Keeping transformers in peak condition

Power transformers are one of the most important and expensive assets in any power network, it is therefore vital to perform regular diagnostic testing to ensure they are not at risk of failure.
ABB has developed a suite of diagnostic services that help keep transformers from any manufacturer operating at maximum load and energy efficiency, without compromising reliability or safety.

Electrical testing
Using state-of-the-art electronic equipment, operated by our highly skilled and experienced test engineers, we provide a fast, non-invasive, internal health check for power transformers up to 400 kV.
The health check can be carried out at any stage of a transformer’s life, from installation and commissioning, or as part of a condition based asset maintenance programme, right through to diagnosing and locating a potential problem – before it becomes a serious fault.
The transformer diagnostic service utilizes advanced diagnostic tools such as:
SFRA (sweep Frequency Response Analysis)
DFR (Dielectric Frequency Response and general diagnostic tools such as:
Infrared thermography of the transformer and its accessories
Winding resistance with dynamic resistance check for OLTC (online tap changer condition)
Ratio and excitation current
Insulation resistance.

Transformer oil sampling
ABB’s service engineers are trained in the skilled techniques needed to obtain the reliable and uncontaminated samples of transformer oil required for accurate laboratory analysis.
The role of the oil in the transformer is to both cool it and insulate the apparatus inside, and in doing so it bathes every internal component. As a result, the oil contains around 70 percent of the available diagnostic information for the transformer. The challenge is to access this information
and analyse it effectively to provide an early indication of a developing condition such as tap changer arcing.

SFRA test
Benchmarking
We recommend that the best information can be obtained from oil sampling by viewing trends. It is useful therefore to take a benchmark sample when a transformer is energised or an oil treatment performed. Further samples should then be taken at regular intervals so that any variation in quality can be measured in order to monitor developing faults.

Transformer Condition Assessment (TCA)
Traditional oil-testing programmes utlise only a few diagnostic parameters, leaving a vast amount of potential oil-based information unexplored. Yet surveys of failed transformers reveal that many failures can be attributed to problems that could have been properly managed with an early diagnosis through a more detailed analysis of the insulating fluid. ABB works with a leading test laboratory to provide TCA (Transformer Condition Assessment) that offers a comprehensive assessment of the dielectric and mechanical state of the transformer.
Transformer oil analysis services provided by ABB include:
– Routine tests for moisture, acidity and dielectric breakdown
– PCB levels
– DGA (Dissolved Gas Analysis)
– Furan analysis
– Transformer Condition Assessment (TCA).

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