e in house SEDAC field bus was running on an additional MVME 162. The operating system was VxWorks and the application was the EPICS toolkit.
Since this implementation was successful it was also implemented for the utility controls which were looking for a generic solution to supervise their distributed PLC's.
A SELECTION OF PROCESS CONTROL SYSTEMS AT DESY
DCS (D/3)
As a result of a market survey the D/3 system from GSE was selected for the HERA cryogenic plant. The decision was fortunate because of the DCS character of the D/3. The possibility to expand the system on the display- and on the I/O side helped to solve the increasing control demands for HERA. The limiting factor for the size of the system is not the total number of I/O but the traffic on the communication network. This traffic is determined by the total amount of archived data not by the data configured in the alarm system. The technical background of this limitation is the fact that archived data are polled from the display servers whereas the alarms are pushed to configured destinations like alarm-files, (printer) queues or displays.
SCADA Systems with DCS Features (Cube)
The fact that the D/3 system mentioned above had some hard coded limitations with respect to the Y2K problem was forcing us to look for an upgrade or a replacement of the existing system. As a result of a call for tender the company Orsi with their product Cube came into play [2]. The project included a complete replacement of the installed functionality. This included the D/3 as well as the integration of the DESY field bus SEDAC and the temperature conversion in VME. The project started pro
mising. But soon technical and organizational problems were pushing the schedule to it's limits which were determined by the HERA shutdown scheduled at that time. The final acceptance test at the vendors site showed dramatic performance problems. Two factors could be identified as the cause of these problems. The first one was related to the under estimated CPU load of the 6th grade polynomial temperature conversion running at 1 Hz. The second one was the additional CPU load caused by the complex functionality of the existing D/3 system. Here it was underestimated that each digital and analog input and output channel had it's own alarm limits in the D/3 system. In a SCADA like system as Cube the base functionality of a channel is to read the value and make it available to the system. Any additional functionality must be added. Last not least the load on the network for polling all the alarm limits - typically for a SCADA system - was also driving the network to it's limits.
Finally the contract with Orsi was cancelled and an upgrade of the D/3 system was the only possible solution. It was finally carried out in march 2003.
In any case it should be mentioned that the Cube approach had the advantage of a homogeneous co