B. EL Bastawisy1, S. Elmazaly1, N. S. Zaghloul1, M.M.Ali2 and S. Z. Elsayed3


Egyptian Electricity Co. Alex , Egypt


Atomic Energy Authority, Cairo, Egypt


Labour University , Alex, Egypt


The safety in operating the power transformers is one of the essential factors to be considered

to get a reliable high performance source of electrical Energy. The 50 years experience with

laboratory dissolved gas analysis ( DGA ) in the transformer oil tends to be considered a

baseline, however the dynamic behaviour of dissolved gases requires continuity through

periodic manual sampling. Automated on-line DGA brings opportunities for new experiences

to take full advantage of the information the gases can provide to understand what is

happening inside a power transformer.

The gas analysis was carried out many years by Orsat method which was giving rough results.

Therefore, the chromatographic DGA technique has replaced the Orsat method in carrying out

these analysis.

In this study, the DGA method is presented which gives spot lights on the evaluation of

dissolved gas analysis in power transformer oil .

On the other hand, This method has been applied on our case study of power transformer

substations 220/66 Kv & 66/11 Kv Alexandria Electrical power network 220/66/11 Kv using

the DGA chromatographic technique on the basis of the gas content deviation, which will lead

to an early detection of faults inside the power transformer .Further, the threshold fault gas

levels for power transformer in service is also presented in this study. Furthermore, special

Attention is given to on – line DGA data taken from an operating power transformers in

Alexandria power network through our case study as early detection and control of faults

prevent them to develop into accidents causing electric power interruption .

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