2. Space load

The materials used in electrical insulation never behave like perfect insulators. They are liable to become electrically charged by mechanisms whose nature is known and described theoretically in certain idealized situations. In the real-life situations encountered in industrial applications, however, it is difficult, if not impossible, to take a theoretical approach, since the systems involved are so complex and often ill-defined at the microscopic level. It is therefore essential, in the context of an application, to carry out tests using techniques that enable measurement of the load generated or likely to be generated, for given experimental conditions.

We'll call space charge the set of real charges, positive or negative, contained in an insulator, which includes surface and volume charges. We will denote by ρ _c ...