Pumping control system updates aging lift station network.
Electricity, water and sewer services for the residents and businesses of Northeast Florida are served by the municipal-owned utility called Jacksonville Electric Authority (JEA). Established by the City of Jacksonville in 1895, JEA grew from a department of city government to an independent energy authority created by the consolidation of city and county governments in 1967. Thirty years later, the water and sewer systems operated by the city since 1880 also became part of JEA's service offerings.
Today, JEA is the largest community-owned utility in Florida and the eighth largest in the U.S. With a total generating capacity of about 3,050 megawatts, JEA serves more than 417,000 electric customers in Jacksonville and parts of three adjacent counties. JEA's water system serves more than 305,000 water customers and 230,000 sewer customers in Northeast Florida. Its water system consists of 134 artesian wells that tap the Floridian Aquifer, one of the world's most productive aquifers. Water is distributed through 35 water treatment plants and 4,208 miles of water lines. More than 3,760 miles of collection lines and seven regional and eight non-regional sewer treatment plants make up the JEA sewer system. With this large demand, the current control system was not as effective as needed, and an updated system was required, with JEA seeking assistance from a global automation and control solutions provider.
Problems with the Existing System
According to Darren Hollifield, JEA's manager of Access and Control Systems, the existing pumping control system for the 1,273 lift stations that keep wastewater flowing through 14 treatment centers was simply outdated.
“The current system was designed and engineered in the middle 1990s,” he said, “and technology has changed a lot since.”
JEA uses lift stations throughout its sewage system to manage storm water flows and pump wastewater from homes and businesses to its treatment centers. Also, JEA continues to acquire adjacent water systems and work with current septic tank owners to connect to JEA's system.
As a result, it will need to add more pumping capacity and communications capabilities in the future among its existing and any newly built remote lift stations. Hollifield explained that JEA's current SCADA (supervisory control and data acquisition) pump control system consisted of multiple operator interfaces, two input/output servers (primary and backup), seven data concentrators, and 32 master radio sites.
JEA's remote lift stations used programmable logic controllers (PLC). The data concentrators were Modbus master pollers, each featuring eight master channels. Each master channel, in turn, could poll up to 100 Modbus slaves. The communication path used inverse multiplexing over fiber equipment on each end from JEA's Systems Operations Control Center (SOCC) to each remote station's master radio over narrowband, spread spectrum radio. Pat Harwood, the control system's technician, explained that with the current system, verifying communication between the data concentrators and the remote lift stations is primitive.
“We do it by checking a counter which is always changing and incrementing or resetting the counter, if a certain value changes or does not change.”
Such limited, one-way communications prevented Harwood and his team from conducting remote diagnostics or remote programming. As a result, each time a lift station had a problem or needed a software fix, patch or upgrade, a technician was dispatched at a typical cost of several hundred dollars. Harwood also noted that communications were only updated when the Modbus polling device requested data and the more remote terminal units (RTUs) on a channel, the slower the update times were. If communications with the RTU were lost, the RTU had no buffering capacity to hold its data until communication was restored.
The Solution
Working both with its distributor AWC, Hollifield, Pat Harwood and other JEA team members, an automation and control provider developed an advanced and comprehensive solution based on the proven PLC platform and the telecontrol system using Profibus. Each lift station's PLC was also integrated with an intelligent motor management system.
The PLC system provides local logic as well as data collection for the telecontrol system. It is also the PROFIBUS master for two motor management systems. The two intelligent motor management systems provide motor overload protection, local I/O to read in the analog well level and the digital floats' signals. If the PROFIBUS connection is lost between the motor management system and the PLC, the intelligent motor management system provides redundancy and can take over full control of the pumping operation until the network is restored. The motor management system also provides key diagnostic and operational data that is eventually sent to the control center. This includes power measurement data that is recorded and sent to the SCADA system, which is used to evaluate energy savings projects and control strategies.
The telecontrol system extends the PLC's automation system by integrating special hardware and software components that enable remote data transmission. This interconnects the PLC platform's CPUs with one another through a wide area network (WAN) and with a control center system that provides fully automatic monitoring and control of the lift stations from the master control center.
The software in each lift station provides event-driven process data transmission between each lifting station PLC's CPU and with the control center. Now for example, Harwood and his fellow technicians can see connection failures, disrupted CPUs or a disrupted control center on PC displays via WinCC–PC-based SCADA software. It updates data automatically after a problem is corrected or after an RTU's CPU or the control center is restarted. Date and time throughout the network's CPUs and control center can be synchronized via a DCF77 radio clock or a global positioning system (GPS). Either way the systems always have the exact time of day. Also, daylight-saving/standard time is updated automatically. Time-stamped data messages or automatic scheduling of program starts are therefore standard features of the system. A DC UPS system also provides backup power to retain communications to the lift station if 480VAC power is lost, for example during storm conditions.
Project Successes
The PLC platform solution helped Hollifield
