Assessing mechanical deformations in two-winding transformer unit using reduced-order circuit model

A novel methodology for high‐frequency lumped equivalent circuit of an isolated transformer winding construction based on frequency response analysis signal morphology interpretation

“…At higher frequencies, the capacitive effect can be represented by Equation () [6], the curve decreases with increasing frequency as shown in Figure 3. The global capacitance represents the equivalent of shunt and series capacitances of all sections, and its value must remain considerably constant.…”

“…The inductive effect in low frequencies can be modelled by an equivalent inductance in series with an equivalent resistance, which follows linear increasing values of impedance, and this may not be exactly linear due to the nonlinearity of the core in case of the winding with iron core. Actually, in practice, it is possible to limit the influence of the core and the effect of neighbouring windings by choosing proper terminal connection [6,15]. There are two objectives to choosing the end-to-end short-circuit connection: the first is to significantly reduce the model of a multi-winding transformer to a single ladder network (reduced model) [6], and the second if when windings in transformers need to be checked individually as mentioned in the worldwide standardisation activities for the FRA test and Kulkarni et al [16], the response is influenced by the leakage inductance rather than the magnetizing inductance.…”

“…Among the two main methodologies that exist to model, the frequency response of the transformer winding is the lumped parameter circuit model, which has been widely adopted in the literatures for FRA studies. It reflects the transformer internal physical structure and able to investigate the impacts of various winding deformations on the FRA response, generally used by [2,3,[5][6][7][8] etc.…”

BA to construction of equivalent circuit of a transformer winding from frequency response analysis measurement

“…Elsewhere, using an experimental investigation, Pramanik and Satish [19] argue that the influence of an LV winding (when it is shorted and grounded) on the driving point impedance (DPI) measurement of high-voltage winding is much ignored. Consequently, as reported by Shah and Ragavan [20], the transformer can be considered as an isolated coil (outside of the transformer) and the system can be represented by a single ladder network. Thus, Soyosal [21] and Miki et al [22] also have found that if neighbouring windings are short circuited, then the transformer behaviour with iron core is same as to that without iron core (with air core).…”

“…For mutual capacitances between the transformer windings, few works have treated this problem. However, Shah and Ragavan in [20] have noted that when the adjacent windings to the investigated winding are shorted, the windings are considered equivalent to shields.…”