Brazilian National Electrical System Operator (ONS) has recommended the replacement of all GE-manufactured CTH-550 current transformers. According to the ONS, in the last six years, 53 explosions were recorded exclusively in this model and no similar occurrences were observed in equipment manufactured by other companies.
The information was made public in a Reuters news report on January 15. The CanalEnergia Agency had access to the confidential report submitted to the Electric Sector Monitoring Committee (CMSE) and sent to the Ministry of Mines and Energy (MME).
If the recommendation is accepted by the concessionaires, up to 662 transformers should be replaced.
Per report, the problem could be in the early aging of the insulation. Although the equipment is in compliance with the technical standards, it cannot be ruled out that they were built with less robust insulation than others.
In a note sent by the advisory, the manufacturer GE reported that it did not have access to the ONS report but confirmed that it is aware that incidents occurred with some of its customers in Brazil. However, the company claims there is no evidence that the cause is related to the product's design, materials or manufacturing processes.
According to the ONS, the problem has been monitored since January 2014. The agency said that the equipment has been "failing more than expected" and that the survey is still ongoing.