Impulse (BIL) Testing Reactors & Transformers: A Short Explanation
Docta Reacta: Power Magnetics was in the news again recently, this time for BIL testing. In case you missed it, this is just a quick update on some news you may be able to use, intended to help you be smarter buyers of magnetics. If you want to read the article, check out the links below – including the one on the Institute Blog. Don’t miss the links to the photos in the article (or see them in the blog post), in particular the one at the testing lab. (Frankenstein could have used that setup!)
BIL is an abbreviation for Basic Impulse Level. Impulse tests are dielectric tests that consist of the application of a high frequency steep wave front voltage between windings, and between windings and ground. The BIL of a transformer is a method of expressing the voltage surge that a transformer will tolerate without breakdown.
In the design of lines and equipment considering the minimum level of insulation required, it is necessary to define surge voltage in terms of its peak value and return to lower values in terms of time or duration. Although the peak voltage may be considerably higher than normal voltage, the stress in the insulation may exist for only a very short period of time.
Epoxy material is strong and requires little maintenance. As a dry type transformer, there are no hazardous liquids or materials to pose a safety risk. Since they do not contain hazardous materials, Epoxycast transformers do not require transformer vaults that limit placement options and significantly add to the cost of liquid transformers.
Complete transformer test systems
Transformers are an integral part of the power grid. Their reliability directly impacts the reliability of the grid. The failure of this critical asset can handicap the grid and increase its volatility. As replacing a high voltage transformer requires planning for many reasons, including long manufacturing lead times that can exceed a full year, it is widely accepted that asset management, particularly of transformers, is a beneficial contribution to the operation of the grid.
Voltage oscillogram method: Fault or failure appears as a partial or complete collapse of the applied voltage wave. Figure 10.14 gives the typical waveform. The sensitivity of this method is low and does not detect faults which occur on less than 5% of the winding.
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Northern Transformer builds
The instrument rated transformers manufactured at GEC Astra are kept to the highest standards just like The Durham Company counterpart products. There are three types of current transformer: standard, extended range and high accuracy. We have a wide range of current transformers to fit your service needs. GEC Asta also produces 600 V class voltage transformers. The units are fully encapsulated with an epoxy and rated for indoor-outdoor use.