NDL has developed expertise for fault detection in transformers at an early stage so you can be rest assured for zero breakdown maintenance & production losses. There are various forces acting inside the transformer which degrade its performance over the period of time. Aging, chemical actions and reactions, electric fields, magnetic fields, thermal contraction and expansion, load variations, gravity, and other forces all interact inside the tank. Externally, through-faults, voltage surges, wide ambient temperature changes, and other forces such as the earth's magnetic field and gravity affect the transformer. There are few if any "cut and dried" DGA interpretations; even experts disagree. Consultation with others, experience, study, comparing earlier DGA's, keeping accurate records of a transformer's history, and noting information found when a transformer is disassembled will increase expertise and provide life extension to this critical equipment.

In the case of a fault; it’s type and its severity may often be inferred from the composition of the gases and the rate at which they are formed. In the case of an incipient fault the gases are formed remain partially dissolved in liquid insulation; Free gases will be found only in special cases. The dissolved gases will divided between the gases and liquid phases by diffusion. Diffusion and achievement of saturation both take time, during which serious damage to the equipment can occur undetected.

Periodic analysis of the oil sample for the amount and composition of dissolved gases forms a means of detecting fault.

Dissolved Gas Analysis (DGA) is the most important test that you can perform on your transformer. It is the only test that can determine the operating status of oil filled electrical equipments.

DGA reports have a diagnostic section where an analysis is performed on the dissolved gas results using IS:10593 (Ratio Method) & Roger Method. The information provided by the report is often sufficient to properly evaluate the operating status of the transformer but gassing history is also an extremely important aspect of fault detection.

At NDL, all DGA results are kept in a readily accessible database and historical data is checked every time a sample is analyzed. When a significant change in gas concentrations is observed, the client is contacted immediately through Telephone, fax or e-mail.

At NDL Automation of Testing & Reporting led to better management of transformer oil tests. Re sampling schedule, gas history graphs, and fault assessment algorithms based on stored DGA results are provided to offer a quick and simple way of deciding which transformers should be tested and in which priority.

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