Darney's Circuit Theory and Modelling

The equipotential earth is a fundamental requirement of circuit theory, because it dramatically reduces the complexity of the mathematics required to simulate a circuit. Unfortunately, in the real world, no such equipotential earth exists, nor can it ever do so, which means simulating a circuit to evaluate its electromagnetic compatibility (EMC) and susceptibility to electromagnetic interference (EMI) is largely dependent on using the Maxwell equations. The Maxwell equations are inherently complex, however, and so have high processing power requirements and, as with all complex systems, there is a propensity to generate and magnify errors.