en05000220.vsdRZmARGLdARGLdARGLd ARGLdRLdFwRLdRvZLIEC05000220 V1 EN-USFigure 187: Characteristic for zone measurement for a long line[6]8.13.2.6 Parallel line application with mutual coupling GUID-1F856628-0CEE-4679-BB71-40177187390D v1General GUID-1D633249-8BF6-4992-A06E-E8BD23B2C315 v3Introduction of parallel lines in the network is increasing due to difficulties to getnecessary area for new lines.Parallel lines introduce an error in the zero sequence measurement due to themutual coupling between the parallel lines. The lines need not be of the samevoltage in order to have mutual coupling, and some coupling exists even for linesthat are separated by 100 meters or more. The mutual coupling does not normallycause voltage inversion.It can be shown from analytical calculations of line impedances that the mutualimpedances for positive and negative sequence are very small (< 1-2%) of the selfimpedance and it is a practice to neglect them.From an application point of view there exists three types of networkconfigurations (classes) that must be considered when making the settings for theprotection function.The different network configuration classes are:1. Parallel line with common positive and zero sequence network2. Parallel circuits with common positive but separated zero sequence network3. Parallel circuits with positive and zero sequence sources separated.[6] RLdRv=RLdRvFactor*RLdFw.1MRK 506 369-UEN B Section 8Impedance protectionLine distance protection REL670 2.2 IEC 365Application manual
