Enhanced alpha plane line protection

The ratio of currents at both ends of the transmission line is utilized in alpha plane differential principle to detect an internal fault. Such a scheme uses either phase current or sequence currents. As the ratio computed using phase current and sequence currents has their own demerits, both are combined to enhance the security and sensitivity of the protection scheme. However, such a scheme which uses both phase and sequence current demands large communication channel requirement and has limited performance during high resistance fault during single pole tripping and Metal oxide Varistor (MOV) operation in series compensated line. In this work, phase current based adaptive alpha plane differential protection scheme is proposed which uses change in current and phase angle between voltage and current at both ends of the line. The proposed method is tested for Western-System-Coordinating-Council 9-bus system and results show it works for all circumstances and it is also valid for series compensated line.