Development of low voltage distribution grids with the focus on maximal value of short circuit impedance
The supply territory of the E.ON Distribution in the Czech Republic accounts for approxi-mately 1.5 million customers. The most of them are supplied from the low voltage (LV) dis-tribution network when E.ON Distribution runs 40 thousand km of LV power lines. Distribu-tion network operator (DNO) should guarantee voltage quality according to the EN 50160 standard in delivery points of all the LV customers. The level of individual VQ parameters depends on the real value of short circuit power and the value of short circuit power depends on the length of the feeder. The paper describes a proposal of minimal values of short circuit power in LV grid with the focus on keeping with the EN 50160 standard. Proposed minimal value of short circuit power is tested in practice when E.ON Distribution has in database more than 2 thousand VQ measurements from LV distribution grid with known value of short cir-cuit impedance which is measured by each VQ measurement in LV grid. The minimal value of short circuit power (maximal value of short circuit impedance) is recalculated to the maximal length of the commonly used types of conductors. Keeping of the maximal length of the feeder is necessary condition (but not sufficient condition) for meeting of the standard EN 50160 and gives the technician a smart tool by grid projecting.