By Jason Styron, FLIR Systems Inc.
Our power grid, the world’s largest interconnected energy machine, consists of more than 9,200 electric generating units with more than 1 million MW of capacity, connected to more than 300,000 miles of transmission lines and countless electrical distribution substations.
Because of the grid’s aging infrastructure, however, electric utilities and their customers are facing an increasing risk of blackouts and brownouts, costly unplanned maintenance, security threats to remote facilities and rising costs.
As part of the government and industry’s smart grid initiative, utilities and researchers are looking for ways to address these issues and improve the reliability of electric power delivery while reducing expense.
The U.S. Department of Energy (DOE) has been charged with coordinating grid modernization. Heading this effort is the Office of Electricity Delivery and Energy Reliability.
The office’s Smart Grid Task Force is responsible for coordinating standards development, guiding research and development projects, and reconciling the agendas of stakeholders.
The objective is a major overhaul that creates a smarter grid—one that operates more reliably and efficiently.
This objective is endorsed and supported by the GridWise Alliance, a consortium of public and private stakeholders who share a similar vision. The realization of that vision will be an electric system that integrates the infrastructure, processes, devices and technology to make power delivery more resilient, secure and reliable. Electric utilities are in the vanguard of those applying new technologies to meet these objectives, particularly in transmission and distribution.
Substation Technology Development
The DOE’s National Energy Technology Lab (NETL) has identified five technology areas that are essential for a modern grid (see Figure 1):
- Sensing and measurement: technologies to support faster and more accurate response,
- Advanced components: employing the latest technologies to, among other things, improve equipment diagnostics,
- Integrated communications: connecting components in an open architecture for real-time information and control,
- Advanced control methods: to monitor essential components, support rapid diagnosis and enable precise solutions appropriate for any event, and
- Improved interfaces and decision support: to amplify human decision-making and transform grid operators and managers into knowledge workers.
One pivotal sensing and measurement technology utilities have been adopting is infrared (IR) thermography. For several years, utilities have found that handheld IR cameras can play a major role in preventing unplanned outages that result from substation component failures. Handheld cameras, however, do not meet all the NETL technology criteria.
Now, through the efforts of IR camera manufacturers and automation equipment suppliers, systems are being developed that support all five NETL technology objectives. These systems use permanent IR camera installations that provide early warning of impending component failures and unauthorized intruders. By monitoring the heat signatures of equipment and human beings, these automated systems provide remote detection and alarm signals that are communicated to a central control room. This allows an operator to dispatch maintenance personnel to a substation before equipment fails or dispatch security personnel in case of intruders. Furthermore, data is collected and archived for trend analysis, providing valuable insight into equipment that needs to be replaced or upgraded.
Why Use IR Imaging?
The first principle of IR sensing is that many components heat up before they fail. Second, all objects emit thermal radiation in the infrared spectrum not seen by the human eye. Third, IR cameras convert that radiation to visual images calibrated to a temperature scale. This noncontact temperature data can be displayed on a monitor in real time and sent to a digital storage device for analysis. (Measurement accuracy is typically ±2 C.)
Essentially, modern IR video cameras are smart sensors incorporating features that facilitate their use in supervisory control and data acquisition (SCADA) systems. The most useful ones have various communications interfaces, such as Fire Wire, Ethernet (including fiber-optic and wireless adaptors), digital I/O, analog data output, etc. This connectivity allows:
- The instant triggering of audible and visual alarms,
- Analog thermographic images to be sent to a TV monitor,
- The transmission of digitized images and temperatures in MPEG-4 format to a PC monitor,
- Authorized personnel access to digitized temperature data on a LAN/WAN network, and
- The notification of key personnel of problems via e-mail and intranet connections.
IR video cameras do not require lighting to produce their images and can see hot spots well before excessive heat or loss of insulation leads to failure. They can see through moisture in the air to obtain good images and relative temperature readings of target objects or monitored areas. They can be mounted in weather-tight housings and placed on pan and tilt drive mechanisms to survey large areas of a substation. With different focal length lenses, they can be placed wherever required. Therefore, they support 24/7 monitoring in all types of weather and locations. Video frames can be easily captured as still images for closer analysis.
IR cameras recognize differences in the heat signatures of electrical components and surrounding backgrounds (such as the sky or clouds), and can compare temperatures of similar components in close proximity with one another. Built-in logic, memory and data communications allow them to compare the temperatures in their images with user-defined settings. This makes them ideal for unattended monitoring of substation equipment and detection of unauthorized intruders.
