<p>In practical applications, the partial equivalent circuit (PEEC) obtained through transformation of electric field equations can be modeled as neutral delay differential equations (NDDEs). Due to the fragility of the solutions to NDDEs, studying the stability of such systems is of great significance. This study addresses the fault estimation problem in neutral systems subject to multi-source interference, including actuator faults, unknown input disturbances, sensor faults, measurement noise interference, and nonlinear terms. Traditional fault estimation methods often require satisfying observer matching conditions (OMC), which can be challenging to achieve for many practical systems. To overcome this limitation, this paper designs two appropriate variables and proposes an improved intermediate estimator for neutral systems, which simultaneously estimates the states and actuator faults, among other issues, in the considered neutral systems, demonstrating significant improvements in both accuracy and response speed. Sufficient conditions ensuring the existence of the intermediate estimator are derived based on linear matrix inequalities (LMIs). Subsequently, according to Lyapunov’s stability theory, this paper proves that the states of the error system are ultimately bounded, not only validating the effectiveness of the intermediate estimator method in dealing with multi-source interference in neutral systems but also highlighting the important role of the PEEC model transformed from the electric field equation in the analysis and design of complex control systems. Finally, we validate the effectiveness and practicality of the proposed method through examples.</p>