Sensitivity and stability of superimposed component based directional comparison protection

Superimposed voltage and current signals are fault generated changes, they constitute the earliest potential evidence of a fault, and are inherently independent from loads on the protected systems, less affected by CT saturation phenomena. This paper presents the superimposed components based Delta Directional Comparison algorithm and its superior fast and secure directional decisions for the protection of HV/EHV transmission lines. The scheme provides fast fault clearance over 100% of the protected lines. The paper also analyzes the sensitivity and stability issues associated with the Delta Directional Comparison schemes, and the need for current reversal guard in parallel line protection.