Using Robot Subs for Transformer Inspections

The New York Power Authority recently used a mini submersible robot to navigate through the transformer oils in a power transformer to identify operation issues while reducing unplanned down time as well as risk to personnel. The power authority carried out the inspection as part of an Electric Power Research Institute project evaluating transformer inspection technologies at the power authoritys Robert Moses Niagara Power Plant in Lewiston. The remote-controlled inspection submarine - an ABB TXplore robot - was submersed into an oil-filled transformer without requiring the removal of the oil from the transformer or a human inspection. This specific demonstration focused on the ease and speed of deployment, quality of the visual inspection, and typical inspection times when using robotic inspections of transformers, Electric Power Research Institute Technical Executive Luke Van der Zel, who helped lead the tests, said in a Jan. 24 news release. The results will guide future research on how this technology functions in highly contaminated, and therefore very dark, transformer oils. The power authority said that the toaster-sized robot can be used when a power transformer experiences unusual gas accumulation in the insulation oil and requires further investigation inside the tank to determine whether the transformer has an internal defect. ABB developed the technology and is part of an institute collaborative research project that aims to help understand how to specify and apply the new inspection tools. According to the power authority, conventional internal inspection requires draining the transformer oil so that an inspector can enter the transformer to verify the absence of internal defects. After the inspection, the transformer oil needs to be processed to ensure the required quality of the oil - a process that can take several days. The activity poses potential safety issues, and a rescue team must be available in case the inspector faces an unexpected event inside the transformers tank. The commercially available submersible robot technology can maneuver inside a transformer and transmit a live video feed that can be viewed from outside the transformer. The robot is also designed to be retrievable in case communication or power is lost. According to ABB's website, the robot is compatible with mineral or ester fluids. At the power authority, a transformer started to develop hot metal gassing in its insulation oil as a response to an unexpected event on the grind. An inspection by the submersible robot revealed a problem involving bits of insulating paper on the tank floor. Based on the inspection, the transformer was taken out of service for repairs and replaced with a spare transformer so the generating unit could continue operations. Transformer oil is usually a highly-refined mineral oil that is stable at high temperatures and has excellent electrical insulating properties.
mini-submersible robot

Photo courtesy of New York Power Authority