COMPUTING THE INTERNAL TRANSIENT VOLTAGE RESPONSE OF A TRANSFORMER WITH A NONLINEAR CORE USING GEARS METHOD .1. THEORY

An EHV transformer's insulation structure must be designed to withstan d the internal stresses generated during transients. Computer models a re employed for predetermination of these stresses. This paper develop s a detailed transformer model and solution method which represents th e nonlinear, saturable characteristic of the magnetic core during tran sients. The resulting set of stiff nonlinear differential algebraic eq uations (DAE's) are solved by application of Gear's method. Part 1 des cribes the transformer model and the necessary set of equations based on linearization of the iron core's saturable magnetic characteristic at each time interval. Part 2 presents data verifying the methodology.