Hydro-Québec Research Institute (IREQ)
Energy System Infrastructure Group, Hydro-Québec
Robotics technologies offer promising benefits for several applications in substations. Substations critical equipments require meticulous, periodic and systematic monitoring. Inspection robots are seen as an extension of monitoring technologies to cover condition assessment needs in complement to traditional sensors. Benefits of using robotics for substation inspection can be divided into four groups: asset management, operational efficiency, worker safety and environment protection. Although inspection robots have been developed for decades, these were at first mainly R&D projects that failed to reach broad deployment.
Today, coming mainly from Asia, but also from Europe and North America, robots are now more mature and entering substations in an irreversible trend. At Hydro-Québec, given its research institute expertise in robotics applied to electric utilities, substation inspection robots are now being developed and gradually deployed. These robots must specially be tolerant to harsh winter conditions and offer completely automated functions. The first breakthrough of robotics into substations is now happening worldwide, but there is likely much more to come. Applications like automated construction and maintenance/intervention on energized equipment are good examples of future trends to come. Of particular interest, robot systems operating on energized equipment will offer major benefits in terms of operational efficiency.
This paper presents the benefits of using robotics into substations, the current trends with the use of automated inspection robots and the future trends that is set to tackle challenging new applications.
Over the last half-century, utilities experienced numerous initiatives to optimize its maintenance practices by moving from a systematic to a conditional approach, by implementing structured methodologies such as RCM (Reliability Centered Maintenance), TPM (Total Productive Maintenance) or APM (Asset Performance Management) and by experimenting with online condition monitoring (OLCM) technology. Despite these efforts, there is still room for improvement in maintenance practices, particularly in task relevance, task intervals, and diagnostic techniques, as well as in data collection and processing to extract all the relevant information.
Substation maintenance includes a series of routine and repetitive tasks performed by operations personnel in order to evaluate asset condition. Experience shows that in general, a very small minority of apparatus are found defective during condition assessment tasks, but early detection of a small defect is of a great value as it can prevent some catastrophic failures. These two characteristics of being repetitive and fruitful on a very small number of cases tend to consider such problem-finding tasks to be inappropriate for operations personnel. It is believed that technologies are now mature enough to play a significant role in this area.
With recent advances in monitoring and information technology, OLCM appears to be among the more promising solutions for improving and optimizing maintenance practices, in particular for substation apparatus. Installation of sensors is important but has to be complemented to cover a larger span of condition assessment activities. “Despite there being many tests available to evaluate apparatus condition, experience shows that visual inspection is very effective, and sometimes the only way, to detect certain problems” (1). Thermographic inspection is also a very good tool for verifying the condition of any current transfer path in a substation. Automated inspections through fixed cameras or through moving cameras installed on automatized vehicles is seen as one component of the innovative approaches to be used in conjunction with monitoring technologies to cover a wider range of substation condition assessment activities.
Main Applications for Robot Systems into Substations
Robotics applied to substations was initiated in Japan in the 1980’s but acceptance was limited by the required investments on the system itself and modifications required on site. Starting in the 2000’s the same type of robot reappeared in China but at a much more affordable cost and without requiring important modifications of the substation. Figure 1 shows both types of robots coming from Asia. While there are other examples of other applications and other types of vehicles like drones, such ground-based inspection robots represent the main and almost only application deployed today into substations worldwide. For a more thorough review of robotics applied to substations, there are a few state-of-the-art surveys available (2) and a CIGRE working group technical brochure (3).
Applications, where robotics is currently in use or at least in serious development and prototyping, can be grouped into for categories, which are monitoring and inspection, maintenance, operations, and construction of substations. Table 1 shows each of these categories with examples of applications.
As mentioned earlier, monitoring and inspection is the only group of applications for which a broad acceptance and deployment has been observed worldwide, more specifically automated inspection robots. Automated inspection robots come as a complementary tool with other modern monitoring technologies in order to efficiently implement OLCM strategies (4), as shown in Figure 2. Utilities mainly in Asia and the Americas are starting to use such robots in a seamless fashion into their substation operations.
