Products inside: Data center design-build upgrade is easier with process controls
M.C. Dean also was responsible for the controls portion that included mechanical process control, SCADA interface, designing and building the control panels, and designing the network infrastructure.
The project included 6 control panels (2 PLC and 4 remote I/O), 2 redundant Siemens S7-400 automation stations, 16 remote I/O racks with more than 1,800 hard I/O points, 5 operator workstations, 2 server racks, 10 network cabinets, and 45 network switches which were responsible for collecting over 35,000 soft I/O points.
As a Siemens Solution Partner, M.C. Dean had a lot of previous experience with the Simatic PCS 7 process control system in mission critical process plants but never in a critical operating environment such as a data center. PCS 7 was the best fit to integrate with the Siemens automation stations we had chosen for control over the mechanical equipment.
PCS 7 has two add-ins that were specifically designed for integrating different communication protocols directly into the OS tag servers. The first add-in, TeleControl, gives the user the ability to integrate hardware devices that use different protocols into PCS 7. The second add-in, PowerControl, works in much the same way as TeleControl with the exception that it includes a driver for the IEC-61850 protocol.
Both add-ins included the framework that PCS 7 needed to communicate to the soft I/O devices.
To use the add-ins efficiently, we used the Siemens' database automation (DBA) tool. The DBA tool automatically generates the OS database with the display hierarchy, required variables, alarm signals, and faceplates. Using the DBA tool, we created one device "type" for each unique piece of hardware and then replicated that type to save engineering time.
The same concept increased engineering efficiency when working with the hard I/O points through the use of Siemens Advanced ES, a bulk engineering tool that uses Microsoft Excel spreadsheets to format the individual I/O points for import into PCS 7. We first created our control module types in the PCS 7 CFC-editor. We then organized all of our individual I/O points in the Excel template file, including rack, slot, and point locations; which control module type they belonged to; any interconnections they would have; and other relevant information that PCS 7 would need. We then imported both items into Advanced ES, at which point PCS 7 would auto-generate a control sheet for each device that was assigned in the Excel spreadsheet.
Siemens Energy's representative introduced us to the Siprotec line of relays as a possible alternate solution.
The Siemens state-of-the-art IEC-61850 platform averaged a 0.7-second delay, compared to a 3.8-sec delay with the prior solution, because the Siemens relay has flexibility to allow end users to determine the scan time at which they wanted to process logic within the relay. Recovery time was 5 ms, compared to 900 ms with the prior solution.
Siemens Optical Link Modules (OLMs) allowed us to convert the Profibus drop between the I/O racks in each panel to fiber to carry the signal over the long distances between panels. Because each of the redundant OLMs was connected to its own communication module within the I/O rack, it allowed the system to tolerate a failure down to the rack level without data loss.
Siemens S7-417H automation stations were used for redundant capabilities. The "H" stands for high availability, which allows for two PLCs to operate in an active/standby configuration so that no loss of functionality or data occurs in the event of a failure. The panels also contained a hot-swappable backplane, which allowed us to swap I/O cards and communication modules without service interruption, critical to achieving the redundancy requirements of the Uptime Institute's Tier III standards.
The S7-400 automation stations met our requirements to keep the plant up and running in the event that one PLC was to fail. From a software perspective, PCS 7 had many redundancy features to automatically switch over its clients and servers to avoid any interruption of service. Tools such as AdvancedES and DBA made it easy to configure thousands of points and devices without having to do manual entry of each occurrence. This saved us hundreds of engineering hours and also ensured that mistakes were not made when duplicating like devices. Overall, PCS 7 turned out to be the right choice for us, and we look forward to implementing it on future projects.
- Anthony Pannone is control engineer for M.C. Dean Inc., Washington, D.C.; edited by Mark T. Hoske, content manager, Control Engineering, firstname.lastname@example.org.
- Learn more about M.C. Dean's data center upgrade project below.
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