Patent Number: 048150142
Section: summary

Related Application U.S. patent application Ser. No. 825,427 filed Feb. 3, 1986. BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is directed to a method and apparatus for aiding an operator in executing step-by-step procedures during the operation of a complex process facility such as a nuclear power plant. More particularly, it involves a computer based system which incorporates monitored plant data and interactive plant operator responses to recommended actions for step-by-step progression through a selected procedure and includes verification of operator responses, on-line review of completed steps, and logging of all data pertinent to procedure execution. 2. Background Information As large process facilities become more complex, the burden placed on the operator to assimilate large amounts of data, evaluate the status of the process and various components and systems from those data, and take informed, decisive action based upon such evaluations becomes greater. Such a complex process facility where this is true is the nuclear power plant. Due to concern for public safety and to the significance of nuclear power generation to the world, there has been steadily increasing emphasis on the need to operate nuclear power plants safely and reliably. To satisfy this need, written procedures have been developed to guide the operator in controlling the plant. However, many of these procedures are difficult for the operator to manage in a purely paper format because they require him to continuously monitor and comprehend numerous plant conditions over an extended period of time. Several attempts have been made to alleviate this problem. One such attempt has resulted in the safety parameter display system covered by U.S. Pat. No. 4,552,718. This system generates meaningful information for the operator of a pressurized water reactor (PWR) on six critical safety functions which must be maintained, or reestablished if lost, during emergency operation. The system uses a status tree approach to generate automatically, or through manual responses by an operator, a visual indication of the current status of all six critical safety functions. This system is used in conjunction with the paper procedures t alert the operator, who is absorbed in the steps of a particular emergency procedure, to the overall condition of the plant. While the status tree system advises the operator of any threats to the critical safety functions, and suggests a procedure to be followed, the operator must still locate the recommended procedure in the paper procedures and then follow it manually step-by-step. The status tree system also does not keep the operator apprised of other plant conditions which the paper procedures require be monitored, but which do not directly affect the critical safety functions. U.S. patent application Ser. No. 825,427 filed on Feb. 3, 1986, and referred to above under the heading, Related Application, is directed to a computer based system which both assesses the plant data and provides guidance in light of predefined procedures. In this system, current plant data are used by the computer to trace a path through the logic of appropriate procedure steps in order to identify a recommended course of action. The course of action along, with related data, is displayed for the operator on one or more electronic display devices. The computer then uses the plant data and the operator's interactive response to proceed to the next appropriate procedure step. In addition, the computer simultaneously monitors certain functions which must normally be continuously monitored by the operator. If a problem becomes apparent in any of these functions, the operator is alerted and appropriate actions are displayed. In this manner, the operator is relieved of the duty of continually gathering and assessing large amounts of data, as required by the purely paper form of the procedures. This frees the operator to concentrate on operating the plant in a safe manner when hazardous conditions are not present, and to alleviate potential emergency situations when hazardous conditions exist. Although this computer based system performs its intended function, development and testing uncovered some areas where improvements in performance of the system could be made. Hence, it is the primary object of the subject invention to provide improved apparatus and method for a computer based system for assisting the operator of a complex process facility in carrying out step-by-step procedures. It is a more specific object of the invention to provide such an apparatus and method in which the operator maintains control of procedure implementation, but in which progression cannot be made to the next step until an action taken by the operator has been verified by the plant sensors, or until the operator overrides the system. It is another object of the invention to provide such an apparatus and method which assists the operator in detecting malfunctioning equipment. It is still another object of the invention to provide such an apparatus and method which permits on-line review of prior steps without interrupting execution of the current step. Yet another object of the invention is to provide such an apparatus and method with improved logging capability. SUMMARY OF THE INVENTION These and other objects are realized by a method and apparatus for on-line, machine assisted execution by a human operator of procedures for a complex process facility in which the steps of a selected procedure stored in computer memory are sequentially presented to the operator on a display device. Process parameter signals are repetitively processed to automatically determine the status of a process condition addressed by the current step. Where the process condition is not verified by the parameter values, a visible textual statement of recommended operator action is presented on a display device together with instructions for the operator to generate an "ACTION COMPLETED" or "OVERRIDE" response. If the operator performs the recommended action, the repetitive processing of the parameter signals will detect a change in the associated parameter value and update the process condition. Then, when the operator enters an "ACTION COMPLETED" response, the next step in the procedure is selected as the current step. If the process condition is not verified when the operator enters an "ACTION COMPLETED" response, the next step will not be selected, and the step logic is repeated until an acceptable response is registered. Thus, the system requires verification by parameter sensors that the recommended action has been effective. The operator may enter an "OVERRIDE" response, and thus advance to the next step, but he is aware then that the recommended action is not verified by the sensors. This feature allows the system to advance to the next step when a component which should have been operated by the recommended action does not respond. It can also help the operator identify a faulty sensor when he knows from other indications that the action taken has been successful. By requiring the operator to enter the override response, the erroneous sensor reading is brought to his attention. If the process condition addressed by the current step is verified when the step is entered, instructions are displayed for the operator to generate a "CONTINUE" response or an "OVERRIDE" response. If the operator enters a "CONTINUE" response the program will continue to the next step in the current procedure. If an "OVERRIDE" response is entered for a current step in which the process condition is verified when the step is entered, the recommended action which would have been presented had the process condition not been verified is presented on the display together with the prompts for indicating completion of the action. This is useful where the operator knows from other information available to him that the condition is not in fact verified, and therefore a sensor is faulty. This acknowledgment of this condition will appear in the permanent record maintained by the system as discussed below. In some instances, a recommended action may require a prolonged period of time for completion. In order that execution of the remaining steps of the procedure is not delayed, an "ACTION INITIATED" prompt is generated for such a step. When the operator generates the "ACTION INITIATED" response, indicating that the suggested action has been initiated, the system advances to the appropriate next step without waiting for verification of operator action. Upon completion of each step, the full display at the time of completion is stored as a permanent record for later review. This is especially useful in the case of an event where it is desired later to review the actions taken by the operator. The visual representations are also stored for on-line review of the previously executed steps without interruption of the current step. This is especially useful during a shift change to apprise the incoming crew of the course of events which have led to the current condition of the facility while the prior crew continues to execute the steps of the active procedure. Another aspect of the invention permits the operator to scan forward or backward in the active procedure, and to execute or re-execute prior steps if desired. This enables the operator to view the active procedure as a whole and provides improved flexibility. The invention encompasses both method and apparatus for implementing the above functions.