Developing model of transient processes in transformer under capacitive load

Abstract

Voltage transformers with capacitive loading during transients can cause significant distortion of the secondary voltage of the ship's network. For the analysis, a well-known nonlinear model of a single-phase two-winding transformer is used, in which the magnetic flux is divided into “working” and leakage fluxes coupled to individual windings that close outside the core. For practical purposes, when using such transformers, it is important to know both the conditions for the occurrence of autoparametric oscillations and the dynamics of the transient process. It is convenient to carry out a comparative evaluation of capacitive power take-off schemes on a computer, which makes it possible to reproduce non-linear characteristics and vary parameters over a wide range, which is difficult in physical modeling. The results of the study of a short circuit downstream of the reactor in the capacitor selection circuit proved that the short circuit at the terminals of the intermediate transformer does not affect the elements of the upper arm of the voltage divider, but significantly affects the lower arm of the divider and the compensating reactor, as a result, subharmonics appear. It is shown that the developed model is convenient for studying the influence of transient processes (short circuits) on the elements of a voltage divider. The applied model is universal for ship power networks and can be used for both capacitive and inductive dividers. A divider circuit with specific parameters has been modeled and relevant studies have been carried out. Mathematical results are verified on a physical model, which confirmed the correctness of the mathematical model. It has been inferred that a decrease in the phase voltage leads to a decrease in the overvoltage on the divider elements during a short circuit behind the compensating reactor of the power take-off circuit.