Substation Robotics at Hydro-Québec
Inspection and Maintenance Robotics Curriculum
Hydro-Québec Research Institute (IREQ) achieved decades of research and development on robotics applied into the utility vast field of operations: power generation, transmission and distribution. Robot systems tackling challenging applications have been developed and most of them have been deployed or least tested in real and often harsh environments. The utility power generation infrastructures are mainly power dams along with other hydraulic control structures. To inspect such hydraulic infrastructures, many versions of underwater remotely operated vehicles (ROV) have been developed (5). Power dams main components include tunnels, gates and turbine generators. A specialized multi-process robotic arm has been developed (6) to accomplish in situ work (i.e. construction and repairs) on such components. These are two examples of different robot systems developed at IREQ for power generation applications. Other systems were developed for distribution network applications but here is not the purpose to document all of the institute realizations.
Power line inspection is one field that has been invested with great R&D efforts for over 20 years (7). Many systems developed over this period are of particular interest as they may offer solutions for some types of inspections into substations, notably for overhead conductors, insulator chains, and bus bars. Multiple generations of wheeled vehicles have been developed, starting with LineROVer, then LineScout and more recently LineRanger. A specialized drone able to land on and inspect power lines, called LineDrone (8), is also a candidate inspection vehicle for substations. Figure 3 shows these various types of line inspection robot vehicles. Inspection capabilities of these vehicles have been continuously improving, starting with high-resolution visual and thermal inspection, and pursuing with more specialized sensors offering more detailed insights of conductors’ health. Sensing technologies include resistance of conductor splice sleeves (LineOhm), Eddy current for zinc loss detection (LineCore), magnetic-based sensing of large steel core (LineMag) and finally X-ray scanning of conductor internals (LineScan).
Substation robotics have also been addressed at IREQ years before what will be presented next in this paper. Starting in 2012, a first remotely operated robot vehicle was developed and tested, providing access to restricted areas of substations to achieve visual and thermal inspection capabilities. Built on this first prototype, a second one was developed offering improved characteristics to sustain harsh winter conditions while integrating a robotic arm to achieve remotely operated maneuvers into electrical cabinets (9). This second prototype of substation robot is shown in Figure 4.
Automated Inspection Robot for Electrical Substations
Current development track at Hydro-Québec related to substation robotics is focused on automating simple but valuable tasks, accomplished by ruggedized and reliable robot vehicles. The R&D project and its robots are named RIAUPEL which is a French acronym meaning “Automated Inspection Robot for Electrical Substations.” Development efforts are concentrated on designing all of the system main components: vehicle and its main components (cameras, power system, etc.), onboard software for autonomy, automation and safety, and finally peripheral software to allow for remote supervision and inspection data capture.
3 successive prototypes are being developed and tested at Hydro-Québec, RIAUPEL-1 being the first one, deployed in a 315kV substation in 2020 and having traveled over 100km autonomously. RIAUPEL-3 will be the last prototype before going into an industrialization phase in 2023 and broader deployment phase starting in 2024.
What is described in next paragraphs is a good representation of current trend observed throughout electric utilities worldwide: robot vehicles reliably automating simple inspection tasks. A notable specific characteristic of proposed system is its specialization to operate in harsh winter conditions (10).
Automating Visual and Thermal Inspection Capabilities
Visual inspection is typically applied monthly or quarterly, depending on the asset type. This task is very repetitive and generally only a very small minority of the inspected apparatus shows a problem. Visual inspection also includes the reading of some indicators for which only alarms to the network operator are provided (SF6 density, oil level, etc.). Reporting is made by exception, which means that information about assets becomes available only if a problem has been identified.
Thermographic inspection is typically applied once a year and should be performed when the load is sufficient to reveal any hot spot (typically at least 30% of the maximum load applied on the inspected component). Unfortunately, numerous operational constraints mean that thermographic inspections are not always made at the right time to revel anomalies. Automated inspections using fixed or mobile cameras and advanced imagery are a very good alternative to repetitive inspections made by maintenance staff. Inspection time intervals can be set without any restriction and a specific inspection can be applied as needed. Employees don’t have to travel and walk-through substations to inspect apparatus as the robot is taking all required pictures and data and structure it in order to facilitate consultation remotely from technical staff offices.
For thermographic inspections, the information about the current load can be used to select the best moment to proceed with the inspection. When a hot spot is detected, it can be monitored in a continuous way to detect any further deterioration and prevent a major failure.
The automated inspection robot system is composed of two main subsystems. First, the robot vehicle itself which includes an elaborate set of components. Second, its docking station which allows for recharging the vehicle along with communications and remote surveillance functions. The complete RIAUPEL-1 system is shown in Figure 5.
