As equipment ages in fossil-fueled power plants, component wear leading to machinery failure increases as a result. Extending equipment life requires increased attention to maintenance, and one way to improve maintenance planning is to detect faults prior to failure so maintenance can be scheduled at the most cost-effective, opportune time. This type of strategy benefits from the use of additional sensors, and wireless ones can often be installed with the least time and cost.
For many years the normal practice in power plants and other process industry facilities has been to hardwire important sensors from their location in the plant to a central equipment room, where monitoring systems are installed to collect data from the sensors. This arrangement worked well, but the cost of installing all the wiring to connect each sensor to the central location was quite high, often many times more than the cost of the sensor itself. The high cost of sensor installation has discouraged companies from installing all the desired sensors to fully monitor their plants.
In the past few years a new class of wireless sensors has been developed that features a standard physical communication layer, a self-forming mesh network, and low enough power usage to enable battery life of a year or more. These new wireless sensors have the potential in the next few years to dramatically change not only the wireless sensor landscape but also the process-monitoring landscape. Consequently, exploring the potential of wireless sensors for monitoring power plants has become important.
Before any new technology can be accepted by the electric power industry it must be tested in a realistic power plant environment. This article describes a low-cost wireless sensor testing in the coal-fired E.C. Gaston Electric Generating Plant, which is located in Wilsonville, Alabama. Two different sets of tests were conducted by Southern Co. and the University of North Carolina at Charlotte. The focus of the first phase was on the wireless communication and battery life. The second phase involved development of practical monitoring solutions using the low-cost wireless sensor nodes.
Equipment Description
The equipment tested was purchased from Crossbow Inc. and initially consisted of two wireless sensor network development kits and two additional input/output (I/O) boards, which provided low-level analog input capability. Each kit contained six motes (sensor nodes), each with a multifunction sensor board, a base station with a USB port, a spare mote, and software. Later, two additional network gateways were purchased to enable diverse sensor testing.
The wireless mote has a low-power microcontroller with 128 kb of program flash memory and 512 kb of measurement flash memory. The radio operates at 2.4 GHz and has a maximum transmission power of 3 dBm. The mote runs an operating system that is based on the open source TinyOS operating system. It operates on very low power and has a sleep mode that draws only 8 µA. It has an on-board 10-bit analog-to-digital converter and a 51-pin I/O expansion connector. This connector is where sensor boards are attached. The mote is powered by two AA alkaline batteries.
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