker if a relay on another phase has also operated, a condition which has been found not to obtain in the case of a source fault.

Abstract: A method of detecting manual trips and reclose operations in an intelligent electronic device, e.g., electronic trip unit or protective relay, is presented. The intelligent electronic device includes a microcontroller and associated memories. An algorithm (program) stored in a memory of the intelligent electronic device detects manual trips when the following conditions are satisfied: (1) no trip event message has been issued by the trip unit within the reaction time required to trip the circuit breaker; (2) current becomes zero on all phases of the line; and (3) voltage downstream from the circuit breaker becomes zero on all phases. Reclose operations are detected when load side voltages on all phases return from 0V to nominal levels of the line side of the breaker.

Abstract: A residential load center includes an electronic trip unit as the main circuit breaker for overcurrent and arcing fault protection while connecting with thermal magnetic circuit breakers in each of the branch circuits for overcurrent protection within the individual branch circuits.

Abstract: An arc fault detector system detects arcing faults in an electrical distribution system by monitoring one or more conductors and producing an input signal representing one or more electrical signal conditions in the circuit to be monitored. This input signal is processed to develop signals representing the electrical current flow through the monitored circuit and broadband noise signal components. The system analyzes these signals to determine whether an arcing fault is present, and if so, outputs a trip signal which may be used directly or indirectly to trip a circuit breaker or other circuit interruption device.

Abstract: An active current limiter controls the flow of current between a power source and a load. The active current limiter includes a power switch coupled between the power source an the load, a current sensor coupled between the power source and the load to sense the level of current flow through the power switch, and one or more fault detection circuits coupled to the current sensor for sensing one or more current fault conditions between the power source and the load and configured to switch of the power switch when a current fault condition is detected.

Abstract: For use in a power distribution system having first and second output power feeds having corresponding first and second circuit protection devices associated therewith, a monitoring system and a method of monitoring a utilization of the power distribution system. In one embodiment, the monitoring system includes: (1) first and second status sensors that sense statuses of the first and second circuit protection devices, respectively and (2) a controller, coupled to the first and second status sensors, that employs the statuses to determine a loading of the first and second output power feeds and calculates a utilization of the power distribution system based on the loading.

Abstract: A selective electronic trip unit comprises at least one current sensor supplying a secondary signal representative of a primary current, a first detection circuit to detect a first overshoot of a first threshold, and a second detection circuit to detect signals representative of contact repulses interrupting the primary current, said first and second detection circuits receiving the secondary signal. An analysis circuit connected to the second detection circuit disables instantaneous tripping of the trip unit if the signals representative of repulses are representative of currents lower than a second threshold.Application, in particular to selective circuit breakers.

Abstract: A constant-current regulator regulates and monitors the current fed to one or more downstream loads. It also serves to even out the current fed to the downstream load or loads at the control level or when there is a change in the control level. In order to enhance the security and reliability of operation of such a constant-current regulator when installed in a control and monitoring circuit, control signals having a similar regulating/monitoring content are applied to the constant-current regulator by means of two separate busses (3, 4) in a mutually independent manner. The constant-current regulator is used to carry out a separate plausibility/conformity check of the control signals from the first bus (3) and the control signals from the second bus (4). If a lack of plausibility/conformity is ascertained for the control signals of the first bus (3), the control signals of the second bus (4) are taken as the basis for operation of the constant-current regulator.

Abstract: A controller for a starter/generator used with an aircraft engine, includes means for monitoring field return current in a generator field winding; means for monitoring generator voltage; and microprocessor control means for adjusting generator field current as a function of the field current and voltage and field return current. The field return current and output voltage monitoring functions allow for open field, field integrity, over voltage, field weakening and torque limiting functions to be realized in an integrated programmable system configuration.

Abstract: A method of performing instantaneous protection in a trip unit is presented. The electronic trip unit includes a microcontroller and associated ROM having trip unit application code, e.g., main functionality firmware, including initializing parameters, and boot code, stored therein and EEPROM having operational parameter code stored therein. An instantaneous protection algorithm (program) stored in the memory of the trip unit has a `WAIT` state and a `RUN` state. In the RUN state samples of the sensed current that classify as points that are accumulated in a point register. Accumulation of a determined number of points qualifies as a peak. These peaks are accumulated in a peak register. If a point is not detected within a determined time period, then the count of peaks accumulated in the peak register is decremented, thereby provided a cooling function. When the count in the peak register exceeds the sensor limit a signal is generated by the microcontroller to initiate the trip.

Abstract: The present invention is concerned with an audio equipment capable of processing video signals and a method of displaying operation of the acoustic equipment. An input selector switch 1 is supplied with reproduced audio signals from devices connected to a tuner unit 2 and input terminals 3, and supplies a signal to a sound field processing DSP unit 4. A signal processed by the DSP unit 4 is applied through a muting switch 5 to an output terminal 6. An input selector switch 7 is supplied with reproduced video signals from devices connected to input terminals 8, and supplies a signal to a graphic controller (GDC) 9 which generates a video signal to display an image. One of a signal generated by the GDC 9 and an original video signal are selected by a switch 10, and applied to an output terminal 11. The GDC 9 also generates an image simulating a control panel. When a key switch 13 is operated, the display corresponding to the operated key in the simulating image is varied.

Abstract: An adaptive distance relaying system provides improved performance for parallel circuit distance protection. The system utilizes the parallel circuit's current, when available, in conjunction with measurements of voltage and current on the protected line to compensate for the zero sequence current mutual coupling effect. The sequence current ratio (zero or negative sequence) is used to avoid incorrect compensation for relays on the healthy circuit. If the parallel circuit current is not available and the line operating status is, the best zero sequence current compensation factors are selected accordingly as a next level adaptation. If both the parallel circuit current and line operating status are unavailable, a fallback scheme that offers better results than classical distance protection schemes is employed.