Abstract
The condition of the internal cellulosic paper and oil insulation are of concern for the performance of power transformers. Over the years, a number of methods have been developed to diagnose and monitor the degradation/aging of the transformer internal insulation system. Some of this degradation/aging can be assessed from electrical responses. Currently there are a variety of electrical-based diagnostic techniques available for insulation condition monitoring of power transformers. In most cases, the electrical signals being monitored are due to mechanical or electric changes caused by physical changes in resistivity, inductance or capacitance, moisture, contamination or aging by-products in the insulation. This paper presents a description of commonly used and modern electrical-based diagnostic techniques along with their interpretation schemes.
Highlights
Power transformers, are indispensable components of power generation plants, transmission systems and large industrial plants
The core ground test is performed by disconnecting the core grounding outside the tank and the insulation resistance (IR) of the core to ground measured. This test is performed as a routine maintenance task to detect if the core has shifted, making contact with its tank, but usually performed when a transformer is first installed, moved or if a problem is indicated by dissolved gas analysis (DGA) with an increase in the combustible gases [2,54]
This paper was authored by focusing on recent developments in electrical-based diagnostic techniques and to shed light on the opportunities provided for the diagnosis of faults in power transformers
Summary
Power transformers, are indispensable components of power generation plants, transmission systems and large industrial plants. Since most installed power transformers are approaching the end of their design life, it is important to know, by means of suitable diagnostic tests, the condition of their insulation. The life of the transformer being connected with that of its insulation, the evaluation of the transformer insulation is essential to assess the condition of the unit when new and after several years This evaluation evaluation necessarily necessarily involves involves both both electrical electrical and and physicochemical physicochemical techniques of in-use in-use service. Together with the physicochemical methods, electrical-based diagnostic methods are very for the condition monitoring or for studying the electrical-based diagnostic methods areimportant very important for the condition monitoring or for the degradation of the insulation in power transformer. In recent research works havehave been undertaken to develop or improve electricalelectrical-based diagnostic methods while the basic concept has stayed almost the same. Changer; DF: dissipation factor, PF: power factor; PD: partial discharge; UHF: ultra high frequency
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