NGC experience on ferroresonance in power transformers and voltage transformers on HV transmission systems

Time‐domain finite‐element technique for quantifying the effect of sustained ferroresonance on power transformer core bolts

“…However, acquiring suitable real-scale test results during switching operations, especially on 400 kV system networks, is difficult, because they are very rare, and those that are undertaken are rarely reported [1,17]. Furthermore, the resolution of available ferroresonance field measurements of voltage and current at the 400 kV level may be insufficient for use directly in the finite-element calculation.…”

“…The magnitude of the voltages is close to 1 pu (in contrast to chaotic modes of ferroresonance, where there are significant overvoltages >1.2 pu). However, UK experience [1] suggests that the sustained fundamental mode of ferroresonance is the most severe case because of the high energy transferred to the transformer. Phases R and B are in anti‐phase with phase Y , suggesting that all the three‐phase limbs would become highly saturated at the same instant.…”

“…As a consequence, a number of power transformers are exposed to ferroresonance where they are connected to mesh corner and circuit tee configurations. UK experience [1] suggests that one in ten circuit de‐energisation can be driven into ferroresonance, the probability depending upon the appropriate initial conditions being established. It is believed that ferroresonance is a contributing factor to the eventual failure mode by exposing the transformer's components to electromagnetic and thermal stresses.…”

Impacts of ferroresonance and inrush current forces on transformer windings

“…The previous studies mainly focus on the fundamental and sub‐harmonic modes during the steady‐state, and ferroresonance modelling still remains a problem because the corresponding magnetic hysteresis must be modelled precisely [6]. It has been pointed out that the overvoltages and currents can rise up to 4 and 10 pu at fundamental frequency, respectively [7]. Moreover, it has been shown that the overvoltage during ferroresonance in chaotic mode can reach 5 pu, theoretically [8].…”

Investigating Ferroresonance Phenomenon in a Single-Phase Transformer with the Effect of Magnetic Hysteresis

“…So that in the ferroresonance phenomenon, there are more than one response for a set of identical parameters [2]. In ferroresonance mode, relationship between voltage and current in addition to the frequency is related to other factors such as voltage, initial conditions and circuit losses [3]. Nowadays, from soft magnetic materials are used strongly in the structure of electrical equipment.…”