Troubleshooting of DCS Control System Download Process

I. INTRODUCTION The Phase 5 of the Taizhou Power Plant in Zhejiang Province was a 2×30 OMW unit, which passed the 168-hour test run on 19 September 2007 and 4 April 2008 respectively. The whole plant thermal process control adopts OVATIONDCS control system for a total of six sets, respectively for #9 unit, #10 unit, #9 unit common system, four desulfurization, five desulfurization, four and five public desulfurization systems. The Ovation system is a new generation of process control system introduced by Westinghouse Process Control Co., Ltd. following its CLASSIC, WESTATION. Westinghouse's new concept of the control system is the information system. It adopts a completely open architecture, an industry-standard PENTIUM processor, a 100MBFDDI network conforming to the TCP/IP protocol, an ORACLE database, a UNIX or WINDOWSNT operating system. The configuration software of the AUTOCAD interface is configured in the form of a SAMA diagram instead of the page configuration of the overlapping of the algorithm modules. Its reliable security mechanism and system architecture ensure that the system can freely and securely connect PLC, FCS and INTERNVET. Therefore, the system is not only a distributed control system, but also an open computing platform that can support any commercial application and has real-time mission critical process control capabilities. It is unique with its powerful database features and stable operating performance. However, there are also some problems in the DCS configuration downloading process. This article analyzes and discusses the problems encountered in the field work and proposes corresponding treatment solutions.

Second, the control system configuration Bottom control system configuration download function, is a number of DCS in the field using a necessary function, but also an important indicator to determine the reliability of a DCS function. This function can be divided into online download and offline download.

Online download refers to downloading the compiled program (configuration) to the DPU through the download software without affecting the unit's operating status under the unit operation status. Because online downloading has the advantages of maneuverability and time-independentness, during commissioning and debugging of the whole set of the unit, the commissioning personnel often perform online download after logical modification. However, the online download function is rarely used after the unit is put into commercial operation. The reason for this is that the downloading function is accompanied by a certain risk of tripping (multiple brands of DCS have occasionally experienced a trip failure during the online download process).

Off-line download refers to downloading the DCS when the unit is in a down state. Off-line downloading will not affect the safety of the unit, but it cannot be seen immediately due to off-line downloading. Moreover, because the hidden equipment may cause some hidden defects, there is no effective inspection and confirmation method.

In addition, the download function is divided into incremental download and full download. Under normal circumstances, incremental download, the system will automatically download the changes. Full download means clearing the controller (cleardrop operation) and then downloading the configuration to the controller. The important difference between the two download methods is whether to retain the original status information in the controller.

Third, the configuration of the bottom of the phenomenon of failure and analysis of the reasons This year, Taizhou Power Plant OVATION control system has occurred in the secondary download failure, the process and the phenomenon is as follows:

(1) On May 30th, 2008, during the period of the desulfurization and shutdown of the fifth phase, the thermal workers carried out off-line incremental downloads of the DCS network for the logic amendments proposed by the operators. On May 31, the operator informed that the 9A oxidation fan could not be started. After checking the temperature of a certain point on the fan, the temperature of 9OHTGlOCTO14 was 75.1 degrees, exceeding the high limit of 70 degrees of the starting condition, and was in the state of scanning and cutting. The thermal worker scanned the point and the point indicated a value of 26 degrees. The pump started normally.

(2) On July 1, 2008, during the fourth phase of desulfurization and shutdown, thermal workers performed off-line incremental loading of the DCS network. After the bottom-loading was completed, no abnormalities were detected. However, after the operator resumed the desulfurization system, it was informed that the sequence control function of the absorber defogger flushing water had failed and the operation screen was not responding. The logic plan page DROP2/SHEET 551 corresponding to the operation screen was not downloaded into the current main control, resulting in that the KEYBOARD function block corresponding to the operation screen was not operated in the main control.

In view of the above causes of failure events caused by the second download, the author conducted a serious search and analysis:

In the search for the cause of the failure caused by downloading on May 30th, 2008, it was found that at the instant of downloading, some points were abruptly swept and long-term valued. The scan removal time was 9:18 on May 30, which coincided with the download time. Further inspection revealed that at the time there was an operator station at the engineer level, and the control system mistakenly thought that the download was an operator's misoperation and forced the point. However, in the system's Data Analysis and Maintenance menu/Historical Review/Point Review, the search for the "scanremove" feature was performed. This point was not found in the list. No record of operations for this point was found in the system's Data Analysis and Maintenance menu/Historcal Review/Operator Event Review operator event query window. However, by making a historical trend curve for this point and comparing it with the history of alarm information retrieved during that period of time, it was found that after the temperature point experienced a communication timeout of more than ten seconds, the temperature value suddenly rose from the original 45 degrees. At 75.1 degrees, the scan is then cut off. This time period is just the time for downloading, so the decision is that the download causes the point to be removed by scanning. After analysis, the conclusion is: this station logic has made more modifications before downloading on May 30, including increasing and decreasing algorithm blocks. There are many differences between the offline configuration and the configuration in the controller. Because in the OVATION network, the unique identifier of a point is its SID. At the moment of downloading, there was a conflict with the SID number, which caused the point to not recognize the broadcast properly.

