Power Transformer Fault Severity Estimation Based on Dissolved Gas Analysis and Energy of Fault Formation Technique

Abstract

Decision making on transformer insulation condition based on the evaluated incipient faults and aging stresses has been the norm for many asset managers. Despite being the extensively applied methodology in power transformer incipient fault detection, solely dissolved gas analysis (DGA) techniques cannot quantify the detected fault severity. Fault severity is the core property in transformer maintenance rankings. This paper presents a fuzzy logic methodology in determining transformer faults and severity through use of energy of fault formation of the evolved gasses during transformer faulting event. Additionally, the energy of fault formation is a temperature-dependent factor for all the associated evolved gases. Instead of using the energy-weighted DGA, the calculated total energy of related incipient fault is used for severity determination. Severity of faults detected by fuzzy logic-based key gas method is evaluated through the use of collected data from several in-service and faulty transformers. DGA results of oil samples drawn from transformers of different specifications and age are used to validate the model. Model results show that correctly detecting fault type and its severity determination based on total energy released during faults can enhance decision-making in prioritizing maintenance of faulty transformers.

Towards Precise Interpretation of Oil Transformers via Novel Combined Techniques Based on DGA and Partial Discharge Sensors

“…This technique is used to rise the correctness of Rogers’s four ratio method by adapting the ratio limits and their association between them to achieve the modified fault types link to the actual fault [ 37 , 38 ]. These four gas ratios are CH 4 /H 2 , C 2 H 6 /CH 4 , C 2 H 4 /C 2 H 6 , and C 2 H 2 /C 2 H 4 .…”

“…The transformer fault is classified as partial discharge (PD), arcing (D1 and D2), or thermal (T1, T2, and T3). Based on the percentage ratio for each gas with respect to the sum of the five gases, the limit of each fault type in this method is determined [ 37 , 38 ].…”

“…Induced voltage test with PD measurement according to IEC St. 60076-3 and IEC St. 60270 [ 36 , 37 ]. In the case of the test, frequency surpasses twice the nominal frequency, the computed time in seconds of the test will be (see Equation (1)) …”

A Fuzzy Logic Model for Power Transformer Faults’ Severity Determination Based on Gas Level, Gas Rate, and Dissolved Gas Analysis Interpretation

“…Fuzzy logic is employed to gain benefits from using a fuzzy rather than a crisp value. The use of fuzzy logic for DGA assessment has also been reported in References [19][20][21][22][23][24][25]. The results were evaluated by comparing to two widely used approaches, scoring and weighting of Dissolved Gas Analysis Factor (DGAF) proposed in Reference [9] and total dissolved combustible gas (TDCG), as suggested in Reference [26].…”

Application of Dissolved Gas Analysis in Assessing Degree of Healthiness or Faultiness with Fault Identification in Oil-Immersed Equipment

“…The authors in [22] proposed a method of determining fault severity based on energy released or absorbed during faulting from an eicosane (C 20 H 42 ) paraffinic oil molecule when it decomposes to generate; H 2 , CH 4 , C 2 H 2 , C 2 H 6 , C 2 H 4 and cellulose disintegrate to produce CO, H 2 , and CO 2 . A similar school of thought was suggested by researchers in [23], but they used the n-octane (C 8 H 18 ) molecule instead of eicosane.…”