Nov 10, 2014

Modern SCADA

Italian utility upgrades SCADA system & assesses water management plan

Modern SCADA
Modern SCADA
Modern SCADA

Lake Como, located in northern Italy, is served by an industrial waterworks comprising almost 40 miles of aqueducts. It was originally constructed in the 1980s as a fully automated system. After 30 years of service, the technology of the supervisory control and data acquisition (SCADA) system was in need of modernization. 

The aqueduct system draws its water directly from Lake Como and then pumps it to storage tanks. From these tanks the water flows via aqueducts through a distribution network that serves businesses located around the lake. The reliability of the entire infrastructure is paramount, as any disruption in water supply can lead to lost production for the manufacturing businesses. 

To monitor the network, a system-wide SCADA control room is staffed during normal working hours; the waterworks is operated without human supervision the rest of the time. If a fault is detected off-hours, an on-call maintenance contractor automatically is dispatched by the system.

Like most places in the world, energy costs at Lake Como have risen significantly during the past 30 years. The geography of the lake, with the mountainous terrain surrounding it, is particularly challenging to water management. Pumping is the largest component of the associated energy costs. 

The redesign of the SCADA system created the opportunity to both take advantage of new technology but also review the concepts of water management and maintainability. The simplified architecture chosen was based on commercially available standard hardware, with a modular open architecture for improved maintainability. 

A New Network Design

The telecommunications of the SCADA system also was evaluated in the early phases of the project. The system owner made the decision to move away from a proprietary fieldbus strategy, which had been employed in the past, to an Ethernet-based network design. The design goal was to make the telecommunications system independent of the programmable logic controller (PLC) choice and SCADA software vendors, and provide for future services. 

Another critical aspect of the project was that the replacement system had to come online with minimal disruption to service. Because the original design incorporated a fully automated infrastructure, it was not easy to manage the system manually, and even then it was only possible for a short amount of time, such as in emergencies. In order to replace the centralized control, a total halt of the entire waterworks was required. A major challenge for project management was to create well-organized, well-coordinated work teams that could work simultaneously on all sites, so that installation and commissioning was absolutely minimized.

The physical media connecting the PLCs and the interface to the SCADA host are existing telephone landlines. HDSL provides the Ethernet network over the telephone system. The network allows the ACS500 PLCs programmed with CoDeSys language to use TCP/IP-based communication. Only a few of the sites have a local control panel. Most sites are maintained and, if necessary, controlled via a Web browser interface that can be directed to the local PLC.

 At the main plant control room, a client-server architecture was chosen for the SCADA solution. The primary server is a Windows Server 2008 platform with widescreen monitor. The SCADA platform is PcVue, which provides a clean and versatile display, thanks to the availability of graphical objects and symbols for visualization and animation. In addition, the management of the variables (tags) in PcVue using the branching structure reduces implementation time. The deployment of client stations is, for all practical purposes, automatic. The clients are enabled by copying the project to the client machine and declaring it a client. This architecture also allows for simplified maintainability.  Any modification required for the project can be made on the server and copied to the client stations. As soon as the copy is complete, the changes are immediately active. In most cases, this is accomplished without restarting the client stations.

The Ethernet-based network provides many advantages to a fieldbus architecture as well as the potential for future revenue sources that may partially offset the investment required to implement it. Today, Modbus TCP is the remote control protocol interfacing the PLC to the SCADA host. In the future, without further changes to the telecommunications architecture, it is possible to have other services on the network. For example, other Lake Como utilities may lease bandwidth for their own industrial protocols, and network services or other applications such as surveillance and telephony may be deployed on the network. 

Security & Availability

Two critical aspects of the communication reliability had to be addressed with the new telecommunications architecture: network security and network availability. Standard IT practices are used for security on the new network. Because the system is connected to the Internet, firewalls and VPNs are used to ensure that the appropriate policy is deployed, allowing only access to recognized users of the system. Due to the critical nature of the network, cellular modems are connected to each PLC. In the case of a complete failure of the landline telephone network, system operators can bypass the HDSL network and reach the PLC directly using mobile devices.

Direct access to the PLC via the network also has the advantage of reducing the time to resolve an alarm or other system problems. By virtue of the Internet connection, it is possible to have vendors access their equipment directly as first-level support to diagnose problems and, if necessary, provide software patches or programming code modifications without the time and expense of travel. Today, this is done using remote desktop software, but the ability to have the supervision graphics displayed on a tablet device already has been proven.

Intelligent Pump Management

The system has about 1,000 alarms defined, which are divided into priority levels, from simple warning reports to critical alarms requiring human intervention. All alarms are stored in the SCADA software and are available in both textual forms and with graphic animations. When alarms are raised, the SCADA system uses contextual logic to determine the appropriate course of action. For all high priority alarms, SMS text messages are sent to the operator based on the concept that the operator can connect to the network and acknowledge the alarm. If the operator does not respond within a designated time, the system will resend the SMS message to the operators until the alarm is acknowledged. The redesign of the remote control of the aqueduct system provided the opportunity to introduce the concept of energy profile management. Optimization strategies were introduced to intelligently manage the use of the pumps. Analyzing the daily consumption of water and comparing with the level of the lake as measured at various levees, made it possible to estimate the amount of water required in the storage tanks. 

Using this strategy, the set point for the pumps is modified dynamically, such that the tanks are filled at night when electricity is less expensive. Operating the pumps during the day is still possible, if required, but is minimized in order to reduce costs. The SCADA system allows the collection of all relevant operational data, including continuous recording of pressure, level, flow rates and volumetric meter readings. In the future, further optimization of energy costs may be possible with increasingly effective algorithms.

The choice of the contractors for this project was strategic and made after careful evaluation. The decision was made to request proposals for design-build of the new SCADA solution. This was done by using only qualified system integrators capable of design and implementation of the entire system with full autonomy on the project. The selected system integrator, T.S.A. Automation, formed a partnership with Borghi, which had previously been responsible for the design and installation of new electrical switchgear and control. The synergy between the two partners allowed for a competitive proposal with a substantial savings in cost. More importantly, the team had all the necessary areas of expertise to execute all stages from design to commissioning without depending on third-party subcontractors. 

About the author

Simone Giudici is owner of T.S.A. Automation. Giudici can be reached at [email protected]
or +39 031 483292.

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