Substation components whose thermal signatures are precursors to failure include:
- Power transformers (inadequate oil levels and pump operation),
- Load tap changers (oil levels, other internal problems),
- Insulator bushings (oil levels and bad connections),
- Standoff insulators (moisture, contamination, degradation),
- Lightning arrestors (degradation of metal oxide disks),
- Circuit breakers (oil or SF6 leakage),
- Mechanical disconnects (bad connections, contamination),
- Control cabinets (wear and tear on fans, pumps and other components), and
In addition to excessive heat, thermography can identify nonfunctioning equipment that has lower than normal temperatures. Human heat signatures easily stand out from background IR radiation, and motion-detection software can trigger intrusion alarms. In some systems, IR cameras and visual cameras are combined for expanded monitoring capabilities.
The Smart Grid and ROI
For years, utilities have employed handheld IR cameras in predictive and preventative maintenance (PPM) programs to inspect substation equipment. This approach has provided an excellent return on investment (ROI) by anticipating, detecting and responding rapidly to impending problems. This reduces maintenance costs and the probability of failures, blackouts and lost productivity. One large U.S. utility discovered a hot bushing rod in a substation transformer and repaired it for $16,000. A similar problem that occurred before the firm instituted its IR program resulted in a $3 million catastrophic failure (see Figure 2, page 30).
500kV- 161kV INTERTIE TRANSFORMER
|Example of a failed 500kV-161kV interie transformer die to low oil level in the insulator bushing.|
Bushing oil leaks can be slow and continuous. Sometimes a leak can be seen, but it might develop inside the tank. When that happens, oil continues to flow from the bushing and moist air replaces the oil. The paper becomes void of oil, causing increased areas of electrical stress and corona discharges that tunnel through the paper. Ultimately, the foil layers short out, resulting in a catastrophic failure.
Depending on the PPM cycle for a substation, an oil leak might not be caught in time by a walk-around inspection program. With a permanently installed IR camera on a pan and tilt mechanism and appropriate focal length lens, problems such as these can be detected early. Figure 3 shows how an IR camera detects oil levels through temperature differences.
By permanently mounting an IR camera with automation features at a substation, the need for on-site inspections is reduced or eliminated. The reduced inspection expense provides an excellent ROI that quickly pays back the cost of the hardware and software for an automated system. Moreover, this modification of the IR thermography model, from one of manual inspections to automated monitoring, helps advance the smart grid concept.
Implementing Automated Substation Monitoring
As indicated earlier, IR cameras are available with hardware and firmware features that facilitate automated monitoring. To make them suitable for 24/7 outdoor monitoring, an appropriate weatherproof housing is needed, and, in many cases, it needs to be mounted on a motorized pan and tilt mechanism. In addition, the camera must be fitted with a lens focal length suitable for the scope of the area to be monitored and size of the targets within that area. Depending on the camera, electronic zoom from about 2X to 8X may be available, which can help in spotting a problem area if the camera’s detector resolution is properly selected.
IR camera manufacturers often partner with automation system suppliers to create customized thermal imaging and noncontact temperature measurement systems for electric substations. For instance, FLIR Systems Inc. sup-plies IR cameras to Pivotal Vision LLC for substation monitoring and other applications. Pivotal Vision integrates the FLIR cameras with its pan and tilt housings and automation software to create the firm’s ScadaCam Intelligent Surveillance systems. These systems can automatically perform site patrols, monitor equipment temperatures and scan for security breaches without human supervision. The video images and their temperature data are carried over Ethernet, wireless or fiber-optic cables to an appropriate interface that communicates this data to the central monitoring location. Automation also provides data collection on equipment operation without sending people to substations. This provides for better management of assets at a lower cost.
Figure 4 is a diagram of a typical ScadaCam substation monitoring system that uses FLIR A-320 cameras plus visible light cameras for intrusion-monitoring applications. A system of this type has been installed at one of Xcel Energy’s “Substations of the Future” in Minnesota. The most advanced versions of these systems provide time-stamped 3-D thermal modeling of critical equipment and areas, plus intrusion monitoring with motion detection features.
Jaon Styron is an automation business development manager with FLIR Systems Inc. He has an electrical engineering degree from Auburn University and 12 years’ experience in industrial automation. For five years he has focused on infrared thermography in automated monitoring and control. E-mail email@example.com.