The main network components of interest are the transmission lines, transformers, and synchronous machines.
(a) The conductors of a transmission line, being passive and stationary, do not have an inherent direction. Thus they always have the same positive sequence impedance and negative sequence impedance. However, as the zero sequence path also involves the earth wire and or the earth return path, the zero sequence impedance is higher in value.
(b) The transformer too, being passive and stationary, do not have an inherent direction. Thus it always has the same positive sequence impedance, negative sequence impedance and even the zero sequence impedance. However, the zero sequence path across the windings of a transformer depends on the winding connections and even grounding impedance.
(c) The generator (or a synchronous machine), on the other hand, has an inherent direction of rotation, and the sequence considered may either have the same direction (no relative motion) or the opposite direction (relative motion at twice the speed). Thus the rotational emf developed for the positive sequence and the negative sequence would also be different. Thus the generator has different values of positive sequence, negative sequence and zero sequence impedance.
(a) The conductors of a transmission line, being passive and stationary, do not have an inherent direction. Thus they always have the same positive sequence impedance and negative sequence impedance. However, as the zero sequence path also involves the earth wire and or the earth return path, the zero sequence impedance is higher in value.
(b) The transformer too, being passive and stationary, do not have an inherent direction. Thus it always has the same positive sequence impedance, negative sequence impedance and even the zero sequence impedance. However, the zero sequence path across the windings of a transformer depends on the winding connections and even grounding impedance.
(c) The generator (or a synchronous machine), on the other hand, has an inherent direction of rotation, and the sequence considered may either have the same direction (no relative motion) or the opposite direction (relative motion at twice the speed). Thus the rotational emf developed for the positive sequence and the negative sequence would also be different. Thus the generator has different values of positive sequence, negative sequence and zero sequence impedance.