With the development of power systems

the originally nonexistent problem of current reversal on series compensated transmission lines due to overcompensation is getting more and more apparent. An in-depth analysis is made on the factors related to current reversal

and the influence of current reversal on current differential protection. The results show that current reversal may cause reduced sensitivity of zero sequence differential protection for high resistance earth fault

and even rejection of operation for internal fault. A novel algorithm for zero sequence current differential protection is proposed

which is capable of not only solving the problem of sensitivity reduction

but also universal application to various types of series compensated lines. Simulation test and actual application have proved the effectiveness and reliability of the method proposed.