Westinghouse Electric Corporation

Eaton Corporation

Thomas J Kenny

James F Sutherland

Joseph C Engel

John Robert Moffat, Jr

David M Oravetz

Robert Tracy Elms

James A Neuner

Albert W Crew

Frank Klancher

Robert Yanniello

John C Schlotterer

Steven Edward Meiners

Douglas A Bauman

Kingsley F Graham

David Robert Smith

John R Smith

Robert E Hager

Carl A Vitalbo

Timothy F Thompson

Gilbert W Remley

William W Wassel

Dhulipala M Rao

Susan A Wilbur

David G Theriault

Eric A Delava

George M Chambers

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.

Network protector relay and method of controlling a circuit breaker employing two trip characteristics

A network protector relay for a circuit breaker includes a microcontroller routine which provides a positive sequence network voltage from polyphase network voltages on a network bus. Another microcontroller routine provides a positive sequence phasing voltage from the polyphase network voltages on the network bus and polyphase feeder voltages on a feeder bus. A recloser circuit automatically recloses the circuit breaker connected between the polyphase feeder bus and the polyphase network bus in response to a function of a plurality of setpoints and the positive sequence phasing voltage which indicates a first flow of power from the polyphase feeder bus to the polyphase network bus. A receiver receives a remote close command. Another routine temporarily changes at least one of the setpoints in response to the received close command, in order to conditionally close the circuit breaker for a second flow of power from the polyphase feeder bus to the polyphase network bus, with the second flow of power being less than the first flow of power.

Network protector relay providing a close function

A network protector is provided with diagnostics which alert a utility of component problems in detail. Selected measurements are used to assess the condition of various components such as for example, main contact electrical resistance, a blown fuse, the availability of sufficient voltage for charging the springs which close the main contacts and adequate voltage for tripping the contacts open. These abnormal operating conditions are transmitted to a remote station at the utility so that proper maintenance can be efficiently provided.

Network protector with diagnostics

The frequency and sampling interval for synchronous sampling of an ac signal of unknown or varying frequency are accurately determined within one cycle by apparatus including an input circuit which generates a single input pulse for each cycle of the ac signal. The count of clock pulses maintained by a free running counter is recorded at each input pulse. The frequency of the ac signal is determined from the period of the ac signal calculated from the difference in the count stored at consecutive input pulses. This difference in the count is divided by the desired sampling rate to generate the sampling count which is repetitively added to the current running count to generate an interrupt count. A sampling interrupt utilized by an analog to digital converter to digitize the ac signal is generated when the running count equals the interrupt count. The same sampling interval is used for each phase of a multiphase signal; however, a separate sampling interval is established for each ac signal in a multisignal system.

Apparatus for digitizing ac signals of unknown or changing frequency

A PC computer monitors the energy consumed at a plurality of local stations placed behind the electrical meter of the utility company for individual billing of the local users, a bidirectional communication line being used therebetween. A command from the PC computer causes at each station the totalized energy to be stored, and thereafter the PC computer derives individually the results for separate estimations and central billing.

Energy monitoring system for a plurality of local stations with snapshot

A PC computer monitors the energy, power, voltage, and current consumed at a plurality of local stations placed behind the electrical meter of the utility company for individual billing of the local users, a bidirectional communication line being used therebetween. A command from the PC computer causes at each station the power, voltage, current and totalized energy to be stored, and thereafter the PC computer derives individually the results for separate estimations and central billing.

A sampled digital filter system for filtering a signal that has a frequency lower than an unwanted signal component in the input signal. The digital filter system samples the input signal in bursts at a rate satisfying the Nyquist criterion for the unwanted signal component.

Sampled digital filter system

Signals from redundant sensors located throughout a pressurized water reactor (PWR) nuclear power plant are processed in four independent channel sets each of which includes a plurality of independent microcomputers which calibrate, convert to engineering units and calculate partial trip signals and engineered safeguard actuation signals from the sensor signals for use in the conventional voting logic of a plant protection system. The primary and secondary partial trip and engineered safeguard actuation functions associated with various postulated abnormal events are allocated to different independent microcomputers in the channel set for reliability. A test unit common to the channel set automatically, rapidly bypasses and tests each protection function independently while the other protection functions in the channel set remain on-line and also continually tests each microcomputer through a dummy test function performed along with the assigned protection functions. Signals representative of the analog value of the sensor signals are stored by the microcomputers and are transmitted by a serial data link through a common electrical isolation unit to a common analog output device for use by the plant control and monitoring systems under the control of a communication processor common to a group of microcomputers in the channel set.

