Stress distributions within windings were simulated for single-turn and multi-turn coil machines.
The probabilities controlling these contingencies were estimated. The overvoltages for each contingency were modeled in detail, typically using the ElectroMagnetic Transient Program, with more » the results also quantified in terms of simpler formulas. Power frequency overvoltages include self excitation, harmonic line resonance, HV to LV faults in transformers, stuck breaker pole and bus faults and several kinds of ferroresonance.
#DIGITAL TECHNIQUES PDF SERIES#
Medium frequency oscillatory overvoltages include the transfer of lighting induced surges through transformers, line faults, fault clearing, multiple reignitions, arcing bus faults, series arcing on busses, and HV switching. Steep-fronted surge sources include lightning, nearby faults, circuit breaker closing, reignitions and restrikes.
#DIGITAL TECHNIQUES PDF GENERATOR#
Generator windings may be stressed beyond their normal power frequency duty by a variety of disturbances. We wish to ackn owledge Drew Padgett for provid ing a technical review of the manuscript. ACKNOWLEDGEMENTS Ray Martinez, James Taylor and Jordy Machado - Lopez were instrumental in building the high voltage test sources, conducting experiment s and acquiring the breakdown data contained herein. Methods of nanosecond - scale capacitive discharge unit high voltage source development, suggestions for de - rating of 60 Hz insulation maximum electrical fields for EMP nanosecond pulse voltage withstand rating, and po tential methods for increasing transformer resilience to such fast rise time pulses are described.
We developed modeling methods and measured breakdown electrical field statistical distributions for direct current, 60 Hz, lightning and EMP characteristic voltage rise times. This i nitial project is a path toward establishing electrical grid transformer failure criteria for EMP voltage transients. Part 2 of this report details assessme nts of internal voltage and electrical field holdoff testing of transformer insulation dielectric breakdown, including comparison of low frequency (DC/60 Hz) holdoff to rise times characteristic of lightning (1 s) and EMP E1 transients (10 - 30 ns). A proposed modeling scheme for a HV transformer is described in Part 1 of this report.
This broad - band, high - fidelity model would enable the prediction of unwanted effects through more » simulation. The model constructed should cover the frequency band of interest while capturing the internal physical and elec trical characteristics. To help identify these potential occurrences, it is n ecessary to develop a transformer model that not only captures the input / output response of the transformer but also the internal behavior. The response of a high - voltage (HV) transformer to fast rise time voltages, such as that from a electromagnetic pulse (EMP) can result in interruption of power distribution and possibly system failure.
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