Critical asset failures resulting in unplanned shutdowns of power generation must be avoided as they can cause lost production, environmental issues, litigation arising from injuries or fatalities, and repair and/or replacement of the damaged assets. These issues can amount to millions of dollars of direct and indirect costs.
Jonathan Murray, director of IntelliSAW products at Emerson, shows in his article, Facilitating Predictive Maintenance of Electrical Assets with Pervasive Sensing Strategies in Power magazine, how modern sensing technology makes it possible to continuously monitor the health of these assets. Jonathan explains the three main problems:
Electrical assets are subject to overheating due to excessive loads, normal wear and tear, and challenging environmental conditions. Left unattended, these conditions can lead to failures or costly damage to the asset and surrounding equipment, power production loss, and in extreme cases, severe injury or death. Three of the main sources of electrical failures are overheating of conductors, insulation breakdown, and problems related to high levels of moisture.
These electrical assets are typically checked with manual inspections during an outage. All manual inspections require trained technicians and specialized test equipment, which is why they are often performed by an outside service provider. Electrical problems occurring after an inspection can go undetected until the next inspection, but this problem can be solved by following Jonathan’s advice:
A better solution is to employ continuous condition-based monitoring. This allows utility companies to collect data generated during the asset’s normal operating conditions, thereby providing awareness to problems in real time. Monitoring and trending data of electrical stresses, vibration, insulation breakdown, and environmental influences during full load also provides new insights into the health of the assets.
Complete critical asset monitoring systems are available with temperature, humidity, and partial discharge (PD) sensing capabilities. In addition to the wireless temperature and PD sensors, wired sensors are often installed inside the asset enclosure to provide ambient temperature and humidity readings. Ambient temperature readings are important because critical issues involve temperature rise of hot spots above ambient. IntelliSAW provides such systems, as Jonathan explains:
A typical continuous condition-based monitoring system for an electrical asset includes a monitoring unit connecting temperature, humidity, and partial discharge. Each “Temp & PD Air Interface,” a branded system provided by Emerson, uses banded UHF technology to sense PD directly. Each air interface device can also wirelessly link to three or more SAW temperature sensors.
Jonathan reports how various utilities use IntelliSAW monitoring systems. The first is a large utility in the southeastern U.S. operating a multiunit peaking combustion turbine power plant:
The high-humidity environment in this part of the U.S. was causing corrosion of generator circuit breaker (GCB) switch contacts. A continuous asset monitoring system was installed on the GCBs and bus ducts. The asset monitoring system detected excessive temperatures on four of the six GCB bushings. This averted a failure that could have cost about $250,000 to repair and may have caused weeks of downtime.
Jonathan’s second example is a major utility in the western U.S. operating a number of unmanned hydroelectric power plants on various rivers:
Temperature, PD, and humidity monitoring systems were installed in the bus ducts, transformer connections, and disconnect switches. All data is transmitted wirelessly back to servers for data analysis, allowing the utility to operate these remote facilities with confidence.
According to Jonathan, electrical asset maintenance in power plants is transitioning to continuous condition-based monitoring. Modern sensing technology makes it possible to continuously monitor the health of these assets and inform plant personnel when—or even before—problems arise.