Distributed microprocessor based sensor signal processing system for a

A method and apparatus for controlling the magnitude of an analog current through a load to be proportional to the magnitude of an input voltage. A sensing resistor is connected in series with the load. A controllable voltage is applied across the series connection of the load and sensing resistor for driving a current therethrough. A pulse width modulator receives the input voltage and a feedback voltage corresponding to the voltage drop across the sensing resistors when current is conducted thereby and produces square wave pulses each having a pulse width which is adjusted in response to a difference between the magnitudes of the input voltage and the feedback voltage. The magnitude of the controllable voltage is adjusted as a function of the pulse width of the square wave pulses until the magnitude of the current flowing through the load and sensing resistor causes the magnitude of feedback voltage to correspond to the magnitude of the input voltage so that the current through the load is maintained proportional to the magnitude of the input voltage.

Low power dissipation analog current loop output circuit

Apparatus and a method for use therein are disclosed for an analog signal processor, particularly one suited for use in nuclear power plant applications, which converts analog process signals to digital form and employs continuous on-line automatic calibration in order to accurately compensate for gain and bias errors occurring in its input analog circuitry.

Analog signal processor

A power contact with low off current for switching a-c loads in response to a logic signal includes a rectifier bridge circuit in a series with the load and the a-c power source, a MOSFET connected across the d-c terminals of the bridge, and a series RC filter circuit in parallel with the MOSFET. A metal oxide varistor connected across the d-c side of the bridge protects the MOSFET from transients in the a-c circuit. While this power contact is capable of switching sizable a-c currents, the leakage current with the MOSFET off is less than 1/10 of a milliamp so that it can also be used to switch loads which draw very low level currents. The MOSFET is electrically isolated from the logic signal by an opto-isolator which has a unique switchable output which permits the power contact to be readily adapted for use with normally energized or normally deenergized loads.

Low leakage, solid state a-c power contact

A redundant power supply for digital control systems, such as one using a MULTI-BUS backplane which utilizes remote sensing power supplies and level holding capacitors to provide continuous operation when one of the power supplies fails. Embodiments of the invention include a dual redundant power supply system for a backplane having a pair of power buses which provide positive five volts, positive twelve volts and negative twelve volts with reference to ground. Equipment drawing relatively high currents, e.g., 40 amperes, can be continuously supplied with power at a voltage regulated to within .+-.0.1% of nominal values for each 10% change in current.

Redundant power supply system

A redundant d.c. power supply arrangement for supplying power to a load circuit, wherein the power supply arrangement is subjected to voltage transients of high frequency and magnitude which emanate from the load circuit. The arrangement includes first and second power supply branches connected in electrical parallel with the load circuit. Each power supply branch includes a d.c. voltage supply and a Zener diode connected in electrical series with the voltage supply. The Zener diodes are selected and arranged for causing at least one of the voltage supplies to deliver power to the load circuit. Each Zener diode has a reverse breakdown voltage for clamping a voltage transient emanating from the load circuit to that Zener breakdown voltage and provides a low impedance path for a resulting current surge associated with the voltage transient.

Redundant power supply arrangement with surge protection

Numerous signal conditioning circuits on a plurality of printed circuit boards are calibrated remotely by a signal processing unit which sends coded signals to each board, either sequentially or in parallel, to connect either on-board or off-board test signals to one of the conditioning circuits in place of its field generated input. The processing unit utilizes the actual and expected responses of each conditioning circuit to low and high test signals to generate a gain and an offset which are applied to the conditioned field signal to provide a calibrated signal. The time constant for each conditioning circuit is also measured periodically, or upon a selected temperature change, for use in generating a minimum waiting period for obtaining valid data following transfers between the field generated signals and the test signals.

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Pittsburgh, PA, United States of America

Thomas J Kenny