Dielectric strength test of transformers
The electric transformer is a static device that converts electric energy from one circuit to another circuit without any direct electrical connection. Transformer works on Faraday mutual induction. Simply it is used to increase and decrease the voltage.
we need to know the historical backdrop of the transformer, we need to return long during the 1880s. Around 50 years before that in 1830 the property of induction was found, and this is the working guideline of the transformer. Later the transformer configuration was improved bringing about more productivity and lesser size. Progressively the enormous limit of transformers in the scope of a few KVA, MVA appeared. In the year 1950, 400KV electrical force transformer was presented in high voltage electrical force framework. In the mid-1970s, unit rating as extensive as 1100 MVA was delivered. Different producers made 800KV and considerably higher KV class transformers in the year 1980
Transformer oil is a mineral-based oil that is regularly utilized in transformers for its compound properties and dielectric strength. This oil in your transformer goes about as a cover and a cooling specialist. Over a long time, the oil will corrupt bringing about the potential for issues and expensive fixes. With an appropriate safeguard support program. The nature of your transformer oil will impact its protection and cooling properties. Under ordinary working conditions, a negligible breakdown of oil quality will happen from oxidization and pollution.
Testing your transformer oil ought to be essential for your yearly safeguard support program. Testing the oil will assist with deciding when remedial measures are required. Introductory testing will build up a benchmark for examination and yearly testing will plot any progressions inside in your transformer. Dielectric breakdown: Dielectric strength is a proportion of voltage the oil will protect against. Numerous foreign substances direct power in a way that is better than oil accordingly bringing down the dielectric breakdown.
The dielectric strength of transformer oil is otherwise called the breakdown voltage (BDV) of transformer oil. Breakdown voltage is estimated by seeing at what voltage, starting strands between two terminals drenched in the oil, isolated by a particular hole. Low estimation of BDV demonstrates the presence of dampness substance and leading substances in the oil.
For estimating BDV of transformer oil, convenient BDV estimating unit is by and large accessible at the site. In this pack, oil is kept in a pot in which one set of terminals are fixed with a hole of 4mm between them. Presently gradually rising voltage is applied between the cathodes. The pace of rising voltage is controlled at 2 KV/s and notice the voltage at which sparking begins between the terminals. That implies at which voltage dielectric strength of transformer oil between the anodes has been separated.
This estimation is taken three to six times in a similar example of oil, and we take the normal estimation of these readings. BDV is a significant and famous trial of transformer oil, as it is the essential marker of the strength of oil and it tends to be handily completed at the site.
Dry and clean oil gives BDV results, better than the oil with wetness content and other directing pollutants. Least breakdown voltage of transformer oil or dielectric strength of transformer oil at which this oil can securely be utilized in a transformer is considered as 30 kV.
There are two principal kinds of transformer oil utilized in transformers:
Ø Paraffin based transformer oil
Ø Naphtha based transformer oil
Naphtha oil is more effectively oxidized than paraffin oil. In any case, the result of oxidation – for example ooze – in the naphtha oil is more dissolvable than the muck from the paraffin oil. Subsequently, the sludge of naphtha-based oil isn't accelerated in the lower part of the transformer. Consequently, it doesn't block convection dissemination of the oil
Even though Paraffin oil has a lower oxidation rate than Naphtha oil, the oxidation item (slop) is insoluble and encouraged at the lower part of the tank. This muck goes about as a deterrent to the transformer cooling framework. Another issue with paraffin-based oil that the broke up waxes within it can prompt a high pour point. Even though this isn't an issue in hotter atmosphere conditions. Despite the inconveniences referenced above, paraffin-based oil is still usually utilized in several nations because of its high accessibility. To know more about The dielectric strength of transformer oil you can visit Hering VPT.
Some properties of transformer oil ought to be considered to decide the usefulness of the oil.
The properties of transformer oil are:
1. High dielectric breakdown
2. Low consistency - protection from continuous disfigurement by shear pressure or tractable pressure.
3. Very much refined and liberated from materials that they may consume the metallic parts
4. Be liberated from dampness and polar ionic or colloidal foreign substances
5. To have a low pour point (the temperature at which a fluid lost its stream qualities become semi-strong)
6. Low glimmer point (the most reduced temperature at which a fluid disintegrates to make the ignitable combination in the air).