Engineering news
Power transformers are high-value and critical machines that step voltage up and down for transmission and distribution. However, many of the world’s transformers are getting older. Many were installed more than 30 years ago, and over the years they have experienced wear and tear from overvoltages and short circuits.
For operators, an unplanned outage can have huge consequences. Replacement transformers are costly and have a lead time of months, so it’s important for operators to understand the condition of internal components such as tap changers, windings, insulation, gaskets and seals.
Normally, operators need to drain oil from transformers and send in a technician for a visual survey, along with the support of a confined-space entry team. Now, a new robotic inspection service called TXplore has been launched to avoid the need to put a technician at risk.
How does the TXplore service work?
A team of two technicians launch a swimming robot into a transformer while it’s still full of oil. The robot is a bit smaller than a football and is controlled via a wireless link using a controller that is based on gaming controllers.
Propellers control speed, direction and position. The technicians use cameras and lights to guide the robot through the transformer’s interior, capturing photos and video on the way. The survey results can be shared in almost real-time to experts anywhere in the world.
What is the most challenging set of conditions where the robot can operate?
When designing the robot, ABB’s development team set itself several challenges. One example is very old transformer oil, which has become darkened over time. Bright on-board lights ensure that the robot will capture clear photography, even in the darkest oils.
Another example is the varying densities of the many different oils that exist, changing the buoyancy of the robot.
A third example is the likelihood of encountering PCBs, a toxic substance that was used in some transformers before 1987. The composition of oil is tested before and after inspection. This not only determines the correct buoyancy but also enables the technicians to plan for licenced disposal if PCBs are present. Post-inspection testing is also used to demonstrate that the oil is unaffected and the robot undergoes rigorous cleaning after every inspection.
What are the benefits?
The main benefit is that robotic inspection eliminates risks to health, safety and the environment. It doesn’t expose a technician to the risk of squeezing into a transformer in hot conditions, where they may be injured or cause damage.
Because the oil remains in place, there is no risk to the environment from oil spills and the service can be completed during an outage of less than one day, whereas a manual inspection can take as long as three days.
Where has robotic inspection been used so far?
Having developed the robot, ABB tested it with an inspection at a power transformer factory in St Louis in the US and also a substation serving an ABB high-voltage test facility. The robot then completed an inspection on a 50-year-old transformer at a North American utility substation, demonstrating the control, mobility and image capture potential, as well as the ability to share survey images with remote sites.
The service has just launched in the UK and the robot will be at the EuroTechCon conference in Cardiff from Tuesday to Thursday (4-6 December).
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.