Each subsystem’s main components are shown in Figure 6. Basically, the vehicle has an embedded computer at its heart, which interacts with each component: tracked powertrain, multiple types of cameras, speaker and microphone, multiple sensors and LTE modem. The docking station is also connected through LTE modem to allow for surveillance of its surroundings. Here are summarized specifications of the vehicle key components:
- Bi-spectral PTZ Camera: mounted on pan-tilt unit, a HD visual camera with at least 25X optical zoom is combined with a 640×480 thermal radiometric camera.
- LIDAR: three multi-beam 360° laswer intensity and ranging (LIDAR) sensors, strategically positioned for localization and safety functions.
- Battery (not shown in figure): Li-ion battery containing at least 4kWh of energy to allow for long inspection missions.
All-Weather Robot System
One major challenge of the robot system design is to ensure its reliability throughout a wide range of weather conditions. Québec province is a vast territory where both cold winter and hot summer temperatures is observed. Substation monitoring can be most relevant during the coldest temperatures at highest loads or during storms for integrity checks, the system must be designed to operate in those harsh conditions.
Strict requirements must be met on exposed devices, like an ingress protection level of IP65 and operating temperatures of -30° to 40°C. The cabinet where most of the electronics components are placed is heated to keep the temperature above 0°C during winter and ventilated to avoid overheating during summer.
During winter, only main pathways of substations are cleared, therefore leaving most areas of substations with deep snow coverage. Snow mobility capacity is studied and incrementally improved on successive generations of robot vehicles. A specialized tracked powertrain has been developed to allow for efficient and stable navigation into deep snow. Figure 7 shows examples of trials during such winter conditions. Such powertrain is also efficient on paved or gravel ground to be used all-year long.
Onboard Robot Software
In order to achieve completely automated inspection routines, the robot vehicle must count on sophisticated software running on its embedded computer. The system software is built around Robot Operating System (ROS), a framework able to manage and interconnect every system software modules.
Automated navigation is accomplished by an assembly of modules: robot localization and sensor fusion, path planning, high-level vehicle controller and low-level motor controllers. Vehicle localization sources include a dual-antenna RTK GNSS receiver, wheel odometry, an inertial-measurement unit (IMU) and 3D LIDAR-based localization.
Automated inspections are accomplished by a combination of specialized algorithms and specially trained neural networks. Algorithms are used to precisely control movements of the PTZ camera to point towards recorded inspection points while a first neural network is used to visually detect objects of interest like equipments to inspect. In some cases, like reading of dial gauges, a second neural network is used to perform a digital readout. Figure 8 shows examples of automatically inspected items.
Safety functions are of particular importance on an automated substation robot. Here is a summary of these functions:
- Speed reduction: maximum speed of the vehicle is restricted by low-level controllers.
- Obstacle detection: 3D point clouds from LIDARs are used to detect obstacles.
- Safety brake: automated braking is applied in the presence of obstacles.
- Watchdog: module checking that required components are operating correctly.
A system simulator is available to help software development by offering a virtual robot with simulated physics. Mostly every part of software can be tested in simulation therefore limiting chances of errors and helping reliability on the physical robot system.
Remote Supervision and Data Capture Software Modules
Since the automated inspection robot system is to be deployed in a substation without requiring any human assistance on-site, it is important to count on peripheral software modules to remotely supervise the system and capture and consult generated inspection data. These software modules are key to drive adoption of the inspection technology within groups of substation technicians and engineers.
Remote supervision software module is called RIAUPEL-Mission and allows to visualize telemetry data and live video feeds from the robot system, send commands to the vehicle and most importantly define and program automated inspection routines. RIAUPEL-IPES is at the other end of the system and serves as a storage server of inspection data and presents it in a structured fashion to the user. For example, a user can consult pictures taken of all apparatus sorted by date with the capability to go back in time to evaluate the progression rate of a deficiency. Readings of temperature or SF6 gauges are transferred to the corporate monitoring center that has the capability to warn maintenance teams. Both software modules are web-based applications for simplified access through corporate network. Figure 9 provides an overview of interactions between these software modules and the robot system.
Other Robot and Inspection Systems
From the start of this project, different robot vehicle types and inspection systems have been compared so to select the best system depending on the various substation environments.
