When a moderate earthquake shook Mexico City just after midnight in June 2013, an eerie staccato of bright flashes punctured the darkened metropolis. They came from distribution and power transformers exploding around the city. It wasn’t an isolated incident. In December of the same year, another exploding station transformer shut down an NBA game between San Antonio Spurs and Minnesota Timberwolves in the Mexico City Arena. “Transformer failures can be disruptive and dangerous,” says Enrique Betancourt, an R&D leader from the transformer manufacturer Prolec-GE, a joint venture between GE and Mexico’s Xignux consortium.
To be sure, transformers may fail and incidentally catch fire everywhere – most memorably in New York City during Hurricane Sandy. But in Mexico City, a densely packed metropolis of more than 21 million inhabitants, such failures carry special urgency. “Large transformers are located near the public and though fire prevention measures are available, balancing cost and transformer performance can be difficult,” Betancourt says.
Top GIF and video: A conventional network transformer ruptures and spews coolant during a case rupture test. These tests are necessary for building safe transformers and a key part of their design. Credits: GE Energy Management
That’s why Prolec-GE started working with Mexico’s largest utility, Comision Federal de Electricidad (CFE), to develop a less flammable transformer design using an ester-based liquid that cools the insides of the transformers. “The synthetic ester makes them safer and prevents fires,” Betancourt says. “It has a high flash point, which makes it virtually impossible to burn in the event of an accident.”
Why do transformers need cooling? Like most cities, Mexico City gets electricity from large power plants located on the outskirts. The electricity flows along power lines to a series of substations located in more central neighborhoods. The substations transform the electricity from high voltage to low voltage and send it to homes and businesses.
There is always some power lost in the transformation process and these losses create copious amounts of heat. That’s why large transformers hold up to 10,000 gallons of coolant, traditionally flammable mineral oil. When there is an accident, this oil can start burning.
“Fires in transformers can be highly dangerous and devastating to areas in close proximity to the substation,” says Federico Ibarra, technical manager at CFE. “When a transformer fire occurs in indoor substations or densely populated areas, the impact can be amplified exponentially.”
The ester-based coolant in the new transformers was developed by CFE and Prolec-GE engineers. It requires more than twice as much heat as mineral oil to catch fire. The fluid is also biodegradable, which makes it more manageable in the event of a spill.
The fluid’s applications will reach beyond Mexico City. According to the UN, more than half of the world’s population already lives in cities and that number will likely grow to 66 percent by 2050. At the same time, electricity demand is estimated to increase by 78 percent by 2040. “Clearly, we will have more power equipment near where more people are living closer together,” Betancourt says. “We need to keep them as safe as possible.”