WIRELESS COMMUNICATIONS
Reaching remote substations without fiber
Smaller distribution companies may feel they can't afford to take off their training wheels and ride into the streets of wireless industrial automation. But shed the wheels of network cables and a distribution company (disco) can bring connectivity to remote infrastructure over a wide area without compromising data security or breaking the bank.
Just ask the Clinton Utilities Board (CUB), which serves 29,000 customers from the Tennessee town of the same name in the Cumberland Mountains. In 2002, CUB installed the first pieces of a supervisory control and data acquisition (Scada) system from Survalent Corp. (Mississauga, Ont.) on its lines, and then set up an Ethernet network (using fiber-optic cables and TCP/IP). CUB planned to expand the system's hardware and software over time, eventually making it capable of remotely polling the remote terminal units of all of the disco's substations.
Cumberland gap
Undaunted, CUB began investigating alternative telemetry methods: leased phone lines, licensed radio, unlicensed radio, even satellite. At the end of the day, the disco picked unlicensed radio as the most cost-effective, reliable, and secure option. The vendor chosen was ProSoft Technology Inc. (Bakersfield, Calif.), whose industrial-strength RadioLinx brand is known for its ability to intermix serial and Ethernet radios with embedded servers on the same network.
According to Todd Loggins of CUB, "The terrain made installing the wireless network quite a challenge. But the benefits it has produced made the effort well worth it. We've saved countless man-hours by being able to remotely monitor and control devices that normally would take us hours to get to."
Complicating the task at hand, each of the two substations lacked a line of sight to CUB's main offices. ProSoft Technology's tech support personnel helped develop a path study that concluded that if repeaters were placed on two mountaintop locations, both substations could be "seen."
One of the required repeaters was already in place; CUB had put it there to improve voice communications with company vehicles. The second location was then identified using GPS, but the top of that mountain was inaccessible to an ordinary vehicle. So CUB hired a local grading contractor to hump a 60-foot wood pole up the hill and plant it with the help of a bulldozer. ProSoft Technology then placed a solar-powered repeater kit and the necessary antennas on the pole, completing the new infrastructure part of the wireless project in December 2004.
At that point, ProSoft took over. The company installed RadioLinx Frequency Hopping Ethernet radios with serial servers at both substations. At the first, one radio monitors station loading from a Schlumberger Q1000 meter using the DNP 3.0 protocol. The meter has an RS-232 connection to the radio's serial port and is directly polled from the Scada system's master station using the radio's port and IP address. To provide Ethernet connectivity, the old feeder breakers in this station were replaced with new VSA breakers and Form 6 recloser controls from Cooper Power Systems (Waukesha, Wis.). The new electronic controls are connected to the ProSoft radio through an additional Ethernet switch from RuggedCom Inc. (Woodbridge, Ont.). As a result, an RTU will never need to be installed at this substation.
The second substation has a Schlumberger Q1000 meter connected to the serial port of the radio, while a Cooper Form 6 control connects to the Ethernet port of the radio. Both are polled using DNP 3.0 over TCP/IP directly from the Scada master station. Plans call for upgrading the substation's regulator controls to M2001C units from Beckwith Electric Co. Inc. (Largo, Fla.), which also have available Ethernet ports and use DNP 3.0. Although the upgrade will make an additional Ethernet switch or hub necessary, it will require only one radio—and no RTU.
Adding functionality
CUB recently began the second phase of its Scada system installation: enabling communications with pole-top devices (reclosers, regulator controls, automated switch controls, and capacitor controls) on distribution lines (Figure 12). ProSoft's RadioLinx radios will be the primary communications vehicles. So far, the radios have been connected to Cooper Form 4C and Form 6 recloser controls and to Model 5801 automated switch controls from Chicago-based S&C Electric Co. The only protocol available for the Cooper Form 4C controls is Cooper 2179, which is not supported by the Scada master. The communications path to each of those controls starts at the "com" port on a substation RTU, goes through a serial radio to the same repeaters used for substation communications, and ends at the serial radio connected to the control.
1
2. Off the beaten path. In Tennessee's Cumberland Mountains, Clinton Utilities Board is four years into a project whose ultimate goal is to wirelessly interconnect its Scada system, 13 substations (two extremely remote ones), and thousands of pole-top devices. Courtesy: ProSoft Technology Inc.
Currently, Clinton Utilities Board has ProSoft 23 radios installed, and it hopes to double that number within the next six months. With such robust integration in its remote networks, any installed radio can then become a repeater for future radios.
—Contributed by ProSoft Technology Inc. (www.prosoft-technology.com)
Email
Comments
Print
Reuse
