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--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.　©　2019　by　the　authors.　Licensee　MDPI,　Basel,　Switzerland.