Real-time data acquisition with WirelessHART technology

In this installment of What Works, an electric utility works to stamp out inefficiency with portable data acquisition systems.

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Progress Energy, a publicly owned electric utility serving North Carolina, South Carolina and Florida, has a sort of internal SWAT team to stamp out inefficiency. That team, called the Performance Testing Group, consists of four engineers and technicians led by Dick Fletcher, the team manager. It keeps plant equipment and systems running smoothly by traveling from plant to plant and testing, troubleshooting, and verifying performance standards on new and upgraded equipment.

The team members, sometimes in groups of two, service the utility’s 32 locations. Together, the plant’s capacity is more than 22,000 MW, and it serves 3.1 million consumers across Florida and the Carolinas. Testing supplements each plant’s individual efforts to ensure peak efficiency and output.

Field testing requires portable data acquisition systems that collect data from multiple process instruments located throughout a facility. Typically, the test records time-stamped data through a gateway and into a laptop-based spreadsheet-type application. Additionally, test equipment must be portable and flexible enough to operate with a constantly changing number of instruments and scan rates.

The problem with hard wires

The group maintains 240 transmitters, mainly for temperature and pressure, and some flow devices. These have traditionally been hardwired to HART multiplexers to accommodate cable runs across facilities, even over streets, to conduct tests. Setting up a test run occupied significant time and labor.

Conducting a test entails more than the test itself. Any test could entail days for setup and another for teardown.

Conducting a test entails more than the test itself. Any test could entail days for setup and another for teardown. Hardwired network multiplexers were well-worn and, in some cases, failing because of wear and tear. Likewise, the profusion of wiring risked damage as cables were used and reused from one site to the next connecting at times more than 100 far-flung sensing and transmitting instruments across a facility and crossing not just the plant, but also roadways.

With the introduction of the WirelessHART protocol and the commercial availability of network WirelessHART adapters that conform to the standard, the group sought to replace its aging test equipment and streamline testing with a new wireless system. Fletcher explains that the traveling test engineers had a major investment in existing HART Smart Transmitters. “The logical thing to do was get a common data acquisition system to be shared across the system by Performance Testing,” he says.

He set short-term goals for a new system that could handle a variety of instruments, with special emphasis on high-accuracy pressure and temperature transmitters. The system also had to be easy to configure, because every plant requires its own configuration. And, of course, the system would have to interface with standard commercial instruments using standard protocols.

Fletcher also set longer-term goals for a new, wireless system as a way to broaden the scope of testing and as a means of achieving a remote data flow over the corporate wide-area network (WAN) for remote testing and analysis. But first, the group had to establish a system to serve as the proof of concept.

Project objectives

Test setup was arduous before commercial products, particularly network adapters that bring HART transmitter data, had implemented the WirelessHART specification. One such adapter, the MACTek Bullet, provided Fletcher’s group with the ability to connect eight existing HART-enabled devices operating in an all-digital multidrop network mode. Knowing this, the Performance Testing Group hoped to achieve five specific objectives:

  • Develop a common field data acquisition system the testing group can use across the company
  • Allow equipment sharing across the system and minimize the total company inventory
  • Take advantage of HART’s ability to collect data digitally and in multidrop mode
  • Ease the installation of the test equipment to minimize time and effort
  • Benefit from a flexible, easily expandable and easily configurable system.

These objectives exceeded Fletcher’s initial expectations. The project focus in the early, research phase was mainly upon wired multiplexer-based systems, because “the wireless equipment that we were initially aware of was expected to be out of our financial reach,” says Fletcher.

Implementing wirelessly

“Like everyone else in these economically challenging times, we had to get the best bang for the buck,” says Fletcher, “and that meant that we had to maintain compatibility with our existing investment in HART-enabled transmitters. When we were planning our purchase, we learned that MACTek had working prototypes of the Bullet.”

The prototype Bullet, introduced in 2009, could support six HART transmitters in field-proven HART multidrop mode. It has since expanded to eight, which is what the Performance Testing Group now uses. For either iteration, Fletcher explains this capability meant a wireless gateway could replace the failing multiplexers, and far fewer cables would need to be deployed for temporary test transmitter installations. “The economics of a hybrid wireless-wired HART system became more feasible for us to consider,” he says.

The Performance Testing Group’s wireless solution uses pre-existing Rosemount Smart HART transmitters and some key pieces of new equipment:

  • MACTek Bullets
  • MACTek HART modems
  • Siemens Simatic PDM software
  • Emerson Smart Wireless gateways
  • 24 VDC power supplies from Acopian
  • Electrical enclosures from Lowe’s Hardware
  • Mody transmitter cables — three-conductor with Neutrik 3-pin XLR connectors and five-conductor RTD cables with Neutrik 5-pin XLR connectors.

The resulting system uses the Bullets to communicate HART data, including the process variables, through the Emerson gateway, into a laptop PC, where data are imported to an Excel spreadsheet using Matricon Analytics’ plug-in Excel Reporter, an OPC plug-in.

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