Experimental and numerical analysis of fast transient phenomena in distribution transformers

Evaluation of surge-transferred overvoltages in distribution transformers

“…So the frequency interval is Ω = 2π × 10 8 rad/s, and dω = 2π × 10 4 rad/s. The constant b normally varies 10 3 < b < 10 5 , and for fast transients is taken to be b = 10 5 . More explanation about the choice of these parameters can be found in Ref.…”

“…So far there was significant research done on the investigation of transients in transformers [3][4][5][6][7][8]. In Refs.…”

“…In Refs. [3,4], the lumped parameter analysis was used for transformer modelling, and [5,6] deal with the modelling of transformer based on the well-known Rabins method. It was also shown that transformer can be modelled by considering the windings or group of windings as transmission lines [7,8].…”

Computation of Very Fast Transient Overvoltages in Transformer Windings

“…The matrix is calculated through the capacitance matrix (2) where the velocity of wave propagation is calculated as (3) where is the speed of light and is the dielectric constant of the transformer insulation. We have to point out that the matrix in (2) takes into account the mutual inductances within a specific coil.…”

“…Also, in medium voltage systems where vacuum circuit breakers [2], [3] are used, reignition causes high-frequency oscillation which can be dangerous because of their short rise time. Under special circumstances, the terminal overvoltages can arise close to the transformer BIL.…”