Westinghouse Electric Corporation

Robert E Hager

James A Neuner

Thomas J Kenny

James F Sutherland

Albert W Crew

Gilbert W Remley

Jerzy Gutman

Susan A Wilbur

Eric A Delava

George M Chambers

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 control system for a trip coil in a switchgear mechanism which controls the supply of power to a process control device and ensures de-energization of the trip coil shortly after the trip coil is energized. A transformer is supplied with power by the switchgear and outputs reduced power to a rectifier which is connected to the trip coil via a trip activation device. The output of the rectifier can be monitored to determine the ability of the control system to activate the trip coil and the condition of the power supplied to the process control device.

Reactor trip control with voltage sensing

A power interface circuit for normally deenergized loads includes the capability to test the operation and connections thereof without any possibility of accidental activation of the load. Three input signals may be received by the power interface circuit which supplies power to a load if two out of three of the input signals indicates activation of the load. A normally closed switch which ordinarily provides power directly to the voter is opened during testing so that the voter is supplied with a reduced power that is insufficient to activate the load. The normally closed switch is closed if any of the input signals indicate activation of the load. Current sensors are included in the power interface circuit to detect all possible logic combinations for activating the load and to detect the operation of the normally closed switch.

Testable, fault-tolerant power interface circuit for normally

In a protection system for a complex process control system which generates three independent actuation signals, the power interface circuit includes three pairs of switches arranged in three parallel groups of switches connected in series with the load and a voltage source. Each group of switches includes two switches selected from different pairs of switches and connected in series. Normally closed switches are used with normally energized loads and normally open switches with normally de-energized loads. Logic gates control actuation of each individual switch in response either to an associated actuation signal or a test signal generated by a microprocessor. The microprocessor generates a sequence of patterns of test signals which result in various combinations of switch actuations. The current through each group of switches resulting from each combination of switch actuations is compared by the microprocessor with expected values to evaluate circuit performance.

Testable voted logic power interface

A visual indicator in parallel with a zener diode, positioned in series with a load is provided to monitor the presence of current flow in a circuit over a range of several orders of magnitude. In addition, a circuit arrangement is described to monitor the continuity and current flow in two separate parallel paths, feeding a common load in order to check the continuity of the circuitry and associated switching devices. For this purpose, a second current monitor, including a series switch, is placed in parallel with a first series arrangement of a current monitor and a switch. Alternate polarity arrangements of the respective zener diodes associated with the corresonding current monitors are illustrated to show the varing modes of operation contemplated by this invention.

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Penn Hills, PA, United States of America

Robert E Hager