This　paper　presents　a　novel　model　of　the　electric　arc　furnace　(EAF)　based　on　energy　conservation　theory.　Starting　from　the　arc　energy　balancing　equation　for　the　electric　arc,　the　proposed　model　is　able　to　reflect　the　steady-state　operating　characteristic　of　arc　furnace　accurately.　Then　the　dynamic　arc　furnace　model　can　be　obtained　by　modulating　the　definitive　model　with　white　noises.　The　model　is　proved　to　be　accurate　and　valid　tested　by　simulation.　Due　to　the　adverse　effects　produced　by　the　operation　of　arc　furnace,　it　also　analyzes　the　influence　on　the　protective　relay,　which　includes:　the　mal-operation　of　negative　sequence　relay　and　frequent　operation　of　startup　component.　The　suppressing　measures　with　reasonable　results　for　these　problems　are　also　presented　in　this　paper.　©　2010　Chinese　Soc　for　Elec　Eng.