needed in the Two-ended over-head transmission line in a solidly grounded networkapplication.For line protection, set the parameters for the Global base values for settings functionsaccording to instrument transformer primary rated values (recommended):1. Set IBase to 1 000 A2. Set VBase to 143 kV3. Set SBase to 247.7 MVA(SBase=√3·VBase·IBase)The GlobalBaseSel setting in a protection and control function referencesa Global base values for setting function for reference of primary values.3.1.3 Calculating settings for five zone distance protection,quadrilateral and mho characteristic ZQMPDIS (21)The settings for the distance protection function are done in primary values. Theinstrument transformer ratio that has been set for the analog input card is used toautomatically convert the measured secondary input signals to primary values used in thedistance protection function. The following basics should be considered, depending onapplication, when doing the setting calculations:• Errors introduced by current and voltage instrument transformers, particularly undertransient conditions.• Inaccuracies in the line zero-sequence impedance data, and their effect on thecalculated value of the ground-return compensation factor.• The effect of in feed between the IED and the fault location, including the influenceof different Z0/Z1 ratios of the various sources.• The phase impedance of non transposed lines is not identical for all fault loops. Thedifference between the impedances for different phase to ground loops can be as largeas 5-10% of the total line impedance.The purpose of distance protection is:• Main protection for all short circuits (phase to ground, phase to phase, double phaseto ground and three phase) on the line.• Main protection for all short circuits on the adjacent 138 kV busbar (no busbarprotection).• Remote back-up protection for all short circuits on the 138 kV lines out from theadjacent busbar.• Remote back-up protection for all short circuits in the transformer connected to theadjacent 138 kV busbar.Section 3 1MRK 506 334-UUS AREL650 setting examples44Application manual
