April 5, 2022

Simple ageless methods for field testing power transformers of no-load condition at the low induced voltage – Part II

According to the C57.93-2019 standard [13], the measure of transformer excitation current is one of 15 proposed tests during commissioning, the scope / list of which is...

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According to the C57.93-2019 standard [13], the measure of transformer excitation current is one of 15 proposed tests during commissioning, the scope / list of which is determined depending on the equipment available and the importance of the particular transformer.

This test is often referred to simply as the Doble Test. As reported by Mark Lachman [14], the single-phase exciting-current test was introduced as a diagnostic tool in 1967 in Doble Engineering Company. In subsequent years, this test became more widespread, and in 1995 the test was the first included in the IEEE-1995 standard [15] (however, it had not yet been included in the IEEE-1978 standard).

Note that the IEEE-1995 clause “6.1.3 Exciting Current” is only two pages long. Further development of American practice, especially after the works of Lachman [14, 16, etc.], led to a greater detail of the testing process. This detail was reflected in works Doble 72A-2244 Rev. A, 2000 [17] and repeated in 72A-2244-03 Rev. A, 2006. In the updated 2013 standard, clause “7.2.11 Excitation current” already contains six pages of text [1]. It is important to note that in the 2013 standard, in addition to measuring current, a loss measurement was also added.

See the PDF here

In the years after 2013, Lachman and Shafir continue to theoretically and practically improve the diagnostic properties of this test. The inductive, capacitive, and resistive components of the current, the influence of the core / coil configuration on the measured current and losses are investigated, and the hardware implementation of new knowledge is carried out [18, 19, 20, 21, etc.].

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