During a recent project we helped BC Hydro perform a condition assessment of a transmission line which included a unique crossing support structure. This was a great opportunity not only to get spectacular views of British Columbia coastline, but also to demonstrate another use case for drone inspections of hard to reach structures.
Because this structure supports a transmission line crossing a 2 mile wide inlet, it needs to be very tall — around 500ft, to allow enough conductor clearance for marine traffic. It is also located on a rugged bluff accessible only by hiking in. This makes inspection of this structure particularly challenging using conventional approaches such as foot patrol or climbing inspection.
In the past, a detailed inspection of this structure has been done by dropping off the lineworkers using a helicopter, which is a complex and challenging operation. An inspection from the ground would not provide the necessary detail and vantage points to detect potential defects at the top of the structure. A thorough inspection is very important on such a critical crossing tower.
Together with BC Hydro we wanted to explore the option of doing a drone based inspection from the opposite side of the inlet.
Aeriosense setup operating procedures to manage possible risks associated with this inspection and created a flight plan by processing LiDAR data supplied by BC Hydro to allow autonomous navigation of the UAS around the structure.
The automated inspection allowed the data to be collected quickly and efficiently. This large structure required only 2 flights, about 20 minutes each, with 30% of battery capacity remaining in reserve at the end of each flight in accordance with procedures put in place for this particular inspection.
Having a pre-programmed flight plan also allowed to easily resume the inspection where it was paused for the battery swap.
As with other UAS inspections, the high level of detail and exceptional vantage points allowed with this approach provided a comprehensive record of the structure condition, which was reviewed by an Aeriosense powerline inspector for deficiencies.
This project was a success and demonstrated how an Automated UAS inspection can provide significant cost savings and reduce safety risks for inspection of hard to reach transmission structures.
As Alex Au, of BC Hydro Transmission Sustainment Planning said:
“Overall, drone inspections have been an effective addition to our inspection programs. The technology has proven to provide pictures with superior quality (details and angles) from conventional inspection methods.”
The data collected during the inspection will be used by the field crews in planning of mitigation work and by engineering in asset maintenance planning. This allows BC Hydro to leverage inspection data, creating value for multiple stakeholders and operating units within their organization.