Investigation of surge propagation in transient voltage surge suppressors and experimental verification

An on-going question in the field of surge protection study is how to predict incipient failure of power electronics in the event of a short time, high voltage, and high energy transient surge propagation. The work presented in this thesis addresses the above question by investigating how a high voltage transient surge, whose duration is in the microseconds range, will propagate through the two-level transient voltage suppressor system that is intended to protect sophisticated electronics situated close to the service entrance of a building. In this work the energy patterns relevant to the individual components of the system are evaluated using numerical methods and some of the results are also compared with those obtained using SPICE simulations. Although several mathematical models for surge protection components are discussed in the literature and some device specific ones are provided by manufacturers, there is no evidence to show that a complete analysis, using any such model, has been performed to predict the energy absorptions and associated time lags between the components in a TVSS. Numerical simulation techniques using MATLAB are used to estimate the energy absorption and associated time delays in relation to the propagated transient surge, in individual components of a transient voltage surge suppressor. This study develops mathematical models for particular nonlinear transient surge absorbing elements, specifically for the metal oxide varistor and transient voltage suppressor diode, formulates the state equations which are used to numerically simulate several instances of the transient voltage surge suppressor system, and presents simulation results. All results are validated experimentally using a lightning surge simulator. The outcomes established using the two approaches indicate that the theoretical energy calculations are within 10% of the experimental validations for the metal oxide varistor, which is the main energy absorbing element in the system. The remaining energy distributions in the line-filter components and the transient voltage suppressor diode, which are at least 10 times smaller, are all within 20% of the experimental results. The times at which, the metal oxide varistor and the transient voltage suppressor diode switches to heavy conduction mode are also simulated accurately