The insulation resistance test of transformer complements other transformer tests. The solid winding insulation tests are not conclusive in themselves but provide valuable information on winding conditions, such as moisture content, and carbonization. These tests are considered non-destructive even though at times they may cause a winding failure. It should be pointed out that a […]
The hot collar test on bushings may be performed on compound-type, porcelain dry-type bushing, oil-filled bushings, and cable potheads. The collar is energized by the test voltage (thus the term hot collar), while the center conductor is grounded. It is well-established fact that the compound and dry type bushing fail from leaks that develop in
Power transformers are critical and costly assets in the electric power system. They are one of the most important electric apparatuses for providing reliable energy flow. They also constitute one of the largest investments in a utility system or in an industrial complex. For this reason, transformer condition assessment and management are a high priority.
An oil-filled transformer insulation system consists of insulating oil and cellulose (paper) materials. Under normal use, transformer insulation deteriorates and generates certain combustible and noncombustible gases. This effect becomes more pronounced when the transformer insulation is exposed to higher temperatures. When cellulose insulation (i.e., winding insulation) is overheated to temperatures as low as 140°C, carbon
The power factor test and dissipation factor test are considered to be synonymous because they both refer to the AC dielectric loss test. PF and DF are but two of the several measurable characteristics that can be obtained from an AC dielectric loss test used for evaluating the condition of the insulation system. Both of
Transformer absorbs moisture sometimes which is very harmful to its health. Presence of moisture can be detected by two following tests: Checking Insulation Resistance of Winding: Insulation resistance of winding should be checked with a 1000 V megger, the voltage should be applied for one minute. All the windings except the winding under test should
The transformer oil or insulating oil is used in transformers as well as some electrical equipment to: This oil should be clean, free from moisture and other harmful contaminants and possess the following characteristics: Dielectric strength (one minute)- 40 KV (RMS) with a 4 mm gap.Viscosity at 27oC in centistokes-max.– 27Pour point-max. – minus 10oC.Flash point-min.
Hi friends, in this article, I am going to describe the significance of vector group of transformer. It is very essential information for parallel operation of transformers and is very interesting as well. Connection of transformer windings can be made in a number of ways. Accordingly, different types of connections have been standardized depending upon
Hi friends, in this article, I am going to discuss the polarity of transformer windings, if you are interested, keep reading. Unlike DC system, there are no fixed positive and negative poles in AC system, and hence, transformers cannot have fixed positive and negative terminals. The relative direction in which primary and secondary windings of a
Auto Transformer Working Principle The auto transformer working principle and construction is similar to that of conventional two winding transformers. However, it differs in the way in which the primary and the secondary are inter-related. In a two-winding transformer, primary and secondary are only magnetically linked by a common core but are completely insulated from