Utility upgrades SCADA with effective combination of PLCs & Ethernet
In 2012, the Lynnwood (Wash.) Water & Sewer Utility updated its 20-year-old SCADA system with Programmable Logic Controllers (PLCs) and Ethernet communications. The existing “telemetry” computer was an 80386 PC running SCADA software installed sometime around 1990. This “blinking box” in the closet, which few people in the utility knew anything about, was connected to a master meter, a pressure relief valve and reservoir tanks on the water side, and to six lift stations and the wastewater treatment plant (WWTP) on the sewer side. All communication took place via a telephone system with dial-up modems.
Utility staff knew that, while the phone lines were a dependable communications infrastructure, the old PC platform was a tremendous maintenance issue. The version of SCADA software owned by the city would only run on the 80386 platform, and by 2008, that computer technology had been out of mainstream production for years. While the easy fix would have been to purchase updated software from the current provider that could run on a newer model computer, it was generally recognized that there was better, more modern software on the market. A consultant was hired to help with that search, which led them to select the Wonderware Archestra application.
Fiber Optic Cable
While Wonderware was more powerful and flexible than the old software, budget constraints allowed the utility to only replicate functionality of the old system. Only those devices monitored before would be monitored. Only those devices controlled before would be controlled. The utility had the money to upgrade the communications backbone; however, the staff was comfortable with the leased phone line communication. There was, however, access to a city-owned fiber optic communication network utilizing Ethernet and other robust communications protocols. Lynnwood’s traffic operations staff had been doing centralized monitoring and control of remote field devices since the early 1980s, when an interconnected traffic signal system was installed.
In the late 1990s, fiber optic cable started coming to Lynnwood, a city of about 10 sq miles. The first projects were two private cross-state fiber laying initiatives. In exchange for the use of city right of way, both projects provided two empty 1.5-in. conduits from one side of the city to the other. The next significant improvement was the reconstruction of the major state highway that runs through Lynnwood. During the rest of late 1990s and early 2000s, when the city’s commercial areas were growing and city funds were plentiful, both city and private projects were leveraged to install buried fiber optic cable on all of Lynnwood’s traffic signals, which totaled 57 by 2008. A new, Ethernet-based, central signal control system was purchased and installed in 2006.
The traffic signals tended to cluster in the commercial areas of town; by a fluke of topography, these also were the areas the sewer lift stations were located. Of all of the water and sewer remote devices, only the water system’s main pressure relief valve was farther than 1/4 mile from a signalized intersection—except, of course, for its WWTP, which actually is located in a Lynnwood-owned island of property in a neighboring city. Still, the WWTP was only one mile from the nearest strand of Lynnwood owned fiber.
For the new SCADA system to communicate over traffic fiber, it would have to operate on a Microsoft Active Directory Domain. This meant that the Wonderware SCADA system would have to grow from one old PC to four servers, hosting Archestra Objects, Archestra Development, Historian and alarm dissemination. More importantly, this would require a part-time network manager—in this case, the city traffic engineer.
Before the new software could be deployed, the utility had to extend the fiber optic cable of the traffic network to the remote utility facilities. The first phase of the SCADA replacement contract totaled $620,000 to have an electrical contractor install:
- • Eleven fiber termination/PLC control cabinets;
- • Eight buried conduit/fiber optic cable extensions;
- • Two radio links; and
- • One aerial fiber extension.
In January 2012, the existing remote devices began to be transferred to the new fiber SCADA cabinets. While the transfer of devices was fairly trouble free, the utility staff struggled for the next six months, trying to decipher new alarms and to understand the new system of servers, modems and PLCs.
After activation of the new SCADA system, the radio link to the pressure relief valve proved unreliable. The utility then switched that connection to a TV cable connection, but that turned out to suffer from late-night service interruptions, each of which resulted in an alarm and a wake-up call to an on-call person. Eventually, fiber-experienced crews installed 2,000 ft of new conduit, and pulled 3,500 ft of new cable, to finally connect the pressure relief valve to fiber.
Soon after the new SCADA project was accepted, the utility contracted a SCADA Phase Two consultant to start adding in some of the devices the original project was not able to get to.
The utility is beginning to enjoy its new system and to appreciate how powerful and flexible the combination of PLCs and Ethernet are. New devices such as rain gauges, flowmeters and site security can be easily added to the system. Once a site has fiber extended to it, and a PLC with enough inputs open, anything can be hooked up and integrated into the Wonderware.
In a few years, the utility has moved from the mysterious blinking “telemetry” box in the closet that no one was allowed to touch, to a state-of-the-art SCADA system that is living and growing.