Nonlinear oscillations due to spuriousenergisation of transformers

Spurious energisation occurs when at least one phase of an otherwise de-energised three-phase transformer remains energised. A transformer spuriously energised will certainly overheat although the probability of its occurrence is low. However, unpredictable nonlinear oscillations, which may be either periodic or quasiperiodic, will be setup as a consequence. The author uses the method of multiple-scales to analytically predict the type of oscillations when a transformer is spuriously energised. This will aid in identifying the conditions that cause qualitative change in the type of oscillation. The author shows that spurious energisation can result in either nonresonant or resonant modes depending on the parameters of the power network. The nature of oscillations in nonresonant mode are of vivid variety. However, the oscillations in the resonant mode are generally periodic.