Abstract: First of all,an analysis is made of the principle of unbalance and differential protection of electrode line prior to proposing the paper.The double end unbalance protection can protect the full length of the electrode line,distinguish between the open circuit and grounding fault,and calculate the fault distance,which is not affected by transition resistance,and the principle of setting values is simple.The EMTDC/PSCAD simulation software is adopted to verify the correctness of theoretical analysis.Finally,real-time digital simulator is used to verify the feasibility of the proposed protection action strategies.