February 1, 2010

Low-Cost Wireless Sensors Can Improve Monitoring in Fossil-Fueled Power Plants

Cyrus W. Taft, PE, Taft Engineering Inc.; Aaron J. Hussey, Electric Power Research Institute; Teja Kuruganti, Oak Ridge National Laboratory; Jo

Phase 1: Mote Testing

The focus of the plant environment testing was to determine how well the sensors communicated in the relatively unfriendly radio environment of a power plant. The goal was to provide guidance for someone deploying a wireless sensor network in a plant on the allowable distance between sensors and what to expect for battery life.

The general arrangement of the wireless sensor network during testing is shown in Figure 1. Only four motes are shown, but more motes were actually tested. The wall of the control room in which the base station was located is made of sheet metal, so to ensure good communication through the wall, one mote was positioned just outside the control room. The bulk of the remaining motes were at least 100 feet away under the Unit 5 turbine.


1. The power of networking: This was the general arrangement of the wireless sensor network during plant tests. Courtesy: Southern Co.

The computer communicates with the gateway in one of three ways over an Ethernet network:

• The gateway has a built-in web server, so a web browser in the computer can log in to the gateway and view both sensor and network data.

• A connection also can be made using a secure shell (ssh) program on the computer.

• The disk drive on the gateway can be attached as a network drive (using Samba on the gateway) to the computer for sharing data files.

Mote Communication Testing

Twelve motes were distributed around the area under the Unit 5 turbine. This area has many large steam pipes and structural steel elements that have the potential to obstruct the radio signals from the wireless sensors. In most cases, there was no clear line of sight between motes. Because the test was planned to last only a couple of months, the motes were placed in plastic Zipock bags to protect them from dust and water (Figure 2).


2. On location. Because the test was planned to last only a couple of months, the motes positioned on plant equipment for wireless sensor network testing were placed in plastic Ziplock bags to protect them from dust and water. Courtesy: Southern Co.

The wireless sensor network equipment was powered up, and within about 15 minutes most of the motes were communicating with the base station. A mesh network was established, and all but two motes were able to communicate with the base station either directly or through the mesh. When the two noncommunicating motes were relocated slightly, they began communicating. The motes were left in these locations for several weeks. Sensor data and mesh network performance data were recorded continuously during that time.