Ignition of discharges in macroscopic isolated voids and first electron availability

Internal partial discharges and electrical treeing are some of the main aging mechanisms of all the polymeric insulating materials present in the power net. A better understanding of this process calls for the development of more sophisticated simulation tools, based on the numerical solution of first principles equations, i.e., a set of partial differential equations. The accuracy of the predictions of these models heavily relies on the quality of the set of physical parameters used as, for example, the swarm parameters. A key aspect is the correct representation of the first electron availability which triggers the discharge. These electrons are mainly injected into the gas from the interface between the gas itself and the solid polymeric matrix by means of the Schottky effect. The work function is a very relevant parameter in defining this effect, and so the entire quality of the simulation process depends on it. In this work, we estimate the value of the work function, using electronic structure calculations, and we perform some parametric analyses to show how the discharge simulations are affected by the variation of this quantity. In particular, we assume that the polymeric material is polyethylene, which is used extensively in the electric power transmission industry. The discharge simulations produce some relevant data that can be compared against experimental data for validation purposes. Published under license by AIP Publishing.