ABB completed its first Computed Radiography assessment for a UK customer in January when it delivered the x-ray based condition assessment service for high-voltage (HV) switchgear at National Grid's Greystones 275-kilovolt substation near Middlesbrough, North East England.
The Greystones substation was formerly the feed-in point for a power station that has since been decommissioned and dismantled. As part of a wider scheme to install a new fleet of shunt reactors at several sites, National Grid is now giving the 20-year-old HV switchgear that once controlled the output of the power station a second lease of life as the connection point for two reactor units.
National Grid has engaged ABB to supply the new shunt reactors. As ABB was the original equipment manufacturer for the switchgear at Greystones, National Grid called on ABB's service team to assess the current condition of the switchgear and ensure that it will be ready for its new role. Because it did not originally operate the substation, National Grid did not have a full maintenance history of the switchgear and needed the assessment to evaluate its condition before returning it to service.
In addition to a conventional condition assessment service, National Grid accepted ABB's recommendation for assessment using the technique of Computed Radiography. The service uses an x-ray source and digital capture equipment to see inside the switchgear. It enables operators to gain an accurate picture of the condition of equipment, including wear on contacts and the existence of any defects.
Innovative approaches to service
ABB offered the service, developed originally in the US, to help its UK customers achieve significant savings in the time and expense associated with the inspection of HV switchgear. Traditional switchgear inspection requires extensive downtime to disconnect and earth switchgear before capturing insulating gas for recycling. Switchgear must then be physically dismantled for inspection then reassembled. Not only is this time consuming and expensive but it also introduces risk of damage or error during fitting.
In comparison, radiographic inspection can give an informed picture of switchgear's condition while it is still live, removing the need for extensive downtime. During the condition assessment at Greystones, ABB's specialist high-voltage service technicians delivered a conventional condition assessment, which includes taking DRM (dynamic resistance measurements), monitoring of SF6 insulating gas and timing tests.
Richard Moore, Manager for ABB's High-Voltage Service team in the UK said: "National Grid is committed to delivering value for money for its customers and encourages innovative approaches to delivering services. Because our new Computed Radiography service enabled ABB to give National Grid an accurate picture of the condition of the Greystones switchgear, they are able to proceed with the shunt reactor project with confidence."
The Greystones project built on the success of a pilot radiography demonstration that ABB conducted for National Grid to determine the potential for the service at its Fleet substation in 2014.
ABB's radiography service has several potential applications. Like in Greystones, radiography can deliver insight into the condition of existing equipment. It can also identify flaws or faults across a large installed base. Alternatively, it has a role when installing new switchgear, when it will provide a blueprint of condition at installation, so that subsequent inspection can determine a change of state in the equipment. This can be used to estimate the remaining service life, or where a physical intervention is required. All in all, an innovative use for x-ray technology, which helps give a new lease of life to equipment in operation and greater value for customers.
