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The Grid Doctor Will See You Now: Circuit Breakers Get Health Check With Digital X-Rays

The electrical grid is a lot like the human body. Just as we have the heart, brain and veins, the grid has substations, control rooms and transmission lines, all working in concert. But like the body, it can also get sick — and needs the right diagnosis and medicine to get well quickly.

Engineers at GE Energy Connections are taking these similarities so seriously, they developed a digital radiologist for the grid. It has started seeing patients late last year. Morocco’s national utility, the Office National de l’Electricité et de l’Eau Potable (ONEE), already used it to give its aging circuit breakers a thorough checkup to make sure they were fit to protect and stabilize the grid.

Top: Evaluating the condition of a circuit breaker is a time-consuming process that involves physically opening the unit for inspection. Above: Using digital X-rays, utilities can see any wear or tear that requires maintenance within hours rather than days. Images credit: GE Power.

These industrial-strength circuit breakers are like the valves of the heart — controlling the ebb and flow of electricity and protecting the substation against damage from power surges. Some circuit breakers also help limit reactive current in a network. Reactive current smooths the flow of electricity, but it is like cholesterol: Too much of it in the line can restrict that flow. Limiting reactive current ensures a healthy flow of “good” electricity through the line and also prevents overheating.

In order to evaluate the health of these circuit breakers, utilities must physically open them — a process that requires disconnection from the grid for between three and five days per circuit breaker.

The job is also a workout. A circuit breaker in a 400 kV air-insulated substation is approximately 6 meters (18 feet) tall and has up to six poles that inspectors traditionally have to take down to assess. The process costs the company precious man-hours and potential revenue. What’s more, opening a breaker carries a risk that it will fail when it gets reenergized —and sometimes these investigations reveal nothing was wrong with the circuit breaker in the first place.

These concerns were top of mind in December, when ONEE needed to inspect a substation that channels enough electricity to serve a quarter of Morocco’s needs. “The time to make these inspections was a big issue for the customer,” says Thibaut Mauffrey, engineering manager at GE Power’s Grid Solutions. “We also wanted to make sure we could do the checkup in the least disruptive way possible.”

So, what if a utility could peer inside a circuit breaker rather than open it up for inspection? Mauffrey realized it could, using the same digital X-ray technology GE Oil and Gas has been using to inspect pipelines for the last 10 years.

The concept isn’t entirely new. Other companies had tried using classic X-rays in industrial contexts with poor results — the images weren’t clear enough to make an accurate diagnosis. Digital X-rays, on the other hand, have filters that can enhance the picture quality and accurately capture the dimensions inside the circuit breakers. These images enable specialists to pinpoint a problem and propose the appropriate remedy on the same day.

Mauffrey decided to go for it. His first move was to test the solution with GE Measurement & Control, now part of Baker Hughes, a GE Company, in a controlled environment close to GE’s factory in Lyon, France. Once these tests proved conclusive, the team approached ONEE, which seized the opportunity to be the first customer to use this solution.

ONEE planned a one-day outage from the grid for each of the four circuit breakers they were checking. GE shipped a digital X-ray machine from France, and taking all the necessary precautions, the team got to work. Within about half a day, the machine had produced its images, a specialist had reviewed them, and ONEE had received the good news: Only one of the three units needed work.

Having now seen digital X-rays used this way, Mauffrey says he and his team will be proposing this option for other customers.

“ONEE was very pleased at the speed of which we could provide our diagnosis,” Mauffrey said. “It’s amazing how digitizing a classic solution could open so many doors for our customers.”

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