Vaisala Optimus™ DGA Monitor OPT100 produces real time information about fault-generated gases in transformers for Fingrid

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.

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Fingrid Oyj is a transmission system operator, whose mission is to ensure disturbance-free access to electricity in Finland. Fingrid secures energy supply by transmitting electricity through the main grid – the high-voltage network or ”highway” of the power system – from production facilities to industrial customers and electricity companies.

The Vaisala Optimus™ DGA Monitor OPT100 dissolved gas analyzer has been developed to measure transformer gases. It is used to measure all main fault-generated gasses and their quantities. It is a great advantage if the fault-generated gas analyzer measures all these gases. The temperature of the fault area in the transformer and the materials in contact with it affect the type and amount of gases formed. From the gases, it is usually possible to deduce the transformer fault type and its severity, and to possibly start correcting the fault.

Reducing visits to the transformers

In 2020, Finland’s transmission system operator Fingrid invested in new fault-generated gas analyzers for transformers. ”Some of our fault-generated gas analyzers were coming to the end of their service life and we organized a tender to procure replacement analyzers. As a result, we selected the Vaisala Optimus DGA Monitor OPT100 gas analyzers. 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 analyzers 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 analyzers, and during the installation, we discussed with the Vaisala team. The whole process was smooth,” explains Takala.

OPT100 dissolved gas analyzers 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.

Each transformer is an individual

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.

”It is essential to know the behavior of the transformer in different situations and to identify the changes. Fault-generated gas analyzers 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.”

In the past, monitoring has been done by taking an oil sample from the transformer a few times annually and by analyzing the fault-generated gases from the sample. The new OPT100 dissolved gas analyzer provides accurate data about the transformer regularly.

”Of course, the daily data is much better for us than the analysis of a less frequently taken oil sample. Both methods are still needed, but a gas analyzer helps us to detect problems quickly. Visits to the transformer are significantly reduced, and we save on costs,” Mertanen concludes.