Online DGA Monitoring

DGA is known as the “blood test” of the transformer. Both the test and the instrument used must therefore be very accurate and cover all required parameters.

An online DGA system monitors important transformers 24/7: it automatically analyses the gases dissolved in the oil, sends data and reports and raises an alarm as soon as it detects an unusual increase.

This protects critical transformers through precise diagnosis and proactive failure prevention – provided the instrument is 100 % in line with ASTM D3612 / IEC 60567 and achieves true lab accuracy.

Any gas evolved in the oil relates to the energy released by a thermal, electrical or mechanical fault – including small, unnoticed ones.

Other instruments cannot detect propane and propylene: they occur in very low quantities and require a highly accurate instrument following ASTM D3612. As “memory gases”, even traces of them indicate that

• a fault did occur, but was so minor that the oil quenched it instantly, or
• a very small fault exists that is currently still covered by the insulating property of the oil.

The transformer should then be monitored carefully for some time.

Ignoring the memory gases and waiting for a fault to evolve defeats the purpose of DGA. The volume of gas from a fault cannot be controlled – but even the slightest increase can be detected.

All gases dissolve in oil, but to different degrees; only after saturation do they collect in the Buchholz relay. A special pressure sensor therefore determines the total gas content of the oil sample online – a key criterion for the transformer's health.