I am curious to know what people are using for transformer inrush current on time current curves. I have seen anything from 8x FLA to 12x FLA for 6 cycles. The software I use defaults to 8x but that can be changed.
Below is an excerpt from various sources indicating the estimated inrush of MV dry type and oil-insulated transformers. A few observations are offered to consider: a) Although today dry-type transformer design is available up to 145 kV and 63 MVA, the traditional application is mainly in LV and MV network and seldom used by power utilities.
b) It appears that most modern dry-type transformers are manufactured with inrush lower in most cases than the oil immersed units.
c) The time constant that control the inrush current duration is also lower than similar oil insulated transformers in most cases.
d) The inrush current decrease as the standard temperature-rise increases for dry type transformers.
e)Microprocessor multifunctional relays are not only used in HV application but also in many MV projects and can be set to provide optimal reliability and functionality avoiding unnecessary nuisance tripping.