Current　research　on　electricity-gas–integrated　energy　systems　(EG-IESs)　often　overlooks　power　quality　issues　prevalent　in　power　systems.　Voltage　sags,　critical　and　frequent　power　quality　disturbance,　significantly　affect　the　EG-IES　due　to　sensitive　coupling　devices.　To　minimize　economic　losses　from　voltage　sags　in　the　EG-IES,　this　study　introduces　an　optimal　configuration　methodology　for　EG-IES　coupling　devices,　considering　fault　propagation　within　both　electrical　and　gas　subsystems.　Initially,　the　impact　of　voltage　sags　on　the　bidirectional　interaction　of　the　EG-IES　is　analyzed,　with　a　focus　on　the　influence　of　coupling　devices.　Subsequently,　tolerance　characteristic　curves　for　compressors　and　gas　turbines　are　presented,　and　a　system　economic　loss　model,　based　on　the　tolerance　curves　of　coupling　devices,　is　developed.　An　objective　function　is　then　formulated　to　minimize　economic　losses,　incorporating　a　coupling　device　cost　model,　and　solved　using　an　enhanced　particle　swarm　optimization　algorithm　to　determine　the　optimal　configuration　of　coupling　devices.　The　efficacy　and　applicability　of　the　proposed　method　are　validated　using　an　EG-IES　model　comprising　the　IEEE　14-bus　system　and　an　11-node　gas　network.　The　results　indicate　that　the　proposed　optimal　configuration　method　for　EG-IES　coupling　devices,　implemented　during　the　planning　phase,　effectively　reduces　losses　caused　by　voltage　sags　in　the　EG-IES　while　accounting　for　equipment　installation　costs.　Copyright　©　2025　Wei　Zhao　et　al.　International　Transactions　on　Electrical　Energy　Systems　published　by　John　Wiley　&　Sons　Ltd.