In the troubleshooting of July 1, 2008, the thermal worker opened the sequence logic corresponding to the operation screen according to the defect submitted by the operator. It was found that the sequence logic basemap could be called out in the window, but the screen data was not refreshed. Including the point information in the logic diagram can not be forced, KEYBOARD module can not operate and so on. This issue was examined in the following areas:

(1) Enter the UNIX system and check the file information of the sequential logic page on the disk. The program page file is found in WDPF/REL/DATA/CBDATA/DROP2 and the display attribute is normal.

(2) In the "User Reconciliation" checkpoint information consistency function module, point information consistency check was performed for the DROP2/DROP52 station, and the result was "Primary/DB", "Partner/DB", and "Primary/Partner". Found an exception.

(3) Enter "CONTROLBUILDER" function, open SHEOP551 program page in DROP2, check normal, save, compile normally.

(4) Enter the diagnosis function of the "Controller Diagnostics" controller and compare the Controllerinfo, ProcessingTaskInfo, and SheetInfo in the DROP2 and DROP52 controllers. In the comparison, it is found that the SHEET 551 scheme page is missing in the DROP 52 currently in the master state, and the scheme page is in DROP2.

Based on the above analysis, it is determined that the cause of the failure is caused by incomplete loading and unloading. The cause of incompleteness is related to the rationality of the configuration operations before downloading and downloading.

Fourth, the configuration of download failure prevention According to the above mentioned faults and analysis, in order to prevent the occurrence of similar failures, improve the reliability of OVATIONDCS, for the DCS configuration and download the standardization, the following recommendations for peer reference:

(1) Do a good job of recording DCS logic changes. Any changes made to the logic and configuration of the DCS should be documented accordingly. Before doing the DCS logic modification work, check the consistency of the point information of the controller station that needs to be modified to ensure that the point information is completely consistent. If there is any inconsistency in the inspection, it should be possible to have logical changes in the text record to confirm and assist the certificate.

(2) In the CB software, the modification logic must save the compilation in time. If any error report occurs during the compilation process, it must be confirmed one by one. Do zero error download. Before the next download, you should also do a good job of checking the status of the system, such as checking the active and standby status of the controller, alarm information, checking the point forcing in the system, and spotting alarms, and making records to facilitate the comparison with the state of the system after downloading. To work.

(3) Before downloading work, it is determined whether it is an incremental download or a full download depending on the situation. Because the incremental download has as much original information about the state of the controller midpoint as possible, it ensures that the controller's engineering information achieves a "smooth" transition before and after downloading. Therefore, under normal circumstances, it is recommended that the download work be selected during the outage of the unit. Try to take incremental downloads. The full download is more suitable for operation after an error occurs in the incremental download. The specific operation will require the controller to be emptied, and after the emptying is completed, the normal download operation is performed.

(4) To implement online downloading, it is necessary to make adequate accident predictions and preparations, and to formulate effective safety measures, including all main and important operating equipment controlled by the control module, such as operating licenses, before the download. Local operation, all communication points are isolated (communication points are all sorted out), and the corresponding control module has interlocking points and the hard wiring points of different controller cabinets are enforced to prevent the old and new logic from downloading instantaneously, or return to During the initial scan in the execution state, the software initial value causes the out-of-control state value to be output, causing the device to malfunction.

In addition, in accordance with the requirements of the OVATION system, following the principle of "first under the main control, after the next pay control," after the controller download, it is recommended to conduct the following checks:

(1) Check the system status, including checking whether the status of the 1800 system on the CRT corresponds to the operating status of the field controller. The active and standby status correspond and there is no abnormal alarm.

(2) Enter the "Controller Diagnostics" controller diagnostic function to observe the operation of the controller, including the load of each task area of ​​the controller, I / O information, logical page information and so on.

(3) Check the logical page of the revision to confirm that the new logic is in normal operation.

(4) Selectively check the information of the point of revision, check the version information of the point.

(5) Check the status of the main equipment, such as checking whether the start, stop, automatic stop, and automatic start of the equipment in the DCS are in line with the current operation before the main equipment is switched back to the DCS control state from the local place. Status is consistent.

V. Concluding remarks This paper combines the faults and analysis process of desulfurization DCS of Taizhou Power Plant due to downloading, and proposes the analysis and processing methods of the OVATIONDCS bottom loading faults, which guarantees the smooth loading of the OVATION DCS with a certain reference effect. Meanwhile, for other types The download of DCS also has some reference significance.

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