TRAVELLING WAVES ON TRANSMISSION LINES INCLUDING CORONA EFFECTS

Corona is the dominating effect in attenuating and distorting a travelling wave or surge on a power transmission line. A mathematical model to predict both capacitive changes and resistive losses due to corona is developed.; The capacitive changes are attributed to an equivalent increase in conductor radius and ionized charge. This equivalent radius is defined as the radial distance to the point where the electric field is equal to the breakdown strength of air. The effective capacitance is defined according to dQ/dv and is thus a function of voltage, C(V). Below the corona threshold voltage, V(,th), the capacitance is constant and equal to the natural capacitance of the line. Above V(,th), the capacitance increases. Because of the distributed nature of a transmission line, C(V) is a per unit length quantity, farads/meter.; Corona resistance, R(,loss), is a series resistance that accounts for the hysteresis loop losses as a surge travels down a transmission line. The hysteresis loop in the Q-V relationship of the transmission line above V(,th). It is defined in terms of line geometry and peak waveform voltage, V(,max). The area within the loop is the energy lost by the wave per unit of length travelled. Dividing this energy loss by the integral over time of the line current squared produces the R(,loss) value.; The corona effects cause the telegraph equations to be non-linear. To solve the problem, the functions C(V) and R(V) are approximated as step functions over given voltage ranges. This linearizes the telegraph equation over the voltage range of interest. This method is a piecewise linearization where a step function is used to model the non-linearity over the given voltage range.; This model is based on various experimental data. To validate the model presented, a computer simulation is developed. A total of 18 different test cases are simulated and comparisons to experimental data are presented. The validity of the model is also verified using the finite difference method of Courant-Isaacson-Rees.; These various test cases verify that the simulator operates properly and that the analytical model presented is valid under the conditions specified.