Computer Simulation of Partial Discharges in Voids inside Epoxy Resins Using Three-Capacitance and Analytical Models

Abstract

Epoxy resin is one of the most common polymers used as part of the insulation system in key electrical assets such as power transformers and hydrogenerators. Thus, it is necessary to know their main characteristics and to evaluate their condition when subjected to High Voltage (HV). A brief review of epoxy resins’ applications as insulating materials is made, their main characteristics as insulating media are given, the improvements with nano-fillers are summarized and the main electric properties required for Partial Discharges (PD) modelling are listed. In addition, the theoretical background and state-of-the-art of the three-capacitance and analytical models for simulating PD in solid dielectrics, such as epoxy resins, are reviewed in detail. Besides, their main advantages and disadvantages are presented, some critical arguments to the modelling procedure and assumptions are made and some improvements are proposed, taking into account conclusions made from other authors using models related to the PD development process. Finally, a case study was simulated using a modified three-capacitance model and the analytical model. The PD rate, q-φ-n diagrams and the minimum, mean and maximum PD electric charge are compared with measurements reported in the literature. Simulation results are in reasonable agreement with measured values. Capacitance models can be implemented in general purpose electric circuit simulation packages; however, its simulation is computationally expensive. Additional to this, although the modified three-capacitance model is not as accurate as finite elements or analytical models, results are also in agreement with real data.

A Comparative Analysis Applied to the Partial Discharges Identification in Dry-Type Transformers by Hall and Acoustic Emission Sensors

“…(2019) to evaluate the degradation of epoxy resins [28]. Nakamura et al (2020) [26] assessed the electrical charge produced in epoxy materials when they are subjected to the effect of temperature.…”

Quality Control Approach for the Detection of Internal Lower Density Areas in Composite Disks in Industrial Conditions Based on a Combination of NDT Techniques

“…In the case when a strong electric field interacts with entrapped gases or water in internal voids, partial discharges appear in their location, launching local chemical degradation mechanisms. This in turn makes the material locally conductive, and as a result of the prolonged action, causes the initiation and propagation of mechanical damage, primarily in the form of cracks [27][28][29].…”

Finite‐element‐analysis models for numerical simulation of partial discharges in spherical cavities within solid dielectrics: a review and a novel method

“…Variations in the equivalent circuit have been implemented to consider the effect of the surface charge distribution, in which some use an additional capacitor [18], others use mathematical functions for controlling the PD process externally and consider the effect of charge on the void surface left by previous PD [19]. The three‐capacitance model, despite its simplicity, is difficult to solve numerically because of the non‐linearities related to PD phenomena [20]. The induced and real PD charges are calculated as a function of capacitances and currents in the equivalent circuit.…”