Long transmission line protection based on the principle of balance of energy

A new technique for long transmission line protection based on the balance of energy principle is described in this paper. It can distinguish between internal and external faults by comparing the net energy fed into the protected line in a short time interval. Energy is calculated by two different methods. The results calculated by EMTP show that under any condition of power system the proposed technique has excellent performance for the earth-fault distance protection under high-resistance earth-fault conditions and a short operation time.