For large air-insulated substations (i.e., vast majority of substations), it has been concluded that wheeled or tracked vehicles are best suited because of large distances to be driven in open areas. Furthermore, tracked vehicles are the most efficient ones into snow conditions. Automated drones are also considered for this type of substation, but trials led to conclusion that they are not ready yet for a permanent remote deployment, because of reliability issues and required maintenance. Nonetheless, drone technology will continue evolving and it should become a valuable automated inspection tool, complementary to ground vehicles.
For smaller substations with less equipments requiring monitoring and smaller areas to cover, fixed PTZ inspection cameras combining visual and thermal inspection can be an efficient solution. Depending on the number of camera systems required for sufficient coverage, it can be an affordable solution compared to a more expensive robot system traveling the inspection camera around. There are manufacturers offering specialized solutions for substation inspection. One such system is currently under trial at Hydro-Québec into a HVDC converter station valve room.
One type of robot vehicle that has been receiving great visibility in the industrial inspection field, including substations, is the quadruped robot dog. National Grid (11) and FPL are the first known utilities to use this type of robot in the United States. Canadian utilities are also beginning to use it for inspection purposes. At Hydro-Québec, indoor substations typically containing tight spaces and stairs are identified as the perfect terrain for this type of robot. A trial is yet to be started in 2023.
Benefits and Value of Substations Inspection Robots
Asset Management: precise, high frequency, and systematic data
Experience shows that visual and thermographic inspection is very effective, and sometimes the only way, to detect certain problems. Ideally, these inspections should be applied at relatively short intervals (days). Nevertheless, considering limitations in terms of human and financial resources, these inspections task intervals is usually made few times per year, that let enough time to some slow-evolving problem to become important. Automized inspections can be applied with no restriction on task interval that allow to detect at a very early stage any minor failure that is visually detectable. Thus, when used in conjunction with online monitoring, automatized inspection may reduce significantly the current major failure rate that is now around 0,3-0,5% per year for most apparatus.
Operational Efficiency: workforce focused on added value tasks and projects
In general, one can say that the time spent by human resource in maintenance activity is divided in two categories: about on half of the time is used to look for problems and the other half is used to fix problems. When problems are found, a priority level is applied to each problem to determine when it has to be corrected. In this way of doing, some workers are still looking for other problem when many found problems are not corrected. The idea of using on-line monitoring and automized inspections to find problems allow human resource to fix more problems and so, being used to make tasks with higher added value.
Workers Safety: reduced exposure to risks of accidents into substations and on roads
In a utility as Hydro-Quebec, road accidents are one of the most important cause of injuries. By implementing on-line monitoring and automized inspection, it reduces the need to ask workers to travel several hours a week to reach on of the numerous substations, some of them can be at several hundreds of kilometers from the local headquarter and so, reduce the risk of accident. Similarly, by reducing the duration of time employee are exposed to energized equipment, it also reduces the risk of injuries.
Environment: reduced vehicle transits, SF6 and oil leaks
A part of this benefit comes from the reduction of the traveling time discussed in the previous section. Moreover, early detection of SF6 and oil leaks may contribute to the reduction of environmental impacts.
Future Trends for Substation Robotics
From technology penetration observed in the present tense combined with technology developments being prepared in multiple aspects of matter (robotics, substation monitoring, AI, etc.), it is possible to foresee some future trends for robotics applied into substations. Clearly, automated substation robots will continue to make their way into substations, but they will continue to evolve in terms of types, sizes, capabilities, and intelligence. Meanwhile, other types of robots tackling new applications will appear into substation operations.
Broad Use of Artificial Intelligence for Autonomy and Inspection
Substation robots deployed today already variants of artificial intelligence (AI). AI usage will continue to improve and contribute to two main functions: autonomy and inspection. Sceane understanding, a key capacity for autonomy, is the term used to determine a robot’s cability to perceive and understand its surroundings. For a substation robot, this means its capability to recognize and localize apparatus such as power transformers but also specific objects like persons and vehicles. The real-time capability of scene understanding will improve considerably by feeding neural networks with richer data like 3D point clouds and motion information. Autonomous car development is pushing this area forward (12).
