In　a　multi-state　system　with　common　bus　performance　sharing,　the　performance　surplus　from　one　element　can　be　transmitted　to　other　deficient　elements　as　long　as　the　total　amount　of　transmission　does　not　exceed　the　transmission　capacity　of　the　common　bus.　Existing　literature　fails　to　consider　the　transmission　loss　during　the　performance　sharing　process.　Transmission　loss　widely　exists　in　practice　and　is　affected　by　many　external　factors.　For　example,　the　power　transmission　loss　is　affected　by　the　distance,　humility　and　temperature.　In　this　research,　we　study　a　common　bus　performance　sharing　system　consisting　of　N　independent　elements　with　consideration　of　performance　loss　during　transmission.　We　propose　three　different　transmission　loss　models　that　are　frequently　encountered　in　practice,　and　suggest　their　corresponding　reliability　evaluation　algorithms.　To　improve　the　system　availability,　maintenance　actions　are　taken　to　improve　the　component　reliability,　and　protection　is　provided　to　defend　the　system　against　external　impacts.　We　analyze　the　optimal　trade-off　between　protection　and　maintenance　by　minimizing　the　system　cost　while　satisfying　a　pre-specified　system　availability　requirement.　The　proposed　reliability　models　and　algorithms　are　illustrated　by　a　regional　power　distribution　system.　The　numerical　study　has　demonstrated　the　importance　of　considering　transmission　loss　in　reliability　modeling　and　optimization.