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Ensuring the condition and operation of transformers is key, as they are the basis of all electricity transmission and distribution.
If there is a fault in a transformer, the temperature may rise sharply at the fault point – depending on the type of fault – which results in fault-generated gases beginning to form in the transformer. Finnish transmission system operator Fingrid Oyj acquired new Vaisala Optimus™ DGA Monitor OPT100s to monitor fault-generated gas levels in its transformers.
Modernising Monitoring
In 2020, Fingrid invested in three new fault-generated gas analysers for its transformers. “Some of our fault-generated gas analysers were coming to the end of their service life and we organised a tender to procure replacement analysers. As a result, we selected the Vaisala Optimus™ DGA Monitor OPT100 gas analysers. They met our technical requirements, and we already had a positive experience using the product earlier,” says Juha Mertanen, Fingrid Oyj’s expert on the matter.
Fingrid’s long-term partner Omexom provides construction, installation and maintenance services for the generation, transmission and distribution of electricity. Cooperation between Vaisala, Omexom and Fingrid has proven to be an effective way of operating, as each company contributes to the project its own expertise. Omexom acquired the dissolved gas analysers and installed them in transformers in October 2020.
Otso Takala, Project Manager at Omexom says that they received good support from Vaisala’s expert in different phases of the project. ”We quickly got the product information we needed from Vaisala’s experts. Our team participated in online training on the installation of dissolved gas analysers, and during the installation, we discussed with the Vaisala team. The whole process was smooth,” explains Takala.
OPT100 DGAs play an important role in condition-monitoring of Fingrid’s transformers. They continuously provide up-to-date information on the concentration of fault-generated gases in transformers. Therefore, the changes in the transformer can be detected already at a very early stage, even in real-time.
”Fault-generated gases as such do not complicate the operation of the transformer. However, they are a symptom of some change. We need to find out that the increase in the amount of gas is not dangerous for the use of transformer,” explains Mertanen.
He notes that transformers are individuals, and each of them generates gases in a slightly different way. Therefore, transformers do not have common, absolute cut-off values to assess the importance of change.
Reducing Visits to the Transformers
”It is essential to know the behavior of the transformer in different situations and to identify the changes. Fault-generated gas analysers help us to catch the turning point, from which we can assess what has caused the change. For example, an external event related to a normal operating load situation can change the operation of the transformer.”
