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Electrical abnormalities in transformers are exhibited by gas in the oil and evaluated by a DGA, which allows detection of two different types of failures: electrical and thermal faults, whereby each type of failure can be subdivided into three different categories according to the international standard IEC 60599.

DGA became a well known and approved technique in recent decades, although different techniques of dissolved gas analysis and its interpretation exist.

As a first step for an evaluation of the actual condition of Transformer insulating system usually a dissolved gas analysis is used, because failures inside the transformer lead to a degradation of the liquid insulation in such a way that different so called failure gases are produced, thus the compound of the gases, which is characteristic for different failure types, enables an identification of the failure cause.

Therefore from the gases that are dissolved in the insulating liquid, which usually consists of a mineral based insulating oil, an assessment of the strains that have been provoked insulation degradation, is possible.

By such an analysis both thermal and electrical overstressing becomes evident, thus allowing early information about the condition of your Transformer

With the new TOGA system, the analysis is done automatically in 2 steps with high selectivity and accuracy.

• Step 1. Degassing of the taken oil sample through vacuum extraction (according to IEC 60567 [2])
• Step 2. Dissolved gas analysis by gas chromatography with TCD (thermal conductivity detector), FID (Flame Ionization detector) and  Methanizer or your existing GC.

Both steps, which are explained in more details in the following, are synchronized by a microcontroller, which guarantees a fast and reliable measurement routine. Also possible is the use of an existing GC

Vacuum Degassing

• A new invented vacuum degassing method (Patent pending DE 102 52 652 4) degases the oil sample in multiple periods. After the extraction by a 4 step vacuum pump the gases are enclosed in a vacuum chamber where they are separated.
• The gases are evacuated from the vacuum chamber with a vacuum pump, therefore a very high sensitivity can be reached.
• In and outlet of the oil sample, as well as the switching valve, are microprocessor controlled and a linear pressure sensor measures online the total gas content (TGC), which is an important parameter concerning bubbling.
• The injection of the gas samples into the gas chromatograph is made via a fixed mounted transfer pipe but also an additional port for withdrawal of gas samples is installed.
• The analysis of the dissolved gases is done after the automatic injection in an automatic
  sample loop of the gas chromatograph.

With the automatic Injection, the VDU gives a start signal that the GC to analyse the injected gas.

An additional modification we also could use our Automatic sampler to contain 16 syringes to run the system overnight.

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To contact Martec Asset Solutions about Vacuum Degassing Gas Analysers Connected with Existing GC use Get a quote.