Research On Electric Power Transformer And Current Limiting Fuse Transient Based On Callahan Numerical Algorithm

Power transformer breakers'asynchronous switching will result in transient saturation over-voltage, which is a great harm to transformer insulation level, may cause blackout accident and bring economic loss and negative social effects.Research on high order nonlinear transformer is difficult in choosing the suitable numerical method, this paper discussed strengths and shortcomings of some kind of method and found semi-implicit format Callahan algorithm is extremely effective in guaranteeing calculation stability,has the merit of explicitly incursion and costs less time. This paper firstly constructed a numerical model for transformer transient saturation over-voltage, and then programmed by Callahan method to solve three-phase breakers'asynchronous operation over-voltage, a 2.32p.u. over-voltage and a inrush current with magnitude 5.14 times of nominal current is obtained. The result is testified to be reasonable and correct. It is also proposed in this paper some affecting factors and improving methods for transformer over-voltage protection.On the other hand, a non-linear high interruption capacity current limiting fuse digital calculation model is constructed, then it is shown the current limiting fuse non-linear resistance characteristics. Using Callahan numerical algorithm together with Richardson extrapolation method, fuse transient characteristics under test duty one and two are studied. Furthermore, comparison between the calculation and test result is done to show the accuracy and reliability of this new digital method. In conclusion, this numerical analysis is more accurate, stable and efficient to perform to obtain fuse transient by Callahan digital simulation, instead of repetitive heavy work on the field test. Finally, analysis on MOA transient and energy absorption is able to provide much reference value on MOA protection design for impulse power generator.