Automated gauges and indicators readings is seen as a key technology for automated inspection in many industries. A few companies are starting to provide such software services and the market for such technology is potentially enormous, substations being only a small part of it. Furthermore, state-of-the-art research in AI will bring anomaly detection capabilities to inspection robots (13). Anomaly detection will save tons of hours to personnel by automatically processing recorded data like inspection images and pinpointing all sorts of anomaly and potential defects: hot spots, animal nests, oil spills, damaged insulators and so on.
Specialization of Sensing and Inspection Capabilities
Today’s substation inspection robots are integrating somehow simple but still efficient inspection capabilities: visual, thermal and audio. As these robots will grow numbers, they will start integrating more elaborate sensing capabilities by using specialized inspection devices.
Leaks of insulating gases like SF6 must be detected as promptly as possible. They must also be localized precisely to plan an appropriate corrective maintenance. Specialized cameras for such gases already exist commercially and smaller versions will make their way onto substation robots. Another promising technology is the use of single or multiple antennas to observe and localize electromagnetic emissions. This type of sensing has been used into substation to localize partial discharges (14). It is foreseen that by combining mobility of robots with artificial intelligence observing emission patterns, such sensing technology will help localizing abnormalities on substation apparatus. X-ray scanning is another promising sensing technology. Already demonstrated experimentally in China, mobile robots providing coordinated X-ray beam and screen will provide valuable data from apparatus internals.
These are only examples of new specialized sensing; many more innovative ideas will make their way onto real life robots.
Weather Resiliency of Robot Systems
Substation inspection robots will prove to be particularly valuable under challenging weather conditions like storms and cold winter.
Storms like hurricanes will inevitably cause substation damage and consequent failures. In order to monitor the situation during and after such storms, mobile robots need to be specially adapted to operate under strong winds and heavy rain. Ground robots will prove to be efficient in such situations but drones are also becoming much more reliable under extreme conditions.
Coldest winter conditions translate to highest loads on the grid and substation power transmission equipments. This is when automated thermal inspection will play a key role, therefore requiring reliable inspection robots in such conditions. Work accomplished at IREQ is one example of avenue towards adapted robot vehicles for harshest winter conditions. Likewise and promising is Norwegian Statnett’s research project on automated drone technology adapted for winter conditions (15).
New Types of Applications and Robots
As with other industrial environments, potential applications for robots are numerous but such new robot development and reliable deployment will depend on technology maturity and engineering efforts motivated by expected benefits and value output. Based on current context, here are examples of foreseen new applications and robots into substations.
As inspection robot vehicles are deployed, one can imagine other types of applications for these vehicles. Vegetation management, whether mechanical or chemical, is one good example. Also, if a robot arm is fitted on such robots, maneuvers can be accomplished.
Live high voltage work is an area of particular interest for substation robotics as major operational efficiency benefits are anticipated. Specially designed robot systems should be able to accomplish maintenance and repair operations on live equipment.
There are also examples of scenarios where robot systems can considerably simplify substation apparatus. Disconnect switches are mechanical devices with limited long-term reliability while providing no added value in terms of substation main functions. Eliminating disconnect switches and replacing them with robotized high-voltage switching is an envisioned technology. We can even imagine robots to install portable grounds in order to let workers to focus on more complex tasks.
Seamless Integration of Robots into Substation Operations
What is observed so far with robotics in substations is that robots are operated separately or independently from the rest of substation operations. For example, a teleoperated robot will be directly driven by personnel on site or an automated robot will be operated through dedicated software modules. As utilities pursue a transition towards automating all of substation operations and monitoring, one can imagine that robot systems in use in such substation will be integrated in a transparent fashion.
In the future, substation automation systems would be able to program detailed inspection routines to be accomplished by robots and trigger on-demand inspections, for example based on current equipment loads. Likewise, robots dedicated to substation operations would also be commanded automatically.
This paper provided an overview of substation robotics as it is applied today and how it is foreseen to evolve. Automated inspection robot systems are representative of the main current trend where the only application currently tackled is monitoring and inspection, although other classes of applications are beginning to appear: maintenance, operations and construction. Like in many other industrial fields, the use of robotics into substations should see continued growth over a long period. Artificial intelligence is one particular technology domain to have a big impact on inspection robots. These robots will also continue to improve on many aspects like sensing capabilities and weather resiliency. New types of robots are also foreseen to make their way into substations, notably for live high-voltage work. Finally, those many types and variants of robot systems should be integrated more transparently into substation automation systems.
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