Due　to　the　limitation　of　a　single　short-circuit　detection　feature,　the　short-circuit　protection　method　of　a　low-voltage　AC　system　based　on　the　over-current　principle　has　been　unable　to　meet　the　requirements　of　operation　protection　under　complex　working　conditions.　With　the　availability　of　flexible　technologies　such　as　distributed　photovoltaic　and　energy　storage,　low-voltage　protection　technology　has　faced　new　hurdles.　Therefore,　a　node-autonomous　fast　short　circuit　protection　method　for　distributed　photovoltaic　low-voltage　AC　systems　is　proposed.　Firstly,　the　characteristics　of　the　branch　state　are　constructed　using　the　instantaneous　amplitudes　of　short-circuit　current　and　voltage,　and　the　early　detection　technique　of　short-circuit　state　is　investigated.　Secondly,　the　polarity　information　of　the　short-circuit　current　in　each　branch　of　the　same　node　is　introduced,　and　the　short　circuit　branch　protection　decision　mechanism　based　on　the　direction　correlation　identification　of　the　short-circuit　current　is　designed.　Finally,　the　protection　experiment　of　the　low　voltage　physical　experiment　system　and　its　simulation　model　are　carried　out.　The　experimental　results　show　that　the　short　circuit　of　both　the　traditional　and　photovoltaic　branches　can　be　detected　within　0.5　ms.　The　protection　response　ranges　between　different　nodes　are　reasonably　matched,　and　for　the　short　circuit　at　the　near　end　of　the　outlet　of　the　same　node,　whether　the　protection　is　triggered　can　be　accurately　determine　in　each　branch　within　1　ms　of　the　short　circuit,　thus　achieving　selective　protection.　The　protection　method　does　not　malfunction　under　the　disturbance　of　various　source　load　operating　conditions.　The　research　results　have　high　theoretical　and　engineering　value.　©　2024　Power　System　Technology　Press.　All　rights　reserved.